Interaction of Macrophomina phaseolina and Meloidogyne javanica on green bean

Both the root-knot nematode (Meloidogyne javanica) and charcoal rot (Macrophomina phaseolina) are serious diseases of green bean farms، each of them can cause significant economic loss annually. Since the probability of simultaneous presence of these two disease agents is high، there is a need for assessing the damage of their interaction according to indigenous isolates as well as local environmental conditions. In this research the interaction of M. javanica and M. phaseolina in green beans cv. 418 Jamaran was studied under green house condition. The test was carried out in a completely randomized design with 6 treatments in 5 replicates. The treatments were control، fungus alone، nematode alone، fungus and nematode simultaneous application، first nematode two weeks later the fungus، and first fungus two weeks later nematode. The nematode inoculum was reared on tomato from asingle egg mass. The fungus inoculums were grown on a sterile medium comprised of sand and cornmeal. Seedlings were inoculated at two-leaf stage with 3 eggs and second stage juveniles (J2) of M. javanica per gram soil and/or with 2 g of fungal inoculum per pot. After seven weeks، plant growth parameter as well as its yield; nematode reproduction factor، number of galls، final nematode population; and fungal damage was evaluated in each treatment. The highest damage to green beans as well as the highest growth reduction was observed in simultaneous inoculation treatments. The least gall number and reproduction factor (Rf) was seen in the treatment that was inoculated with M. phaseolina prior to nematode while the highest gall number and Rf was seen in the treatment that was first inoculated with M. javanica. All treatments inoculated with nematodes had greater root weight than other treatments in the absence of nematodes. The least growth reduction was observed in treatments that were inoculated with one of the pathogens only. The results confirmed high susceptibility of green bean to simultaneous infection by these two pathogens.