Expression profiling of yield related genes in rice cultivars under terminal drought stress.

Background: Rice crop may experience a significant reduction in yield-up to 50%-due to two occurrences during drought stress: unsuccessful peduncle elongation in panicle exertion and ineffective grain filling. The comprehension of mechanisms that promote drought tolerance during these growth phases is crucial for the production of rice that can withstand drought conditions, thus averting a decrease in crop yield.

Methods And Results: The expression of two xyloglucan endo transhydrolase/glucosylase genes (OsXTH 5 and 19) in peduncle tissue and a sucrose transporter gene (OsSUT1) in flag leaf sheath were assessed. An experiment was carried out in a factorial arrangement based on completely randomized design in which, factor A was two rice cultivars (Vandana as tolerant and Tarom mahalli as local susceptible to drought) and factor B was five drought stress treatments (full irrigation, drought stress duration in 72 and 96 h, re-watering after 120 and 192 h). Results showed that expression of OsXTH19 and OsXTH5 genes were upregulated in both Vandana and Tarom mahalli cultivars due to stress treatments. OsXTH19 expression was found to decrease while OsXTH5 expression increased during re-watering treatments. It is likely that the persistence of peduncle growth in the drought-tolerant Vandana cultivar can be attributed to the presence of OsXTH19 under drought conditions and OsXTH5 after re-watering. The expression of OsSUT1 in flag leaf sheath of Vandana in re-watering treatments was reached 8-60-fold re-watering.

Conclusions: Peduncle elongation was attributed to two XTH genes under drought stress condition. Panicle exertion may be promoted by sustaining peduncle growth despite drought stress. Consequently, this may led to reduce in non fertile florets and decrease in grain yield by 50%. As grain filling depend to expression of OsSUT1 in flag leaf sheath under drought stress, to improve rice cultivars under aerobic production system and drought stress, it is advised to apply these findings in rice breeding programs.