CHARCOAL ROT (MACROPHOMINA-PHASEOLINA) RESISTANCE AND THE EFFECTS OF WATER-STRESS ON DISEASE DEVELOPMENT IN SORGHUM

In three field experiments, plants subjected to post-flowering water s tress and inoculated with Macrophomina phaseolina had greater developm ent of charcoal rot symptoms than did inoculated plants not subjected to water stress. Two sorghum genotypes (B35-6 and SC265-14E) were foun d to be consistently more resistant to M. phaseolina, an assessment th at was facilitated by the use of appropriate soil moisture conditions at the time of greatest plant susceptibility to charcoal rot. In addit ion, an isolate of M. phaseolina originally isolated from a sorghum ge notype with resistance to charcoal rot caused greater symptom developm ent than did two other isolates originally obtained from sorghum genot ypes susceptible to charcoal rot.