Abstract
The introduction of closely related species genomic fragments is an effective way to enrich genetic diversity and creates new germplasms in crops. Here, we studied the genetic diversity of an introgression line (IL) population composed of 106 ILs derived from an interspecific tetra cross between O. glaberrima and O. sativa (RAM3/Jin23B//Jin23B///YuetaiB). The proportion of O. glaberrima genome (PGG) in the ILs ranged from 0.3% to 36.7%, with an average value of 12.32% which is close to the theoretically expected proportion. A total of 250 polymorphic alleles were amplified by 21 AFLP primer combinations with an average of 12 alleles per primer. Population structure analysis revealed that the IL population can be divided into four genetically distinct subpopulations. Both principal component analysis and neighbor-joining tree analysis showed that ILs with a higher PGG displayed greater genetic diversity. Canonical discriminant analysis identified six phenotypic traits (plant height, yield per plant, filled grain percentage, panicle length, panicle number and days to flowering) as the main discriminatory traits among the ILs and between the subpopulations and showed significant phenotypic distances between subpopulations. The effects of PGG on phenotypic traits in the ILs were estimated using a linear admixed model, which showed a significant positive effect on grain yield per plant (0.286±0.117), plant height (0.418 ± 0.132), panicle length (0.663 ± 0.107), and spikelet number per panicle (0.339 ± 0.128), and a significant negative effect on filled grain percentage (-0.267 ± 0.123) and days to flowering (-0.324 ± 0.075). We found that an intermediate range (10% − 20%) of PGG was more effective for producing ILs with favorable integrated agronomic traits. Our results confirm that construction of IL population carrying O. glaberrima genomic fragments could be an effective approach to increase the genetic diversity of O. sativa genome and an appropriate level of PGG could facilitate pyramiding more favorable genes for developing more adaptive and productive rice.
Highlights
The cultivated rice species Oryza sativa and Oryza glaberrima were independently domesticated in Southern Asia and Western Africa, respectively, from different wild species progenitors [1]
Our analyses showed that increased proportion of O. glaberrima genome (PGG) had positive effects on yield per plant, plant height, panicle length, panicle number, and spikelet number per panicle, but negative effects on days to flowering, and filled grain percentage
An Introgression lines (IL) population derived from an interspecific cross between Oryza glaberrima and Oryza sativa was divided into four distinct subpopulations by STRUCTURE analysis
Summary
The cultivated rice species Oryza sativa and Oryza glaberrima were independently domesticated in Southern Asia and Western Africa, respectively, from different wild species progenitors [1]. O. glaberrima has the ability to grow in a wide range of challenging ecosystems such as rain-fed hilly areas, deep-water conditions, and in coastal mangrove areas [9, 10]. This species could provide valuable germplasm resources for improving the environmental adaptation of Asian rice varieties. The NERICA varieties are high-yielding, drought and pest resistant, and are adapted to the local conditions of West Africa [10, 16]. Quantitative trait loci (QTLs) for plant height, tiller number, panicle number, sterility percentage, 1000-grain weight, and grain yield have been investigated in chromosome segment substitution lines carrying O. glaberrima genes [18]. It is possible to combine the high yield potential and low yield loss due to stress into ILs carrying African rice genes [19, 20]
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