Character Association in Improved Mulberry Genotypes Exhibiting Delayed Leaf Senescence

Mulberry (Morus spp.) is a perennial tree cultivated for its foliage to rear the domesticated silkworm, Bombyx mori L. Mulberry has improved through conventional breeding in general aims to improve the quantity and quality of leaf yield, which have direct bearing on silk productivity. Leaf senescence is one of the major constraints, which restricts the quantity of quality leaf availability for silkworm rearing. High yielding mulberry varieties often show leaf fall in the range of 20 – 33% in tropical sericultural belts. Hence, in order to increase the leaf availability, it is essential to delay the senescence of leaves. Keeping this in view, the present study was undertaken on 9 mulberry genotypes, which were developed systematically for delayed senescence. The interrelationship among factors that contribute to growth, yield and low foliar senescence were investigated. Correlation between agronomic traits and leaf yield revealed the existence of strong positive associations among plant height, total shoot length (TSL), nodal distance (ND), leaf fall (LF), number of leaves/ plant (NLP), fresh and dry weight of 100 leaves (FWL & DWL), leaf area (LA), leaf area index (LAI), above ground biomass (AGB) with leaf yield. However, leaf harvest index (LHI) had a strong negative correlation with leaf fall % and leaf yield. Significant improvement in the important growth and yield attributing characters viz., FWL, DWL, LA, AGB, LHI and LAI contributed to a higher yield in CT44. Path co-efficient analysis revealed the direct positive effect of the characters viz., AGB (1.233), LHI (0.449), NLP (0.217), and LA (0.181), on leaf yield. From the studies it is concluded that low leaf fall coupled with high LHI can be considered for the selection of varieties with delayed leaf senescence in mulberry.