Abstract
Dry direct-seeded rice (dry-DSR) is typically sown deeply to circumvent
the need for irrigation, and thus seedling emergence is a crucial trait
affecting plant stand and yield. To breed elite cultivars that use less
water and are climate-resilient, understanding the genomic regions and
underlying genes that confer emergence for deeply sown dry-DSR would be
highly advantageous. A combined diversity panel of 470 rice accessions
(RDP1 plus aus subset of 3K RGP) was evaluated with 2.9 million single
nucleotide polymorphisms (SNPs) to identify associations with dry-DSR
traits in the field and component traits in a controlled-environment
experiment. Using genome-wide association study (GWAS) analyses, we
identified 18 unique QTLs on chromosomes 1, 2, 4, 5, 6, 7, 9, 10, and
11, explaining phenotypic variance ranging from 2.6 to 17.8%. Three
QTLs, namely, qSOE-1.1, qEMERG-AUS-1.2, and
qEMERG-AUS-7.1, were co-located with previously reported QTLs for
mesocotyl length. Among the identified QTLs, half were associated with
the emergence in aus, and six were unique to the aus genetic group.
Based on functional annotation, we identified eleven compelling
candidate genes, which primarily regulated phytohormone pathways such as
cytokinin, auxin, gibberellic acid, and jasmonic acid. Prior studies
indicated that these phytohormones play a critical role in mesocotyl
length under deep-sowing. This study provides new insight into the
importance of aus and indica as desirable genetic resources to mine
favorable alleles for deep-sowing tolerance in rice. The candidate genes
and marker-tagged desirable alleles identified in this study should
benefit rice breeding programs directly.