High Phenotypic Variation in Morus alba L. along an Altitudinal Gradient in the Indian Trans-Himalaya

Ten quantitative morphological characters were studied in 56 Morus alba L. trees representing three natural populations from the trans-Himalayan Ladakh region. The altitude of collection sites ranged from 2815 to 3177 m above the sea level(asl). Coefficient of variation(CV) showed high phenotypic variation in M. alba. Linear regression analysis revealed that leaf and fruit size decreases with an increase in altitude. High CV was observed for leaf length, leaf width, petiole length, leaf area, internodal distance, number of nodes, bud length, fruit length, fruit width and fruit weight. Similarly, a high phenotypic plasticity index was observed for bud length, leaf length, leaf width, petiole length, leaf area, inter-nodal distance, number of nodes, fruit length, fruit width and fruit weight. For every 100 m increase in altitude, leaf length, leaf width and leaf area decreased by 1 cm, 0.8 cm and 16.6 cm2, respectively. Analysis of covariance showed a predominant altitudinal effect on the morphological characters in comparison to the population effect. A small change in the altitude caused significant change in the plant morphological characteristics. The present investigation represents to our knowledge the first study addressing phenotypic variation in mulberryalong an altitudinal gradient.