Question

leaf damage in traditional cultivars and HYVs

Answer 1

Explanation:

High-yielding varieties are found naturally less resistant to pests in comparison with their progenitors. Each year, insects destroy about 25% of food crops worldwide. The introduction of plant monocultures and indiscriminate and widespread application of chemical pesticides resulted in an insurgence of pests, development of resistance, and occurrence of residual toxicity. To overcome these problems, development of resistant crop varieties through a transgenic approach will contribute to a reduction in pest attack and decrease the use of chemical insecticides (Slater et al., 2003).

The greatest achievement in the field of agriculture is the development of Bacillus thuringiensis (Bt) insect-resistant crops using plant transgenic technology. Bt toxin is a crystal insecticidal protein (δ-endotoxin) produced from the cryo gene of a spore-forming soil bacterium B. thuringiensis. It is a potent insecticide and very much toxic to lepidopterans (Cohen et al., 2000), dipterans (Andrews et al., 1987), and coleopterans (Herrnstadt et al., 1986). The Bt cry protein is nontoxic to humans and animals, but toxic to insects (BANR, 2000). The first Bt toxin gene was cloned in 1981 (Schnepf and Whiteley, 1981; Jain et al., 2007) and a field trial of transgenic tobacco expressing Bt toxin was performed in 1986. Subsequently, GE tomato and eggplant/brinjal were developed and tested under field conditions in different countries. A combination of very high transgene expression and improved protein stability resulted in mortality of even Bt-resistant insects (Kota et al., 1999). At present, other insecticidal proteins such as lectins, protease inhibitors, antibodies, wasp and spider toxins, microbial insecticides, and insect peptide hormones (Whetstone and Hammock, 2007; Van Damme, 2008) were successfully used for the development of insect-resistant vegetable crops. Bt eggplant (Solanum melongena) was developed and field tested by the collaborative research between the US-based company Monsanto and Maharashtra Hybrid Seeds Company (Mahyco), India, by incorporating a crystal gene (Cry1Ac) from B. thuringiensis (Krattiger, 2010; Cotter, 2011).

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Answer 2

High Yielding Variety seeds (HYV) are were developed by scientists to improve food supplies qnd reduce famine in developing countries.