Factors affecting head rice yield and chalkiness in indica rice

Effects of nitrogen application, genotype, seasons, grain shapes and amylose content (AC) on head rice yield (HRY) and chalkiness were determined in 2012 dry (DS) and wet seasons (WS) in IRRI using 351 indica advanced breeding lines/cultivars from several breeding programs and three N rates (0, 90, and 180 kg ha(-1) and 0, 45, and 90 kg ha(-1) for DS and WS, respectively). HRY was improved with increasing N rates in WS while no significant differences were observed in DS. The average HRY was 10% higher in DS than in WS. Degree of endosperm chalkiness (DEC) and percentage of grains with chalkiness (PGWC) were decreased with increasing N rates in both seasons. AC was only slightly affected by season and N treatment. DEC, PGWC, grain length (GL) and the ratio of grain length to width (LWR) were negatively correlated with HRY in both seasons. 78 and 23 lines had high HRY and low DEC under 180 (DS) and 90 N (WS) rates, respectively. 74 and 21 of these high quality lines had PGWC less than 30%, indicating that visual selection on PGWC could be a quick and simple method for screening for HRY. The low AC subset had lowest DEC but highest HRY in both seasons. Furthermore, the proportions of lines with high HRY and low DEC in different shape classes were significantly different, suggesting that it is possible to select for low chalkiness and high HRY by selecting for PGWC and grain shape. (C) 2014 Elsevier B.V. All rights reserved.