Effect of root-knot nematode infestation on growth and biochemical parameters of Plectranthus rotundifolius (Poir.) Spreng

Abstract

Studies were conducted to assess the crop loss in Coleus, Plectranthus rotundifolius, a short duration tuber yielding vegetable, due to infestation of root knot nematode, Meloidogyne incognita. Plants inoculated with 5000 J, showed 50.78% reduction in the yield of coleus. Five local collections (Alur, Mankada, TCM-9, M-131 and Pulamanthol) and two improved varieties (Sree Dhara and Nidhi) were screened for relative tolerance to M. incognita. Local collection, Alur showed significant superiority in reducing the nematode population in soil and root. Lowest root- knot index (1.00) and reproduction factor (0.39) was recorded by the Alur collection compared to improved varieties. Defence enzyme activity and phenolic content in the resistant variety Alur collection was significantly higher than the improved varieties. Considering the ability to resist nematodes and yield potential, the local variety Alur collection can be used in breeding programmes to develop high yielding nematode resistant varieties suitable for cultivation in Kerala.