Abstract

Low temperatures at the reproductive stages of sorghum limit its performance and promotion in the dry highlands of Kenya. Two hundred and fifty sorghum genotypes were evaluated in 2020 and 2021 on a randomized complete block design (RCBD) with three replications in two sites. Egerton University a cool highland region and Marigat a warm lowland. The daily temperature range at Egerton was recorded as 20/9?C while that of Marigat was 32/20?C during the growing period. The objective of the study was to characterize sorghum genotypes according to their reproductive cold tolerance. Data were collected on plant height, number of tillers, days 0 to 50% heading, panicle length, panicle weight, seed weight and panicle harvest index. A cluster analysis aggregated sorghum genotypes into three clusters at Egerton. The genotypes in cluster one remained vegetative; cluster two had productive panicles, while cluster three produced sterile panicles at Egerton site. The genotypes took between 125 and 213 days to head at Egerton while the same took 55 to 103 days to head at Marigat. Plants were taller in Marigat site as compared to Egerton site. The effect of cold temperatures at the reproductive stage is detrimental and causes irreversible changes which could lead to absence of and/or sterile panicles.

Key words: Reproductive stage, cold tolerance, clusters analysis, vegetative, sterile.