Assessment of susceptibility of Ocimum tenuiflorum to lace wing bug [Cochlochila bullita (Stal.)]: Host’s physico-morphic and biochemical properties

Abstract

Two promising subtypes of tulsi, Ocimum tenuiflorum were field screened under natural infestation of lace wing bug, Cochlochila bullita to assess its reaction. Seven biophysical and ten biochemical attributes of leaves were studied in relation to the expression of their reaction towards lace wing bug. It was observed that highly susceptible O. tenuiflorum subtype Rama had relatively higher leaf length (4.04 cm), leaf width (2.36 cm), leaf area (5.99 cm2), petiole length (1.79 cm), plant height (90.67 cm), wider leaf angle (35°) and canopy diameter (78.33 cm) than the relatively tolerant subtype Krishna. Similarly, with respect to biochemical parameters, chlorophyll B (r value = 0.785, 0.567), total chlorophyll (0.848, 0.703) and carotenoids (0.702, 0.471) showed significant positive correlation with tinged bug incidence and its damage. Susceptible subtype Rama possessed lower reducing (0.189 g/100 g), non-reducing (2.651 g/100 g) and total sugars (2.840 g/100 g) as compared to tolerant subtype Krishna (0.280, 0.906 and 1.185 g/100 g, respectively). In contrast, higher amount of total phenol (6.79 mg/g) and anthocyanin (0.00058 mg/g) contents in leaves were recorded in subtype Krishna and the observed correlations were negative and significant with pest population and its damage. In terms of succulence, leaves of subtype Rama had higher moisture content (80.8%) than the subtype Krishna (78.1%) and showed significant positive correlation with tinged bug population (r value = 0.830) and leaf damage (0.968).