Morphological Basis of Resistance to Stemfly, Melanagromyze Sojae in Soybean

Fourteen leaf (area, lamina thickness, trichome density, moisture content, and dry matter content); petiole (length, diameter, moisture content and dry matter content): and internodal (length, diameter, pith area, moisture content and dry matter content) parameters were studied in relation to the expression of varietal reaction towards stemfly, Melanagromyza sojae (Zehnter) (Agromyzidae: Diptera) in two susceptible (Pusa 16 and PK 1092), one tolerant [DS 93 Br (OT)-2] and two resistant varieties (MACS 212 and JS 335) at unifoliate, first, second, third and fourth trifoliate leaf stages of soybean. Leaf area and trichome density on abaxial leaf surface were positively associated with the resistance and leaf dry matter content was negatively associated. In resistant varieties leaf petioles were significantly shorter and narrower with lower moisture content as compared to susceptible varieties. Internodal length, diameter, pith and moisture content were negatively associated whereas internodal dry matter was positively related with the expression of varietal resistance to M. sojae. It was concluded that the resistance in soybean to M. sojae is governed by a combination of factors which are additive and temporal (age/stage specific).