Major fraction (60%) of seed storage protein in maize is zein which determines the quality of food and feed. Zeins comprise four subfamilies e.g., α , β, γ and δ zeins. Among these, α-zeins are the major prolamin subunits in maize. α-zeins are rich in glutamine, leucine and proline but, deficient in essential amino acids like lysine and tryptophan causing malnutrition. The opaque-2 (o2)-a natural recessive mutation in maize led to nearly double the lysine and tryptophan content in endosperm due to a decrease in the synthesis of zein proteins and increase in the other seed protein bound lysine and tryptophan. RNAi studies proved down regulation of 22kD zeins than the 19kD component as the biochemical basis of QPM phenotype. However, the opaque-2 mutation made the endosperm chalky and soft resulting damaged kernel while harvesting, poor germination, increased susceptibility to pest and diseases, inferior for food processing and in general reduced yield. Later, combining opaque-2 allele with its desirable genetic modifiers made it possible to breed QPM genotypes having hard kernel with high lysine and tryptophan content. Since, opaque-2 is a recessive mutation and endosperm specific, and biochemical analysis of lysine and tryptophan content is expensive; conventional backcross breeding alone is inefficient for the nutritional enrichment of maize. However, use of opaque-2 gene specific markers provided excellent opportunities for conversion of elite normal inbreds to homozygous o2/o2 forms through marker assisted selection (MAS). In India, Vivek QPM-9: a hybrid of two QPM introgression lines is being widely used for commercial cultivation.

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Onion is an important vegetable crop grown in almost all parts of the World as a flavouring agent in food preparation. It is propagated by seeds and the seed crop is affected by several fungal, viral and bacterial diseases which cause lodging and reduces the seed yield and quality. Onion seed crop was sprayed with different concentration of ethephon (0, 100, 200, 400, 600, 800 and 1000 ppm) for two duration at 45 or 45+60 days after planting during (DAP) during 2018-19 and 2019-20 rabi seasons. The effect of ethephon on seed yield and seed quality was studied. In comparison to control ethephon application significantly reduced scape length and % lodging by 38.73% and 42.52% respectively. There was 31.90% and 89% enhancement in scape diameter and yield respectively. Ethephon spray also enhanced seed quality, highest germination and seed vigour was recorded in plants sprayed with 600 ppm ethephon at 45 and 60 DAP which was 19% and 51.65% higher than control. Highest seedling dry weight was observed in plants sprayed with 100 ppm ethephon at 45 DAP. Among the treatments, 100 and 200 ppm ethephon applied at 45 DAP had lower lodging and higher seed yield and seed quality. Hence spraying of onion seed crop with 100 ppm ethephon at 45 DAP is beneficial for getting higher seed yield and quality.

The effect of treating aged onion seeds with 5-azacytidine (5-aza) on germination and vigour was evaluated. Seeds of two onion varieties, ‘Bhima Raj’ (BRJ) and ‘Bhima Red’ (BRD) were treated with 0, 10, 25 or 50 µg mL-1 5-azacytidine (a DNA demethylating agent). In comparison with the control treatment (0 µg mL-1 5-azacytidine), treatment with 5-azacytidine enhanced seed germination, seedling length, seedling dry weight and seed vigour indices. 5-azacytidine treatment also increased the activity of superoxide dismutase (SOD) and total antioxidant capacity (TAC). Seed treatment with 5-azacytidine has the potential to enhance the viability and vigour of aged onion seeds. This study provides phenotypic and biochemical data for further exploring the role of DNA methylation in understanding the process of seed ageing.

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