Silkworm Physiology Department, Central Sericultural Research and Training Institute, Srirampura, Mysore-570 008, Karnataka (India).
The effect of abscisic acid (ABA), a sesquiterpenoid plant hormone, on the growth and economic traits of silkworm, Bombyx mori L., was studied. Six concentrations, viz, 0.1, 0.2, 0.5, 1.0, 2.0 and 5 ppm of the hormone were separately applied topically and administered orally through leaf to different batches of V instar silkworm larvae at 24, 48, 72 and 96 hours. The exogenous administration of ABA resulted in substantial increase in the major economic traits (P<0.05). Oral treatment of 5 and 0.5 ppm ABA at 48 h resulted in highest improvement in cocoon (13.01%) and shell weight (12.56%), respectively. Extension in the feeding period was not noticed as in the case of other juvenoid type compounda The effective rate of rearing (ERR)by weight was enhanced significantly, whereas ERR by number was not much affected. Shell ratio, filament length and denier were stable, irrespective of the treatments. Further, the JH type activity of ABA accelerated the rate of DNA synthesis and enhanced the economic characteristics of silkworm.
