Abstract
BackgroundThe grain number per panicle (GNP), which is one of three grain yield components, is an important trait for the genetic improvement of rice. Although the NAL1 and GNP1 genes regulating the rice GNP and grain yield have been cloned, their allelic diversity, functional differences in rice germplasms, and effects of their combination on GNP and grain yield remain unclear.ResultsBased on DNA sequences of these two genes in 198 cultivated rice (Oryza sativa) and 8–10 wild rice (Oryza rufipogon) germplasms, 16 and 14 haplotypes were identified for NAL1 and GNP1, respectively. The NAL1 gene had the strongest effects on GNP in indica (xian) and japonica (geng) subpopulations. In contrast, GNP1 had no significant effects in the geng subpopulation and was rare in the xian background, in which the superior GNP1 allele (GNP1–6) was detected in only 4.0% of the 198 germplasms. Compared with the transgenic lines with GNP1 or NAL1, the transgenic lines with both genes had a higher GNP (15.5%–25.4% and 11.6%–15.9% higher, respectively) and grain yield (5.7%–9.0% and 8.3%–12.3% higher, respectively) across 3 years. The two genes combined in the introgression lines in Lemont background resulted in especially favorable effects on the GNP.ConclusionsOur results indicated that the GNP1 and NAL1 exhibited obvious differentiation and their combinations can significantly increase the grain yield in geng rice cultivars. These observations provide insights into the molecular basis of the GNP and may be useful for rice breeding of high yield potential by pyramiding GNP1 and NAL1.
Highlights
The grain number per panicle (GNP), which is one of three grain yield components, is an important trait for the genetic improvement of rice
We found that introgression of the superior GNP1 allele from Teqing into Lemont lead to significantly increase in flag leaf length and area (Unpublished)
The superior Narrow leaf 1 (NAL1) allele from the low-yielding Lemont variety can further increase 3.2%–3.8% grain yield of high-yielding Teqing variety in different environments (Xu et al 2015), while the superior GNP1 allele from the high-yielding Teqing variety can increase 5.7%– 9.6% grain yield of low-yielding Lemont variety in different environments (Wu et al 2016). These results suggested that superior NAL1 and GNP1 alleles can potentially be used in high yield rice breeding
Summary
The grain number per panicle (GNP), which is one of three grain yield components, is an important trait for the genetic improvement of rice. Previous studies revealed that NAL1 is associated with pleiotropic effects that regulate the development of multiple traits related to the source (e.g., leaf width, leaf chlorophyll content, and photosynthetic efficiency), the sink (e.g., GNP), and the EPN in diverse genetic backgrounds (Fujita et al 2013; Takai et al 2013; Zhang et al, 2014; Xu et al 2015; Yano et al 2016). Another major QTL, GNP1, encodes the rice gibberellin biosynthesis gene GA20ox. Their relative importance and pyramiding effect on grain yield have not been characterized
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