gp 502 (2)

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HETEROSIS BREEDING Bahader Singh Godara(2010A71M) MSc.(Ag.) Dept.- Seed Sc. & Technology CCS HAU- HISAR

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HETEROSIS

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HETEROSIS The term Heterosis was first used by Shull in 1914. Shull worked on leaming dent variety of maize plant Charles Davenport(1908): Dominance hypothesis East and Shull(1908): Overdominance hypothesis

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Heterosis may be defined as the superiority of F1 hybrid over both of its parents in terms of yield or some other character.

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HETEROSIS AT FIELD LEVEL

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GENERAL ASPECTS OF EXPRESSION OF HETEROSIS Occur more frequently in cross pollinated crops Favours better survival of heterozygote in nature Confined only to the specific F1 or first hybrid generation More in hybrids from genetically diverse sources Associated with the specific combining ability (SCA) of a cross

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MANIFESTATIONS OF HETEROSIS Increased Yield Increased Reproductive Ability Increase in Size and General Vigor Better quality Earlier Flowering and Maturity Greater Resistance to Diseases and Pests

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Greater Adaptability Faster Growth Rate Increase in the number of a plant part

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TYPES OF HETEROSIS HETEROSIS EUHETEROSIS PSEUDOHETEROSIS/ LUXURIANCE MUTATIONAL HETEROSIS BALANCED HETEROSIS

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Types of Heterosis On the basis of origin and nature Euheterosis or true Heterosis Mutational heterosis Balanced heterosis Pseudoheterosis or luxuriance On the basis of types of estimation Average or Relative heterosis Heterobeltiosis Useful or standard or Economic heterosis

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Mutational Heterosis It is simplest type of heterosis. Lethal (mostly), recessive, adaptively unfavorable mutants are either eliminated or sheltered by their non-lethal, dominant and adaptively superior alleles in cross pollinated crops. This is termed as mutational heterosis. Balanced Heterosis Well balanced gene combinations which are more adaptive to environmental conditions and useful from the agriculture point of view result in balanced heterosis. It has application in hybrid production.

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Pseudoheterosis Also termed as luxuriance. Progeny possess superiority over parents is in vegetative growth, but not in yield and adaptation, usually sterile or poorly fertile. This concept cannot be utilized in hybrid varieties production. Average or Relative Heterosis When heterosis is estimated over mid parental value i.e. average of two parents it is referred as average or relative heterosis Formula Average heterosis = [(F1 - MP) / MP] x 100Where, F1 = value of F1, MP = mean value of two parents

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Heterobeltiosis When heterosis is estimated over better parent it is called as heterobeltiosis. Formula Heterobeltiosis = [F1 – BP] / BP x 100 Where, F1 = value of F1, BP = value of better parent Standard Heterosis When heterosis is estimated over standard commercial hybrid it is called as standard heterosis. It has practical importance in plant breeding. It is also referred as useful or economic heterosis. Formula Standard Heterosis = [(F1 - CK) / CK] x 100. Where, F1 = value of F1, CK= Check Variety

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Basis of Heterosis Genetic basis Dominance hypothesis Overdominance hypothesis Epistasis Physiological basis Cytoplasmic basis Biochemical basis

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Dominance hypothesis Proposed by Charles Davenport (1908). Most widely accepted hypothesis among the other explanations for heterosis. Heterosis results due to superiority of dominant alleles over the deleterious recessive alleles by masking their effect and heterosis is in direct proportion with number of dominant genes contributed by each the parent

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Objections Failure in the Isolation of Inbreds as Vigorous as Hybrids. Symmetrical Distribution in F2. Magnitude of Heterosis. Progressive Heterosis in Tetraploids. Faster Inbreeding in Tetraploids

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Overdominance hypothesis Developed by Edward M. East (1908) and George Shull (1908). Heterosis results due to superiority of heterozygote over its both homozygous parents, due to complementation between divergent alleles. Here, heterosis is in proportion with heterozygosis.

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Epistasis Epistasis hypothesis was proposed by Gowden in 1952; suggesting influence of one locus on the other as cause of heterosis. But in general it is concluded that: Heterosis to a large extent is due to dominance gene action but epistasis and Overdominance are also involved.

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SCHEME FOR HETEROSIS BREEDING

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STEPS 1. COLLECTION AND EVALUATION OF GERMPLASM Is the most critical step in heterosis breeding. For a higher expression of heterosis genetically diverse source is essential. Germplasm should posses a high level of heterosis, tolerance to inbreeding and desirable agronomic traits

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2. DEVELOPMENT OF INBRED LINES Conventional method: Through selfing followed by selection Use of monoploids

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3. EVALUATION OF INBRED LINES FOR COMBINING ABILITY Top cross method: inbreds x common tester Polycross method: intermating of inbreds by open pollination in isolation Single cross evaluation by diallel system of mating For n number of inbred lines; possible no. of single crosses : n (n — 1)/2

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In case of hybrids Outstanding single crosses are identified and may be released as hybrid variety. Or may go for prediction of double cross performance. A few double crosses are chosen and they are actually made. these are called experimental double cross hybrids.

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Plant species where heterosis is being commercially exploited Crop species 1. Asexually propagated species 2. Cross pollinated sp.; maize, jowar, bajra, sugarbeets, sunflower, forage grasses, castor, forage legumes and cotton. 3. Self-pollinated crops: rice, pigeonpea Fruit trees In almost all the fruit trees.

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Vegetable crops Tomato, brinjal (solanum melongena), onion, Brussels's sprouts, Watermelon, Pepper, winter squash, muskmelon, cabbage, broccoli, spinach, red beets, carrot, cauliflower, celery, asparagus.

FIXATION OF HETEROSIS : 

FIXATION OF HETEROSIS Vegetative propagation Apomixis Balanced lethal systems Through the use of Biotechnology

Hybrids developed through heterosis breeding : 

Hybrids developed through heterosis breeding Tomato: Rupali, Vaishali, Naveen, Hybrid S-15, Hybrid S-16, Samirudhi, SG-12, SG-9,KT-4, Avinash-2, Carica, Ratna etc. Capsicum: Bharat, Early Bounty, Suttons Gen Gant, KT-1, Indira etc. Watermelon: Madhu, Milan, Arka Jyoti, Arka Rajhans etc. Cabbage: Ganesh Gole, No. 8, Hirirani, Nath-401, BSS-32 etc. Maize: Ganga-1, Ganga-2, Deccan, Ranjeet, VL-54, GANGA-11, Paras, Sartaj, PRO-311, COH-3, KH-528 ETC.

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Pearlmillet: HB-1, HHB-117, HHB-50, HHB-60, Pusa-415, Nandi-35, COH-8, PB-112 etc. Rice: APHR-1, APHR-2, MGR-1, KRH-1,CSR-10, TKM-9, TPS-3,HKR-102, Pusa44-33,Pusa Sugandha, Yamini etc. Cucumber: Priya, Pusa Sanyog etc. Brinjal: PH-5, Azad hybrid, MBH-1, MBH-2, HOE-414 etc. Castor: GCH-3 Sunflower: BSH-1 Pigeon pea: ICPH-8, UPAS-120, AKPH-4101, AKPH-2022, COPH-1, COPH-2 etc.

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. THANK YOU