Morpho-Physiological Responses of Seedlings from UKM Rice Breeding Lines Under Submergence Stress

Abstract

Introgression of the Sub1 QTL into rice mega-varieties through marker-assisted breeding has been proven to increase the tolerance of rice plants to submergence. Due to unpredictable climate change, the development of new rice varieties with improved submergence tolerance is necessary. Currently, only a few local rice varieties exhibit tolerance to submergence, indicating that more varieties tolerant to submergence are needed. Crossbreeding between IR64-Sub1 and UKM5, as well as UKM91, produced several breeding lines, including UKM37, UKM54, and UKM112. However, the response of these lines to submergence has yet to be characterised. Therefore, in this study, we aimed to assess the morpho-physiological responses of these lines by determining their survival percentage and examining changes in plant height, as well as chlorophyll, sugar, and starch contents under submergence. Two-week-old rice seedlings were subjected to submergence treatment for 14 days, and their survival percentage was determined after a 14-day recovery period. Height changes were measured before and after the 14-day treatment. Additionally, chlorophyll, sugar, and starch contents were spectrophotometrically measured at days 0, 7, and 14 of the submergence treatment. Based on the results, all breeding lines exhibited high survival percentages (>75%) and limited growth (less than 16%). There were increases in total chlorophyll content (>50% changes) and starch content (>80% changes) throughout the submergence treatment, but the sugar level was reduced between 50% and 90%. This indicated that these breeding lines were tolerant to submergence and may have adapted to a quiescence strategy by conserving energy until the submergence receded. Characterising these lines will enable their use in further rice improvement programmes.