DISTANT HYBRIDIZATION IN POTATO

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DISTANT HYBRIDIZATION IN POTATO:

1 DISTANT HYBRIDIZATION IN POTATO

Content:

2 Content Introduction Endosperm Balance Number (EBN) and its importance in potato breeding Barriers associated with wide hybridization in potato and methods to over come them Achievements Conclusion Future thrust

Introduction:

3 Introduction Potato ( Solanum tuberosum L., 2n=48) belongs to solanaceae family In world it is grown in an area of 18.6 million hectares with production of 323 million tonnes and in India it is grown in an area of 1.4 million hectares with production of 25 million tonnes (FAO, 2005). It is a tetraploid with a basic chromosome number ( x ) of 12 and is considered to be an autotetraploid because of the tetrasomic inheritance Wild species are self incompatible, but cultivated potato is self compatible, with out-crossing ranging from 10-74 % It includes 9 cultivated species

Table 1: Cultivated Potato species:

4 Table 1: Cultivated Potato species Species Chromosme No. (2n) Location S. ajanhuiri Juz. Et Buk. 24 High altitudes around lake Tilticaca S. goniocalyx Juz. Et. Buk. Humid-temperate maritime climates S. phureja Juz. et. Buk. Northern Andean valleys S. stenotomum Juz. Et. Buk Northerrn high Andes S. vernei Bitt. et. Wittm North-west Argentina S. X chaucha Juz. et. Buk 36 Andean valleys from Ecuador to Bolvia S. tuberosum L. 48 subsp. tuberosum L. Worldwide subsp. andigena Juz. et. Buk. Southern South America S. cutilobium Juz. et. Buk. 60 Central high Andes Hankock (2004)

Constraints in Potato Breeding:

5 Constraints in Potato Breeding Narrow genetic base Cultivated potato is a tetraploid with allogamous nature, leading to complex segregants in the F 2 progeny, making selection difficult Inter-locus interaction (epistatsis) and hetrozygosity are important factors and yield is directly correlated with the amount of hetrozygosity Identification of individual chromosome was very cumbersome by conventional cytogenetic methods

Wild Relatives of Potato:

6 Wild Relatives of Potato Potato cultivar gene pool is relatively narrow but breeders are fortunate to have an access to more than 200 wild species of potato, which is more than any other crop, for use in improvement A series of polyploidy occurs in potato species, ranging from 2x to 6x, with 73% diploid (most wild species), 4% triploid, 15% tetraploid (including the most widely grown cultivated species), 2% pentaploid and 6% hexaploid These wild species are important source of genes for resistance to biotic and abiotic stress In addition these wild species contribute allelic diversity to breeding program, maximising both heterozygosity and epistasis, which are required for yield improvement. (Jansky, 2006) Continue …

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7 Number of wild potato species per 50 X 50 km grid cell. A circular neighborhood with a radius of 50 km was used to assign observations to a grid cell. Hijmans and Spooner (2001)

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8 Table 2: Classification and chromosome numbers of the more important wild and cultivated species and their close relatives. Subsections and series Species arranged by chromosome number (x = 12) 2x 3x 4x 5x 6x Subsection Estolonifera Series 1. Etuberosa S. brevidens S. etuberosum 2. Juglandifolia S. lycopersicoides Subsection Potatoe Series 1. Morelliformia S. morelliforme 2. Bulbocastana S. bulbocastanum S. clarum S. bulbocastanum 3. Pinnatisecta S. brachistotrichum S. cardiophyllum S. jamesii S. pinnatisectum S. trifidum S. cardiophyllum S. jamesii 4. Polyadenia S. polyadenium S. lesteri Continue…

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9 Subsections and series Species arranged by chromosome number (x = 12) 2x 3x 4x 5x 6x 5. Commersoniana S. commersonii S. commersonii 6. Circaeifolia S. capsicibaccatum S. circaeifolium 7. Lignicaulia S. lignicaule 8. Olmosiana S. olmosense 9.. Yungasensa S. chacoense S. tarijense S. yungasense 10. Megistacroloba S. boliviense S. megistacrolobum S. sanctae-rosae S. toralapanum 11. Cuneoalata S. infundibuliforme 12. Conicibaccata S. chomatophilum S. santolallae S. violaceimarmoratum S. grimonifolium S. colombianum S. longiconicum S. oxycarpum S. moscopanum 13. Piurana S. piurae S. tuquerrense 14. Ingifolia S. Ingifolium 15. Maglia S. maglia S. maglia Continue… Continue…

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10 Subsections and series Species arranged by chromosome number (x = 12) 2x 3x 4x 5x 6x 16. Tuberosa S. alandiae S. berthaultii S. brevicaule S. bukasovii S. canasense S. gandarillasii S. gourlayi S. hondelmannii S. kurtzianum S. leptophyes S. marinasense S. mocrodontum S. microdontum S. multidissectum S. neocardenasii S. oplocense S. sparsipilum S. spegazzni S. vernei S. veerrucosum S. microdontum S. gourlayi S. oplocense S. sucrense S. oplocense 16. Tuberosa (Cultivated) S. X ajanhuiri S. phureja S. X chaucha S. X juzepczuki S. tubreosum spp. tuberosum S. tuberosum spp. andigena S. X ciriilobum Continue… Continue…

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11 Subsections and series Species arranged by chromosome number (x = 12) 2x 3x 4x 5x 6x 17. Acaulia S. acaule S. albicans 18. Longipedicellata S. X vallis-mexici S. fendleri S. hjeriingii S. popita S. polytrichon S. stoloniferum 19 . Demissa S. X semidemissum S. X edinense S. brachycarpum S. demissum S. guerreroense S. hougasii S.iopetalum S. schenckii Continue… Source: Gopal et al. (2003)

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12 Table 3: Sources of resistance to the major biotic and abiotic stresses Fungus resistance Phytophthora infestans (late blight) Race specific S. cardiophyllum, S. demissum , S. ediense, S. stoloniferum and S. verrucosum Non-race specific S. berthaultii, S. bulbocastanum, S. chacoense, S. circaeifolium, S. demissum, S. microdontum, S. phureja, S. pinnatisectum, S. polyadenium, S. stoloniferum, S. tarijense, S. tuberosum ssp andigena, S. vernei, S. verrucossum Alternaria solani (early blight) S. bulbocastanum, S. chacoense, and S. tarijense Synchytrium endobioticum (wart) S. acaule, S. berthaultii, S. boliviense, S. demissum, S. gourlayi, S. sparsipilum, S. spegazzinii, S. sucrense, S. tuberosum (both species) and S. vernei Fusarium spp. (Fusarium wilt) S. acaule, S. kurtzianum and S. spegazzinii Bacterial resistance Pseudomonas ( Ralstonia ) solanacearum (bacterial wilt) S. chacoense , S. microdontum , S. phureja , S. sparsipilum and S. stenotomum Erwinia carotovora (soft rot, blackleg) S. acaule , S. breviden , S. bulbocastanum , S. chacoense , S. demissum , S. hjertingii , S. leptophyes , S. megistacrolobum , S. microdontum , S. phureja , S.pinnatisectum , S. tuberosum ssp. andigona and S. vernei . Streptomyces scabies (common scab) S. chacoense , S. commersonii , S. jamessi , S. tuberosum ssp. andigena , S. yungasense and various cultivated varieties Continue…

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13 Virus resistance Potato virus X S. acaule, S. berthaultii, S. brevicaule, S. chacoense, S. commersonii, S. curtilobum, S. phureja, S. sparsipilum, S. sucrene, S. tarijense and S. tuberosum ssp. andigena Potato virus Y S. acaule, S. chacoense, S. demissum, S. gourlayi, S. phureja, S. rybinii, S. stoloniferum, S. tuberosum spp . andigena Potato leaf roll virus S. acaule, S. brevidense , S. chacoense,S. etuberosum, S. raphanifolium, S. stoloniferum and S. tuberosum ssp. andigena Spindle tuber viroid S. acaule, S. berthaultii, S. gurreroense, S. hjertingii and S. multidissectum Insect resistance Leptinotarsa decemlineata (colorado potato beetle) S. berthaultii, S. chacoense , S. commersonii, S. demissum, S. jamesii, S. pinnatisectum, S. polyadenium and S. tarijense Myzus persicae , Macrosiphum euphorbiae (ap[hids) S. berthaultii , S. bukasovii, S. bulbocastanum, S. chomatophilum, S. infundibuliforme, S. lignicaule, S. marinasense, S. medians, S. multidissectum, S. neocardenasii, S. stolonifrum Phthorimaea operculella (Tuber moth) S. chacoense, S. stenotomum and S. tuberosum spp. andigena Nematode resistance Globodera rostochiensis , G. pallida (cyst nematodes) S. acaule , S. berthaultii , S. boliviense , S. bulbocastanum , S. capsicibaccatum , S. cardiophyllum , S. demissum , S. gourlayi , S. kurtzianum , S. leptophyes , S. multidissectum , S. oplocense , S. sparsipilum , S. spegazzinii , S. sucrense , S.tuberosum ssp. andigena and S. vernei . Continue… Continue…

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14 Nematode resistance Meloidogyne incognita S . bulbocastanum, S. cardiophyllum, S. chacoense, S. curtilobum, S. bjertingii, S. kurtzianum, S. microdontum, S.phureja, S. sparsipilum, and S. tuberosum spp. andigena and S. vernei Physiological characters Frost S. acaule , S. ajanhuiri , S. boliviense , S. brachistotrichum , S.. brevicaule , S. brevidens , S. canasense , S. chomatophilum , S. commersonii , S. curtilobum , S. demissum , S. etuberosum , S. juzepczukii , S. megistacrolobum , S. multidissectum , S. pumilum , S. raphanifolium , S. sanctae-rosae , S. toralapanum , and S. vernei . Heat and drought S. acaule , S. bulbocastanum , S. chacense , S. commersonii , S. gourlayi , S. megistacrolobum , S. microdontum , S. ochoae , S. papita , S. pinnatisectum , S. spegazzinii and S. tarijense Lack of tuber blackening S. hjertingii High protein content S. phureja and S. vernei High starch content S. vernei Low reducing sugars at low temperature storage S.phureja , S. ; spegazzinii and S. vernei Continue… Source: Gopal et al. (2003)

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15 Endosperm Balance Number (EBN) hypothesis and its importance in Potato Breeding

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16 Endosperm Balance Number (EBN) hypothesis and its importance in Potato Breeding To account for the Endosperm failure in large number of interploidy-intraspecific and interspecific crosses, a unifying concept of EBN has been proposed to predict the success in these crosses (Johnston and Hanneman,1982) According to this concept, normal seed development depends on the balance of genetic factors in the endosperm which are contributed by both female and male Every species has an “EFFECTIVE PLOIDY” (or EBN) , not necessarily equal to its true ploidy. EBN must be in 2:1 maternal to paternal ratio for a cross to be successful

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17 Figure 1: Ploidy of embryo and endosperm, and female to male EBN ratio in the hybrid endosperm after intra(inter) ploidy and intra(inter) EBN crosses between Solanum species differing in ploidy and EBN.

Endosperm Balance Number:

18 Endosperm Balance Number The EBNs are arbitrary values, assigned to species based on their crossing behavior in matings with known EBN standards Solanum chacoense , a diploid 2EBN species is used as standard in assigning EBN values to tuber bearing Solanum species The most common combinations include 6x (4EBN); 4x(4EBN) (including Tuberosum group); 4x(2EBN); 2x(2EBN) (including most wild species) and 2x(1EBN) EBN, like ploidy level, can be doubled and halved with doubling and halving the chromosome number in the species i.e. tbr (4x,4EBN)haplodization  tbr (2x, 2EBN)

The Potato Gene Pool :

19 The Potato Gene Pool Primary gene pool: Old and New cultivated potato cultivars, 4x andean landraces tetraploid breeding populations, 2n cultivars or breeding populations, diploid (2EBN) tuber-bearing wild species producing 2n gametes and hexaploid (4EBN) population Secondary gene pool: Disomic tetraploid species (2EBN) and diploid (1EBN) tuber-bearing Solanum species Tertiary gene pool: Diploid (1EBN) non-tuber bearing wild species of the series Eutuberosa and other Solanum species Ortiz (2001)

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20 Barriers to wide hybridization and methods to overcome them

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21 Barriers to wide hybridization in Potato Barriers to wide hybridization in Potato External barrier Internal barrier Pre zygotic Post zygotic Pollen-Pistil incompatibility Nuclear-cytoplasmic male sterility barriers Endosperm failure physical separation of populations in time or space Camadro et al. (2004)

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22 Methods for overcoming the hybridization barriers in Potato Following methods are described for circumventing the hybridization barrier in Potato: Ploidy manipulation Bridge crosses Mentor pollination and embryo rescue Somatic fusion Reciprocal crosses and selection of cross compatible genotypes Hormone treatment Jansky (2006)

Ploidy manipulation:

23 Ploidy manipulation Potato has been regarded as the crops species whose chromosome sets can easily be managed mainly because of the knowledge about the following mechanisms: a. 2n gametes formation 2n gametes are unreduced gametes and are produced by plants that are homozygous recessive for any of several naturally occurring meiotic mutations These 2n gametes help in making a cross between 2x (2) and 4x(4) species, if 2x(2) species forms 2n gametes These 2n gametes form the basis for unilateral sexual polyploidization [USP-4x X 2x (2n) or 2x(2n) X 4x] and bilateral sexual polyplodization [BSP- 2x (2n) X 2x (2n)]

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24 b. Maternal haploids (sporophytes with gametic chromosome no.) can be easily extracted following crosses with S. phureja . c. EBN For successful interspecific cross the ratio of maternal to paternal EBN should be 2:1 Otherwise leading to failure of endosperm, a post –zygotic barrier EBN number can be scaled up and down like ploidy level and 2n gametes and maternal haploids of cultivated potato help in achieving this i.e. S. tuberosum (2n =48) x S. phureja (2n =24) S. tuberosum (2n= 24)

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25 Ortiz and Ehlenfeldt (1992) Figure 2: Ploidy and EBN manipulation in the production of 4x (4EBN) compatible lines and in the production of 4x (4EBN) and 2x (2EBN) chromosome addition lines. EBN in brackets. EC = extra-chromosomes(s). 2x (1) 2x (2) 4x (2) 4x (2) 4x (4) 6x(4) 2 X (2) 4 X (4) Crossing parent Colchicine or 2n gamete cross cross cross 3x (2) 3x (2) 2n gamete production or colchicine cross cross cross cross cross cross cross 5x (4) 4x (4) 6x (4) 5x (4) 4x (4) 5x (4) Species parent Hybrid parent 3 X (2) 5 X (4) 2x EC(2) 4x + EC(4) chromosome addition lines

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26 Figure 3: Breeding scheme followed to introgress S. commersonii (Cmm) 2n (1) into S. tuberosum 4x (4) Group Tuberosum (Tbr-4 x ) gene pool USA Carputo et al . (1997a)

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27 S. acaule (2n=4x, 2 EBN) X S. tuberosum (2n=4x, 4EBN) (2n egg) 6x Hybrid X S. tuberosun 5x BC 1 X S. tuberosum 4x-near 4x BC 2 Figure 4: Ploidy manipulation to overcome crossing barrier between S. acaule and S. tuberosum Argentina Camrado and Espinillo (1990)

Bridge crosses:

28 Bridge crosses Sometimes ploidy manipulations are combined with bridge crosses. Bridge crosses provide intermediate hybrids that, through ploidy manipulations, can be crossed with cultivated potato This is especially needed when the donor parent cannot be directly hybridized to the recipient parent One of major limitation of bridge crosses is that they require a considerable amount of time and there are chances of introduction of undesirable characters from the species used as the bridge parent

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29 2n Gamets S. chacoense 2x (2EBN) S. brevidens 2x (1EBN) S. brevidens 4x (2EBN) BrC Hybrid 3x (2EBN) Gp. Tuberosum 4x (4EBN) BrCT Hybrid 5x (4EBN) TBrCT Hybrid 4x (4EBN) Gp. Tuberosum 4x (4EBN) colchicine X X X Figure 5: Germplasm transfer from non tuber bearing species S. brevidens to a 4x (4EBN) cultivated form using S. chacoense as bridge species USA Johnston and Hanneman (1982)

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30 sysy S. Cmm 2 X (1EBN) SySy S. Chc 2 X (2EBN) sysySy CC Hybri 3 X (2EBN) SySySySy Tuberosum 4 X (4EBN) SysySySySy CCT Hybrid 5 X (4EBN) 1 sysy: 9Sy-Haploid 2 X(2EBN) Phu. pollinator 2n n X 2n n X Figure 6: Transfer of a valuable gene sy2 from a 2x (1EBN) species S. commersonii to a 2x (2EBN) cultivated potato using S. chacoense as a bridge species USA Ehlenfeldt and Hannemman (1987)

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31 Figure 7: Double Bridge Cross to Transfer Genes from S. bulbocastum to S. tuberosum Netherland Hermsen and Ramanna (1973) S. bulbocastum (2n=2x=24) X S. acaule (2n=4x) 3x ABH 4x ABPT hybrid 6x ABH X S. phureja (2n=2x) 4x ABPH X S. tuberosa colchicine

Mentor pollination and Embryo Rescue:

32 Mentor pollination and Embryo Rescue Mentor pollination, also known as second compatible pollination refers to pollination by a compatible second pollen (mentor pollen), usually one day after pollination with incompatible pollen So, here pollination is done twice, once with the pollen of incompatible species and on the next day with pollen of compatible species Growth of pollen tube in the ovary of distantly related species is greatly reduced and the ovary has few seeds and it usually stop developing to fruit and falls from the plant before artificial rescue can be made. Mentor pollination helps in reducing the fruit drop due to formation of seeds of compatible species in addition to incompatible species Mentor pollen contains typically a dominant seed spot marker gene, so that its hybrid can be visually identified and eliminated When both pre-zygotic and post-zygotic crossing barriers exist, the combination of mentor pollination and embryo rescue can be used

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33 (ii) In vivo colchicine doubling 107 genotypes from 24 families used : 2928 buds treated 87 genotypes from 23 families : 312 shoots recovered from treatment 177 shoots checked at L1 and (or) L3 layers five genotypes, one shoot each is 6x at L1, L2 and L3 layers 5 of 107 genotypes are 6x (4.6%) Taken 10-12 weeks after pollination (i) Selection of 3x with fertile 2n pollen 4x (female) X 3x (male) and 2x with 2n eggs X 3x 16 3x genotypes from four families: crossed to two 4x and two 2x genotypes with 864 pollinations No fruit set 0% success to transfer acl genes (iii) In vitro chromosome doubling 17 genotypes from four families used: 528 internodes used Four genotypes from three families : abundant shoots regenerated from calli At least one shoot from each genotype is 6x at both L2 and L3 layers 4 of 17 genotypes are 6x (23.5%) Taken 14-16 weeks after pollination 59 cross combinations; max. 10 polli. / cross; second compatible polli by Ivp 35 1 day after polli. 106 fruit set in 52 cross combination 729 embryos rescued, selection made on embryo spot as a marker 40 plantlets from 19 combinations 8 ( 7.6%) identified as tetraploid (iv) 4x potatoes X 4x species 4x acl X 2x 3x hybrids (generally sterile) Figure 8: Relative efficiency of different schemes for the enhancement of S. acaule ( acl ) 4x (2EBN) genes into cultivated gene pools CIP, Peru Watanabe et al. (1991)

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34 Table 4: Effect of compatible second pollination by IvP 35 on seed set in interspecific cross between S. tuberosum ( tbr ) and S. acaule ( acl ) 4x (2EBN) Female (tbr) Total number Average fruit set (%) Male (acl) Pollinations Fruits Bolona 10 68 36 53 7 XY.1 10 44 15 34 Atzimba 3 11 1 9 Blanca 8 24 0 0 Clavelila 2 3 0 0 Puka Tika 6 14 0 0 Tollocan 1 1 0 0 70075 3 7 0 0 Peru Iwanga et al. (1991)

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35 Female (tbr) Male (acl) DAP No. of embryos explanted No. of plantlets obtained Ploidy level 7XY.1 954.3 22 26 3 4x 7XY.1 OCH11890.8 22 11 0 7XY.1 OCH11912.6 16 13 0 7XY.1 OCH11912.8 18 26 0 7XY.1 OCH11912.10 16 25 0 7XY.1 OCH11979.1 15 14 0 7XY.1 OCH11979.3 14 14 0 7XY.1 PG0702 21 17 0 Bolona 954.3 20 42 0 Bolona 954.3 26 8 1 2x Bolona OCH11890.8 21 37 0 Bolona OCH11912.6 20 21 0 Bolona OCH11912.8 22 40 0 Bolona OCH11912.10 22 38 0 Bolona OCH11912.11 19 51 0 Bolona OCH11912.11 27 11 3 2x Bolona OCH11912.15 23 17 1 2x Bolona OCH11979.1 19 37 0 Bolona PG0702.3 18 38 0 Bolona PG0702.3 27 18 0 Atzimba OCH 11979.3 14 14 0 Total 518 8 Table 5. Results of embryo rescue on each berry from the crosses between S. tuberosum and S. acaule followed by the compatible second pollination with Ivp 35.88 Peru Iwanaga et al. (1991)

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36 Table 6: Results of pollinations between 4x cultivar clones and 2n pollen producing triploid hybrids ( tbr - wild species hybrid). All ratios denotes berries/no. of pollinations. (Pistillate) 4x - parent 3x – parent (Pollen) T2 T21 T45 T90 T92 T97 Total HiLite Russet 2/104 0/42 0/34 0/59 0/160 0/46 2/4458* Lemhi Russet 0/52 0/11 - 0/190 0/92 0/334 0/679 Shepody 0/23 - - 0/42 0/29 0/52 0/146 Nooksack 0/59 - - 0/82 0/79 0/67 0/323 OCH 6595.9 0/18 - 0/9 0/26 - - 0/53 OCH 6595.11 0/12 - 0/29 0/18 0/23 - 0/82 Y245.7 0/63 - - - 0/100 - 0/163 Total 2/1891 USA Brown and Adiwilaga (1991) * Seeds were found to be parthenocarpic

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37 Table 7: Number of pollinations (p), number of berries (b), seeds per berry (s/b), and percent of hybrid seedling. Parentage denotes pistillate parent, triplandroid pollen source and rescue pollen parent Parentage Rescue Pollen p b s/b Percent hybrid 4 x parent 3 x parent Frontier Russet T92 Katahdin 4 3 41.3 20.6 Lemhi Russet T92 Katahdin 26 9 49.6 6.1 HiLite Russet T92 Katahdin 24 15 65.5 3.3 295 T92 Lemhi 4 2 70.0 0.8 211 T92 Lemhi 6 4 80.0 0.3 211 T2 Lemhi 14 10 17.1 0.7 Krantz T92 Katahdin 16 11 46.5 0 USA Brown and Adiwilaga (1991)

Somatic hybrids:

38 Table 8: Solanum somatic hybrids expressing traits transferred from wild species or traits combined from two dihaploid lines Components Traits transferred to somatic hybrids S. tuberosum (+) S. brevidens Transfer of resistance to potato leaf roll virus (PLRV) Incresed resistance to Phytopthora infestans Incresed tuber resistance to bacterial sofr rot Ervinia sp. Incresed resistance to Ervinia carotovora spp. carotovora Transfer of resistance to potato leaf roll virus (PLRV) and potato virus Y Transfer of reisitance against Erwinia and P. infestans to sexual progeny of somati hybrids Introgression and stabilization of resistance to Erwinia S. tuberosum x S. berthaulii (+) S. etuberosum Higher reistance to potato virus Y S. tuberosum (+) S. bulbocastum Transfer of reistance to nematode Meloidogyne chitwoodi S. tuberosum (+) S. commwesoni i Transfer of cold hardiness to somatic hybrid Transfer of reisistance to bacterial wilt Ralstonia solanacearum S. tuberosum (+) S. brevidens Incresed frost tolerance and higher capacity to cold acclimation S. tuberosum (+) S. phureja Transfer of resistance to bacterial wilt Ralstonia solanacearum S. tuberosum (+) S. bulbocastum Transfer of resistance to late blight Phytopthora infestans S. tuberosum (+) S. verrucosum Transfer of resistance to potato leaf roll virus (PLRV) S. tuberosum (+) S. brevidens Reduced concentrarion of aglycones in ‘second generation’ of somatic hybrids Orczyk et al . (2003) Somatic hybrids

Hormone treatment:

39 Hormone treatment Helps to reduce immature fruit drop and unlike mentor pollen does not require any marker gene Chen et al. (2004) succeeded with S. pinnatisectun 2x (1EBN) x S. cardiophylllum 2x (1EBN) crosses when flowers were treated with 2,4-D the day after flowering. They suggested a need to identify optimal treatment regimes

Reciprocal crosses and selection of cross compatible genome:

40 Reciprocal crosses and selection of cross compatible genome In potato, unilateral incompatibility (UI) occurs between self-compatible and self-incompatible species Crosses are successful only when Self compatible species is used as a female and not as a male It may be due to interaction between incompatible cytoplasm and nuclear genome

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41 tbr parent Huinkul Kennebec ktz parent (1) (2) (1) (2) oka 5026 100 a /25 b 29/8 75/0 11/0 oka 6003 0/100 0/20 50/0 0/0 oka 6125 90/50 0/0 100/0 0/0 ORH 4285 100/0 0/0 75/0 0/0 SCI 4560 100/60 0/0 67/0 11/0 CIH 872 100/100 11/0 63/0 22/0 Table 9: Percentage of (1) compatible genetic combination and (2) genotypic combinations that produced seeds in interspecific crosses between S. tuberosum spp. tuberosum (tbr) and S. kurtzianum (ktz) Argentina Raimundi and Camarado (2003) a 4x tbr X ktz b ktz X 4x tbr

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42 Achievements 1. Yield and quality traits

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43 Genome Family Fall Trials Spring Trials Tuber set Tuber Yield kg/hill ATW Tuber set Tuber Yield kg/hill ATW Family Means a TTTT Cultivated Potato 1 14 c 05 de 24 b 17 abc 2.4 a 145 a 2 23 c 0.8 bcde 37 b 33 ab 1.5 ab 49 cd 3 28 c 1.1 bcde 45 b 24 abc 2.0 ab 87 abcd 4 18 c 0.8 bcde 41 b 16 abc 1.4 ab 76 bcd 5 12 c 0.8 bcde 56 b 17 abc 1.5 ab 97 abc 6 37 c 1.8 abc 65 b 4 a 0.4 b 71 bcd 7 25 c 0.8 bcde 41 b 17 abc 1.0 ab 57 bcd 8 14 c 0.4 e 26 b -- -- -- TTPP Hybrid of tuberosum and phureja 9 26 c 0.9 bcde 37 b 28 abc 1.8 ab 66 bcd 10 9 c 0.8 bcde 95 a 17 abc 2.1 ab 119 ab 11 18 c 0.8 bcde 44 b 32 ab 2.4 a 89 abcd 12 10 c 0.4 e 35 b 22 abc 1.6 ab 72 bcd 13 9 c 0.2 e 26 b 30 ab 1.4 ab 52 bcd Table 10: Means for tuber set, tuber yield and average tuber appearance (ATW) of 4x hybrids of three genomes in fall and spring trials

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44 49 b 1.1 c 22 b 36 ns 1.6 a 48 a TTPC 77 a 1.8 a 27 a 40 ns 0.6 c 15 b TTPP 83 a 1.5 b 18 c 45 ns 0.9 b 22 b TTTT Genomic means b 27 d 0.6 b 22 abc 37 b 2.3 a 77 a 19 55 bcd 0.4 b 12bc 26 b 1.6 abcd 67 ab 18 54 bcd 0.4 b 7 bc 31 b 1.2 bcde 36 bd 17 35 cd 0.7 ab 16 abc 35 b 1.3 bcde 35 bd 16 55 bcd 1.8 ab 33 ab 44 b 2.0 ab 47 bd 15 62 bcd 2.4 a 40 a 45 b 1.5 abcde 34 bc 14 TTPC Triple hybrid between tuberosum, phureja and chacoense ATW Tuber yield kg/hill Tuber set ATW Tuber Yield kg/hill Tuber set Spring Trials Fall Trials Family Genome USA Bani-Aameur et.al. (1990) a Family menas within columns followed by the same letter are not significantly different (SNK, 5%) b Genomic menas within columns followed by the same letter are not significantly different (SNK, 5%)

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45 Cross Tuber yield kg/hill Sp. gr. 1 Chip colour 2 Tuber uniformity 3 General Tuber appearance 4 Vine Maturity 1. 4x X 2x 1.04 81.4 2.3 2.5 2.4 3.6 Range (0.79-1.34) (75.5-91.9) (1.7-3.2) (2.2-2.7) (1.9-2.8) (2.5-4.3) 2. 4x X 4x 0.77 78.8 1.9 1.9 2.1 3.7 Range (0.57-0.95) (71.8-87.3) (1.6-2.3) (1.2-2.5) (1.9-2.0) (2.6-4.7) 3. 4x clones 0.78 79.3 2.0 2.6 2.0 2.7 Range (0.50-0.97) (68.4-85.0) (1.7-2.5) (2.4-2.8) (1.6-2.4) (1.5-3.4) Comparisons 1 vs 3 ** * ** ns ** ** 1 vs 2 ** ** ** ** ** ns 2 vs 3 ns ns ns ** ns ** Table 11: Means, ranges and comparisions of 4x (tbr) X 2x (tbr X wild species) and 4x (tbr) X 4x (tbr) families and 4x (tbr) parental clones USA Peloquin and Darmo (1991) 1 - Specific gravity is coded such that Sp. gr. =(1 - Sp. gr. ) X 1000 2 – Rating 1= white; 4=dark colour 3 - Rating 1= highly non uniformed; 3= uniform 4 – Rating 1 = Undesirable; 3 = desirable

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46 Progeny Superior (kg/hill) Atlantic (kg/hill) Merrimade (kg/hill) WI31 (kg/hill) 4x X 2x 1.14 1.02 0.98 1.03 4x parent 0.50 0.97 0.91 0.72 % Hetrosis for TTY 127.1 5.2 7.9 42.7 USA Peloquin and Darmo (1991) TABLE 12: 4x (tbr) X 2x (tbr- wild species) family means by 4x parent and percentage of hetrosis over 4x parent for TTY (Total Tuber Yield)

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47 Tuber Yield Chip colour Specific Gravity GTA Tuber Uniformity Vine maturity Females (F) ns ns * ** ns * Males (M) ns ** ns * ns ** F X M ns ns * ns ns ns E X F * ns * ns ns ns E X M * ns * ns ns ns E x F x M * * ns ns ns ns CV% 13.6 10.8 3.7 151 13.5 15.3 USA Peloquin and Darmo (1991) Table 13: Anova for six traits, by 2x ( tbr -wild species hybrid) males and 4x (t br ) parent * and ** significant at 5% and 1% probability level respectively

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48 2. Insect resistance

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49 Population or cultivar No of Genotypes or plots Tuber Size (g) Solanine mg/100g fw Chaconine mg/100g fw Total GA mg/100g fw Chac:Sol Ratio 1992 1993 1992 1993 1992 1993 1992 1993 1992 1993 1992 1993 P1472810 35 10 7a 7a 115a 106a 146a 78a 232a 186a 1.19a 0.78a TBR 21 20 93d 21c 1e 5e 2e 7e 3e 13e 1.95d 1.50cd F 2 50 55 52c 12a 15b 42b 19b 47b 35b 90b 1.30b 1.13b F 4 31 54 36b 10a 13b 49b 18b 49b 31b 99b 1.36b 1.02ab F2BC 1 42 56 91d 15ab 5c 19c 8c 26c 13c 46c 1.65c 1.40c F2BC 2 33 57 119e 18bc 3d 13d 5d 21d 8d 34d 1.87d 1.59d Kennebec 6 4 163f 27d 1e 10d 2e 10e 3e 20e 1.40bc 1.00ab USA Sanford et al. (1994) Table 14: Least square means for tuber content of solanine, chaconine and total glycoalkaloids (GA), the ratio of chaconine:solanine, and the average tuber size in six populations derived from a croos between S. tuberosum X S. chacoense and cv. kennebec

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50 Table 15: The resistance of hybrid families derived from crosses between wild and cultivated potato species to the potato tuber moth, P. opercullela after exposure in an infested potato store PTM family Cross Resistant parent No. of clones evaluated No. of clones % resistant Resistant Susceptible PTM 12 stn X spl spl MBN 4.69 100 13 87 13.0 PTM 13 spl X stn spl MBN 4.69 75 11 64 14.6 PTM 14 phu X spl spl MBN 4.69 72 7 65 9.7 PTM 15 spl X phu spl MBN 4.69 54 16 38 29.6 PTM. 15C* gon X spl spl MBN 4.69 45 4 41 8.8 PTM.16 spl X gon spl MBN 4.69 99 6 93 6.0 PTM.17 2x-tbr X spl spl MBN 4.69 83 12 71 14.6 PTM.18 spl X 2x-tbr spl MBN 4.69 15 3 12 20.0 PTM.19 spl X 2x-tbr spl MBN 4.69 96 21 75 21.8 PTM.22 spl X 2x-tbr spl MBN 4.188 100 1 99 10. PTM.23 spl X 2x-tbr spl MBN 4.188 100 4 96 4.0 PTM.26 spl X 2x-tbr spl MBN 4.41 89 9 80 10.1 PTM.27 spl X 2x-tbr spl MBN 4.41 70 2 68 2.8 PTM.28 spl X 2x-tbr spl MBN 4.188 86 5 81 5.8 PTM.33 spl X 2x-tbr spl MBN 4.90 100 1 99 1.0 PTM.36 adg X scr scr HHC 4596.3 98 5 93 5.1 PTM.38 cmm X cap cmm OKA 507/4 64 1 63 1.5 PTM.39 cmm X lgl cmm OKA 507/4 56 1 55 1.7 PTM.42 2x-tbr X tar tar OKA 5886.2 24 0 24 0 PTM.43 2x-tbr X tar tar OKA 5886.2 13 0 13 0 PTM.47 scr self scr HHC 4596.1 32 13 19 14.6 Peru Chavex (1988) *Colchicine doubled of Family 15

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51 3. Disease resistance

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52 Table 16: Comparisons between cultivars and test clones for resistance to soft rot, common scab and black scurf a Clone Soft rot b Scab c Pitted scab d (1996) Pitted scab (1998) e Black scurf f Comp Mean Comp Comp Comp Comp Mean RN Atl RN RB Mean Atl Mean Atl RN Mean Atl RN C118 4.4 ** 7.9 ** * - 6.7 ** 20.0 - - 20.0 ** - C206 18.9 - 21.2 - - - 8.0 * 0.0 - - 0.0 ** * C251 12.2 - 33.0 - - - 46.7 - 10.0 - - 40.0 * - C264 nt nt 65.8 - - - 31.7 - 25.0 - - 10.0 ** * C287 nt nt 6.2 ** ** - 0 ** 0 - * 33.3 * - C292 10.2 - 2.5 * * * 0.0 * 20.0 - - 60.0 - - C41 13.3 - 0.7 * * * 0.0 * 20.0 - - 0.0 ** * C414 nt nt 29.4 - - - 0.0 ** 5.0 - - 0.0 ** ** C442 8.6 - 12.6 * - - 0.0 ** 0.0 * * 5.0 ** ** C447 nt nt 4.5 * * * 0.0 * 20.0 - - 0.0 ** * C470 18.2 - 17.0 - - - 20.0 - 13.3 - - 13.3 ** * C499 nt nt nt nt nt nt nt nt 0.0 * * 20.0 ** - C51 6.9 - 35.3 - - - 22.2 - 20.0 - - 65.0 - - C52 nt nt 33.3 - - - 6.7 ** 0.0 - - 0.0 ** * Continue…

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53 Clone Soft rot Scab Pitted scab (1996) Pitted scab (1998) Black scurf Comp Mean Comp Comp Comp Comp Mean RN Atl RN RB Mean Atl Mean Atl RN Mean Atl RN C545 4.6 * 12.7 * - - 2.2 ** 0.0 * * 57.5 - - C558 NT NT 12.4 * - - 0.0 ** 5.0 - - 10.0 ** * C571 8.8 - 16.0 - - - 5.0 ** 40.0 - - 30.0 ** - C589 12.8 - 20.4 - - - 48.0 - 45.0 - - 10.0 ** * C590 16.6 - 11.3 * - - 5.0 ** 15.0 - - 10.0 ** - C635 nt nt 8.4 ** * * 42.2 - 20.0 - - 15.0 ** - 135.05 10.3 - 17.3 - - - 2.5 ** 12.5 - - 10.0 ** * T56.08 nt nt 21.4 - - - 0.0 ** 10.0 - - 40.0 ** - T56.17 6.0 - 8.0 ** * * 5.0 ** 0.0 * * 45.0 * - T58.10 11.9 nt 16.7 - - - 0.0 ** 0.0 - - 0.0 ** * V54.19 0.6 ** 12.5 - - - 0.0 ** 0.0 * * 0.0 ** ** USA Jansky and Rouse (2004) a Cultivars: RN = Russet Norkotah, Atl = Atlantic, and RB= Russet Burbank; comp = comparison, nt= not tested ** and * : Clone is more resistant than cultivar at P = 0.01 and 0.05 respectively b Mean diameter of decayed tissue around two sites on each tuber injected with Erwinia carotovora subsp. atroseptica following harvest in 1996. Mean value for Russet Norkotah was 8.4 mm c Mean percent tuber surface area covered with scab lesions in 1996. Mean values for Atlantic, Russet Norkotah, and Russet Burbank were 27, 19, and 18%, respectively. Clones were not different from commercial cultivars in 1998 ( data not shown ). d Mean percentage of tubers with pitted scab in 1996. Mean values for Atlantic, Russet Norkotah, and Russet Burbank were 44, 7, and 0%, respectively. e Mean percentage of tubers with pitted scab in 1998. Mean values for Atlantic and Russet Norkotah were 25 and 30%, respectively. f Mean percentage of tubers with black scurf lesions in 1998. Mean values for Atlantic and Russet Norkotah were 90 and 70%, respectively. Clones were not different from commercial cultivars in 1996 ( data not shown ). Continue...

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54 Clone 1996 sap b 1998 sap c Comp Comp Mean Alt a RN a Mean Atl RN C118 2.5 ** - 1.4 * - C206 1.1 ** ** 0.7 * - C251 2.4 ** - 0.3 ** - C264 1.2 ** ** 1.9 - - C287 0.2 ** ** 0.3 ** * C292 - nt nt 2.3 - - C41 - nt nt 0.6 ** ** C414 3.0 - - 1.6 - - C442 2.9 - - 2.2 - - C447 2.4 - - 1.7 * - C470 1.6 * ** 1.9 - - C499 - nt nt 0.9 ** - C51 2.1 ** - 1.3 ** - C52 - nt nt 0.8 ** - Table 17: Comparision of population of Verticilium dahliae in stem tissue between cultivar and clones Continue……

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55 Clone 1996 sap b 1998 sap c Comp Comp Mean Alt a RN a Mean Atl RN C545 1.1 ** ** 0.2 ** * C558 2.3 ** - 1.9 - - C571 0.7 * ** 1.8 - - C589 2.2 * - 0.9 ** - C590 2.2 ** - 2.0 - - C635 3.1 - - 2.4 - - 135.05 2.2 - * 0.7 ** * T56.08 2.7 - - 1.0 ** - T56.17 2.1 ** * 1.1 ** - T58.10 - nt nt 1.9 - - V54.19 2.4 * * 0.5 ** ** Continue…… USA Jansky and Rouse (2003) a Cultivars: RN = Russet Norkotah, Atl = Atlantic, and RB= Russet Burbank; comp = comparison, nt= not tested ** and * : Clone is more resistant than cultivar at P = 0.01 and 0.05 respectively b Clones grown in soil infested with V. dahliae (50 CFU/g of soil) in 1996. Log10(CFU + 1) V. dahliae in 100 μl of stem sap. Mean values for Atlantic and Russet Norkotah were 3.0 and respectively. b c Clones inoculated with 107 CFU of V. dahliae and grown in soil infested with V. dahliae (50 cfu/g soil) in 1998. Log10(CFU + 1) V. dahliae in 100 μl of stem sap. Mean values for Atlantic and Russet Norkotah were 2.4 and 1.4, respectively

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56 USA Jansky et al .(2004) Year Cross Type of cross Stem source R b S b χ2c 2001 C545 × C287 R × R Apical dry 78 17 2.56 C545 × C287 R × R Basal dry 74 21 0.42 2002 C545 × C287 R × R Apical dry 46 9 2.19 C545 × C287 R × R Basal dry 42 13 0.05 2003 C545 × C287 R × R Basal dry 46 10 1.52 Atl175 x C287 S x R Basal dry 35 11 0.03 ` Atl175 x C287 S x R Basal dry 33 12 0.01 a Proposed parental genotypes are C287 and C545 = V w v w V t V t , and Atl175 = V w v w v t v t . b R = resistant, S = susceptible. For the C545 × C287 family, susceptible = significantly more susceptible than both parents; for the Atl175 × C287 family, susceptible = at least as susceptible as Atl175. c Critical χ2 value = 3.841 at P = 0.05. Table 18: Numbers of Verticillium dahliae resistant and susceptible plants in C287 × C545 and Atl175 × C287 families and χ2 values based on a 3:1 resistant:susceptible ratio a

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57 Table 19: Screening for resistance to blackleg in different interspecific clones Hybrid family 1 Ploidy Clones analyzed no. Eca 4 Ecc 5 R 2 I S R I S W457 × mlt 1a 2X 17 14 3 0 11 5 1 Red2 × tar 2b 2X 4 1 3 0 0 1 3 W730 × tar 11b 2X 3 3 0 0 3 0 0 Atl10 × mlt 1a 2x 3 2 1 0 2 0 4 Alt10 × tar 2b 2X 10 0 0 10 0 0 10 Atl10 × can 1b 2X 10 nt 3 nt nt 4 4 2 AVI 25 × can 1b 2X 10 nt nt nt 7 2 1 SVP11(+) cmm IT 4X 1 1 0 0 1 0 0 SVP11(+) cmm IT 6X 2 1 1 0 0 2 6 Total 60 22 8 10 28 14 18 1 W457, Red2, W730, Atl 10, SVP 11=S. tubersosum haploids 2 R=resistant, I=Intermediate, and S = susceptible 3 nt=not tested 4 Eca: Ervinia carotovora subsp. astroseptica 5 Ecc: Ervinia carotovora subsp. carotovora Italy Carputo et al. (1997b)

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58 4. Nematode resistance

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59 Table 20: Total marketable yield (Total) and yield > 113-g tuber size (4 oz-No 1 s) in MT/ha of M. chitwoodi resistant and susceptible breeding line and susceptible standard commercial variety at two locations in 2003. Identity BC generation (source 1 ) Phenotypes Roza Paterson Total Sign* No. 1s** Sign* Total Sign* No. 1s** Sign* POR00HG5-1 2 (hou) res 29.2 fgh 8.5 I 18.6 g 18.6 fgh PO94A9-2 3(blb) res 36.0 dfg 20.2 fghi 66.9 ab 34.2 defg PO94A9-7 3(blb) susc 32.1 efgh 28.0 cdefgh 44.8 cdef 38.3 efgh PO94A9-10 3(blb) susc 38.3 edefg 23.4 efghi 58.7 abcde 33.0 cdefg PO94A10-3 3(blb) res 44.8 bcde 38.9 bcde 43.7 cdef 34.6 bcde PO94A12-2 3(blb) susc 55.6 b 43.6 bcd 42.2 def 16.4 h PA95B1-53 4(blb) res 52.0 bc 39.1 bcdef 38.7 ef 23.0 bc PA95B2-4 4(blb) res 35.5 defg 25.9 defghi 50.4 bcde 36.1 defg PA95B4-67 4(blb) res 45.1 bcde 37.0 bcdef 55.6 bcde 40.5 bcde PA98N4-2 4(blb) res 20.1 h 13.8 hi 27.1 fg 15.9 h PA98N5-2 4(blb) res 54.2 b 48.0 b 64.5 ab 54.5 b PA98N13-3 4(blb) res 42.8 bcdef 32.4 bcdefg 74.7 a 52.4 bcdef PA98NM38-1 4(blb) res 47.4 bcd 38.5 ghi 52.6 bcde 35.3 bcd PA94NM38-8 4(blb) susc 29.6 fgh 18.8 ghi 48.8 bcde 28.9 fgh PA98NM39-1 4(blb) res 72.9 a 66.0 a 75.1 a 57.6 a PA99N82-4 5(blb) res 54.2 b 46.3 bc 56.7 abcde 42.8 b PA99N88-2 5(blb) res 36.2 defg 30.3 bcdefgh 51.5 bcde 19.5 defg Russet Burbank -- susc 26.0 gh 19.3 fghi 62.8 abc 44.1 gh Norkotah Russet -- susc 49.6 bcd 44.1 bcd 46.7 abcde 46.7 bcd Dark Red Norland -- susc 51.1 bc 41.1 bcde 61.9 abc 47.3 bc source: blb: S. bulbocastanum and hou: S. hougasii; * Treatments followed by same letter do not differ significanly; ** yield of tuber >113 gms USA Brown et al. (2006)

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60 Table 21: Reproductive efficiency (Rf) against M. chitwoodi of standards, S. hougasioi (hgs) x S. tuberosum , spp. tuberosum (tbr) hybrids and parents of hybrids Genotypes Standards Rf = Pf/Pi Race 1 R Race 2 R Tomato (cv. Columbia) 12.8 a 32.2 a Potato (cv. Russet Burbank) 29.5 a 23.6 a Parents A8341.5 (tbr) 21.2 a 14.2 ab COO8014.1 (tbr) 5.5 ab 13.0 ab 161726.2 (hgs) < 0.01 g 0.13 e S. hougasii x S. tuberosum spp. tuberosum hybrids (161726.2 x A8341.5).2 0.01 def 0.66 bcde (161726.2 x A8341.5).3 < 0.01 fg 0.08 ef 1 (161726.2 x A8341.5).4 < 0.01 efg 0.37 de (161726.2 x A8341.5).5 < 0.01 defg 0.52 cde (161726.2 x A8341.5).6 0.04 cde 12.0 ab (161726.2 x A8341.5).7 0.02 def 9.4 abcde (161726.2 x A8341.5).9 < 0.01 defg 4.4 abcd

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61 Genotypes Standards88 Rf = Pf/Pi Race 1 R Race 2 R (161726.2 x A8341.5).10 < 0.01 fg 0.8 bcde (161726.2 x A8341.5).11 8.7 a 5.4 abcd (161726.2 x A8341.5).13 9.05 a 3.1 abcd (161726.2 x A8341.5).14 6.0 ab 3.6 abcd (161726.2 x A8341.5).15 0.5 bc < 0.01 f 1 (161726.2 x A8341.5).16 < 0.01 fg 12.1 ab (161726.2 x COO8014.1).1 0.06 cd 6.5 abcd Reproductive factor Rf values represent geometric means of Pf/5000, the initial egg population (Pi). Means not sharing a letter are significantly different (p < 0.05) according to DMRT. Separation test was performed on means of ln (x+1) or the geometric mean. The Rf=Pf/Pi=[antilog geometric mean)]/5000 is presented in the table. 1 Geometric means are misleadingly low because several replications were zero values. These progenies are considered to be poor hosts. USA Brown et al. (1991)

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62 Table 22: Segregation in the S. sparsipilum X S. tuberosum F 1 (92T) and BC (97T) Progenies Genotypes F 1 (92T) Female progenitors 385.344.2 385.484.13 Suscepptible 106 19 Resistant 105 21 χ2 (1 df) 0.005 NS 0.10 NS BC (97T) Female progenitors F1 (92T) S. tuberosum Susceptible 107 39 Resistant 74 34 χ2 (1 df) 6.02* 0.34 NS France Berthou et al . (2003) * significant at 5% probasbility level

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63 France Berthou et al . (2003) Figure 10: Distribution of genotypes resistant to RKN under assessment with regard to yield and tuber characters during year 2000 and 2001 from cross S. sparsipilum X S. tuberosum Score of tuber aspect* Score of tuber aspect* Yield (Kg/Plot) Yield (Kg/Plot) Check Discarded Selected genotypes *Score : 1 = poor quality ; 9 = good quality

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64 5. Abiotic stress resistance

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65 Cross P 1 P 2 Hybrids Hybrids – PM Ratio a Genomic ratio b acl X arz 0.2 4.2 1.4 -0.8* 70 % c 2:1 acl X ber 0.0 3.3 0.9 -0.8* 73 % 2:1 acl X chc 0.0 3.4 0.7 -1.0 79 % 2:1 chc X acl d 3.1 0.0 0.6 -0.9* 81 % 2:1 acl X hap 0.0 3.3 0.4 -1.3 88 % 2:1 acl X mcd 0.0 4.0 1.0 -1.0** 75 % 2:1 8x-acl X opl 0.1 1.1 0.1 -0.5* 100 % 4:2 8x-acl X scr 0.0 3.0 0.4 -1.2* 87 % 4:2 4x-cmm X arz 0.0 4.1 0.2 -1.9** 95 % 2:1 4x-cmm X ber 0.0 3.6 0.3 -1.5* 92 % 2:1 4x-cmm X chc 0.0 2.8 0.4 -1.0 86 % 2:1 4x-cmm X mcd 0.1 3.3 0.2 -1.5** 97 % 1:1 hap X 4x-cmm 3.0 0.0 0.3 -1.2 90 % 1:1 cmm X bst 0.0 3.5 0.1 -1.6* 97 % 1:1 cmm X cph 0.0 3.0 1.1 -0.5 63 % 1:1 Continue….. Table 23: Frost tolerance rating scores of interspecific F 1 hybrids and parental species (P1 and P2)

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66 Cross P 1 P 2 Hybrids Hybrids – PM Ratio a Genomic ratio b buk X ber 0.0 3.3 2.1 0.5* 36 % c 1:1 buk X chc 0.1 3.1 2.3 0.7 27 % 1:1 buk X mcd 0.0 3.9 2.1 0.2 46 % 1:1 mcd X buk d 3.1 0.0 2.3 0.8* 26 % 1:1 mcd X tor 4.0 0.3 2.9 0.7 30 % 1:1 tor X mcd d 1.0 4.3 3.0 0.4 39 % 1:1 mga X mcd 0.0 3.5 2.2 0.5 37 % 1:1 4x-cmm X buk e 0.0 0.0 0.0 0.0 - 2:1 *,** significant at the 0.05 and 0.01 probability level, respectively. a calculated by the following formula : |(Hybrids – Sensitive parent)/(P1-P2)| X 100 b Ratio of hardy:sensitive genome number in the hybrids c > 50% indicates that frost tolerance is somewhat dominant. < 50% indicates that frost tolerance is somewhat recessive d Indented entries indicate reciprocal crosses e crosses between hardy species USA Chen et al . (1999)

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67 France Sherraf et al . (1994) Figure 11: Salt tolerance in MS medium containing 3, 6, 9 and 12 g/l NaCl. % growth reduction expressed in height growth of the treated plants as compared to controls in NaCl free medium for Lycopersicon pennili (Lp); S. tuberosum (St); and there somatic hybrids (SH1 and SH2)

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68 6. Virus resistance

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69 Table 24: PVY transmission (% of infected plants) and tuber formation in S. tuberosum (+) S. etuberosum somatic hybrids and BC1 progenies after mechanical inoculation under in vitro, greenhouse, field and grafting conditions (n = 10 - 40) Genotype In vitro PVY transfer (%) Grafting S. tuberosum S. etuberosum Tuber formation* Greenhouse Field S. etuberosum 0 0 0 0 NT, NS S. tuberosum T67 97 87 50 100 T (ET) S.H. (AAEE) 31/1/2/1 - 0 0 0 26 24 T (EST) 10/1/1/1 0 0 2 0 24 22 T (EST) 29/2/1/1 0 0 0 0 24 24 T (EST) S.H. (AAEEEE) 8/1/2/1 0 0 - 0 24 46 NT 27/2/14/1 0 0 - 0 24 46 NT 6/1/2/1 0 0 0 0 24 48 NT S.H. (AAAAEE) 27/2/12/1 70 24 33 41 48 24 T (ET) Continue….

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70 Genotype In vitro PVY transfer (%) Grafting S. tuberosum S. etuberosum Tuber formation* Greenhouse Field BC1 progeny of the hexaploid somatic hybrid 27/2/14/1 : 64/2 17 63 - - 48 12 - 64/3 23 90 - - - - - 64/4 43 73 - - - - - 64/5 23 40 - - - - - 64/6 0 0 - 0 37 22 - 64/7 30 47 - - - - - 64/9 13 47 - - - - - 64/10 3 5 41 0 - - T (EST) BC1 progeny of the hexaploid somatic hybrid 6/1/2/1 : 61/1 0 0 0 0 36 24 T (EST) Continue…. * Tuber performance of the field grown plants : NT – no tubers, NS – no stolons, T- tuber formation, EST – elongate-shaped tubers, ET – elliptic tubers, ‘-’ data have not been analyzed St. Petersburg Garilenko et al. (2003)

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71 Table 25: Mean ELISA readings ( ± standard error) of fully expanded leaves after graft inoculation with potato virus Y° or potato virus A Genotype Strain Potato virus Y° Potato virus A ELISA readings ELISA readings Symptoms Experiment 1 Experiment 2 Symptoms* Parental S. tuberos um 87HW13.7 1.63 ±0.12 2.03±0.09 M 0.80±0.07 ns S. brevidens CPC 2451 0.00±0.00 0.01±0.01 ns 0.06±0.02 ns Sexual hybrids TET 38.2 0.26±0.20 0.54±0.22 ns 0.26±0.05 ns TET 38.9 0.02±0.02 0.00±0.00 ns 0.21±0.04 ns TET 38.12 0.02±0.01 0.00±0.01 ns 0.32±0.05 ns TET 38.13 0.98±0.26 1.10±0.31 ns 0.35±0.06 ns Controls S. phureja IvP35 0.00±0.01 0.01±0.00 ns 0.33±0.04 ns S. multidissectum PI473355 not determined 2.05±0.05 M,S not determined Infected potato sap dilution 2.5 x10 -1 1.60±0.01 1.80±0.10 M 0.88±0.02 MM 2.5x10 -2 121±0.01 1.47±0.11 0.66±0.02 2.5x10 -3 0.40±0.07 0.50±0.06 0.30±0.05 2.4x10 -4 0.05±0.07 0.04±0.01 0.04±0.05 Non inoculated Control 0.01±0.01 0.03±0.02 0.04±0.01 LSD(0.05%) 0.22 0.26 0.13 USA Valkonen et al . (1995) *ns = No symptoms; M = mosaic

Conclusion:

72 Conclusion Immense potential is there for the use of wild relatives in potato improvement Understanding of certain special mechanism in potato (EBN and unreduced gametes) have been exploited to produce distant hybrids As the majority of the wild species are 2x (2EBN), the production of tbr -wild species hybrid following the USP or BSP provides an easy mechanism to transfer the trait of interest Some other techniques like ploidy manipulation, auxin treatment, bridge crosses, mentor pollinations, embryo rescue provide means for sexual hybridization, whereas somatic hybrids provide an alternative to sexual hybridization

Future Thrust:

73 Future Thrust Identification of wild genotypes with trait of interest, 2n gamete formation and superior agronomic traits for there use in wide crosses Use of wild relatives for quality improvement needs special attention Complex interspecific hybrids with multiple disease and pest resistance is the need of future

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74 Thank you

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