Agriculture Notes On – Heterosis – For W.B.C.S. Examination.
Agriculture as an optional subject is useful from numerous points of view. A decent hold over the subject helps you massively in taking care of the geography, economics, social issues in General Studies as the learning comes conveniently. Indeed, even essay paper, there is absolutely no less than one subject from Agriculture. Any W.B.C.S. aspirants who have scholarly foundation in Agriculture, Life Sciences, Botany, and other related fields can choose this subject as their optional. Paper I of agriculture is generic in nature where Paper- II is technical. Candidates with no prior knowledge of agriculture or Biology should not opt this subject as their optional for W.B.C.S. Mains Exam.Hetero sis, also called hybrid vigour, the increase in such characteristics as size, growth rate, fertility, and yield of a hybrid organism over those of its parents. Plant and animal breeders exploit heterosis by mating two different pure-bred lines that have certain desirable traits.Continue Reading Agriculture Notes On – Heterosis – For W.B.C.S. Examination.
The first-generation offspring generally show, in greater measure, the desired characteristics of both parents. This vigour may decrease, however, if the hybrids are mated together; so the parental lines must be maintained and crossed for each new crop or group desired.
An understanding of heterosis in genetic terms had to await the rediscovery of Mendel’s laws in 1900. It was immediately apparent that hybrids are more heterozygous than their parents. A decrease in the number of heterozygotes implied an increase in the number of homozygotes. This immediately gave rise to two explanations. The ‘dominance’ hypothesis notes that most recessive mutants are deleterious, so inbred lines are weakened by having an increase in the number of homozygous recessive genes. Hybrids, in contrast, are stronger because the recessives from each parent are usually concealed by dominants from the other. The ‘overdominance’ hypothesis assumes that there are some loci at which the heterozygote is superior to either homozygote. Although the two ideas are not mutually exclusive, the dominance hypothesis is now generally favored. This explanation also applies to variety and species hybrids, because the hybrids are always more heterozygous than their parents, the more so as the parents diverge. The contrast is greatest, however, when the parents are highly homozygous inbred lines.To view Agricultire Syllabus , CLICK HERE.
Heterosis or hybrid vigor is a phenomenon in which a hybrid progeny exhibits superior performance compared to their parental inbred lines. F1 hybrid seed production system is used for many crops and vegetables because of the high yield due to hybrid vigor. It has been over 100 years since the discovery of the hybrid vigor phenomenon; however, the molecular mechanism of hybrid vigor is still a mystery. Understanding the mechanism of hybrid vigor will allow developing more efficient breeding systems and contribute to food security. At this time, hybrid vigor research has mainly used genetic approaches providing a number of findings in many plant species. High throughput sequencing will make genetic analysis more efficient, and large-scale quantitative trait analysis or genome wide association analysis has been performed in some plant species. However recent works have revealed that epigenetic regulations also contribute to hybrid vigor.
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