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【Objective】The present paper aimed to illustrate the potential utilization of the gene of resistance to bacterial blight and bacterial leaf streak, so as to provide reference for enriching genetic base of rice breeding.【Method】A total of 102 rice cultivars were used to screen by molecular marker for the gene xa5, which mediated the resistance for both for resistance to bacterial blight and bacterial leaf streak. The parents carrying xa5 gene and having good resistance to bacterial blight and bacterial leaf streak were used as resistant sources to cross with susceptible cultivated rice. Through pedigree method and molecular marker-assisted selection（MAS）, elite hybrid rice restorer lines were cultivated. The excellent restorer lines and sterile lines were combined with strong heterosis combinations to analyze the resistance and comprehensive agronomic traits of strong heterosis combinations.【Result】A total of 17 cultivars were screened, which carried xa5 gene from 102 rice germplasm resources（materials）. Among these cultivars, DP3, IRBB5, N36, N776, N777, N779 and P89 were well resistant to both bacterial blight and bacterial leaf streak. An elite line Y240-1 was selected from the cross between DP3 and 9311. Moreover, 998 R was crossed with elite individual Y240-1. With molecular MAS, an elite restorer line Yexiangzhan with xa5 was developed from the cross of 998 R and Y240-1, after multiple generations of selfing. Yexiangzhan was combined with sterile line Pingfeng A to produce an elite hybrid cultivar Pingfengyouxiangzhan, which showed higher resistance to bacterial blight and bacterial leaf streak in comparison with Pingfeng A. Pingfengyouxiangzhan was resistant to rice blast at moderate level and meet the 2nd class standard of fine quality issued by Ministry of Agriculture of China.【Conclusion】xa5 gene with resistance to bacterial blight and bacterial leaf streak of rice has partial dominant effect, which can be used for breeding improvement of hybrid rice; It is helpful to enrich and broaden the genetic basis of rice breeding by cultivating the superior hybrid combinations of rice with moderate resistance to bacterial blight and stripe disease with wild rice blood. [ABSTRACT FROM AUTHOR]

[Objectives] The paper aims to clarify the dry matter accumulation and translocation of nutrient of rice plant under different soil tillage systems in a Chinese milk vetch(Astragalus sinicus L.) and double-cropping rice system. [Methods] The effects of different soil tillage systems on the dry matter accumulation and translocation of nitrogen(N), phosphorous(P) and potassium(K) of early and late rice plants by small area plot experimental method in double-cropping rice paddy field were analyzed in the present paper. The experiments were including four different soil tillage treatments:conventional tillage with residue incorporation(CT), rotary tillage with residue incorporation(RT), no tillage with residue retention(NT), rotary tillage with residue removed as a control(RTO). [Results] The results showed that the total dry matter accumulation of aboveground in different parts of rice plant and the amount of translocation of stem and leaves with RT and CT treatments were higher than those of the other treatments at mature stage of early rice and late rice. And the material translocation rate and material contribution rate of stem and leaves with CT, RT and NT treatments were higher than those of the RTO treatment at mature stage of early rice and late rice. Meanwhile, the contribution rate of material assimilation after heading stage with NT treatment was higher than that of the other treatments of early rice and late rice. The N accumulation amount in stem of rice plant with RT treatment was higher than those of the CT, NT and RTO treatments, and the N accumulation amount in panicle and aboveground of rice plant with CT, RT and NT treatments was higher than those of the RTO treatment at mature stage of early rice and late rice, respectively. And the P accumulation amount in stem and leaves of rice plant with CT and RT treatments was higher than those of the NT and RTO treatments, and the P accumulation amount in panicle and aboveground of rice plant with CT, RT and NT treatments was higher than those of the RTO treatment at mature stage of early rice and late rice, respectively. Meanwhile, the K accumulation amount in stem and aboveground of rice plant with CT and RT treatments was higher than that of the RTO treatment, and the K accumulation amount in leaves and panicle of rice plant with CT treatments was higher than that of the RTO treatment, respectively. [Conclusions] As a result, the total dry matter accumulation of aboveground in different parts of rice plant and the amount of translocation of stem and leaves were higher under application of residue incorporation, it is benefitial to the nutrients accumulation and translocation of rice plants by combined application of crop residues with soil conventional tillage, rotary tillage practices under double-cropping rice system in Southern China paddy field. [ABSTRACT FROM AUTHOR]

Heat stress is a common agrometeorological disaster during rice production in the middle and lower reaches of Yangtze River of China, and rice yield decreases due to the heat stress. Exogenous chemical solutions have been sprayed on rice leaves to improve the heat tolerance of rice and reduce the damage during the heat stress. This paper was aimed to evaluate the effects of 3 different exogenous chemical solutions on photosynthesis, chlorophyll fluorescence characteristics of flag leaves and rice yield under the heat stress condition. Pot experiments were conducted at Agricultural Meteorological Experimental Station of Nanjing University of Information Science and Technology (32.2°N, 118.7°E), in China in the year of 2016 and 2017. Early indica hybrid rice variety named Lingliangyou 268 (Oryza.sativa L.) was used in the experiments. High temperature treatments were conducted at late jointing stage (20th June, 2016) and late booting stage (5th July, 2017), respectively. Before the high temperature treatment, 3 different chemical solutions, including KH2PO4 (T1) solution with concentration of 22.04 mmol/L , CaCl2 solution (T2) of 20.0 mmol/L and Na2SiO3·9H2O solution (T3) of 2.5 mmol/L, were sprayed separately and evenly on all leaves for 3 days. For comparison, distilled water was sprayed as the control treatment (CK). After that, all treatments were put in climate chambers for 5 days to simulate a severe heat-stressed environment during the rice key stages, in which (40±0.5) °C from 6:00-18:00 was set as daytime temperature and (30±0.5) °C from 18:00 to 6:00 next day was set as nighttime temperature with an average of 35 °C in each day. In 2017, the photosynthetic light response curve and chlorophyll fluorescence of flag leaves of different treatments were measured at the 5th day of the heat-stress treatment and the 5th day after heat-stress respectively. The parameters related to the photosynthetic light response characteristics, such as the light saturation point (LSP), light compensation point (LCP), apparent quantum yield (AQY), dark respiration rate (Rd) and maximum net photosynthesis rate (Pmax) were calculated on the basis of observed data. And the chlorophyll fluorescence parameters, such as the maximum photochemical efficiency(Fv′/Fm′) of photosystem II (PSII) under light adaptation, actual photochemical efficiency (ΦPS II ) of PSII, photochemical quenching coefficient (qP) and non-photochemical quenching coefficient (NPQ) were also calculated. The final yields were observed too. The results showed that, compared with CK, all 3 chemical solutions were able to increase the photosynthetic activity, particularly to raise the LSP, Pmax, Fv′/Fm′, ΦPSII, and qP of flag leaves, and the NPQ was reduced. Furthermore, based on the evaluation by the subordinate function, it indicated that all 3 chemical solutions demonstrated positive effects on the resistance of rice leaves to heat stresswith the effect order of T1>T2>T3. In the terms of yield, when compared with CK, the yields of T1, T2 and T3 increased by 42.67%, 29.70% and 20.01%, respectively. It was demonstrated that spraying KH2PO4, CaCl2 and Na2SiO3·9H2O chemical solutions were beneficial to promote photosynthetic activity of rice flag leaves and significantly increased the rice yield. [ABSTRACT FROM AUTHOR]

Rice is the most important food crop in China. Rice seed vigor is a complex quantitative trait controlled by multiple genes and it is of great significance to improve rice seed vigor for high yield, quality and efficiency of production under direct seedling rice. This paper reviewed the main research advances including evaluation index, gene identification and cloning, molecular regulation mechanism relate to rice seed vigor in recent years. Based on the molecular markers and map-based cloning, genome-wide association study(GWAS), high throughput sequencing, and omics techonology, more than twenty-three key genes related to seed vigor have been cloned, including transcription factor genes, metabolism-related genes of plant hormone ABA and GA. Through the balance of ABA and GA metabolism, it regulates maturing of embryos, seed dormancy and germination, seedling growth. It will be very helpful to improve genetics of rice seed vigor by molecular design breeding technology in the future. [ABSTRACT FROM AUTHOR]