Yield stability of selected rice donors and breeding lines for drought resistance

Mild-moderate drought stress occurs commonly anytime during the crop duration especially in rain-fed and partially irrigated fields. Sixty rice genotypes were selected from different rice breeding programs at IRRI and evaluated under well-watered (WW) and mild moderate drought (DRT) conditions to identify stable and high yielder parents for drought resistance breeding or for adoption by farmers in rice areas prone to water deficit. The experiments were conducted during the wet season (WS) and dry season (DS) from 2008 DS to 2013 DS. The experiments were continued on 12 selected genotypes in three consecutive crop seasons starting from 2013 DS to obtain more detailed information on their physiological response to drought. Drought reduced the mean grain yield by 38 to 61% during DS and by 0 to 23% during WS. It also reduced the plant height, total dry matter yield and harvest index during DS but the number of days to flowering was not affected in both seasons. Highest grain yields were obtained from IR83142-B-7-B-B and Binuhangin in the DRT, and from Apo and PSB Rc68 in the WW treatment. Based on AMMI analysis, IR83142-B-7-B-B, Binuhangin, IR77298-H-1-2-13, IR70215-70-CPA-3-4-1-3 and IR77298-14-1-2 had the highest and most stable yields in both WW and DRT environments. Grain yield increased with higher leaf area at panicle initiation stage. Leaf area was highest in Binuhangin and IR83142-B-7-B-B. The physiological response of rice to drought such as canopy temperature, NDVI, stomatal conductance, root dry weight, number of days to flowering, and plant height were not directly related to grain yield. Although seasonal crop performance varied within the same field, there were genotypes identified which have sustained high yields under a wide range of soil moisture variability that are useful to breeders and farmers.