Identification of Quantitative Trait Loci Controlling Floral Morphology of Rice Using a Backcross Population between Common Cultivated Rice, <i>Oryza sativa</i> and Asian Wild Rice, <i>O. rufipogon</i>

Abstract

Differences in floral morphologies affect pollination behaviour in many flowering plants. In the genus Oryza, several differences in the size of floral organs are known. In this study, we focused on the differences in the size of floral organs between common cultivated rice, Oryza sativa L. and its wild ancestor, O. rufipogon. We compared floral morphologies between cultivated rice O. sativa cv. Nipponbare and O. rufipogon W630. We first evaluated temporal changes in filament and anther lengths. W630 had longer filaments with rapid elongation within 15 min after spikelet opening. W630 also had longer anthers than Nipponbare, and size of anther was consistent throughout all time examined. We also analysed other six floral traits, and found that W630 had higher stigma and style length, as well as lemma and palea length, but lower lemma and palea width. Quantitative trait locus (QTL) analysis was performed to identify the loci controlling these floral traits, using backcross recombinant inbred lines derived from a cross between Nipponbare and W630. A total of 11 significant QTLs were identified. Of these, two pairs of QTLs for lemma and palea length and one pair for lemma and palea width overlapped, suggesting that common genetic factors may be the reason for the differences in these traits. In addition, we performed QTL analysis for grain size, and found that QTLs for grain size coincided with those for lemma and palea size, indicating that grain size is partly controlled by glume capacity. The QTLs identified in this study will be informative for understanding genetic changes associated with rice domestication.

Development of New Restorer Lines Carrying Some Restoring Fertility Genes with Flowering, Yield and Grains Quality Characteristics in Rice (Oryza sativa L.)

“…The authors of [ 38 ] report that the choice of the parents is a crucial step in breeding programs for improving new lines. Floral morphologies are important, decisive factors in mating systems in rice [ 27 ]. The highest mean values of floral traits studied, i.e., anther length (mm), anther breadth (mm), filament length (mm), and duration of floret opening (min), of all the studied genotypes were observed in the genotype NRL 54-2 ( Table S4 ).…”

“…An increase in the length of filament thread leads to an increase in the opportunity for pollen to spread, which leads to an improvement in the cross-pollination rate (outcrossing) and thus an increase in the seed set in seed production of hybrid rice. A major factor in the increase in the rate of outcrossing in parental lines is the duration of flowering in flowers [ 27 ]. Anther length, anther breadth, and filament elongation are the most important floral traits for pollen parents in hybrid rice seed production fields [ 47 ].…”

“…The characterization of the parental lines of floral traits is an essential aspect of every breeder and this should be kept in mind while selecting the parental lines in a hybrid rice breeding program. The extent of outcrossing on male cytoplasmic sterile lines (CMSs) is influenced by their floral traits, that is, the length and width of the anther as well as the length of the filaments, in the pollen parent [ 27 ].…”

Evaluation of New Promising Rice Hybrid and Its Parental Lines for Floral, Agronomic Traits and Genetic Purity Assessment

“…The extent of outcrossing on cytoplasmic male sterile lines (CMS) is influenced by its floral traits viz., stigma size, stigma exsertion rate, style length and anther size, filament length, pollen number anther -1 in pollen parent. The flowering behavior traits influencing outcrossing in rice are time of blooming, number of days of blooming, duration of blooming, duration of floret opening, and angle of floret opening (Ishikawa et al, 2017). During the last ten years, Rice Research and Training Center (RRTC) in Egypt developed a large number of new rice hybrids and their parental lines through testcross nurseries (El-Mowafi et al, 2008;Abd Allah, 2008;Anis, 2013;El-Mowafi et al, 2015;El-Badawy, 2016;Anis et al, 2016 a,b;Anis et al, 2017;Hassan et al, 2017).…”

Characterization of Oryza nivara introgression lines: A potential prebreeding resource to improve net photosynthetic rate in elite cultivars of rice

“…RM122 on chromosome 5 is associated with gs, Ci, ΦPSII, TNG, and YLDP. It was linked to BLB resistance gene Xa5 in rice genotypes (Sabar et al 2016) and lemma width (Ishikawa et al 2017). RM204 on chromosome 6 was associated with PN, gs, Ci, E, ΦPSII, and qN.…”