ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 66 Number 2
Effect of different dates of sowing cowpea on the severity of leaf rust caused by Uromyces phaseoli var. vignea
The effects of date of sowing on the rust, Uromyces phaseoli var. vignae, was studied on four cowpea cultivars, C-152, KBC-I, TVX-944 and V-37. The cultivars were sown on 27 July, 12 August, 6 September and 16 September in 1985 and on 22 July, 6 August, 1 September and 18 September in 1986. Maximum susceptibility to rust, measured as the area under the disease progress curve (AUDPC), was recorded for the third (1986) or fourth (1985) sowings during the first or third week of September, respectively. Irrespective of the year or the sowing time, C-152 was the most susceptible cultivar with TVX 944 and KBC-I as intermediates; V-37 was the least susceptible and exhibited slow rusting behaviour over all sowings. Analysis of variance of a split-plot design revealed the effects of cultivars, dates of sowing, and their interaction during 1985 to be significant (P < 0.01), suggesting a degree of environmental specificity in varietal response to the rust.
Keywords: Cowpea; Rust; Sowing time; Vigna; Uromyces