Introgression of submergence tolerance QTL (Sub 1) into drought tolerant rice lines using marker-assisted selection

Abstract

Rice (Oryza sativa L.) is Asia's main crop. Increasing flood and drought frequency due to climate change has affected rice cultivation and urged breeding for submergence and drought-tolerant varieties. Marker-assisted breeding was conducted by crossing two drought-tolerant rice lines viz. IR99784-226-335-1-5-1-1 (UKM5) and IR99784-255-91-1-1-1-1 (UKM91) having drought yield quantitative trait locus (qDTY) as the recipient parents with a submergence tolerance locus (Sub1) donor, IR64-Sub1. Molecular markers that are linked to the qDTY12.1, qDTY3.1 and Sub1 were used for hybrid confirmation and validation of QTLs in each generation. A total of 103 and 156 F1 individuals from the crossings of UKM5 and UKM91 with IR64- Sub1, respectively, were successfully generated and the introgression of Sub1 was confirmed using peak marker ART5. BC1F4 lines with different QTL combinations from both populations were evaluated for morpho-physiological and yield-related traits in vegetative stage submergence stress (VS), reproductive stage drought stress (RS) and non-stress (NS) trials at Terrace Q and R in Greenhouse Complex of Universiti Kebangsaan Malaysia. Higher survival rates (SR) were recorded by BC1F4 lines with Sub1, ranged between 60 to 100% compared to IR64-Sub1 (86.67%) and MR219 (40.00%) at the seventh day of recovery after submerged for 14 days. The BC1F4 lines utilized quiescence strategy to survive VS by maintaining a lower percentage of chlorophyll content change (CCC), percentage of non-structural carbohydrate change (NSCC) and shoot elongation percentage (EP). Evaluation of selected lines from both populations in 18 days of VS trial also proven that the traits were closely related with SR. Combinations of Sub1 with qDTY/s were proven to increase SR of BC1F4 lines from UKM5*/IR64-Sub1 population but the interaction of Sub1 and qDTY3.1 showed less beneficial effect to BC1F4 lines from UKM91*/IR64- Sub1 population. In RS trial, plant height (PH), the number of panicle per plant (NP), chlorophyll content (CC), length of panicle (LP), thousand-grain weight (TGW) and grain yield (GY) were reduced compared to in NS trial while days to 50% flowering (DTF) increased. However, BC1F4 lines recorded better morpho-physiological traits and produced higher GY than checks in RS and NS trials. The effect of Sub1+qDTY3.1 combination was the best in both populations for improvement of GY under RS trials. Lines with high SR, low EP and low CCC in VS trial and high GY in NS and RS trials were selected for future trials.