RESUMO
Polished rice is widely consumed staple food across the globe, however, it contains limited nutrients especially iron (Fe) and zinc (Zn). To identify promising genotypes for grain Zn, a total of 40 genotypes consisting 20 rice landraces, and 20 released high yielding rice varieties were evaluated in three environments (wet seasons 2014, 2015 and 2016) for nine traits including days to 50% flowering (DFF), plant height (PH), panicle length (PL), total number of tillers (TNT), single plant yield (SPY), Fe and Zn in brown (IBR, ZBR) and polished rice (IPR, ZPR). Additive Main Effect and Multiplicative Interaction (AMMI), Genotype and Genotype × Environment Interaction (GGE) analyses identified genotypes G22 (Edavankudi Pokkali), G17 (Taraori Basmati), G27 (Chittimuthyalu) and G26 (Kalanamak) stable for ZPR and G8 (Savitri) stable for SPY across three environments. Significant negative correlation between yield and grain Zn was reaffirmed. Regression analysis indicated the contribution of traits toward ZPR and SPY and also desirable level of grain Zn in brown rice. A total of 39,137 polymorphic single nucleotide polymorphisms (SNPs) were obtained through double digest restriction site associated DNA (dd-RAD) sequencing of 40 genotypes. Association analyses with nine phenotypic traits revealed 188 stable SNPs with six traits across three environments. ZPR was associated with SNPs located in three putative candidate genes (LOC_Os03g47980, LOC_Os07g47950 and LOC_Os07g48050) on chromosomes 3 and 7. The genomic region of chromosome 7 co localized with reported genomic regions (rMQTL7.1) and OsNAS3 candidate gene. SPY was found to be associated with 12 stable SNPs located in 11 putative candidate genes on chromosome 1, 6, and 12. Characterization of rice landraces and varieties in terms of stability for their grain Zn and yield identified promising donors and recipients along with genomic regions in the present study to be deployed rice Zn biofortification breeding program.
RESUMO
KEY MESSAGE: A new epicuticular wax (bloom) locus has been identified and fine mapped to the 207.89 kb genomic region on chromosome 1. A putative candidate gene, Sobic.001G269200, annotated as GDSL-like lipase/acylhydrolase, is proposed as the most probable candidate gene involved in bloom synthesis/deposition. Deposition of epicuticular wax on plant aerial surface is one strategy that plants adapt to reduce non-transpiration water loss. Epicuticular wax (bloom)-less mutants in sorghum with their glossy phenotypes exhibit changes in the accumulation of epicuticular wax on leaf and culm surfaces. We report molecular mapping of a new sorghum locus, bloomless mutant (bm39), involved in epicuticular wax biosynthesis in sorghum. Inheritance studies involving a profusely bloom parent (BTx623) and a spontaneous bloomless mutant (RS647) indicated that the parents differed in a single gene for bloom synthesis. Bloomless was recessive to bloom deposition. Genetic mapping involving F2 and F7 mapping populations in diverse genetic backgrounds (BTx623 × RS647; 296A × RS647 and 27A × RS647) identified and validated the map location of bm39 to a region of 207.89 kb on chromosome 1. SSR markers, Sblm13 and Sblm16, flanked the bm39 locus to a map interval of 0.3 cM on either side. Nine candidate genes were identified, of which Sobic.001G269200 annotated for GDSL-like lipase/acylhydrolase is the most likely gene associated with epicuticular wax deposition. Gene expression analysis in parents, isogenic lines and sets of near isogenic lines also confirmed the reduced expression of the putative candidate gene. The study opens possibilities for a detailed molecular analysis of the gene, its role in epicuticular wax synthesis and deposition, and may help to understand its function in moisture stress tolerance and insect and pathogen resistance in sorghum.
