Effect of partial shading on yield and morphological characteristics of mungbean (Vigna radiata L.)

The reduction in the quantity and quality of light received by the intercrop under partial shade condition often leads to reduction in the productivity of the intercrop. In this light, a varietal development project for partial shade tolerance in mungbean was initiated at the Institute of Plant Breeding. Preliminary screening of a total of 160 mungbean entries grown under shade. Fourteen entries from this trial were further field tested in Tranca, Bay, Laguna [Philippines]. Three shade levels; full sunlight, 50% and 70% shade levels were the main plots with mungbean genotypes assigned to subplots. Morphological characters such as biomass production, leaf area, relative leaf greenness, nodule weight and nodule score was measured during the flowering stage. Days to flowering and growth habit were also monitored together with yield and yield components. In general, partial shading caused significant reduction in pod and grain yield and biomass production. Yield reductions of 82 to 100% were observed in 50% and 70% shade, respectively. Fifty percent shade significantly increased total leaf area while 70% shade increased the number of days to flowering from 36 to 48. Nodule score and dry weight were also adversely affected by 70% shading while most of the plants grown under 70% shade exhibited indeterminate growth. Significant genotype-shade level interaction was observed in terms of yield and yield components, biomass production, internode distance and days to flowering which validates the need for varietal development for partial shade condition. Morphological characteristics such as roots and green leaves dry weight, relative leaf greenness (using SPAD 502), total leaf area, nodule score, nodules dry weight had positive significant positive correlations with grain yield and yield components whereas significant negative correlations were observed with growth habit and number of days to flowering.