Relationship between Grain Yield and Yield Components of Various Rice Cultivars

[Objective] The relationship between grain yield and yield components was investigated in .different rice cultivars at the target yield of 10.5-11.25 t/hm2, to provide theoretical basis for cultivation of high-yield rice. [Method] The yield performance of various super rice and non-super rice cultivars that were cultivated in large area in Sichuan Chengdu was studied under high-yielding cultivation conditions from 2006 to 2008. [Result] The rice yield was closely correlated with the productive panicle number, grain number per panicle, seed setting rate and 1 000-grain weight. The four yield components showed different influences on the yield of different rice culti- vars. By adopting the high yielding cultivation technology （that the seedlings were planted in a triangle shape） at the target yield of 10.5-11.25 t/hm~, we found that the rice yield of super rice cultivars was closely correlated with productive panicle number and 1 000-grain weight, negatively correlated with grain number per panicle, and significantly negatively correlated with seed setting rate; the grain yield of non- super rice cultivars was negatively correlated with grain number per panicle and seed setting rate, and significantly negatively correlated with the productive panicle number and 1 000-grain weight. [Conclusion] The results revealed the relationship between grain yield and yield components in different rice cultivars, which provided references for developing reasonable cultivation measures and thus to improve the yield of super rice in large acreage.

Characteristics of Retoon Rice Yield Components and Relationship of the Characteristics with Rate of Bud Emergence and Root Activity

[Objective] The aim was to study on characteristics of retoon rice yield components, and relationship of the characteristics with born bud rate and root ac- tivity of retoon rice before harvesting. [Method] Eighteen mid-season hybrid rice va- rieties approved recently were taken as materials in high-yield cultivation conditions. Characteristics of retoon rice yield components were analyzed, and relationship of yield components characteristics with the rate of bud emergence and root activity of retoon rice before harvesting was explored, based on related data. [Result] Highly- yielding retoon rice is characterized by high effective ear number （Xl） and high set- ting percentage （X4）; the number of germinated shoots the 5^＊ d after first-batch rice was cut is a key factor for retoon rice yield and was of positive correlation with re- toon rice seedlings and effective ears, with correlation coefficients at 0.80^＊＊ and 0.76^＊＊. In addition, bleeding sap was of positive correlation with grain number and setting percentage of retoon rice and correlation coefficients were 0.50^＊ and 0.48^＊＊, and of positive correlation with average panicle weight, with correlation coefficient at 0.63. [Conclusion] It is an effective way for the rate of bud emergence and root activity at lar ecological zones. mproving retoon rice yield to increase harvesting in the test sites and simi lar ecological zones.

Effect of Fulvic Acid on Growth and Yield Components of Direct Seeding Rice

ObjectiveThis study aimed to investigate the effect of fulvic acid on the growth and yield components of direct seeding rice （Nanjing 44）. MethodThe rice seeds were soaked in 0 （water as a control）, 1, 2, 4 and 6 g/L fulvic acid （FA） before sowed. Then, the rice morphological indices, leaf chlorophyll content, photosynthesis parameters, root activity and chlorophyll fluorescence parameters were measured in the following field studies. ResultCompared with the control, the leaf area index, chlorophyll content, net photosynthetic rate, stomatal conductance and dry matter weight and some fluorescence parameters such as the maximum photochemical efficiency of photosystem II （PSII） （Fv/Fm）, excitation energy capture efficiency of opened PSII reaction center （Fv’/Fm’） and efficiency of the open reaction centre （ΦPS II） increased by different levels at both jointing stage and heading stage of direct seeding rice, whose seeds were soaked by FA with different concentrations. High FA concentration （4-6 g/L） significantly increased the cultivated rice leaf area index, chlorophyll content, net photosynthetic rate, stomatal conductance, transpiration rate and dry matter weight by 10.32% -22.88% , 5.88% -13.11% , 12.16% -26.84% , 11.43% -88.46% , 10.63% -21.63% , 18.49% -19.68% , respectively, thereby improving the physiological function and light energy transform efficiency of rice at the growth stage. With FA concentration increasing, the yield, effective panicles, grain number per panicle and seed setting rate were increased significantly compared with the control by 17.52%-18.71%, 3.46%-3.85%, 6.30%- 6.51% and 7.82%-8.69% respectively. ConclusionSoaking rice seed with FA could be considered as an effective way to improve the rice competitiveness at early growth stage.

Relationship Between Canopy Temperature at Flowering Stage and Soil Water Content,Yield Components in Rice

The canopy temperature of rice at the flowering stage and the soil water content were investigated under different soil water treatments （the soil water contents were 24%, 55%, 90% and 175% at the flowering stage）. The canopy temperature was lower than air temperature, and the soil water content significantly influenced the canopy temperature. The lower the soil water content, the higher the canopy temperature, the less the accumulative absolute value of canopy-air temperature difference. Moreover, the maximum difference between treatments and CK in the accumulative absolute value of canopy-air temperature difference appeared at 13：00 μm. in a day, thus, it could be considered as a suitable measuring time. Under the lowest water content treatment, the peak flowering occurred in the first three days （about 70% of panicles flowered）, resulting in shortened and lightened panicle of rice. As to the CK and the high water content treatments, the peak flowering appeared in the middle of flowering duration, with longer panicle length and higher panicle weight. Results indicated the lower the soil water content, the less the filled grain number and grain yield.

Influence of Organic and Inorganic Nitrogen on Grain Yield andYield Components of Hybrid Rice in Northwestern Pakistan

Field experiments were conducted to assess the impact of various organic sources, inorganicnitrogen （N） and the different combinations of inorganic N （urea） ＋ organic source on the yieldcomponents （YC） and grain yield （GY） of hybrid rice （Oryza sativa L., Pukhraj） under rice-wheat system.The experiments were conducted at Batkhela （Malakand）, Northwestern Pakistan, in 2011 and 2012.Our results revealed that YC and GY ranked first for the hybrid rice when applied with sole inorganic N（urea）, followed by the application of N in mixture （urea ＋ organic sources）, while the control plots （no Napplied） ranked in the bottom. Among the six organic sources （three animal manures： poultry, sheepand cattle; three crop residues： onion, berseem and wheat）, application of N in the form of poultrymanure was superior in terms of higher YC and GY. When applying 120 kg/hm2 N source, 75% N fromurea ＋ 25% N from organic source resulted in higher YC and GY in 2011, while applying 50% N fromurea ＋ 50% N from organic sources caused higher YC and GY in 2012. Therefore, the combinedapplication of N sources in the form of urea ＋ organic source can produce good performances in termsof higher YC and GY of rice under rice-wheat cropping system.

Effect of Planting Date, Spacing and Seeding Methods on Disease Development and Yield Components of Rice （Oryza sativa L.） in Southeastern Nigeria

To investigate the effect of planting date, spacing and seeding methods on disease development and yield components ofrice, a factorial experiment in randomized complete block design （RCBD） with four replications was conducted during 2011 plantingseason at Izzi Local Government Area （LGA） of Ebonyi State, Nigeria. This experiment was carried out with four levels of plantingdates （early June, late June, early July and late July）, three levels of spacing （15, 20 and 25 cm） and two levels of seeding method（direct seeding and seedling transplanting）. The studied traits included plant height （PH）, number of tillers （NT）, leaf area （LA）, rootlength （RL）, panicle length （PL）, 1,000 seed weight （SW）, disease incidence and severity. The result showed that all the factors hadsignificant effect on the parameters measured. Sowing in early July had the highest LA of 65.38 cm^2, PH of 122.00 cm, RL of 29.04cm and TN of 10.54, and the second largest PL of 25.08 cm and SW of 25.12 g. Also sowing in early July had the highest diseaseseverity of 3.21, followed by 3.14 which occurred in late July, while the least 2.17 occurred in early June. The direct seeding methodhad the highest disease incidence of 70.83%, followed by plant spacing of 15 cm × 15 cm which had the disease incidence of 69.72%,while sowing in early June had the least disease incidence of 57.50%. In conclusion, planting of rice in Southeastern Nigeria shouldbe done in early July, as the yield components were significantly better than in other dates though with the highest disease severity.

Combining Ability Analysis for Yield and Yield Components of Yinshui-type Japonica Hybrid Rice

[Objective] This study aimed to analyze the yield potential of newly developed Yinshui-type japonica hybrid rice parents and provide the theoretical basis for breeding of Yinshui-type japonica hybrid rice. [Method] An incomplete diallel cross of four cytoplasmic male sterile （CMS） lines and four restorer lines was designed to investigate the combining ability for yield and yield components of Yinshui-type japonica hybrid rice. [Result] The variances of general combining ability （GCA） for yield traits were extremely significantly different. GCA variances of male parents were higher than that of female parents except for seed-setting rate. The variances of specific combining ability （SCA） for grain yield per plant, number of effective spikes and seed-setting rate were significantly or extremely significantly different. 139A and Wanlun 422 exhibited higher GCA effects. Most yield traits of these two parents be- longed to type II. Combinations 139AxWanlun 422 and Liaojingl0AxWanlun 422 had relatively high grain yield per plant and SCA effects. GCA effects of restorer lines and SCA effects of combinations greatly affected yield traits, while GCA ef- fects of CMS lines slightly affected yield traits. [Conclusion] In this study, restorer lines exhibited greater genetic differences and impact on yield traits than CMS lines; 139A and Wanlun 422 possessed higher application potential.

Effects of "Three Controls" Nutrient Management on Population Quality and Yield Components of Rice

[Objectives]This study was conducted to explore the control mechanism of agricultural non-point source pollution,and investigate the feasibility of promoting rice"three controls"nutrient management in Enping City.[Methods]With high-quality conventional rice as a material,such three treatments as three controls fertilization A(ZHY)and B(ZHY)and farmers conventional fertilization method FFP(ZXL)were set up,and the whole process of the late-season plot experiment was recorded.The agronomic characteristics of rice population quality and yield components during rice growth and development under the"three controls"fertilization technology were analyzed.[Results]Compared with the conventional fertilization method,the three controls A(ZHY)fertilization method improved rice yield by 27.13%,seed setting rate by 2.11%and 1 000-grain weight by 3.30%when reducing N,P and K by 27.13%,10.89%and 27.31%,respectively.In the case of three controls B(ZHY)omitting the last fertilization in the three controls fertilization method(4∶2∶3∶1),which saved the formula fertilizer by 11.25%,no difference was caused in yield,but the seed setting rate and 1 000-grain weight were still improved by 3.47%and 2.79%,respectively.Compared with the conventional fertilization method,the top first,second and third basal nodes of the three controls A(ZHY)fertilization method were shortened by 18.82%,17.06%and 20.52%,respectively,which plays an important role in combating typhoon and resisting lodging.[Conclusions]Compared with the conventional fertilization method,rice"three controls"nutrient management can improve yield and lodging resistance of rice,reduce fertilizer loss and agricultural non-point source pollution,and protect ecological environment.

Root morphological traits and their relations with yield components of dry-raised mid-season indica rice

Research on root morphological traits of dry-raised seedlings (D-RS) at different growth stages of rice have so far attracted less attention. In this study, using mid-season indica hy-

Influence of water potential and soil type on conventional japonica super rice yield and soil enzyme activities

We carried out a pool culture experiment to determine the optimal water treatment depth in loam and clay soils during the late growth stage of super rice. Three controlled water depth treatments of 0-5, 0-10 and 0-15 cm below the soil surface were established using alternate wetting and drying irrigation, and the soil water potential （0 to -25 kPa） was measured at 5, 10 and 15 cm. A 2-cm water layer was used as the control. We measured soil enzyme activities, root antioxidant enzyme activities, chlorophyll fluorescence parameters, and rice yield. The results showed that the 0-5-cm water depth treatment significantly increased root antioxidant enzyme activities in loam soil compared with the control, whereas soil enzyme activities, chlorophyll fluorescence parameters and yield did not differ from those of the control. The 0-10- and 0-15-cm water depth treatments also increased root antioxidant enzyme activities, whereas soil enzyme activities, chlorophyll fluorescence parameters and yield decreased. In clay soil, the soil enzyme activities, root antioxidant enzyme activities, chlorophyll fluorescence parameters, and yield did not change with the 0-5-cm water treatment, whereas the 0-10- and 0-15-cm water treatments improved these parameters. Therefore,the appropriate depths for soil water during the late growth period of rice with a 0 to -25 kPa water potential were 5 cm in loam and 15 cm in clay soil.

Substituting nitrogen and phosphorus fertilizer with optimal amount of crop straw improves rice grain yield,nutrient use efficiency and soil carbon sequestration

Crop straw return after harvest is considered an important way to achieve both agronomic and environmental benefits.However,the appropriate amount of straw to substitute for fertilizer remains unclear.A field experiment was performed from 2016 to 2018 to explore the effect of different amounts of straw to substitute for fertilizer on soil properties,soil organic carbon(SOC)storage,grain yield,yield components,nitrogen(N)use efficiency,phosphorus(P)use efficiency,N surplus,and P surplus after rice harvesting.Relative to mineral fertilization alone,straw substitution at 5 t ha^(-1)improved the number of spikelets per panicle,effective panicle,seed setting rate,1000-grain weight,and grain yield,and also increased the aboveground N and P uptake in rice.Straw substitution exceeding 2.5 t ha^(-1)increased the soil available N,P,and K concentrations as compared with mineral fertilization,and different amounts of straw substitution improved SOC storage compared with mineral fertilization.Furthermore,straw substitution at 5 t ha^(-1)decreased the N surplus and P surplus by up to 68.3 and 28.9%,respectively,compared to mineral fertilization.Rice aboveground N and P uptake and soil properties together contributed 19.3%to the variation in rice grain yield and yield components.Straw substitution at 5 t ha^(-1),an optimal fertilization regime,improved soil properties,SOC storage,grain yield,yield components,N use efficiency(NUE),and P use efficiency(PUE)while simultaneously decreasing the risk of environmental contamination.

Analysis of High-Resolution QTL Markers Associated with Rice Yields Using Data for Two Consecutive Years in Different Environmental Conditions

Previously we reported the identification of seven quantitative trait loci (QTLs) associated with the rice yield measuring five parameters including panicles per plant (PPP), spikelets per panicle (SPP), seed set percentage (SSP), 1000-grain weight (TGW) and yield in 2012. Here we report the analysis of QTLs using the same trait parameters data of the mapping population in 2013 for detecting highly conserved QTL markers. A total of 6 QTLs were identified from chromosomes 1, 7, 8, 10, 11, and 12, which were contrasted with our previous results (chromosomes 1, 2, 4, 5, 6, 8, and 11). In this comparison, three QTLs from chromosome 1, 8, and 11 were only found to be associated with the components of yield over two consecutive years indicating high sensitivity of QTL markers to the environment. Of those three QTLs, SPP-associated marker RM12285 was found to be dominantly expressed by real-time PCR (qPCR). In addition, compared to our previous report the numbers of mapping population and markers were significantly increased for higher resolution markers from 70 to 120, and from 143 to 217, respectively. We also found that the parameter SPP was dominantly correlated with the rice yield. Furthermore, the double haploid (DH) population facilitated to analyze the epistatic effects for yield and yield components in rice. Taken together, combining multiple mapping population data over years possibly enables narrowing down to the highly conserved QTL markers against diverse environmental fluctuation caused by such as drought and high temperature. Thus, these data would be critically exploited to improve for the crop breeding strategy.

Quantitative Evaluation on the Comprehensive Benefit of Controlled-Release Fertilizer in Typically Middle-Low Yield Rice Field

Quantitative evaluation and analysis was made to the soil nutrients,rice yield,rice and fertilizer utilization rate,and economic and ecological benefits of the slow controlled release fertilizer in typical rice fields with middle-low yield by comparing the one-time application and split applications of slow-or controlledrelease fertilizer（ CRF） with farmers fertilizer practice as the control,with the aim to explore the effect of CRF. Results showed that compared with the control,the application of CRF could meet balance nutrients required for rice growth,and the effective panicles and seed-setting rate were higher in the treatment groups of FVOL,SVOL,LADVOLwhich applied CRF. As for soil nutrients,soil pH maintained balance in FVOL,FCAI,SVOL,LADVOL. In addition,differences in soil nutrient reduction amount reached the extremely significant level between FVOLand SXNK.SVOLwhich applied CRF provided reasonable regulation of N,P and K release rate,which showed advantages over blending fertilization and farmers fertilizer practice. Comprehensive analysis found that the application of CRF could make rice tillering growth and decline leveled off,which effectively improved the quality of rice population,and it also had higher input-output ratio than that of the control and good economic benefits. In general,CRF suits to be used widely on rice crop in the regions with medium-low yield.

Effect of Interplanting with Zero Tillage and Straw Manure on Rice Growth and Rice Quality

The interplanting with zero-tillage of rice, i.e. direct sowing rice 10-20 days before wheat harvesting, and remaining about 30-cm high stubble after cutting wheat or rice with no tillage, is a new cultivation technology in wheat-rice rotation system. To study the effects of interplanting with zero tillage and straw manure on rice growth and quality, an experiment was conducted in a wheat-rotation rotation system. Four treatments, i.e. ZIS （Zero-tillage, straw manure and rice interplanting）, Zt （Zero-tillage, no straw manure and rice interplanting）, PTS （Plowing tillage, straw manure and rice transplanting）, and PT （Plowing tillage, no straw manure and rice transplanting）, were used. ZtS reduced plant height, leaf area per plant and the biomass of rice plants, but the biomass accumulation of rice at the late stage was quicker than that under conventional transplanting cultivation. In the first year （2002）, there was no significant difference in rice yield among the four treatments. However, rice yield decreased in interplanting with zero-tillage in the second year （2003）. Compared with the transplanting treatments, the number of filled grains per panicle decreased but l000-grain weight increased in interplanting with zero-tillage, which were the main factors resulting in higher yield, tnterplanting with zero-tillage improved the milling and appearance qualities of rice. The rates of milled and head rice increased while chalky rice rate and chalkiness decreased in interplanting with zero-tillage. Zero-tillage and interplanting also affected rice nutritional and cooking qualities. In 2002, ZIS showed raised protein content, decreased amylose content, softer gel consistency, resulting in improved rice quality. In 2003, zero-tillage and interplanting decreased protein content and showed similar amylose content as compared with transplanting treatments. Moreover, protein content in PTS was obviously increased in comparison with the other three treatments. The rice in interplanting with zero-tillage treatments had higher peak viscosity and breakdown, lower setback, showing better rice taste quality. The straw manure had no significant effect on rice viscosity under interplanting with zero-tillage, but had the negative influence on the rice taste quality under transplanting with plowing tillage.

Quantifying the effects of short-term heat stress at booting stage on nonstructural carbohydrates remobilization in rice

Extreme heat stress events are becoming more frequent under anticipated climate change,which can have devastating impacts on rice growth and yield.To quantify the effects of short-term heat stress at booting stage on nonstructural carbohydrates(NSC)remobilization in rice,two varieties(Nanjing 41 and Wuyunjing 24)were subjected to 32/22/27°C(maximum/minimum/mean),36/26/31°C,40/30/35°C,and 44/34/39°C for 2,4 and 6 days in phytotrons at booting stage during 2014 and 2015.Yield and yield components,dry matter partitioning index(DMPI),NSC accumulation and translocation were measured and calculated.The results showed that the increase of high-temperature level and duration significantly reduced grain yield by suppressing spikelet number per panicle,seed-setting rate,and grain weight.Heat stress at booting decreased DMPI in panicles,increased DMPI in stems,but had no significant effect on photosynthetic rate.Stem NSC concentration increased whereas panicles NSC concentration,stem NSC translocation efficiency,and contribution of stem NSC to grain yield decreased.Severe heat stress even transformed the stem into a carbohydrate sink during grain filling.The heat-tolerant Wuyunjing 24 showed a higher NSC transport capacity under heat stress than the heat-sensitive Nanjing 41.Heat degree-days(HDD),which combines the effects of the intensity and duration of heat stress,used for quantifying the impacts of heat stress indicates the threshold HDD for the termination of NSC translocation is 9.82°C day.Grain yield was negatively correlated with stem NSC concentration and accumulation at maturity,and yield reduction was tightly related to NSC translocation reduction.The results suggest that heat stress at booting inhibits NSC translocation due to sink size reduction.Therefore,genotypes with higher NSC transport capacity under heat stress could be beneficial for rice yield formation.

Study on intermittent irrigation for Paddy Rice: Ⅱ. Crop Responses

Effect of intermittent irrigation on the production of paddy rice was studied in a well-puddled paddy field with four treatments and 2 replicates: continuous flooding irrigation (CFI), and intermittent irrigation Ⅱ-O, Ⅱ-1 and Ⅱ-2, in which plants were re-irrigated when the soil water potential fell below 0, -10, and -20 kPa, respectively, at soil depth of about 5 cm. Results showed that the reduction in soil water potential to about -10 or -20 kPa did not significantly affect the number of grains and the percentage of ripened grains. While, a lower crop growth rate (CGR) resulted from a decrease in the net assimilation rate (NAR) during intermittent irrigation Ⅱ-1 and Ⅱ-2, and there was also a reduction in the leaf area index (LAI) during intermittent irrigation Ⅱ-2. Senescence of lower leaves on stems was promoted in treatments Ⅱ-1 and Ⅱ-2 at the ripening stage. Early senescence at ripening stage and water stress around midday decreased the rate of photosynthesis in leaves, causing the lower NAR. These physiological responses of the plants were responsible for the reduction in the dry matter production and grain yield in the intermittent irrigation treatments.

Growth and Physiological Performance of Aerobic and Lowland Rice as Affected by Water Stress at Selected Growth Stages

Aerobic rice technology is still new in Malaysia, and information regarding MARDI Aerob 1(MA1), the first local aerobic rice variety, is still lacking. Therefore, comparative studies were carried out to determine the physiological performance of aerobic rice variety MA1 and lowland rice variety MR253 under water stress given at the panicle initiation, flowering and ripening stages. This experiment was arranged in a randomized complete block design. Stomatal conductance(g_s), chlorophyll a fluorescence(F_v/F_m), leaf relative water content(leaf RWC), and soil moisture content(SMC) as well as yield component parameters such as panicle number, grain yield and 100-grain weight were measured. Results revealed that gs and leaf RWC for both varieties decreased with depletion of SMC. The correlation study between the physiological parameters and SMC indicated that F_v/F_m was not affected by water stress, regardless of varieties. The yield components(panicle number, grain yield and 100-grain weight) for both varieties greatly decreased when water stress was imposed at the panicle initiation stage. This study showed that the panicle initiation period was the most sensitive stage to water stress that contributed to a substantial reduction in yield for both varieties. Under the aerobic condition(control), MR253 produced higher panicle number, 100-grain weight and yield than MA1. Although MR253 is bred for lowland, it is well adapted to aerobic condition.

Performance of Four Rice Cultivars Transplanted Monthly over Full Year under Irrigated Conditions in Tanzania

In Tanzania, the phenology and seasonal variations of the yields of different rice cultivars have rarely been studied, especially under fully-irrigated conditions. A trial was conducted to identify the most suitable calendar for rice production in Tanzania under fully-irrigated conditions. Four popular rice cultivars, NERICA1, Wahiwahi, IR64 and TXD306, were transplanted monthly from January to December 2011. The four cultivars recorded similarly higher or lower yields than the annual means when transplanted in July （0.50-0.57 kg/m2） and April （0.07-0.31 kg/m2）. A yield-ranking analysis showed that plants transplanted in July was the most productive while those transplanted in April was the least productive, and also revealed a yield-seasonality for irrigated rice in Tanzania, a low-yield season （April-May）, a high-yield season （June-August）, and an unstable-yield season （September-March）. These yield seasons would appear to be closely linked to seasonal temperature variations. When transplanted in April-May, plants were exposed to very low temperatures between panicle initiation and flowering, apparently reducing yield through cold-induced sterility. Those transplanted in June-August prolonged their growth under relatively low temperatures and increased yield through increasing biomass production. In September- March, yield levels varied greatly due to the shortened phenological growth durations at higher temperatures. We conclude that under fully-irrigated conditions in Tanzania, rice should be transplanted in July to ensure the maximum production and yield stability. The yield-seasonality suggests that implementing measures to protect plants from low and high temperature stress at critical phenological stages may allow year-round rice production under fully-irrigated conditions in Tanzania.

Effects of Different Transplanting Densities on Yield and Yield Components of Japonica Longke 16

[Objective] This study was conducted to improve unit yield of rice in Longyang District and find the relationship between transplanting density and rice yield. [Method] Under the condition of field plot test, effects of cultivation density on yield and yield components were investigated with japonica rice Longke 16 as a test material. [Result] Under a planting density of 2.7-3.3×10^5 clusters/hm^2, equivalent to a density of seedlings with tillers of 5.4-6.6×10^5/hm^2, the yield reached 11 250-12 000 kg/hm^2. [Conclusion] Longke 16 is a japonica rice variety with good comprehensive characters, and rational dense planting and accurate quantitative cultivation could give full play to its high yield potential.

Identification and mapping of genes for improving yield from Chinese common wild rice (O.rufipogon Griff.) using advanced backcross QTL analysis

To identify useful genes from wild rice which have been lost or weakened in cultivated rice has become more and more important for modern breeding strategy. In this study, a BC4 population derived from 94W1, an accession of common wild rice (Oryza rufipogon Griff.) from Dongxiang in Jiangxi Province of China, as the donor, and a high-yielding Indica cultivar (O. sativa L.), 'Guichao 2', as the recipient, was used to identify quantitative trait loci (QTL) associated with yield and its components. Based on the analysis for the genotype of BC4F1 population with 87 SSR markers distributed throughout the genome and investigation of the plant height, yield and yield components of BC4F2, a total of 52 QTLs, were detected. Of 7 QTLs associated with grain yield per plant, 2 QTLs on chromosome 2 and chromosome 11 for grain yield, explaining 16% and 11% of the phenotypic variance respectively, were identified. The alleles from Dongxiang common wild rice in those two loci could increase the yield of 'Guichao 2' by