Response of mungbean cultivars (Vigna radiata (L.) Wilczek) to young leaf removal
1992
Ekkachai Phrompheat
Low grain yield of mungbean cultivars is a consequence of their indeterminate growth habit. As such, vegetative growth during reproductive phase competes for assimilates with reproductive growth. The objective of the experiment was to evaluate the degree of such competition in terms of grain yield by removing young, folded leaves and investigate the effect of young leaf removal on yield, seed growth rate (SGR) and effective seed filling period (EFP). Treatments were arranged in split plot in RCB and replicated 4 times. KPS 1, KPS 2, UT 1 and PSU 1 cultivars were main plots and the sub plots were no defoliation (control, C) and removal of young, folded leaflets (YLRs) as 1 (central leaflet, 1/3, 2 (left and right leaflets 2/3) and 3 (all leaflets, 3/3). The experiment was conducted at the National Corn and Sorghum Research Center during the dry (Feb.-Apr. 1991) and early rainy (Apr.-Jun. 1991) seasons. The results showed that the greatest grain yield (1,130 kg/ha) was obtained from the 2/3 YLR in the dry season whereas in the early rainy season the 1/3 YLR gave the greatest grain yield (943 kg/ha). The data indicated the existence of the competition. SGR and EFP were significantly affected by cultivar and YLRs. The greatest SGR, 3.67 and 3.62 mg seed** (-1)d** (-1) were obtained from UT 1 and longest EFP, 16.7 and 14.1 days were obtained from PSU 1 in the dry and early rainy seasons, respectively. For YLRs, the greatest SGP, 4.10 and 3.96 mg seed** (-1)d** (-1) were obtained from C and longest EFP, 16.3 and 13.9 days, were obtained from 2/3 and 1/3 YLRs in the dry and early rainy seasons, respectively. Finally, SGR and EFP were negatively and positively (respectively) correlated with grain yield.
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