Distribution of Rice Grains on Panicle Axis and Its Relationship with Seed-Setting Ability in Liaoning, China

Studies were conducted with rice varieties developed in recent years in Liaoning Province of China as test materials. Results showed that the varieties tested could be divided into three types： （1） the high-yielding （HYV）, （2） the mediumyielding （MYV）, and （3） the low-yielding （LYV）. The panicle population was in the order of HYV〈 MYV 〈 LYV, while the grain number per panicle and seed-setting rate were just opposite. There was no significant difference in the 1 000-grain weight. Biomass was higher in HYV than in MYV and LYV, while the harvest index was higher in HYV and MYV than in LYV. Yield was inversely correlated with panicle population, but positively correlated with the grain number per panicle, seed-setting rate, the number of primary and secondary branch grains, seed density and harvest index. Yield was most closely linked with the grain number per panicle which was determined chiefly by the number of secondary branch grains and to a lesser degree by seed density and the number of primary branch grains. The seed-setting rate of the secondary branches was positively correlated with that of the whole panicle and yield. The peak value of primary branches for HYV, MYV and LYV was 12-14, 10-13 and 8-12, respectively. LYV had fewer secondary branch grains, while MYV and HYV had more. Such grains distributed mainly in the middle and lower parts of panicle axis for LYV and in the middle and upper parts for MYV and HYV.

Analysis of the Correlation between Seed-setting Characters and Seed Investigation Time in Rice

With super hybrid rice cultivar Y Liangyou 1 as the experimental material, seed-setting rate, abortive grain rate, empty grain rate and 1 000-seed weight were investigated for continuous 10 days since the first day post-harvest to reveal the correlation between differences in seed-setting characters of rice and seed investiga- tion time. The results indicated that seed-setting rate, abortive grain rate, empty grain rate and 1 000-seed weight varied at different seed investigation time. With the postponement of seed investigation, seed-setting rate and 1 000-seed weight showed downward trends, abortive grain rate showed an upward trend, while empty grain rate exhibited a significant correlation with seed investigation time. Seed-setting rate, abortive grain rate and 1 000-seed weight exhibited no significant differences within the first three days after the harvest; since day 4, seed-setting rate and 1000-seed weight declined remarkably, while abortive grain rate increased signifi- cantly. Based on the correlation between seed-setting characters of rice and seed investigation time, the analysis of seed-setting characters of rice and other cereal crops should be completed within the first three days after the harvest, thereby im- proving the accuracy of relative conclusion.

Methods for Improving Hybrid Seed-setting Rate of a Potato Cultivar Linshu 17

[Objective] This study aimed to explore methods for improving hybrid seed-setting rate of a potato cultivar Linshu 17. [Method] L0527-4 was taken as male parent and Linshu 17 was taken as female parent to breed a new potato cul- tivar, so as to take advantage of the excellent characters of Linshu 17. [Result] The optimum pollination time of Linshu 17 was 10：00-12：00 am or after 04：00 pm. Spraying 10 mg/L of 2, 4-D, 50 mg/L of gibberellin or 20 mg/L of 6-BA ＋ 50 mg/L of gibberellin once every 7 days since the 3^rd day after hybridization all could im- prove the hybrid seed-setting rate of Linshu 17. [Conclusion] The hybrid seed-setting rate-improving effect of 2, 4-D sprayed on the 3^rd d after hybridization was best for Linshu 17. This study will provide technical references for other varieties to improve the hybrid seed-setting rate.

Effects of proline on the seed-setting rate of hybrid rice

The seed-setting rate of hybrid rice is general-ly lower than that of conventional varieties.One of the factors explained this phenomenonis the proline concentration in anthers.Fiveconcentrations(30,50,80,120,and240 mg/kg)of exogenous proline were sprayedat meiosis stage of the early hybrid rice combi-nation Shanyou R3-2.Anthers were collected

A New-Nipponbare Rice Germplasm with High Seed-Setting Rate

Rice （Oryza sativa L.） is an important crop providing staple food for more than half the world＇s population and also considered as a model plant for molecular biological study of the cereals. In 1998, the large-scale sequencing of japonica rice cultivar Nipponbare （bred at Aichi Agricultural Center in Japan and released in 1963） was initiated by International Rice Genome Sequencing Project （IRGSP） and the high-quality draft of genome was announced in 2002 （Goff et al,, 2002）. Owing to its easy genetic transformation and released whole genome sequencing data, Nipponbare is widely used in functional genomic research （Piffanelli et al., 2007; Luan et al., 2008; Hu et al., 2010; Thang et al., 2010; Tabuchi et al., 2011; Zhang et al., 2011; Jiang et al., 2012; Lu et al.. 2013）.

Effects of Heat Stress at Vegetative and Reproductive Stages on Spikelet Fertility

Seed-setting rate, yield components and grain quality traits of 169 accessions from an exotic rice germplasm were tested under high temperatures from 40 oC to 45 oC for 6 h during the daytime at the vegetative and reproductive stages, respectively. The results showed that heat stress significantly decreased the seed-setting rate of all the accessions, but the heat stress effects varied among accessions. Based on the decreases in seed-setting rate at high temperatures, N22 was the most tolerant, followed by AUS17, M9962, SONALEE and AUS16. Moreover, the reductions in seed-setting rate and yield under heat stress were more serious at the vegetative stage （45 d before heading） than at the booting stage （15 d before heading）. In addition, heat stress also affected grain quality, especially by conferring chalkiness to most of the accessions, but SONALEE did not change much. The heat-tolerant accessions identified here and the phenotype protocols developed could be used in future genetic studies and breeding programmes focused on heat tolerance.

Seed Setting and Its Spatial Characteristics in Tartary Buckwheat(Fagopyrum tataricum)

A low seed-setting rate is the main limiting factor influencing Tartary buckwheat production under high-yield cultivation conditions.To investigate the seed setting and its spatial characteristics,two Tartary buckwheat cultivars(high seed-setting rate cultivar Qianku 3;low seed-setting rate cultivar Liuku 3)were compared by a two-year field trial in 2017 and 2018.The results showed that the Tartary buckwheat underwent simultaneous flowering and fruiting.Flowers,generated from branch,were still blooming during the mature stage of grains on stem,which resulting in a greater number of flowers and grains on the branch than those on the stem at the low part of plant.The seed-setting characteristics significantly differed between two cultivars.The high seed-setting rate of Qianku 3 was 26.6%and 33.2%higher than Liuku 3 in 2017 and 2018,respectively.Meanwhile,Qianku 3 showed a higher filled grain number(157.8%)and seed-setting rate(66.4%)on branch than Liuku 3.A network analysis showed that the whole-plant seed-setting rate was positively correlated with grain number,which was closely correlated with flower number at the same position of plant.The path-coefficient analysis revealed that grains number on branches was the most dominant component(Path coefficient(P)=2.19)of the seed-setting rate,followed by grains number on stem(P=0.60).The grains number on branches showed the greatest positive direct effect with significant correlation(r=0.76 and P<0.01)on the seed-setting rate.Overall,the present study indicated that the grain number of branches may play a vital role in improving the seed-setting rate in Tartary buckwheat.

Study on Effect of Different Varieties Configuration upon Yield of Yan Mountain Chestnut

In order to improve the yield and quality of 5 new Castanea mollissima varieties “Zipo”, “Zunyu” and traditional Yan Mountain Castanea mollissima cultivars “Duanci”, “Yanhong” and “Donglingmingzhu”, we carried out an experiment to study effect from different varieties configuration on yield of Yan Mountain chestnut. The result indicated that: cross-pollination had a significant impact on both fruiting rate and seed-setting rate;cross-pollination improved the nut number in each burr of each variety, in which “Duanci” was the biggest beneficiary, whose number of nut per burr increased from 1.08 to 2.77, 156% higher than that of the self-pollination combination;nut weight showed no significant difference in Xenia Effection;“Zunyu” improved the yield of “Yanhong” most;“Donglingmingzhu” was regarded as the best tree to improve “Zunyu”’s yield;the best variety to improve yield of “Zipo” was “Zunyu”;“Donglingmingzhu” and “Duanci” improved yield of each other most.

Study on Varieties Combination Suitable for Mutual Pollination of Yan Mountain Chestnut

In order to improve the yield and quality of new varieties Castanea mollissima cv. “Zipo”, Castanea mollissima cv. “Zunyu” and traditional Yan Mountain cultivars Castanea mollissima cv. “Duanci”, Castanea mollissima cv. “Yanhong”, Castanea mollissima cv. “Donglingmingzhu”, an experiment was carried out to study varieties combination that was suitable for their pollination. Fruiting rate and seed-setting rate were used to decide which the most suitable configuration was. The result indicated that: Castanea mollissima cv. “Zunyu” was the best pollination tree for Castanea mollissima cv. “Yanhong”, Castanea mollissima cv. “Zipo” and Castanea mollissima cv. “Duanci”;Castanea mollissima cv. “Duanci” was regarded as the best pollination tree for Castanea mollissima cv. “Zunyu”;the best variety to comply with Castanea mollissima cv. “Donglingmingzhu” was Castanea mollissima “Zunyu” and Castanea mollissima cv. “Duanci”;Castanea mollissima cv. “Zunyu” and Castanea mollissima cv. “Duanci” complied with each other best. Appropriate configuration of pollination varieties turned out to be one of the key measures to improve the yield and quality of chestnut, while irrational combination may even bring the reduction of output.

The Endosperm-Specific Expression of YUCCA Genes Enhances Rice Grain Filling

Grain filling is a crucial process that affects yield in rice(Oryza sativa L.).Auxin biosynthesis and signaling are closely related to rice yield;therefore,it is important to understand the effects of auxin biosynthesis on rice grain filling to improve crop yield.In this study,we used physiological and molecular strategies to identify the roles of auxin in rice grain filling.Exogenous application of auxin(IAA)or auxin analogues(2,4-D)to young spikelets and flag leaves improved the seed-setting rate and yield per spike.Furthermore,real-time quantitative PCR assays confirmed that nine members of the OsYUCCA family of auxin biosynthetic genes were upregulated during grain filling,implication that auxin biosynthesis plays a major role in grain development.The specific expression of either Arabidopsis AtYUCCA1 or OsYUCCA2 in the endosperm or leaves resulted in increased expression of OsIAA genes and auxin content of seeds,as well as increased grain filling and seed-setting rate.This result establishes that the auxin content in grains and leaves is important for grain development.Our findings further highlight the potential applications for improving rice yield by elevating targeted gene expression in specific tissues.

A synthetic light-inducible photorespiratory bypass enhances photosynthesis to improve rice growth and grain yield

Bioengineering of photorespiratory bypasses is an effective strategy for improving plant productivity by modulating photosynthesis.In previouswork,two photorespiratory bypasses,theGOC andGCGT bypasses,increased photosynthetic rates but decreased seed-setting rate in rice(Oryza sativa),probably owing to excess photosynthate accumulation in the stem.To solve this bottleneck,we successfully developed a newsynthetic photorespiratory bypass(called theGMAbypass)in rice chloroplasts by introducing Oryza sativa glycolate oxidase 1(OsGLO1),Cucurbita maxima malate synthase(CmMS),and Oryza sativa ascorbate peroxidase7(OsAPX7)into the rice genome using a high-efficiency transgene stacking system.Unlike the GOC and GCGT bypass genes driven by constitutive promoters,OsGLO1 in GMA plants was driven by a light-inducible Rubisco small subunit promoter(pRbcS);its expression dynamically changed in response to light,producing a more moderate increase in photosynthate.Photosynthetic rates were significantly increased inGMA plants,and grain yieldswere significantly improved under greenhouse and field conditions.Transgenic GMA rice showed no reduction in seed-setting rate under either test condition,unlike previous photorespiratory-bypass rice,probably reflecting proper modulation of the photorespiratory bypass.Together,these results imply that appropriate engineering of the GMA bypass can enhance rice growth and grain yield without affecting seed-setting rate.

Do different measures of maternal fitness affect estimation of natural selection on floral traits? A lesson from Linum pubescens (Linaceae)

Aims Floral traits in animal-pollinated plants are proposed to be selected by the behavior of pollinators,which create differential fitness.However,fitness estimation is not trivial and there is no agreed or universal measure of fitness.in plants,fitness can be measured in various ways,including the number of fruits or seeds,probability of survival,or growth rate.Methods Because each fitness measure can be associated with different pol-linator behavior,estimating pollinator-mediated selection on floral traits can differ among various fitness measures.We used the annual Mediterranean plant,Linum pubescens,as a model to assess the relative role of various fitness measures in estimating pollinator-mediated selection on floral traits.We compared four maternal fit-ness measures and estimated their relative advantage in assessing natural selection on floral traits of L.pubescens.To identify whether each trait is under pollinator-mediated selection,we used media-tional analysis.Important Findings We found that each floral trait was under natural selection assessed by a different fitness measure.The color combination of floral tube throat and stamen color was under selection when using seed mass as a fitness measure,and floral diameter was under positive direc-tional selection when the number of seeds or number of fruits was used as a fitness measure.Selection on floral color was not mediated by pollinators’visitation rates,while flower diameter showed par-tial pollinator-mediated selection.We conclude that using several fitness measures gives an insight into the mechanisms underlying phenotypic selection on a floral trait,and facilitates the understand-ing of pollinator-mediated selection.