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Plant Breeding 2

Onion and sunflower show:

Onion Allium cepa and sunflower Helianthus annuus exhibit relatively low inbreeding depression compared to highly sensitive cross-pollinated crops. Genetic basis involves fewer lethal equivalents and prevalence of additive gene action for bulb weight and head diameter. Upon selfing, reduction in size about 10 to 20 percent observed, plants retain viability, flowering and seed set adequate for line maintenance. Low depression suggests partial self-compatibility evolved, some purging during domestication and reliance on additive QTL not strongly influenced by dominance. Breeding exploits this to

Ref: FSS e-courses Onion breeding depression; Janick Encyclopedia Sunflower; Singh BD Table depression categories.

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Plant Classification

Ray florets of sunflower are generally

Capitulum of Helianthus annuus comprises outer showy ray florets and central disc florets with distinct sexuality. Ray florets are zygomorphic, ligulate, adapted for pollinator attraction, generally pistillate with reduced or absent androecium or completely neutral lacking both androecium and gynoecium. They often lack functional stamens allocating resources to display. Bisexual fertile disc florets produce cypsela fruits after fertilization. Staminate ray condition is rare in composites. Distinction between ray pistillate or sterile and disc bisexual underlies heterogamous adaptation for cros

Ref: Raven Biology of Plants, 8th ed., Chapter 20: Capitulum heterogamy ray vs disc florets

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