Evaluation of advanced back cross lines for drought tolerance in rice (Oryza sativa L.)

Drought is the largest abiotic constraint to rice production which cause significant yield loss depending upon the severity. Development of rice varieties with tolerance to drought and high use water use efficiency is the need of the hour. Despite the importance of drought as major abiotic constraint, the efforts to develop drought tolerant rice varieties are very low. Breeding efforts until recent past were focused on understanding and improvement of secondary traits that are putatively associated with drought tolerance. However, the genetic gain in yield by improvement of secondary traits is very low. Hence, improvement of yield per se under drought conditions will be better solution. Introgression of yield QTLs under drought in the genetic background of high yielding varieties will be helpful to overcome the problem to a certain extent. In the present study, 31 advanced back cross lines (BILs) derived from drought susceptible mega variety Samba Mahsuri (BT 5204) and a drought tolerant tolerant land race Azucena were evaluated under drought. Thirty one advanced back cross inbred lines (BC2F4) lines having yield QTLs viz., qDTY3.1 on chromosome 3 and qDTY2.1 on chromosome 2 were phenotyped under drought conditions. The results suggested that wide range of variation was observed for yield and its component traits in the BILs generated in the background of BPT 5204 and direct selection for yield under water stress coupled with marker assisted screening would help in development of drought tolerant version of mega varieties with improved yield under stress. Thermo tolerance studies indicated that high variability was observed for the BILs in terms of % seedling survival, % reduction in root and shoot growth under stress.