Back Cross Breeding

Category: Education

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By: venkatchalla (89 month(s) ago)

this presentation is very informative i would like to thank you for presenting this , can you send to me this ppt to my mail, i have seminor on this topic.

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Monogenic / Oligogenic Transfer : 

Monogenic / Oligogenic Transfer HYBRIDIZATION

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Back Cross A cross between F1 and one of its parents Objectives To remove 1-2 defects of otherwise highly adaptable variety Parents involved Recipient Parent = Recurrent Parent = Otherwise high yielding var. Donor Parent = Non-recurrent parent = genotype having desirable trait to be transferred to recipient variety

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Requirements of a Back Cross Method A suitable recurrent parent (lacking in 1-2 characters) A suitable donor parent (with high intensity of the character to be transferred) Character to be transferred should be mono/oligogenic with high heritability Sufficient no. of back crosses should be made (6-7), generally 4-5 are made.

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Applications of Back Cross Method

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Susceptible BUT high yielding resistant 50% 50% 75% 25 87.5% 93.75% 96.87% x x x x x F1 BC1 BC2 BC3 BC4 99.999 % GENERAL Back-Cross Scheme to Transfer Resistance Genes Susceptible variety converted to Resistant Variety BC1F2 BC2F2 BC3F2 BC4F2 BCnF2 Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year n

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Dominant gene to transfer This is a breeding scheme to transfer a resistance gene (governed by dominant gene) in a susceptible variety (having recessive gene) which is otherwise high yielding i.e. this back cross scheme is to remove the defect of an existing highly adapted variety Year 1 Year 2 Year 3 Year 4 Year 5 Year 9 Year 10 Year 11

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Dominant gene to transfer One extra year Another extra year Another extra year Almost double time taken

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H √

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Recurrent Parent Plants with minor differences More and more plants from recurrent parent should be involved to recover the original genotype of the recurrent parent Selection for the recurrent parent genotype in early back cross generations with minimum of 6 Back Cross Generations are required

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Transfer of Leaf Rust Resistance to Malviya 12 Wheat EXAMPLES Malwia 12 Wheat High yielding wheat variety Became susceptible to stem and leaf rusts Sparrow Genes for all the three rusts resistance were transferred through back crossing programme F1 100 PLANTS WERE GROWN All were back crossed to Malwia 12 BC1 >500 PLANTS WERE GROWN EPIDEMIC CONDS. CREATED BY PLANTING INFECTOR ROWS OF AGRA LOCAL 100 rust resistant plants were selected and back crossed to Malwia 12

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