Field evaluation of some cowpea lines for resistance to yellow blister disease (Synclytrium dolichi (Cooke gaum) and rust (Uromyces phaseoli (pers.) Winter var. Vignae arth.)

Two hundred lines of Vigna unguiculate (L) Walp. Were planted in three replicates and data on the relative incidence and severity of Synchytrium dolichi (cooke) Arth. On each line was collected at a 14 day interval, from day 40 to day 60 after planting, to evaluate the cowpea lines for resistance to yellow blister diseases (S.dolichi) and Brown rust (U.phaseoli) and to determine the epidemiology of the two diseases. Data on yield parameters and days to flowering was collected to determine the corrections between S. dolichi and U. phaseoli on these plant characteristics. The results showed that 97% of the cowpea lines were susceptible to S. dolichi and 60% were susceptible to U. phaseoli. The incidence and severity of the diseases increased with time but was limited by low relative humidity due to little rainfall during the study period. The overall mean incidences for S dolichi and U. phaseoli were 32.38 and 18.27 respectively while the respective overall mean severities were 1.40 and 1.34. There was strong relationship between the number of pods per plant and mean seed yield per plant (correlation co-efficient 0.772). The relationship between disease incidence and severity was strong for each disease (correlation coefficient 0.917 for S. dolichi and 0.895 for U. phaseoli).