Triticale wheat crossability, hybrid necrosis & haploid induction

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Gene introgression in wheat is not only limited by crossability but also affected by environmental conditions, genotypic differences and necrotic genes. Hence, the present investigation was formulated to determine the influence of genotypic and environmental factors on the crossability of elite triticale and wheat genotypes, screen the effect of necrotic genes in the F1 hybrids and the relative performance of hybrids towards haploid induction following the Imperata cylindrica-mediated chromosome elimination approach. The dry temperate region was observed to be significantly better than sub-humid mid-hills for seed set in intergeneric crosses. Lower rate of crossability (17.49–48.33% and 14.46–36.51%) was found in triticale × wheat crosses at both locations. The hybrids having HPW236 as one of the parent revealed necrosis ranging from the lowest to highest grade. Further, negative influence of the necrotic genes on the haploid induction parameters was apparent due to significant hybrid necrosis symptoms in F1 hybrids. Statistically significant variation in haploid induction parameters was also evident between and within different cross combinations, indicating that haploid induction parameters were profoundly influenced by genotypic specificity.

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Full Terms Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformationjournalCodesagb20 Download by: navdeep singh jamwal Date: 16 December 2015 At: 13:30 Acta Agriculturae Scandinavica Section B — Soil Plant Science ISSN: 0906-4710 Print 1651-1913 Online Journal homepage: http://www.tandfonline.com/loi/sagb20 Factors influencing crossability among triticale and wheat and its subsequent effect along with hybrid necrosis on haploid induction Navdeep S. Jamwal H. K. Chaudhary Anila Badiyal Waseem Hussain To cite this article: Navdeep S. Jamwal H. K. Chaudhary Anila Badiyal Waseem Hussain 2016 Factors influencing crossability among triticale and wheat and its subsequent effect along with hybrid necrosis on haploid induction Acta Agriculturae Scandinavica Section B — Soil Plant Science 66:3 282-289 DOI: 10.1080/09064710.2015.1095939 To link to this article: http://dx.doi.org/10.1080/09064710.2015.1095939 Published online: 16 Dec 2015. Submit your article to this journal View related articles View Crossmark data

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Factors influencing crossability among triticale and wheat and its subsequent effect along with hybrid necrosis on haploid induction Navdeep S. Jamwal H. K. Chaudhary Anila Badiyal and Waseem Hussain Department CropImprovement Molecular Cytogenetics TissueCultureLabCSKHP AgriculturalUniversity PalampurHimachal Pradesh India ABSTRACT Gene introgression in wheat is not only limited by crossability but also affected by environmental conditions genotypic differences and necrotic genes. Hence the present investigation was formulated to determine the influence of genotypic and environmental factors on the crossability of elite triticale and wheat genotypes screen the effect of necrotic genes in the F 1 hybrids and the relative performance of hybrids towards haploid induction following the Imperata cylindrica-mediated chromosome elimination approach. The dry temperate region was observed to be significantly better than sub-humid mid-hills for seed set in intergeneric crosses. Lower rate of crossability 17.49–48.33 and 14.46–36.51 was found in triticale×wheat crosses at both locations. The hybrids having HPW236 as one of the parent revealed necrosis ranging from the lowest to highest grade. Further negative influence of the necrotic genes on the haploid induction parameters was apparent due to significant hybrid necrosis symptoms in F 1 hybrids. Statistically significant variation in haploid induction parameters was also evident between and within different cross combinations indicating that haploid induction parameters were profoundly influenced by genotypic specificity. ARTICLEHISTORY Received 19 May 2015 Accepted14September2015 KEYWORDS Triticale wheat crossability hybrid necrosis doubled haploids northwestern Himalayas Introduction Wheat production has witnessed a huge leap after the adventofgreenrevolutioninthe1960sand1970swith the introduction of dwarf high-yielding varieties and modern cultivation practices but continuous cultiva- tion of elite cultivars over a wide area has narrowed down the genetic base of wheat leading to enhanced vulnerability towards abiotic as well as biotic stresses Jauhar 2006. To worsen the scenario steadily chan- ging climate and continuously evolving pathogens are major contributors. Hence breeders across the world have joined hands to develop widely adaptable elitecultivars which possess resistance tovarious stres- ses encountered in the fields. For this various wheat improvement programmes are being practiced across the world having a focus on genetic diversification of the wheat genome through gene introgression from distant relatives or alien species Bertin et al. 2009. Till date many genes have been introgressed into the elitewheatcultivarsfromsuchdonorspeciesincluding primary secondary and tertiary gene pool members of the family Chaudhary et al. 2014. Among the tertiary gene pool donors the rye has been assessed as the potent donor for genes encoding resistance to various biotic rusts and mildew and abiotic heat and drought stresses as well as seed quality attributes Friebe et al. 1996. However the approach finds little practicability due to very low crossability between wheatandryethusswitchingthecrossingprogramme to comparatively more favourable wheat and triticale crossingendeavoursBadiyaletal.2014usingtriticale as the bridging species in wheat-wide hybridization programmes. The aim of these wide hybridization pro- grammes is the stable integration of the alien chroma- tin in wheat background which otherwise can be lost on segregation among the hybrids in further generations. The doubled haploid technology has emerged as a boon for the breeders for not only fixing the intro- gressed alien genes in wheat background but also helped in rapid attainment of homozygosity Chaudh- ary 2013. Many approaches of doubled haploid DH breeding such as gamete culture and chromosome elimination technique have been followed in the world since the discovery of haploids in wheat Chaudhary et al. 2013a. Among them chromosome elimination occurring during the wide hybridization of wheat with other genera of family Poaceae has © 2015 Taylor Francis CONTACT Navdeep S. Jamwal navdeeppaugmail.com ACTA AGRICULTURAE SCANDINAVICA SECTION B – SOIL PLANT SCIENCE 2016 VOL. 66 NO. 3 282–289 http://dx.doi.org/10.1080/09064710.2015.1095939 Downloaded by navdeep singh jamwal at 13:30 16 December 2015

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greatly facilitated the doubled haploid production. Various chromosome elimination approaches are being followed across the globe for effective haploid induction in wheat but the Imperata cylindrica- mediated system has emerged as a highly efficient alternative among them Chaudhary et al. 2005 2013b Chaudhary 2010. The system has recorded huge success not only in wheat×wheat hybrids Sharma et al. 2005 but has found immense appli- cations also in triticale×wheat Pratap et al. 2005as well as wheat×rye Kishore et al. 2011 derivatives. However in wide hybridization the genotypic differences and environmental factors are the limiting issues which significantly affect the outcome of gene introgression Bertin et al. 2009. The profound influ- ence of genotypes on haploid induction has been revealed by various studies Badiyal et al. 2014 Chaudhary et al. 2002 Dhiman et al. 2012 Singh et al. 2004 Xynias et al. 2014. Besides environmental and genotypic differences the presence of hybrid necrosis is also a major limiting factor in designing wheat hybridization programmes. Lethal effect of hybrid necrosis on wheat is due to the presence of necrotic genes Ne1 and Ne2 in wheat Hermsen 1963. Additionally in triticale two more genes Ner1 and Ner2 are also present in rye chromosomes Ren Lelley 1989. Till date as per authors’ knowledge no studies have been conducted to infer the effect of hybrid necrosis on haploid induction in wheat. Hence for successful wide hybridization programmes it is imperative to identify the potential genotypes of the parents and their interaction with the environment and screen the resulting hybrids for lethal genes so as to prevent the detrimental effect of necrotic genes on the progeny Singh et al. 2000. Keeping all above issues in consideration the present investigation was formulated to i determine the influence of genotypic and environmental factors on the crossability of elite triticale with desirable wheatgenotypesiiscreeningfortheeffectofnecrotic genes in the F 1 hybrids and iii the relative perform- ance of F 1 hybrids on haploid induction following the I. cylindrica-mediated approach. This study will be helpful in identifying the triticale and wheat lines that are steadily crossable under different environmental conditions and highly responsive genotypes towards haploid induction for successful exploitation of gene introgression in wheat breeding programmes. Materials and methods The present investigation was conducted under two different climatic regimes of northwest Himalayas namely sub-humid mid-hills short photoperiods and dry temperate zone long photoperiods represented by CSK Himachal Pradesh Agricultural University Palampur 32°5 ′ 46 ′′ N 76°32 ′ 43 ′′ E and Highland Agri- cultural Research and Extension Centre Kukumseri Lahaul Spiti 32°41 ′ 58 ′′ N 76°41 ′ 13 ′′ E respectively during winter and summer 2012. During the exper- iment the weather parameters were recorded at both the locations. The experimental material for hybridization included five elite hexaploid triticale genotypes DT123 DT126 TL2900 TL2908 and TL9335 and two released elite bread wheat cultivars C306 and HPW236. The parents also included seven indigenously developed doubled haploids DH5 DH40 DH52 DH84 DH86 DH150 and DH776 aimed at pyramiding genes for drought tolerance and rust resistance. The parental material was staggered sown with an interval of 15 days to ensure regular availability of wheat pollen for a longer period of time. Two rows of each genotype were sown with 1 m row length and 25 cm row×row distance following rec- ommended package of practices. The intervarietal as well as intergeneric hybridization programme was started from first week of April at Palampur sub- humid mid-hills and third week of July at Kukumseri dry temperate zone and continued for four weeks. Further the hybrids were also staggered sown at the Experimental Farm of the Department to coincide the flowering time of the hybrids with that of I. cylindrica. The screening of hybrids for necrosis and I. cylindrica-mediated haploid induction exper- iment were conducted in experimental fields at CSK HP Agricultural University Palampur. Crossability Manual emasculation was done three days before anthesis. Pollination of the emasculated florets was carried out next day in morning with fresh pollen of wheat cultivars. Crossability was expressed as percent seed set out of total florets pollinated in each cross. The F 1 s developed at both locations were tested for their viability through germination at one location Palampur only. Hybrid necrosis The symptoms of necrosis in the hybrids were observed at early seedling stages and were systemati- cally classified according to the scale 0–5 given by Singh et al. 2000. ACTA AGRICULTURAE SCANDINAVICA SECTION B – SOIL PLANT SCIENCE 283 Downloaded by navdeep singh jamwal at 13:30 16 December 2015

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Haploid induction Following Chaudhary et al. 2005 and Pratap et al. 2005 manual emasculation was carried out without cutting the lemma and palea. Emasculated spikes were pollinatednextmorningwithfreshpollenofI.cylindrica. 24-D 250 mg/L and 100mg/L injected at the base of uppermost internode of pollinated spike 24h after pol- lination and repeated for two consecutive days to improve pseudoseed formation in triticale×wheat hybrids and wheat×wheat hybrids respectively. Pseu- doseeds were harvested 18–20 days after pollination. Embryo carrying pseudoseeds were recognized by putting them against the light source. Pseudoseeds were excised under strict aseptic conditions and embryos were cultured on MS medium supplemented with 0.5mg/L kinetin 20mg/L each of L-arginine L- cysteine and L-leucine 30g/L sucrose and 8 g/L agar. The cultured embryos were incubated in the dark at 20±2°C for regeneration. The regenerated plantlets were then placed in the growth room at 20±2°C with the10/14hlight/darkregimeuntiltheydevelopedsuffi- ciently.Thehaploidplantsweresubsequentlysubjected tocolchicinetreatment0.1colchicinesolution+1.5 DMSO for 6h and transplanted intopots. Statistical analysis The analysis of variance was used to find out differential effect of the two environments on F 1 seed set. To assess thesignificantdifferencesinthecrossabilitesamongtriti- cale×wheatandwheat×wheatatbothlocationssimple t-test was used. The line×tester Kempthorne 1957 method detected promising genotypes with good com- biningabilities.Observationspertainingtohaploidinduc- tionwererecordedwithrespecttototalnumberofflorets pollinated number of pseudoseeds number of embryo carrying pseudoseeds and regeneration of embryos in each cross using the formulae given below: Pseudoseed formation frequency Number of pseudoseeds formed Totalnumber of florets pollinated × 100 Embryoformationfrequency Numberofpseudoseedscarryingembryos Totalnumberofpseudoseedsformed ×100 Embryoregenerationfrequency Numberofhaploidplantletsdeveloped Totalnumberofembryoscultured ×100 The significant difference for haploid induction par- ameters namely pseudoseed formation embryo formation and haploid regeneration frequencies was analysed by simple t-test. Results Crossability Both in wheat×wheat and triticale×wheat crosses significant differences p≤.05 in seed setting were observed at the two agroclimatic zones. The higher F 1 mean seed setting of 63.24 and 28.33 in wheat×wheat and triticale×wheat respectively was observed at long photoperiodic zone that is Kukum- seri long photoperiodic zone Table 1 representing weekly average of low rainfall 0.75 mm low relative humidity 57.27 and narrow range of variation in temperature from 13.93°C to 26.87°C. In comparison to Kukumseri lower seed set both in wheat×wheat 54.66 and triticale×wheat 24.27 crosses was observed at Palampur short photoperiodic zone Table 1 representing high rainfall 2.05 mm high RH 64.69 and more temperature variation 12.37° C to 28.36°C during the four-week hybridization period. Besides agroclimatic zones genotypic differences in seed setting among crosses of wheat×wheat and triticale×wheat were also observed. The wheat× wheat crossing programme involving indigenously generated wheat doubled haploids and one released cultivar C306 showed F 1 seed setting frequency ranging from 51.85 C306×DH150 to 77.22 DH86×DH84 at Kukumseri whereas at Palampur on average it ranged from 33.53 DH40×DH52 to 65.22 DH5×DH40 Table 1. The cross DH86× DH84 performed significantly better at both the zones. On an average wheat×wheat combinations revealed higher crossability than triticale×wheat at both the locations. Based on the line×tester analysis in triticale× wheat mean squares due to crosses triticale and wheat genotypes and triticale×wheat interactions were statistically significant p≤.05 at Palampur and Kukumseri respectively. The frequency of F 1 seed setting at Palampur ranged from 17.31 TL9335× HPW236 to 36.51 TL9335×DH84 with an average of 24.27 whereas at Kukumseri it varied from 17.49 DT123×HPW236 to 48.33 TL9335×DH84 with mean seed setting of 28.33 Table 1. At both the locations TL9335×DH84 performed significantly better over all other cross combinations. The general combining ability GCA analysis and compilation of GCA revealed that among female parents TL2908 2.55 and TL9335 3.85 were observed to be highly significant towards crossability at Palampur and 284 N. S. JAMWAL ET AL. Downloaded by navdeep singh jamwal at 13:30 16 December 2015

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Kukumseri respectively. In case of male parent DH84 was observed to be good general combiner 5.81 and 6.91 at both the locations respectively Table 2. Necrosis Hybrids of the wheat×wheat and triticale×wheat derivatives developed at both the locations were further analysed for necrosis at one location only that is Palampur. During two and three leaf stages of seedlings symptoms of necrosis were observed among the F 1 s of both triticale and wheat-derived crosses and the highest necrotic grade 5 was assigned to the cross DT126×HPW236 of which all plants died at the seedling stage followed by DT123×HPW236 with necrotic value of 2 in which plants had empty spikes. Necrotic grade 1 was assigned to TL2900× HPW236 and TL9335×HPW236 which have shown minor symptoms of necrosis but had normal growth and weak seeds Table 3. In addition C306×DH150 and DH150×C306 hybrids of wheat×wheat crosses also showed the symptoms of necrotic grade of 1 Table 3. Haploid induction For haploid induction studies hybrids were grouped into intra-specific hybrids wheat×wheat and inter- generic triticale×wheat hybrids to work out the difference among the primary and secondary gene pools towards haploid induction. Among wheat× wheat group the mean of haploid parameters Table 1. Crossability of various triticale×wheat and wheat×wheat genotypes at two locations. S. no. Crosses Kukumseri Dry temperate zone Palampur Sub-humid mid-hills FP SS SSF FP SS SSF Triticale×wheat 1 DT123×DH84 110 36 32.73 150 41 27.33 2 DT123×DH86 150 36 24.00 119 22 18.49 3 DT123×DH776 208 40 19.23 90 16 17.78 4 DT123×HPW236 183 32 17.49 132 29 21.97 5 DT126×DH84 360 103 28.61 176 38 21.59 6 DT126×DH86 216 49 22.69 166 24 14.46 7 DT126×DH776 178 69 38.76 101 31 30.69 8 DT126×HPW236 148 26 17.57 165 34 20.61 9 TL2900×DH84 300 108 36.00 145 42 28.97 10 TL2900×DH86 330 112 33.94 211 65 30.81 11 TL2900×DH776 244 62 25.41 223 44 19.73 12 TL2900×HPW236 156 37 23.72 190 41 21.58 13 TL2908×DH84 224 97 43.30 89 32 35.96 14 TL2908×DH86 185 58 31.35 203 58 28.57 15 TL2908×DH776 90 27 30.00 198 41 20.71 16 TL2908×HPW236 172 42 24.42 159 35 22.01 17 TL9335×DH84 120 58 48.33 189 69 36.51 18 TL9335×DH86 152 27 17.76 134 32 23.88 19 TL9335×DH776 108 35 32.41 265 70 26.42 20 TL9335×HPW236 201 38 18.91 156 27 17.31 Mean 191.75 54.60 28.33 163.05 40.10 24.27 SE ± 1.37 1.98 Wheat×wheat 1 DH86×DH84 180 139 77.22 146 94 64.38 2 DH5×DH40 122 69 56.56 115 75 65.22 3 DH52×DH40 110 79 71.82 98 56 57.14 4 DH40×DH52 228 137 60.09 167 56 33.53 5 C306×DH150 135 70 51.85 120 78 65.00 6 DH150×C306 42 26 61.90 96 41 42.71 Mean 136.17 86.67 63.24 123.67 66.67 54.66 SE ± 5.50 3.89 Note: FP number of florets pollinated SS number of F 1 seeds set SF seed setting frequency. p≤.05. p≤.01. Table 2. GCA effects of frequencies of seed formation in triticale×wheat crosses at both the locations. S.no. Genotypes GCA Kukumseri GCA Palampur Female 1 DT123 −5.06 −2.89 2 DT126 −1.51 −2.43 3 TL2900 1.36 1.01 4 TL2908 1.36 2.55 5 TL9335 3.85 1.76 Male 1 DH84 6.91 5.81 2 DH86 0.76 −1.02 3 DH776 −0.66 −1.20 4 HPW236 −7.01 −3.58 p≤.05. p≤.01. ACTA AGRICULTURAE SCANDINAVICA SECTION B – SOIL PLANT SCIENCE 285 Downloaded by navdeep singh jamwal at 13:30 16 December 2015

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namely pseudoseed formation haploid embryo for- mation and embryo regeneration was observed to be 80.21 25.61 and 59.79 respectively. The range of pseudoseed frequency varied from 65.04 DH150×C306 to 93.40 DH86×DH84. The highest embryo formation and regeneration was observed in DH86×DH84 34.85 and 78.26 respectively whereas the lowest in C306×DH150 21.05 and DH5×DH40 33.33 respectively Table 3. Among triticale×wheat hybrids the fre- quency of pseudoseed formation ranged from 10.23 in DT123×DH776 to 36.90 in TL9335× DH776 with an average of 21.51 while it was 6.71 DT126×DH776 to 38.73 DT123×DH86 and 7.14 DT126×DH86 to 47.83 TL2900× DH84 with an average of 18.93 and 14.35 for embryo formation and regeneration respectively Table 3. The haploid induction parameters were found to be negatively influenced by hybrid necrosis. As all the progenies of the cross DT126×HPW236 died during the seedling stage hence not included for haploid induction study. Similarly progenies of cross DT123×HPW236 were having empty spikes showing zero value for all haploid induction parameters. Discussion For a wheat gene introgression programme to be suc- cessfulthechoiceofelitecultivarsasparentsindesign- ingcrossesisamajorconcern.Interestinglycrossability is one of the major limiting factors in gene introgres- sion programmes and it has been observed that cross- ability is highly effected by genotypic differences and environmental conditions. The present investigation was thus aimed to find out crossability variation among selected genotypes and genotype×environ- ment interactions at two highly diverse agroclimatic zones and their influence on haploid induction. The presence of statistically significant differences in seed setting at two agroclimatic zones indicates the influ- ence of environment on the crossability. The higher seed set atKukumseri for wheat×wheat and triticale× wheat indicates that dry temperate regions are more favourable than the sub-humid mid-hills Table 1. These differences in seed set may be attributed to Table 3. Screening of hybrids from triticale×wheat and wheat×wheat crosses for necrosis and their various haploid induction parameters at Palampur. S.no. Crosses Necrosis 0–5 FP PSF EFF ERF Triticale×wheat 1 DT123×DH84 0 808 17.70 14.69 19.05 2 DT123×DH86 0 746 23.19 38.73 10.45 3 DT123×DH776 0 987 10.23 23.76 20.83 4 DT123×HPW236 2 129 0 0 0 5 DT126×DH84 0 762 33.60 21.09 9.26 6 DT126×DH86 0 1084 26.66 14.53 7.14 7 DT126×DH776 0 985 30.25 6.71 20.00 8 DT126×HPW236 5 0 0 0 0 9 TL2900×DH84 0 526 31.37 13.94 47.83 10 TL2900×DH86 0 1362 35.68 11.73 15.79 11 TL2900×DH776 0 1042 22.17 15.58 22.22 12 TL2900×HPW236 1 157 14.65 13.04 0 13 TL2908×DH84 0 1098 21.13 25.86 30.00 14 TL2908×DH86 0 972 29.12 28.62 8.64 15 TL2908×DH776 0 788 18.78 22.97 11.76 16 TL2908×HPW236 1 378 12.96 20.41 10.00 17 TL9335×DH84 0 1198 20.45 31.02 13.16 18 TL9335×DH86 0 1003 20.84 37.32 7.69 19 TL9335×DH776 0 748 36.90 19.57 24.07 20 TL9335×HPW236 1 236 24.58 18.97 9.09 Mean 750.45 21.51 18.93 14.35 SE ± 2.27 2.29 2.48 Wheat×wheat 1 DH86×DH84 0 212 93.40 34.85 78.26 2 DH5×DH40 0 231 72.29 25.15 33.33 3 DH52×DH40 0 201 88.56 24.16 48.84 4 DH40×DH52 0 167 91.62 22.22 67.65 5 C306×DH150 1 108 70.37 21.05 68.75 6 DH150×C306 1 123 65.04 26.25 61.90 Mean 173.67 80.21 25.61 59.79 SE± 5.04 2.00 6.60 Note: FP number of florets pollinated PFF pseudoseed formation frequency EFF embryo formation frequency ERF embryo regeneration frequency. p≤.05. p≤.01. 286 N. S. JAMWAL ET AL. Downloaded by navdeep singh jamwal at 13:30 16 December 2015

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conducive environmental conditions such as low rain- fall and less fluctuations in temperature. The results completely align with earlier studies by Badiyal et al. 2014 Bertin et al. 2009 Hills et al. 2007 and Pratap and Chaudhary 2007. The crossability between triticale and wheat is a limiting factor that hinders the gene flow. Lower range of crossability as per Table 1 19.32–39.53 and 10.61–45.37 observed in the present study coincides with the earlier findings of Badiyal et al. 2014 while attempting hybridization at two such locations. Similarly variable ranges of crossability in triticale and wheat gene pools were reported earlier in the literature by Bijral et al. 1996 0.7–59.7 and Hills et al. 2007 less than 23.9. Hence our investi- gation infers that most of the elite spring wheat cultivars resulted in lower seed set with various culti- vars of triticale thereby restricting greatly the use of available germplasm for alien gene introgression in doubled haploid wheat breeding programmes. Limited crossability between wheat and triticale is genetically controlled by the crossability inhibitor genes Kr1 Kr2 Kr3 and Kr4 located on 5B 5A 5D and 1A chromosomes respectively which express in the style of many wheat genotypes and inhibit the germination of pollen and elongation of pollen tube of alien parent Krolow 1970 Riley Chapman 1967 Zheng et al. 1992. Recently another quantitative trait locus SKrwasidentified on the short arm of 5B which along with the aforesaid genes affects the crossability by inhibiting the production of inter- specific as well as intergeneric hybrids Alfares et al. 2009. Consequently the effect of crossability genes revealed in this study points out that the attention must be paid in selecting genotypes that actively do not involve crossability inhibitor genes in the wheat introgression progammes. As per the GCA effect the triticale lines TL2900 TL2908 and TL9335 were proved to be significantly superior contributors towards hybridization while DH84 and DH86 were found to be better pollinators among wheat parents chosen Table 2. Estimates of additive σ 2 a1.17 and dominance σ 2 d30.64 variances indicated that the magnitude of dominant genetic variance is high for seed set revealing preponderanceofnon-additivegeneaction.Further- moregenotypeswithhighpositiveGCAeffectswere found more responsive towards haploid induction parameters thus reveals positive correlation between the crossability and haploid induction. These findings are in agreement with earlier reports by Chaudhary et al. 2002 Sharma et al. 2005 and Kebede et al. 2011. The prevalence of non-additive dominance gene action governing the inheritance of all the haploid induction parameters infers that the haploid induction frequency can be enhanced by using diverse maternal and paternal parents. Necrosis Hybrid necrosis encountered most frequently among intra or interspecific wheat crosses is the gradual pre- mature death of plants in certain F 1 hybrids of wheat Hermsen 1963 Tomar Singh 1998 caused by the interaction of two dominant complementary genes Ne1 and Ne2 located on chromosome arms 5BL and 2BS respectively Chu et al. 2006. Therefore hybrid necrosis is considered a potential barrier for gene flow in gene introgression endeavours. Vikas et al. 2013 revealed that Ne1 and Ne2 genes are widely dis- tributed among the varieties spring and winter wheat wild relatives and advanced lines of wheat in India and northwest Himalayan gene pool. Therefore proper care must be taken in avoiding complementary necrotic genes in desirable doubled haploid and triti- calegenotypestoavoidanyhindranceingenetransfer. Thepresentstudy revealedthatwheatvarietyHPW236 expressednecrosiswithmostofthetriticalegenotypes. Highest necrotic grade 5 resulting in death of plants at the seedling stage was observed in the cross DT126×HPW236 Table 3. This may be due to the possibility that HPW236 may be a carrier of strong necrotic gene whose expression varied with the comp- lementary necrotic genes Ner1 5R and Ner2 7R oftri- ticale and their interaction with necrotic genes on B genome of wheat Ren Lelley 1989. The variation in necrotic symptoms may also be attributed to environmental conditions especially low temperature below 28°C which has an influential role in the expression of necrotic genes Dhaliwal et al. 1986. Such a low temperature prevailed at Palampur sub- humid mid-hills during the germination period. Also wheat×wheat hybrids involving C306 and DH150 showed symptoms of necrosis though very less Table3.Onepossiblereasonforthatmaybethepres- ence of strong necrotic gene Ne1 in C306 Singh et al. 2000 Vikas et al. 2013 and weak Ne2 in DH150 thus showing less symptoms. Further in our study the negative influence of the necrotic genes on the haploid induction parameters was apparent which was revealed by deaths and empty spikes in F 1 plants leading to biasness in the results. However we believe that our study is a preliminary report on hybrid necrosis and has unfortunately received rela- tively less attention even though it has been reported as a major potential barrier for gene flow. Therefore ACTA AGRICULTURAE SCANDINAVICA SECTION B – SOIL PLANT SCIENCE 287 Downloaded by navdeep singh jamwal at 13:30 16 December 2015

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attention must be emphasized on characterization of all genotypes doubled haploids and triticales for the presence of necrotic genes for successful gene introgression. Haploid production In order to enhance the pace of breeding programme haploid production can contribute significantly in attaining instant homozygosity through generation of doubled haploids Chaudhary et al. 2005. The I. cylin- drica-mediated chromosome elimination approach used in the present study for haploid induction has been identified as the most efficient one over all the available systems of haploid production Tayeng et al. 2012. Using this system significant variation between wheat×wheat and triticale×wheat was evident for various haploid induction parameters which may be attributed to genotypic specificities and G×E interactions. Higher frequencies of haploid induction parameters in the crosses of wheat×wheat can be attributed to the same gene pool shared by the parents that is primary gene pool whereas lower frequencies in triticale×wheat derivatives can be due to the fact that triticale lies in the secondary gene pool Table 3. These findings are in agreement with the earlier reports in wheat×wheat hybrids Sharma et al. 2005 Rather et al. 2014 and triticale×wheat hybrids Badiyal et al. 2014 Pratap Chaudhary 2007 Pratap et al. 2005. Thus haploid induction efficiency of wheat×wheat and triticale×wheat cross combi- nations can be enhanced by selecting genotypes that are more responsive for haploid induction par- ameters. Genotypic specificity for haploid induction was also observed by Rather et al. 2014 who empha- sized the use of non-specific parental genotypes in the I. cylindrica-mediated chromosome elimination approach of DH breeding. Conclusively for successful wheat gene introgres- sion programmes and efficient haploid induction through the chromosome elimination approach proper attention towards parental genotypes triticale and wheat as well as location must be stressed. The present study indicated that genotypes TL2900 TL2908 and TL9335 of triticale and DH84 and DH86 of wheat were more responsive under the dry temper- ate zone for seed set and also for haploid induction. Further in wide hybridization programmes hybrid necrosis is a major barrier to gene flow. Hence empha- sis must be put on detecting the carriers of necrotic genes to avoid the unnecessary hindrance in gene introgression programmes. Disclosure statement No potential conflict of interest was reported by the authors. 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