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Investigating Agronomic and Physiological Traits for Yield Improvement in Rice Breeding
Dissertation Abstract:
Agronomists and plant breeders usually rely on the evaluation of various plant traits in the field to select cultivar for further breeding step. Agronomic, physiological, and yield component traits, and their relationship with grain yield were determined in various germplasm sets in the International Rice Research Institute (IRRI) irrigated breeding program. Physiological and yield component traits were investigated in the Diversity Panel with 36 genotypes in wet season (WS) 2015 and dry season (DS) 2016, 36 genotypes, including parent and offspring lines developed by Rapid Generation Advance method (RGA) in DS 2016, advanced breeding lines of Multi-Environmental Yield Trial (MET) stage at WS 2015, and advanced breeding lines of Regional-Yield Trial (RYT) and Preliminary-Yield Trial (PYT) under alternate wetting and drying (AWD) and normal irrigation conditions at DS 2013 and DS 2014. Spectral reflectance measurements for normalized difference vegetation index (NDVI) at key growth stages were done to estimate physiological status of plant genotypes and evaluate the usefulness of this tool in phenotyping. The NDVI at different growth stage, SPAD at 4WAH, agronomic traits, yield component traits, and yield were collected to measure the heritability and relationship of traits with yield in various germplasm sets.
There was a differential response of different germplasms in terms of yield component traits. In Diversity Panel, plant height, number of panicle per m2, number of spikelets per panicle, HI, 1000 GW, NDVI at heading stage, NDVI at late-grain filling stage, and SPAD at 4WAH were highly associated with yield; thus, these traits can be used as reliable selection index for yield improvement during WS. During DS, plant height, NDVI at panicle initiation, and NDVI at late-grain filling stage were more highly associated with yield. For Diversity Panel, the degree of genetic variation among the genotypes and the different seasons were observed.
Plant height, panicle length, NDVI at panicle initiation, and NDVI at late-grain filling were highly associated with yield in parent and advanced breeding lines of RGA method during DS. Thus, the improvement of these traits is possible through hybridization, followed by selection to release high-yielding variety for DS. The different trait selection for early- and late-maturing lines in MET trail stage could be more effective to identify high-yielding advanced breeding lines. A very strong association of yield with biomass under water-saving (AWD) condition, number of spikelets per panicle, and HI are good selection traits under both AWD and normal irrigation condition.