Indica-japonica Hybrid Rice Research Articles

Exogenous N Supply on N Transportation and Reuse during the Rice Grain-Filling Stage and Its Relationship with Leaf Color-Changing Parameters

During the later reproductive period of rice growth, the chlorophyll in the leaves degraded, accompanied by the nitrogen (N) transportation from leaves to panicle, resulting in a change in leaf color from green to yellow. This study aimed to investigate the effects of exogenous N supply on leaf color-changing, N accumulation, N transportation, and N loss of indica-japonica hybrid rice during the grain-filling stage. Two indica-japonica hybrid rice cultivars, Chunyou 167 (CY167) and Chunyou 927 (CY927), which exhibited significant differences in leaf color-changing during the grain-filling stage, were selected as materials for field experiment and hydroponic experiment with low, medium, and high N treatments (LN, MN, and HN). The dynamic changes in SPAD value from heading to maturity were measured and fitted with quadratic function to extract leaf color-changing parameters; labeled 15N was used as N source after heading to trace the source of N in the panicle and the remobilization of vegetative organ N. The results showed that 67.37–72.38% of the panicle N was transported from vegetative organs, the N transport efficiency was the upper three leaves > lower leaves > stem, and about 3.1–35.0% of the transported N was lost via volatilization. The effects of exogenous N concentration on N harvest index, N dry matter/grain production efficiency, N reuse efficiency, and N loss were closely related to leaf color-changing parameters. In MN and HN treatment, the N loss was negatively correlated with the onset time of leaf color-changing (T0) and the final leaf color index (CIf), but positively correlated with the leaf color-changing rate (Rmean). Increasing the supply of exogenous N increased T0 and CIf, but decreased Rmean, N transport/reuse efficiency, N harvest index, and N dry matter/grain production efficiency. Compared to the cultivar CY167 with normal leaf color-changing, the “stay-green” cultivar CY927 had higher T0, CIf, and lower Rmean, resulting in less N volatilization loss, lower N harvest index and N transport efficiency, while higher N reuse efficiency. In conclusion, the exogenous N supply affects leaf color by influencing the transportation and reuse of leaf N during the grain-filling stage.

Preliminary Exploration of Physiology and Genetic Basis Underlying High Yield in Indica–Japonica Hybrid Rice

The utilization of heterosis is of great significance in improving rice yield. To explore the physiological and genetic basis for high yield in indica–japonica hybrid rice, Zheyou18 (z18) and Yongyou12 (y12) were used as materials and compared with indica hybrid rice, Zheyou12 (z12); japonica hybrid rice, Liangyoupeijiu (LYPJ); and the conventional lines zhe04B (04B) and zhehui818 (h818) under seedling growth vigor, functional leaf morphology, chlorophyll content, yield component, panicle trait, and InDel heterosis analysis. Z18 and y12 showed the largest increase in plant height 6 d and 9 d after germination; the root dry weight of z18 was 31.2% and 42.0% higher than its parents on the 12th d. The length of functional leaves ranked in the middle, while the width was the largest, resulting in z18 and y12 having the largest leaf area. Yield components showed that z18 and y12 had the highest number of primary branches, spikelets, and grains, and grain yield, which was 58.1 g in z18, increased by 29.8% and 8.7%, respectively, in comparison with h818 and LYPJ. The InDel genetic distance was significantly positively correlated with single spike weight, with r reaching 0.771, making it the only consistent and most correlated among the seven traits. Therefore, we speculated that as the InDel genetic distance expands, heterosis mainly manifests in the increase in single spike weight. This study comprehensively explored the physiological mechanism of yield improvement in indica–japonica-hybrid rice and used InDel genetic distances to study the genetic basis of heterosis, which will be helpful for future rice yield improvement.

Controlling diurnal flower-opening time by manipulating the jasmonate pathway accelerates development of indica-japonica hybrid rice breeding.

Inter-subspecific indica-japonica hybrid rice (Oryza sativa) has the potential for increased yields over traditional indica intra-subspecies hybrid rice, but limited yield of F1 hybrid seed production (FHSP) hinders the development of indica-japonica hybrid rice breeding. Diurnal flower-opening time (DFOT) divergence between indica and japonica rice has been a major contributing factor to this issue, but few DFOT genes have been cloned. Here, we found that manipulating the expression of jasmonate (JA) pathway genes can effectively modulate DFOT to improve the yield of FHSP in rice. Treating japonica cultivar Zhonghua 11 (ZH11) with methyl jasmonate (MeJA) substantially advanced DFOT. Furthermore, overexpressing the JA biosynthesis gene OPDA REDUCTASE 7 (OsOPR7) and knocking out the JA inactivation gene CHILLING TOLERANCE 1 (OsHAN1) in ZH11 advanced DFOT by 1- and 2-h respectively; and knockout of the JA signal suppressor genes JASMONATE ZIM-DOMAIN PROTEIN 7 (OsJAZ7) and OsJAZ9 resulted in 50-min and 1.5-h earlier DFOT respectively. The yields of FHSP using japonica male-sterile lines GAZS with manipulated JA pathway genes were significantly higher than that of GAZS wildtype. Transcriptome analysis, cytological observations, measurements of elastic modulus and determination of cell wall components indicated that the JA pathway could affect the loosening of the lodicule cell walls by regulating their composition through controlling sugar metabolism, which in turn influences DFOT. This research has vital implications for breeding japonica rice cultivars with early DFOT to facilitate indica-japonica hybrid rice breeding.

Natural variation in OsMYB8 confers diurnal floret opening time divergence between indica and japonica subspecies

The inter-subspecific indica-japonica hybrid rice confer potential higher yield than the widely used indica-indica intra-subspecific hybrid rice. Nevertheless, the utilization of this strong heterosis is currently hindered by asynchronous diurnal floret opening time (DFOT) of indica and japonica parental lines. Here, we identify OsMYB8 as a key regulator of rice DFOT. OsMYB8 induces the transcription of JA-Ile synthetase OsJAR1, thereby regulating the expression of genes related to cell osmolality and cell wall remodeling in lodicules to promote floret opening. Natural variations of OsMYB8 promoter contribute to its differential expression, thus differential transcription of OsJAR1 and accumulation of JA-Ile in lodicules of indica and japonica subspecies. Furthermore, introgression of the indica haplotype of OsMYB8 into japonica effectively promotes DFOT in japonica. Our findings reveal an OsMYB8-OsJAR1 module that regulates differential DFOT in indica and japonica, and provide a strategy for breeding early DFOT japonica to facilitate breeding of indica-japonica hybrids.

Improvement of protein structural and functional properties of indica-japonica hybrid rice by radio frequency treatment

The goal of this work was to evaluate the effect of radio frequency combined with conventional hot air drying (RF-HAD) on the drying efficiency, protein structure and functional properties of indica-japonica hybrid rice. The results showed that RF-HAD significantly improved the drying efficiency. RF treatment did not affect the protein profile. However, secondary changes were observed in protein isolates with an increase in random coil and β-turn structures and a decrease in β-sheets and α-helices. The changed intrinsic fluorescence indicated alterations in tertiary structure. RF treatment noticeably improved the peak temperature and end completion temperature while decreasing the enthalpy of the protein. In addition, the functional properties in terms of solubility, oil holding capacity and emulsifying properties of protein isolates were improved after RF treatment. Thus, RF combined with conventional drying can be applied as a novel drying technology to enhance the nutritional qualities of rice.

Molecular Breeding of Zheyou810, an Indica–Japonica Hybrid Rice Variety with Superior Quality and High Yield

Rice heterosis has played a significant role in improving rice yields in China since the 1970s. The utilization of heterosis between the indica and japonica subspecies of rice is especially important in this regard. However, inter-subspecies hybridization between indica and japonica rice is hampered by the inadequate seed-setting rate and inferior rice quality of hybrid offspring, which has limited its development. The discovery and cloning of wide-compatibility gene S5-n and the granular starch synthase gene Wx have provided a solution to this problem, paving the way for the breeding of inter-subspecies hybrid rice. Here we demonstrated the breeding process of Zheyou810 and its performances in regional trials. Employing marker-assisted selection through the utilization of KASP (Kompetitive Allele-Specific PCR), a high-yielding and superior-quality indica–japonica hybrid rice variety named Zheyou810 was developed. Zheyou810 achieved an average yield of 10,737.75 kg/ha (12.58% higher than control Jiayou5) in the national regional trials across 2019 and 2020, and 11,777.25 kg/ha (13.36% higher than Jiayou5) in the production trial in 2020, respectively. The quality of rice has also been improved, reaching the standards set by the Ministry of Agriculture of the People’s Republic of China for Grade 3 premium rice (NY/T593). In 2021, Zheyou810 was approved by the national examination showing broad application prospects.

Two complementary genes in a presence-absence variation contribute to indica-japonica reproductive isolation in rice

Understanding the evolutionary forces in speciation is a central goal in evolutionary biology. Asian cultivated rice has two subspecies, indica and japonica, but the underlying mechanism of the partial reproductive isolation between them remains obscure. Here we show a presence-absence variation (PAV) at the Se locus functions as an indica-japonica reproductive barrier by causing hybrid sterility (HS) in indica-japonica crosses. The locus comprises two adjacent genes: ORF3 encodes a sporophytic pollen killer, whereas ORF4 protects pollen in a gametophytic manner. In F1 of indica-japonica crosses, pollen with the japonica haplotype, which lacks the sequence containing the protective ORF4, is aborted due to the pollen-killing effect of ORF3 from indica. Evolutionary analysis suggests ORF3 is a gene associated with the Asian cultivated rice species complex, and the PAV has contributed to the reproductive isolation between the two subspecies of Asian cultivated rice. Our analyses provide perspectives on rice inter-subspecies post-zygotic isolation, and will promote efforts to overcome reproductive barriers in indica-japonica hybrid rice breeding.

A natural gene drive system confers reproductive isolation in rice

Hybrid sterility restricts the utilization of superior heterosis of indica-japonica inter-subspecific hybrids. In this study, we report the identification of RHS12, a major locus controlling male gamete sterility in indica-japonica hybrid rice. We show that RHS12 consists of two genes (iORF3/DUYAO and iORF4/JIEYAO) that confer preferential transmission of the RHS12-i type male gamete into the progeny, thereby forming a natural gene drive. DUYAO encodes a mitochondrion-targeted protein that interacts with OsCOX11 to trigger cytotoxicity and cell death, whereas JIEYAO encodes a protein that reroutes DUYAO to the autophagosome for degradation via direct physical interaction, thereby detoxifying DUYAO. Evolutionary trajectory analysis reveals that this system likely formed de novo in the AA genome Oryza clade and contributed to reproductive isolation (RI) between different lineages of rice. Our combined results provide mechanistic insights into the genetic basis of RI as well as insights for strategic designs of hybrid rice breeding.

Advances on the Study of Diurnal Flower-Opening Times of Rice

The principal goal of rice (Oryza sativa L.) breeding is to increase the yield. In the past, hybrid rice was mainly indica intra-subspecies hybrids, but its yield has been difficult to improve. The hybridization between the indica and japonica subspecies has stronger heterosis; the utilization of inter-subspecies heterosis is important for long-term improvement of rice yields. However, the different diurnal flower-opening times (DFOTs) between the indica and japonica subspecies seriously reduce the efficiency of cross-pollination and yield and increase the cost of indica–japonica hybrid rice seeds, which has become one of the main constraints for the development of indica–japonica hybrid rice breeding. The DFOT of plants is adapted to their growing environment and is also closely related to species stability and evolution. Herein, we review the structure and physiological basis of rice flower opening, the factors that affect DFOT, and the progress of cloning and characterization of DFOT genes in rice. We also analyze the problems in the study of DFOT and provide corresponding suggestions.

Experimental warming under field conditions alters starch multi-structure and flour and starch functionality of late-season indica-japonica hybrid rice in southern China

IntroductionThe effects of climate warming on starch multi-structure and flour and starch functionality of late-season indica-japonica hybrid rice (IJHR) in double-rice cropping systems are still unclear to date.MethodsA 2 years field warming experiment was conducted by using free-air temperature increase facilities with an IJHR cultivar (Yongyou1538). The starch multi-structure and flour and starch functionality of IJHR were determined.ResultsExperimental warming (on average 2.1°C over the 2 years) reduced the amylose content and increased the amount of short amylopectin branch-chains (degree of polymerization 6–12), possibly due to decreased granule-bound starch synthase activity and increased starch-branch enzyme activity. Additionally, the protein content, starch granule diameter, relative crystallinity, and swelling power of IJHR were enhanced by experimental warming. The changes in rice components and starch multi-structure under warming conditions resulted in high peak viscosity, breakdown, pasting temperature, gelatinization temperatures and enthalpy and low setback of rice starch and high peak viscosity and pasting temperature and low setback of rice flour.ConclusionOur results indicated that climate warming might improve the pasting viscosities and enhance the thermal stability of late-season IJHR.

Grain yield and quality performances of different late-season rice cultivars in response to experimental warming in subtropical China.

Climate warming has pronounced effects on rice production in China. However, late-seasons rice cultivars are diverse in double rice cropping systems, and the actual responses in grain yield and quality of different late-season rice cultivars to climate warming are still unclear. A two-year field warming experiment was conducted by using free-air temperature increase facilities with three widely-planted late-season rice cultivars, including Taiyou398 (TY, short growth duration indica hybrid rice), Jiuxiangnian (JXN, long growth duration indica inbred rice), and Yongyou1538 (YY, long growth duration indica-japonica hybrid rice) in a double rice cropping system in subtropical China. Warming (1.9-2.0°C) had no significant effects on the grain yields of TY and JXN, but significantly decreased that of YY by 4.8% relative to ambient treatment due to a reduction of spikelet number. Compared to ambient treatment, the head rice yields of TY and YY did not change while that of JXN increased by 6.3% under warming conditions. Warming significantly increased the head rice rates of JXN and YY by 6.6% and 7.8%, and the chalky grain rates of TY, JXN, and YY by 79.1%, 21.6%, and 7.6%, respectively. Under warming conditions, the amylose content of JXN and YY decreased significantly by 7.5% and 8.8%, and the setback of three cultivars decreased significantly by an average of 41.5%. Warming could improve the milling and eating qualities of long growth duration late-season rice (JXN and YY) and increase or maintain their head rice yield, even though decreased the grain yield of indica-japonica hybrid rice (YY). These results will provide a better understanding for the selection of suitable late-season rice cultivars under future climate warming conditions.

Source–Sink Balance Optimization Depends on Soil Nitrogen Condition So as to Increase Rice Yield and N Use Efficiency

Genetic improvement has been devoted to increasing rice yield by increasing the spikelet number per panicle and the spikelet/leaf ratio. As a result, indica-japonica hybrid rice “Yongyou” varieties with large panicles and superhigh yield potential have been developed. These varieties exhibit significantly higher grain yield and nitrogen use efficiency for grain (NUEg) under moderate and high N supply conditions due to their large sink size, but their yield performance remains obscure under low N input and low soil fertility conditions. In the present study, we investigated four varieties including Yongyou2640 (YY2640, large-panicle india-japonica hybrid variety), Yangliangyou6 (YLY6, two-line indica hybrid variety), Quanyou6 (QY6, three-line indica hybrid variety), and Huanghuazhan (HHZ, indica inbred variety) under two low soil fertility treatments [LF (removing half of soil depth) and CK] and two N fertilizer rates (0 and 100 kg N ha−1) in Central China. The results showed that the grain yield of YY2640 was more responsive to fertility than that of other varieties, which was 19.4–42.3% higher than that of the other three varieties under CK N100 treatment, but it was 14.5–19.4% lower than that of YLY6 and QY6 under LF N0 and LF N100. A higher spikelet/leaf ratio resulted in more biomass and N partition to panicles rather than to leaves under LF N0 and N100. Slightly more post-flowering dry matter obtained from higher leaf N content and crop growth rate failed to compensate for the adverse effects of reduced pre-flowering dry matter accumulation and stem-to-grain translocation during grain filling. This led to the lower NUEg of YY2640 than YLY6 and QY6 under low soil fertility conditions. Based on these findings, the present study suggested that the source–sink relationship of the super hybrid varieties should be optimized according to the soil N supply condition.

Greater Propensity to Photosynthesize Enables Superior Grain Quality of Indica–japonica Hybrid Rice under Shading

Indica–japonica hybrid rice (I–JR) typically has greater grain yield than that of Indica hybrid rice (IR) under prolific shading, but it is not known how shading impacts on physiological characteristics underpinning grain quality. Here, we conducted a two-year field experiment in the mid-reaches of the Yangtze River region using I–JR (genotypes Yongyou 1540 and Yongyou 538) and IR (genotypes Y-liangyou 900 and Quanyouhuazhan). We found that shading reduced grain appearance and quality, particularly milling and heading rates, and chalkiness. Shading disrupted carbon and nitrogen metabolism, impacting traits influencing the human perception of the taste of the grain, such that amylose decreased by 5.9% (I–JR) and 12.9% (IR); grain protein significantly increased, with lesser effects in I–JR than IR under shading. Shading also reduced peak, hot, and final viscosities, and breakdown value. I–JR had improved rice quality compared with that of IR due to the greater propensity of the former to photosynthesize under shading, leading to the improved functioning of carbon and nitrogen metabolism.

Breeding of the Long-Grain Restorer of Indica-Japonica Hybrid Rice by Using the Genetic Effects of Grain Shape QTLs

Grain shape improvement, which determines grain yield, quality traits and commercial value, is an extremely important aspect of rice breeding. Grain size is controlled by multiple genes, and Maker Assistant Selection (MAS) breeding is effective for breeders in developing stable and efficient markers to aggregate these genes in order to speed up the selection of new lines with desirable traits during the breeding process. In this study, functional markers were developed based on the sequence differences of five grain-shaped genes (GL7, GW6a, GS6, GW5 and TGW6) between the long-grain japonica rice variety Zhendao and the indica-japonica restorer R2027. We then constructed a population of recombinant inbred lines (RILs) based on their cross. The newly designed functional markers were used to genotype grain-size genes, and a genetic effect analysis was conducted to screen high-quality long-grain restorers. Our results reveal diverse effects of different genes on grain size, and the five genotypes were distributed in the 36 selected BC1F8 lines. Specifically, gw5 positively regulates grain width and 1000-grain weight, gl7 and gs6 positively regulate grain length but negatively regulate grain width and 1000-grain weight, tgw6 positively regulates grain length and gw6a positively regulates 1000-grain weight. The most outstanding outcome is that 5 of the 36 lines achieved in this study showing an excellent performance of long grain and yield characters are ideal materials not only for studying the interaction and genetic effects between polygenes but also as restorers or donors for dominant genes in indica-japonica hybrid rice breeding.

Effect of storage time on chemical compositions, physiological and cooking quality characteristics of different rice types.

Storage affects rice quality significantly. The aim of this study was to investigate the changes in the chemical composition and in the physiological and cooking quality characteristics of three rice types after 1 year storage at 25 °C. Two japonica, two indica, and two indica-japonica hybrid rice varieties were selected. After storage, the total starch content decreased. The amylose content of japonica, indica, and indica-japonica hybrid rice increased by 9.63%-11.65%, 2.99%-4.67%, and 8.07%-8.97%, respectively, and the fat content decreased by 60.00%-65.00%, 37.21%-46.51%, and 41.67%-42.42%, respectively. The abscisic acid (ABA) and raffinose content decreased after 1 year's storage; the former decreased gradually during the storage and the latter increased by 19.35%-45.45%, 7.02%-10.77%, and 16.13%-28.13%, respectively, after 4 months' storage and then decreased to the lowest level after 1 year's storage. The activity of antioxidant enzymes deceased, which resulted in the increases in fatty acid value and malondialdehyde (MDA). The changes in chemical composition after 1 year storage led to the deterioration of rice cooking quality, which was reflected in the decrease in viscosity and increases in gelatinization temperature and cooked rice hardness. After 1 year's storage, the rice chemical composition changed and physiological and cooking quality characteristics decreased. Compared with japonica and indica-japonica hybrid rice, indica rice was more stable during 1 year storage. This may be due to the higher content of ABA and raffinose in fresh rice. Our findings will provide information for the identification and breeding of storable rice cultivars. © 2022 Society of Chemical Industry.

Effects of storage on the starch fine structure and physicochemical properties of different rice variety types

The genotype of rice variety is important factor that affect grain quality during storage. In this study, japonica, indica, and indica–japonica hybrid rice were selected to reveal the changes in amylase activities, starch fine structure, and physicochemical properties after one year of storage. Amylase activities decreased after storage and starch molecules were degraded, which, respectively, decreased and increased the content of the amylopectin long chains (DP 37+) and amylose. Changes in the starch fine structure resulted in lower swelling factors and a higher gelatinization temperature. Compared with japonica and indica–japonica hybrid rice, indica rice had a more stable starch fine structure and physicochemical properties after storage. The information obtained from this study provides a better understanding of the changes that occur in starch at the molecular level during storage and will provide insight into the breeding of storable rice varieties.

Grain yield, nitrogen use efficiency and physiological performance of indica/japonica hybrid rice in response to various nitrogen rates

Utilizing the heterosis of indica/japonica hybrid rice (IJHR) is an effective way to further increase rice grain yield. Rational application of nitrogen (N) fertilizer plays a very important role in using the heterosis of IJHR to achieve its great yield potential. However, the responses of the grain yield and N utilization of IJHR to N application rates and the underlying physiological mechanism remain elusive. The purpose of this study was to clarify these issues. Three rice cultivars currently used in rice production, an IJHR cultivar Yongyou 2640 (YY2640), a japonica cultivar Lianjing 7 (LJ-7) and an indica cultivar Yangdao 6 (YD-6), were grown in the field with six N rates (0, 100, 200, 300, 400, and 500 kg ha−1) in 2018 and 2019. The results showed that with the increase in N application rates, the grain yield of each test cultivar increased at first and then decreased, and the highest grain yield was at the N rate of 400 kg ha−1 for YY2640, with a grain yield of 13.4 t ha−1, and at 300 kg ha−1 for LJ-7 and YD-6, with grain yields of 9.4–10.6 t ha−1. The grain yield and N use efficiency (NUE) of YY2640 were higher than those of LJ-7 or YD-6 at the same N rate, especially at the higher N rates. When compared with LJ-7 or YD-6, YY2640 exhibited better physiological traits, including greater root oxidation activity and leaf photosynthetic rate, higher cytokinin content in the roots and leaves, and more remobilization of assimilates from the stem to the grain during grain filling. The results suggest that IJHR could attain both higher grain yield and higher NUE than inbred rice at either low or high N application rates. Improved shoot and root traits of the IJHR contribute to its higher grain yield and NUE, and a higher content of cytokinins in the IJHR plants plays a vital role in their responses to N application rates and also benefits other physiological processes.

Effects of Storage Temperature on Indica-Japonica Hybrid Rice Metabolites, Analyzed Using Liquid Chromatography and Mass Spectrometry.

The Yongyou series of indica-japonica hybrid rice has excellent production potential and storage performance. However, little is known about the underlying mechanism of its storage resistance. In this study, Yongyou 1540 rice (Oryza sativa cv. yongyou 1540) was stored at different temperatures, and the storability was validated though measuring nutritional components and apparent change. In addition, a broad-targeted metabolomic approach coupled with liquid chromatography-mass spectrometry was applied to analyze the metabolite changes. The study found that under high temperature storage conditions (35 °C), Yongyou 1540 was not significantly worse in terms of fatty acid value, whiteness value, and changes in electron microscope profile. A total of 19 key differential metabolites were screened, and lipid metabolites related to palmitoleic acid were found to affect the aging of rice. At the same time, two substances, guanosine 3′,5′-cyclophosphate and pipecolic acid, were beneficial to enhance the resistance of rice under harsh storage conditions, thereby delaying the deterioration of its quality and maintaining its quality. Significant regulation of galactose metabolism, alanine, aspartate and glutamate metabolism, butyrate metabolism, and arginine and proline metabolism pathways were probably responsible for the good storage capacity of Yongyou 1540.

Understanding the Palatability, Flavor, Starch Functional Properties and Storability of Indica-Japonica Hybrid Rice.

The rice quality and starch functional properties, as well as the storability of three YY-IJHR cultivars, which included YY12 (biased japonica type YY-IJHR), YY1540 (intermedius type YY-IJHR) and YY15 (biased indica type YY-IJHR), were studied and compared to N84 (conventional japonica rice). The study results suggested that the three YY-IJHR varieties all had greater cooking and eating quality than N84, as they had lower amylose and protein content. The starch of YY-IJHR has a higher pasting viscosity and digestibility, and there was a significant difference among the three YY-IJHR cultivars. Rice aroma components were revealed by GC-IMS, which indicated that the content of alcohols vola-tile components of YY-IJHR were generally lower, whereas the content of some aldehydes and esters were higher than N84. In addition, YY-IJHR cultivars’ FFA and MDA contents were lower, which demonstrated that YY-IJHR had a higher palatability and storability than those of N84 in fresh rice and rice stored for 12 months. In conclusion, this study suggested that YY-IJHR had better rice quality and storability than N84. PCA indicated that the grain quality and storability of YY12 and YY15 were similar and performed better than YY1540, while the aroma components and starch functional properties of YY-IJHR cultivars all had significant differences.

Development of Wide-Compatible Indica Lines by Pyramiding Multiple Neutral Alleles of Indica-Japonica Hybrid Sterility Loci.

Since the development of indica hybrid rice in the 1970s, great success has been achieved in hybrid rice production in China and around the world. The utilization of inter-subspecific indica–japonica hybrid rice has always been considered due to its stronger heterosis characteristics. However, indica–japonica hybrids face a serious problem of sterility, which hinders the exploitation of their heterosis. In the past decades, the genetic basis of indica–japonica hybrid sterility has been well studied. It was found that in sterile indica–japonica hybrids, female sterility was mainly controlled by the S5 locus and male sterility by the Sa, Sb, Sc, Sd, and Se loci. In this study, we developed wide-compatible indica lines (WCILs) by pyramiding multiple neutral (n) alleles of the hybrid sterility loci. First, we identified Sn alleles of the loci in single-segment substitution lines (SSSLs) in the genetic background of indica Huajingxian 74 (HJX74). Then, the Sn alleles of S5, Sb, Sc, Sd, and Se loci in SSSLs were pyramided in the HJX74 genetic background. The WCILs carrying Sn alleles at the S5, Sb, Sc, Sd, and Se loci showed wide compatibility with indica and japonica rice varieties. Therefore, the WCILs will be used to develop inter-subspecific indica–japonica hybrid rice with normal fertility.