Department of Plant Breeding, CCS Haryana Agricultural University, Hisar-125004, India.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Cowpea golden mosaic virus (CGMV) earlier known as yellow mosaic virus is a major disease of cowpea (Vigna unguiculata (L.) Walp.) particularly in Asia and Africa. Genetical and biochemical basis of resistance to CGMV was studied using two resistant (CS 39 and CS 55) and two susceptible (GC 2 and HFC 42-1) genotypes. The material for genetical study consists of two resistant and two susceptible parents, F1, F2 and backcross populations of resistant x susceptible, resistant x resistant and susceptible x susceptible crosses grown during summer and rainy seasons for their resistance behavior to CGMV disease in the field and further confirmation in laboratory. The F1 plants in both the crosses involving resistant and susceptible parents were resistant indicating dominance of resistance over susceptibility to this disease. Test for allelism in F1 and F2 population from cross between resistant genotypes indicated that the resistance of CS 39 and CS 55 has been controlled by common loci. No complementary interaction between the genes for susceptibility in the cross between susceptible genotypes was observed. The gene symbols Cym1 and Cym2 have been assigned for resistant genes to CGMV disease. The levels of total phenols and specific activities of polyphenol oxidase (PPO), per oxidase (PO) and catalase in leaves of CGMV resistant (CS 39 and CS 55), tolerant (ARL 25) and susceptible genotypes (HFC 42-1 and GC 2) of cowpea were measured at 40, 50 and 60 days after sowing (DAS). Resistant genotypes had higher activity of PPO and PO along with higher phenolic content in comparison to healthy leaves of susceptible ones at 40 and 50 DAS. PO activity was several times more as compared to PPO activity and increased markedly in response to infection in susceptible genotypes. Total phenols in resistant genotypes remained more or less same at 40 and 50 DAS but increase in susceptible ones, while its level in tolerant genotypes decreased continuously throughout the growth period. Catalase activity was generally higher in resistant genotypes in comparison to both healthy and diseased leaves of susceptible genotypes. There was proportional reduction in catalase activity with respect to disease severity. The stability parameters revealed that the genotypes CS 39 and CS 55 had very less mean values for CGMV disease reaction, negligible ‘b’ values indicated non-responsive of disease expression to the changes in environments and non significant values deviation indicated the stability of these genotypes.
