Conditional genes for grain yield in rice

Grain yield in cereal crops was an etemal theme.     

Path analysis for grain yield and its components in rice

Rice yield, its components and their relations are one of the most important research objects for genetics, cultivation, and breeding. This study was to investigate the genetic relationships between yield and yield components by using the methods of correlation analysis and path analysis with a set of 241 RIL population of Shanyou 63.     

Rapid prediction of head rice yield and grain shape for genome-wide association study in indica rice

Rice milling and appearance qualities are the main determinants of market price of the milled rice, so great breeding efforts have been directed to improve the milling and appearance quality. The success of breeding efforts depends on the accurate and rapid phenotyping of the quality traits in early generations. This study was conducted to first validate the effectiveness of the PaddyCheck to measure head rice yield (HRY) and paddy grain length of 40 indica rice cultivars. The results indicated that the PaddyCheck data had positively correlated with the lab methods of HRY (r = 0.81**) and grain length (r = 0.97**). An association panel including 281 indica rice accessions was phenotyped with the PaddyCheck and the data were used for genome-wide association study (GWAS) to identify quantitative trait locus (QTL) for milling and appearance quality. A total of nine QTLs were identified, among which the major genes GS3 and qSW5 were identified for grain length and width, respectively. Furthermore, a novel QTL on short arm of chromosome 6 was identified for HRY. Our study indicated that PaddyCheck measurement was accurate and effective, and could be applied in rice breeding for improvement of grain shape and milling quality. The nine QTLs identified in indica rice could be used in marker assisted selection in rice breeding programs.     

Genetic dissection of grain nitrogen use efficiency and grain yield and their relationship in rice

Breeding for improved grain yield (GY) and grain nitrogen use efficiency (NUE) is an important objective of many rice breeding programs. A better understanding of the genetics of these two complex traits and their genetic relationship is required for more efficient breeding. This study reports the results of a linkage mapping study conducted for these two traits using 127 rice recombinant inbred lines (RILs) derived from the cross of Zhanshan 97/Minghui 63. Phenotypic data were collected under two nitrogen conditions in 2006 and 2007. For NUE, four and six QTLs were identified in 2006 and 2007, respectively. These QTLs were on chromosomes 1, 2, 6, 7 and 11. For GY, nine and five QTLs were detected on chromosomes 1, 2, 7 and 11 in 2006 and 2007, respectively. The phenotypic and genetic correlations between NUE and GY are positive and highly significant. Four genomic regions, including C86-C2340 on chromosome 1, RZ599-R1738 on chromosome 2, RZ471-C1023 on chromosome 7 and R3203-RM20a on chromosome 11, were found to contain QTLs for both NUE and GY. The effects of the co-located QTLs were in the same direction for NUE and GY, providing a genetic basis for the observed positive genetic correlation between the two traits. These genomic regions might be explored for the simultaneous improvement of NUE and GY in breeding.     

不同免耕方式对水稻产量影响的试验初报

水稻免耕栽培技术是指在收获上一季作物后未经任何翻耕犁耙的稻田,先使用除草剂灭除杂草植株和落粒谷幼苗,摧枯稻桩或绿肥作物后,灌水并施肥沤田,待水层自然落干或排浅水后,将秧苗抛(插)到大田中的一项新的水稻耕作栽培技术,该项新技术是上杭县普及推广抛秧栽培技术后,引进推广     

Dissection of heterotic loci for grain yield using interconnected chromosome segment substitution lines in rice

Heterosis contributes greatly to crop production, but the genetic basis of heterosis is not fully understood.To identify heterotic loci(HLs) for grain yield, 12 yield traits were evaluated in four rice(Oryza sativa L.)mapping populations: one parental population of chromosome segment substitution lines derived from a cross between the japonica cultivar Nipponbare and indica cultivar 9311 and three connected test populations in either a homozygous 9311 genetic background or a heterozygous background. A total of 390 HLs were detected for the measured traits in two environments. The genetic bases of heterosis differed between the backcross and testcross populations. At least 10 HLs were confirmed in F1 hybrids between9311 and near-isogenic lines, each of which carried a heterotic locus of interest in the same 9311 background. All 10 showed overdominant or dominant effects on grain yield and yield components. Among them, three were verified as being associated with yield heterosis and colocalized in the same regions as those containing previously reported heterosis-associated genes. Five HLs were identified to be promising candidate loci that could be used to achieve more than 15% yield heterosis in several commercial rice hybrids. These findings suggest the potential of indica or japonica introgression for increasing yield in hybrid rice breeding programs.     

Genotype-by-environment interactions for grain yield associated with water availability at flowering in rainfed lowland rice

While a large genotype-by-environment (G × E) interaction component of variance for grain yield (GY) has been widely reported for rainfed lowland rice, the reasons for such large interactions are not well known. A random reference population of 34 genotypes taken from the Cambodian rice improvement program was used to examine the magnitude and nature of G × E interactions for GY in Cambodia. These genotypes were evaluated in a multi-environment trial (MET) conducted across 3 years (2000–2002) and eight locations in the rainfed lowlands. The G × E interaction was partitioned into components attributed to genotype-by-location (G × L), genotype-by-year (G × Y) and genotype-by-location-by-year (G × L × Y) interactions. The G × L × Y interaction was the largest component of variance for GY. The G × L interaction was also significant and comparable in size to the genotypic component (G). The significant G component was partly explained by a group of four genotypes that were broadly adapted to different environmental conditions represented by three environmental groups. The three environmental groups were identified from a pattern analysis, and the grouping was partly related to the time of sowing, and hence water availability at flowering. A major factor contributing to the large G × L × Y interactions for GY was late maturing genotypes being affected greatly when soil water availability at flowering was reduced greatly, compared to earlier maturing genotype groups. While the differential genotypic responses to the water availability environment explained part of a large G × E interaction for GY, other non-water related environmental conditions also appeared to have contributed to the interaction. Three target environments were identified for focusing efforts of the breeding programs in Cambodia, and four putative genotypes were selected for their high yield and wide adaptation in the rainfed lowlands.     

喷施粒粒饱对圣稻301稻米品质和产量的影响

圣稻３０１是适于黄淮稻区种植的优质水稻品种 ,常因干旱缺水晚插秧和生育后期遇低温而影响稻米品质和产量。本试验旨在探明喷施中国水稻研究所研制的粒粒饱对圣稻３０１稻米品质和产量的影响。一、材料与方法１.基本情况试验地设在嘉祥县金屯镇钱屯村。前茬小麦 ,肥力中上 ,土壤质地粘重 ,河水灌溉 ,无污染。５月８日半干旱育秧 ,６月３０日插秧。２０００年因麦收前后气候干旱缺水 ,插秧时间比往年推迟１５～１８天 (一般年份为６月１２～１５日 )。试验地每６６７ｍ２ 施磷酸二铵２０ｋｇ、氯化钾１５ｋｇ、硫酸锌２ｋｇ作基肥。病虫草害…     

立丰灵对水稻抗倒性和产量的调控效果

水稻倒伏是高产和机械收割的重大威胁.抗倒性化学调控日益引起关注.20世纪80年代日本研发的多效唑(MET)具有矮化稻株,增强抗倒性的功能.近年中国农业大学开发出一种新型矮化剂立丰灵,主要成分为调环酸钙盐.3a 试验结果表明,立丰灵对水稻具有增强抗倒性和促进生殖生长的双重效能.2005年进行6.7hm2示范,骥以进一步验证立丰灵对水稻抗倒性和产量的调控效果.     

Effect of non-lethal low phytic acid mutations on grain yield and seed viability in rice

Low phytic acid (LPA) crops have recently been considered as a potential way to combat nutritional and environmental issues related to seed phytic acid phosphorus (PA-P). Although, a number of LPA mutant lines have been developed in various crops, they are often featured with lower grain yield and seed viability compared with wild type (WT) parents. We recently developed several LPA mutant lines in rice with PA-P reductions varying from 33.8% to 63.6%. In this study, the performance of grain yield and seed viability of these mutants were investigated. Four of the five mutant lines had 12.5–25.6% reductions in grain yield compared to the corresponding WT parental lines. The reduction in grain weight, varying from 5.4% to 10.7%, was found to be the main causative factor of yield reduction. Similarly, LPA mutants had inferior seed viability to their corresponding WT parent varieties; all mutant lines had a significantly lower simplified vigour index (seed germination rate × seedling dry weight) than their parents, with reductions of 7.8–26.3%, although some mutant lines had similar germination rates as their WT parents. The two mutant lines, which had similar germination rates as their WT parent, however, had significantly lower field emergence rates. More pronounced differences of simplified vigour index were observed after artificial aging treatments between four LPA lines from their WT parents, implying that LPA rice seeds were more susceptible to storage than WT. The yield and yield-related traits of F₂ plants and F₃ lines from three crosses were evaluated; the results showed that while LPA was associated with significantly lower grain yield and grain weight than WT sibs, there were also LPA plants and lines that out-performed WT controls. These results implied that the negative effect of LPA mutations on grain yield might be reduced or minimized through cross and selection breeding. The implications of these findings were discussed with regard to LPA rice breeding and potential commercial production.     

Response to two cycles of divergent selection for grain yield under drought stress in four rice breeding populations

Drought is a major production constraint in rainfed rice (Oryza sativa L.). Lack of effective selection criteria is a major limitation hampering progress in breeding for drought tolerance. In an earlier report, we showed in two populations that one cycle of direct selection was effective in increasing grain yield under stress. In the present study, we retested the efficiency of direct selection for grain yield under drought stress in rice using four populations derived from crossing upland-adapted, drought-tolerant varieties (Apo, Vandana) to high-yielding, lowland-adapted, drought-susceptible varieties (IR64, IR72). Each population was subjected to two cycles of divergent selection either under drought stress in upland or under nonstress conditions in lowland conditions. Following selection, approximately 40 high-yielding lines selected under each protocol from each population, along with a set of unselected lines, were evaluated in a series of selection response trials over a range of moisture levels. Significant response to direct selection under stress was realized in 9 out of 15 combinations of populations and stress environments, and in 6 of the 7 severe stress trials. Averaging over all the populations and stress environments, the stress-selected lines had a yield advantage of 25 and 37% over nonstress-selected and random lines, respectively. In contrast to this, under nonstress, the nonstress-selected lines had an average yield advantage of only 7 and 13% over stress-selected and random lines, respectively. Direct selection in managed stress trials during dry seasons gave significant response (25% on average relative to indirect selection in nonstress conditions) under naturally occurring wet season stress. In addition, direct selection under stress in upland gave an average gain of 16 and 45% over nonstress-selected and random lines, respectively, under stress in lowland. The yield advantage of the stress-selected lines appears to result mainly from maintenance of higher harvest index. These results show that direct selection for grain yield under stress is effective and does not reduce yield potential. Overall, this is the first report in rice demonstrating that (a) selection under managed drought stress in the dry season can result in yield gains under natural stress in the wet season, and (b) that selection under upland drought stress can, at least under the conditions of the present study, result in gains under lowland drought conditions.     

Agronomic performance of rice breeding lines selected based on plant traits or grain yield

Selection for yield per se has greatly contributed to yield improvement in many crops. It is expected that selection based on plant traits is more effective in increasing crop yield potential. This study was conducted to compare the effectiveness of trait-based and yield-based selection in increasing rice yield and to determine whether lines with ideotype traits have the potential to express higher yield under optimal crop management conditions. Lines were selected based on plant traits or on grain yield measured in a breeder's replicated yield trial. The main target traits for selection were plant height, leaf and panicle morphology, grain size, total dry weight, and grain-filling percentage. Yield performance of trait-based selection was compared with that of yield-based selection in an agronomic trial with optimum crop management for three seasons. Trait-based selection increased leaf area index and total dry weight but reduced spikelet number per m² and harvest index compared with yield-based selection. Consequently, selection based on plant traits did not increase grain yield compared with selection based on yield per se. In one of the three seasons, yield of trait-based selection was significantly lower than that of yield-based selection. Among all tested breeding lines, maximum yield was produced by yield-based selection and minimum yield came from trait-based selection. These results suggest that lines with ideotype traits did not express higher grain yield than lines selected based on yield per se under optimal crop management conditions, and yield-based selection was as effective in increasing rice grain yield as trait-based selection in the late generations of the breeding cycle.     

A novel Effective Panicle Number per Plant 4 haplotype enhances grain yield by coordinating panicle number and grain number in rice

Increasing effective panicle number per plant(EPN) is one approach to increase yield potential in rice.However, molecular mechanisms underlying EPN remain unclear. In this study, we integrated mapbased cloning and genome-wide association analysis to identify the EPN4 gene, which is allelic to NARROW LEAF1(NAL1). Overexpression lines containing the Teqing allele(TQ) of EPN4 had significantly increased EPN. NIL-EPN4TQin japonica(geng) cultivar Lemont(LT) exhibited significantly improved EPN but de...     

早稻穗发芽对水稻产量和米质的影响

以田间自然条件下穗发芽的早稻品种为材料,研究了穗发芽对水稻产量和稻米品质的影响。结果表明：穗发芽严重影响水稻的千粒重,千粒重降低6．91％～24．45％,同时,穗发芽导致槌米率、精米率和整精米率下降10％～90％,并使透明度和胶稠度下降,严重影响了稻米的加工品质和蒸煮品质。     

国外近年旱稻选育品种(品系)产量和主要品质性状的综合评价

对国外近几年选育的170份早稻品种(品系)的产量、谷粒形状和部分品质性状进行了评价分析，结果表明，参试早稻备品种产量变幅较大，产量表现中上的品种占27．1％，其中来自印度和哥伦比亚的品种产量潜力较高，而原产巴西和西非国家的品种产量潜力较低。多数国外旱稻品种具有良好的外观品质，谷粒长或特长，粒形细长，千粒重中等以上，垩白小或无。参试品种中，中等和低糊化温度的分布频率略大于高糊化温度：直链淀粉含量以低和中等为主，其中，含量在17%～22％之间的品种占38．8%。根据产量和主要品质性状的评价结果，推荐10份国外优良旱稻品种(品系)供国内旱稻育种利用。     

Nucleotide polymorphisms in OsAGP genes and their possible association with grain weight of rice

ADP-Glucose pyrophosphorylase (AGPase) is a rate-limiting enzyme participating in starch biosynthesis, which may be responsible for the filling rate and starch accumulation in the developing rice kernel. However, it is still unknown whether the naturally occurring variation in the sequence of ADP-Glucose pyrophosphorylase of rice (OsAGP) is related to the grain weight (GW). In this study, we discovered a total of 38 single nucleotide polymorphisms (SNPs) and insertions/deletions (InDels) in the partial sequences of six OsAGP isoform genes from 30 rice accessions with diverse agronomic traits. We then developed ten cleaved amplified polymorphic sequence (CAPS) and derived CAPS (dCAPS) markers for genotyping the SNPs and InDels for an association mapping population consisting of 416 rice accessions. Candidate gene association study indicated that an InDel of OsAGPL4 was associated with GW in two environments and an SNP of OsAGPL2 was associated with GW in one environment. Each gene marker only explained 1% of the variation of GW, thus it could be concluded that both genes contributed little to GW of rice. However, the markers identified in this study could be used for tagging other traits of interests and in molecular breeding.     

Modeling grain yield and grain yield response to nitrogen in spring wheat crops in the Argentinean Southern Pampa

Agronomic efficiency (kg grain yield kg⁻¹ N applied) is conditioned by environmental factors and nitrogen availability during the growing period. Hence, a fertilization model that considers environmental factors affecting wheat crop growth and effective N supply should be based on crop N demand. In this work, a simple model based on N balance during the growing season is used as the frame to simulate both the demand and the availability of N, and to determine grain yield. Fertilization experiments were conducted under different environments (50 sites, 8 y) of the Southern Pampa of Argentina. Nitrogen fertilization rates ranged between 25 and 125 kg N ha⁻¹. Soil initial conditions and water balance during the crop cycle were found to modify both N demand and soil N supply. The amount of N taken up by crops, water balance during the crop growth period and mean maximum temperature during grain filling, all affected grain yield components. The proposed model provided a good agreement between observed independent data sets and simulated values of grain yield (root mean square error = 9% of the mean value). Model operation was performed for one site within the region using climatic records to estimate annual grain yield variability under three levels of N availability.