Question of 12
Q.Resistance is the ability to prevent the pathogen from causing disease.
(1) Elucidate the steps in breeding for disease resistance.
(2) Cite two examples for virus resistant plants.
OR
Tissue culture is an achievement in plant breeding. What is a somaclone? Describe the production of somatic hybrid.
Kerala DhseKerala DHSE Plus Two Board 2016Subjective· 3mImportance★★★★★
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Start your 14-day free trial to unlock the full solution →Disease-resistant crop varieties are bred in three broad steps — screening for a resistance source, hybridising it into a high-yield variety, and selecting/evaluating the resistant progeny; several Indian varieties have been bred this way to resist viral diseases.
(1) Steps in breeding for disease resistance:
- Screening germplasm for resistance: Cultivated varieties and wild relatives are screened to identify individuals/species that carry natural resistance to the target pathogen (fungus, bacterium or virus).
- Hybridisation of the resistant source with a high-yield recipient variety: The identified resistant plant is crossed with an agronomically desirable but susceptible variety, so that resistance genes are transferred into a high-yielding genetic background.
- Selection and evaluation of the hybrids: Progeny are grown and repeatedly selected across generations for both disease resistance and the desirable agronomic traits (yield, quality), and the best-performing resistant line is finally released as a new variety after field testing.
(2) Two examples of virus-resistant plant varieties:
- Mung bean variety 'Pusa Sadabahar' — resistant to Yellow Mosaic Virus (and also to powdery mildew).
- Chilli variety 'Pusa Sadabahar' — resistant to Chilli Mosaic Virus, Tobacco Mosaic Virus (TMV) and leaf curl virus. …
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