Response to cold stress at reproductive stage of introduced and adapted rice genotypes in Uganda

Exposure of rice (Oryza sativa) to cold stress has significant negative impacts on its development and yield. Prospects of increasing production by growing rice in highland areas of Uganda have not been fruitful due to cold stress. It is therefore important to assess the performance of rice varieties to low temperature to identify germplasm that are cold tolerant with a view of growing them in highland Uganda. The goal of this study was to determine the reaction of a collection of rice accessions for tolerance to cold stress. Fifty rice cultivars that included exotic and locally adapted genotypes were evaluated for two seasons, namely, the second season of 2015 and the first season of 2016. These genotypes were planted under normal environmental conditions and later exposed to170C for 30 days when booting began. Data were collected on tiller number, plant height, panicle number, panicle exsertion and spikelet fertility, using standard procedures. The results revealed significant (P<0.001) differences between genotypes. In addition, a significant relationship (r= 0.91, P<0.001) was observed between panicle exertion and spikelet fertility, indicators for cold tolerance at reproductive stage. Low temperature tolerant genotypes were identified. This then calls for further testing in highland regions of Uganda. However, the identified cold tolerant varieties are short grain yet consumers in the region prefer long grain rice. Thus, there is need to incorporate cold tolerance into the preferred varieties.