Genetic response of cowpea varieties/lines against seedling blight disease caused by Macrophomina phaseolina (Tassi) Goid. and its management

Cowpea is the most important crop of the world. The nutritional value of cowpea lies in its protein contents of 20-40%. It suffers from several diseases but among them seedling blight is most destructive disease, caused by Macrophomina phaseolina. Despite all the advancement in production technologies, a considerable portion of cowpea production is lost every year due to this disease over the world. The present study was designed for management of seedling blight of cowpea through host plant resistance, the available chemicals and plant extracts. Seven cultivars were obtained from grain market and Pulses section, AARI, Faisalabad. Standard blotter paper method was used to check fungi associated with seed samples. Five fungus species (Aspergillus flavus, Aspergillus niger, Macrophomina phaseolina, Alternaria alternata, Penicillium spp) were isolated in significant amount from all seed samples. Seven varieties/lines (SA Dandy, Elite, Rawan-2003, White star, CP1, P-518, P-2127) were screened against seedling blight disease. Screening trial was conducted in Research area of Department of Plant Pathology. Data was recorded by using disease rating scale of Pastor Corrales and Abawi, 1988. Among seven cultivars White star and Elite showed resistant behavior, SA dandy, CP1 and Rawan-2003 revealed tolerant, while P-2127 and P-518 showed susceptibility towards test pathogen. The efficacy of different fungicides and plant extracts at various concentrations were evaluated against test pathogen through poison food technique in laboratory and pot culture assay in green house conditions. Among five fungicides (Hombre, Copper oxychloride, Topsin-M, Carbendazim, Metallaxyl+Mancozeb) evaluated Carbendazim gave maximum mycelial inhibition/control, 83.67% at 150 ppm concentration and 76.50% plant survival as compared to control under greenhouse conditions, when used as seed treatment. Minimum mycelial inhibition and plant survival was given by Copper oxychloride, 12.33% and 26.63% respectively. All five plant extracts (Azadirachta indica, Syzgium cumini, Datura stramonium, Eucalyptus comaldulances, Dalbergia sissoo) used in this trial gave significant results. Azadirachta indica gave best results, 70.93% mycelial inhibition/control and 66.50% plant survival as compared to control at 75% concentration. Minimum results were given by Dalbergia sissoo in both cases, 17.20% and 23.63% respectively.