09-08-2013, 03:28 PM
Status of soil borne diseases of brinjal and the frequency of pathogens associated with them
ABSTRACT
Brinjal crop suffers from many biotic stresses, out of which soil borne diseases are of great economic importance. Brinjal or eggplant (Solanum melongena L.) is an important commercial vegetable crop of Jammu region accounting for 950 ha. area with a production of 13,775 MT. Pathogens such as Pythium aphanidermatum, Rhizoctonia solani, Sclerotium rolfsii, Fusarium oxysporum f. sp. melongenae, F. solani, Ralstonia solanacearum and Meloidogyne incognita constitute important bio-hostile elements of the soil ecosystem that the plants encounter before emergence and also at various stages of growth and development. Diverse fungal and bacterial pathogens are responsible for causing a variety of seedling diseases leading to enormous pre and post emergence seedling mortality at the nursery stage. The wilt of brinjal is a complex syndrome known to be caused by fungi, bacteria and root-knot nematodes having synergistic effect on the disease. Studies were carried out from 2007 to 2009 with the objectives to know the status of these diseases, causal agents involved and frequency of the pathogens associated. The soil borne diseases were found to prevail in all the areas surveyed. The pooled data of the years 2008 and 2009 indicated that per cent seedling mortality and wilt incidence ranged from 13.25 to 29.50 and 16.05 to 37.55 per cent, respectively. Pathogenicity tests indicated that Fusarium oxysporum f. sp. melongenae, Pythium aphanidermatum, Rhizoctonia solani, Meloidogyne incognita and Ralastonia solanacearum were the causal organisms associated with the soil borne diseases of brinjal crop. The pathogens were found either alone or in combination with each others. F. oxysporum f. sp. melongenae was the most dominant pathogen with an average occurrence of 14.03 and 13.37 per cent during 2007 and 2008, respectively. Whereas, P. aphanidermatum, R. solani, R. solanacearum and M. incognita occurred with the frequency of 10.27 and 11.03, 5.45 and 7.07, 11.52 and 9.45, and 11.10 and 9.83 per cent during 2007 and 2008, respectively. More than one pathogen was isolated from the same diseased brinjal plant and the combined infection of F. oxysporum f. sp. melongenae, P. aphanidermatum and R. solanacearum was predominantly observed with the frequency of 11.22 and 10.20 per cent during 2007 and 2008, respectively.