Abstract
In the face of global water scarcity, a successful transition of rice cultivation from puddled to dry direct-seeded rice (DDSR) is a future need. A genome-wide association study was performed on a complex mapping population for 39 traits: 9 seedling-establishment traits, 14 root and nutrient-uptake traits, 5 plant morphological traits, 4 lodging resistance traits, and 7 yield and yield-contributing traits. A total of 10 significant marker-trait associations (MTAs) were found along with 25 QTLs associated with 25 traits. The percent phenotypic variance explained by SNPs ranged from 8% to 84%. Grain yield was found to be significantly and positively correlated with seedling-establishment traits, root morphological traits, nutrient uptake-related traits, and grain yield-contributing traits. The genomic colocation of different root morphological traits, nutrient uptake-related traits, and grain-yield-contributing traits further supports the role of root morphological traits in improving nutrient uptake and grain yield under DDSR. The QTLs/candidate genes underlying the significant MTAs were identified. The identified promising progenies carrying these QTLs may serve as potential donors to be exploited in genomics-assisted breeding programs for improving grain yield and adaptability under DDSR.
Highlights
In the face of global water scarcity, a successful transition of rice cultivation from puddled to dry directseeded rice (DDSR) is a future need
No significant variability was observed for relative growth rate from 22 to 29 days after seeding (DAS) and from 15 to 29 DAS, maximum root length at any sampling point, flag-leaf length and width, leaf color chart (LCC), and total biomass at flowering in 2015 wet season (2015WS) (Table 1)
Negative skewness was observed for days to 50% flowering, grain yield (2016DS), SPAD (2016DS), and panicle length
Summary
In the face of global water scarcity, a successful transition of rice cultivation from puddled to dry directseeded rice (DDSR) is a future need. The key challenges under direct-seeded rice cultivation systems include poor crop stand, low yield[2], weeds[3], poor adaptability, reduced nutrient uptake (especially of phosphorus, nitrogen, and iron)[4], and lodging[5]. Plant morphological traits such as leaf area index; leaf size; leaf insertion angle, shape, and thickness[9] contributing to photosynthesis[10]; flowering time[11,12,13]; growth rate; lodging resistance[4,14]; root traits that enhance nutrient uptake, especially nitrogen (N), phosphorus (P), and iron (Fe)[4]; tillering ability; panicle length; and spikelet fertility are important traits that determine crop productivity under DDSR. There is an urgent need to decipher an appropriate plant and root system architecture for improving nutrient uptake, grain yield, and adaptability under DDSR
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