Screening for Spikelet Fertility and Validation of Heat Tolerance in a Large Rice Mutant Population

A total of 10 000 M4 individuals in Jao Hom Nil (JHN) mutant population was treated with high temperature (40 ℃ to 45 ℃) during the day time (6 h) from the booting to the harvesting stages, and ambient temperature (33 ℃ to 35℃) was used as the control. The results of screening and yield trials found that the mutant line M9962 had a high spikelet fertility of 78% under heat stress. In addition, the other mutant lines, including M3181 and M7988, had a spikelet fertility of approximately 70%. However, the JHN wild type, Sin Lek, RD15 and RD33 had very low spikelet fertility of 34%, 14%, 9% and 4%, respectively. The lower spikelet fertility at an elevated temperature resulted in a dramatic decrease of filled grain and contributed to a loss in 100-grain weight. M9962 is a potential genetic stock for use in a heat tolerance breeding programme. In addition, spikelet fertility at high temperature was representative of heat tolerance and can be used as a screening trait for heat tolerance during the reproductive phase on a large scale.

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.

Mining and validation of novel genotyping-bysequencing(GBS)-based simple sequence repeats(SSRs)and their application for the estimation of the genetic diversity and population structure of coconuts(Cocos nucifera L.)in Thailand

Coconut(Cocos nucifera L.)is an important economic crop in tropical countries.However,the lack of a complete reference genome and the limitations of usable DNA markers hinder genomic studies and the molecular breeding of coconut.Here,we present the results of simple sequence repeat(SSR)mining from a high-throughput genotyping-bysequencing(GBS)study of a collection of 38 coconut accessions.A total of 22,748 SSRs with di-,tri-,tetra-,penta-and hexanucleotide repeats of five or more were identified,2451 of which were defined as polymorphic loci based on locus clustering in 38 coconut accessions,and 315 loci were suitable for the development of SSR markers.One hundred loci were selected,and primer pairs for each SSR locus were designed and validated in 40 coconut accessions.The analysis of 74 polymorphic markers identified between 2 and 9 alleles per locus,with an average of 3.01 alleles.The assessment of the genetic diversity and genetic relationships among the 40 coconut varieties based on the analysis of population structure,principal coordinate analysis(PCoA),and phylogenetic tree analysis using the 74 polymorphic SSR markers revealed three main groups of coconuts in Thailand.The identified SSR loci and SSR markers developed in this study will be useful for the study of coconut diversity and molecular breeding.The SSR mining approach used in this study could be applied to other plant species with a complex genome regardless of the availability of reference genome.

Evaluation of Agronomic Traits in Chromosome Segment Substitution Lines of KDML105 Containing Drought Tolerance QTL under Drought Stress

Drought is a major abiotic constraint to rice production in rainfed lowland and insufficiently irrigated areas. The improvement of drought tolerant varieties is one of the strategies to reduce the negative effects of drought. Quantitative trait loci （QTLs） for primary and secondary traits related to drought tolerance （DT） on chromosomes 1, 3, 4, 8 and 9 that determined from double haploid lines derived from a cross between CT9993 and IR62266 were introgressed and dissected into small pieces in the genetic background of Khao Dawk Mall 105 （KDML105） to develop chromosome segment substitution line （CSSL） population. The CSSLs were evaluated at the reproductive stage for their agronomic performance and yield components under drought stress, and results were compared with irrigated condition. The flowering of CSSL lines was 6 to 7 d earlier than KDML105. The mean values of grain yields in the CSSLs were higher than KDML105 under drought and irrigated conditions. At irrigated condition, the grain yields of introgression lines carrying DT-QTLs from chromosomes 4 and 8 were higher than that of KDML105, whereas other traits showed little difference with KDML105. Analysis indicated that grain yield has positive correlation with plant height, tiller and panicle number per plant, and total grain weight per plant under drought stress while negatively correlated with days to flowering. As mentioned above, CSSLs showing good adaptation under drought stress can be used as genetic materials to improve drought tolerance in Thai rainfed lowland rice breeding program, and as materials to dissect genes underlying drought tolerance.

以抗击非传染性慢性疾病和农民贫困为关键点的健康驱动下泰国大米发展经验

近年来,非传染性慢性疾病的发病率迅速上升,已成为一个全球性的问题。过度食用简单的加工碳水化合物食品被认为是导致年轻人和老年人罹患非传染性慢性疾病的主要原因之一。全谷物米是碳水化合物、膳食纤维的重要来源,富含维生素、矿物质和抗氧化剂。然而,糙米的适口性是其在长期以白米消费为主的人群中被接受的关键因素。在初始阶段,我们成功培育出了水稻品种,其全谷物米芳香、柔软且白米具有较高的铁锌密度和中血糖指数(GI)。最成功的品种是独特的具有较软质构的黑紫色稻米,名为紫莓香米(Riceberry),富含蓝莓花青素等营养物质的稻米。针对富含膳食纤维、高抗氧化活性的稻米产品研发一直是学术界、实体部门和中小企业极为活跃的领域,目前共有关于紫莓香米相关的39项专利申请(18项已授权专利)、12项国际出版物、以及18700个与紫莓香米有关的YouTube视频。从2017年开始,紫莓香米已超越泰国Hom茉莉香米(Thai Hommali Rice)成为最受欢迎的产品开发选择原料,已有超过200种作为乳制品替代品、配菜、主餐食品、热饮料、烘焙食品和早餐麦片等的商业化食品和非食品产品。在第二阶段,我们成功地培育出了名为Pink+4的低血糖指数水稻品种,该品种具有对骤发洪水、水稻白叶枯病、稻瘟病和破坏性褐飞虱的首选抗性,适用于有机水稻生产。以紫色紫莓香米为原料的低GI米粉创新产品已成为功能性配料和功能性食品的下一个发展趋势。这些健康的稻米产品在全球具有较好的发展潜力,可以作为健康食品、无麸质、富含纤维、复杂碳水化合物和可持续有机农业的营养密集型产品。

Characterization of Myanmar Paw San Hmwe Accessions Using Functional Genetic Markers

Paw San Hmwe （PSM） rice has been cultivated in many areas of Myanmar for a long time. Strong aroma, good taste and its elongation during cooking are the key characteristics of PSM rice. Thirty-one PSM accessions were genotypically characterized, and their physical grain and cooking quality traits were studied. We used specific gene markers associated with aroma, apparent amylose content （AAC） and alkali spreading value to determine the alleles carried by different PSM accessions. The results revealed that six PSM accessions （PSM10, PSM12, PSM13, PSM21, PSM22 and PSM30） had a 3-bp insertion in Os2AP gene. Gel consistency （GC） allele was predominant among the PSM accessions for gelatinization temperature （GT）, however, the phenotype observed was between low and intermediate GT because of the combination of the GC allele with the presence of low GT allele at heterozygous state from the other loci of the SSIla gene. Intermediate to high AAC was observed among the PSM accessions corresponding to the haplotype identified for the single nucleotide polymorphism G/T and the （Cm）n repeat in the Wx gene. The characterization and grouping data of PSM accessions posted benefits to Myanmar seed banks, and our results will help in maintaining the integrity of PSM rice variety.

国际约稿背景介绍(Ⅱ)

2019年12月15日-18日,由国家粮食和物资储备局科学研究院主办,山东省粮食和物资储备局、滨州市人民政府协办的“2019国际粮食营养改善经验交流研讨会”在中国山东滨州成功召开。我们特邀了大会报告专家泰国农业大学Kamphangsaen农业学院Apichart Vanavichit教授、水稻基因发现和水稻科学中心主任为本刊专门撰写《以抗击非传染性慢性疾病和农民贫困为关键点的健康驱动下泰国大米发展经验》(英文),综述了自2000年以来泰国启动的紫莓香米(Riceberry)研究发展项目取得的系列成效和持续进展。