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.

Thailand Experience in Developing Wellness-driven Rice as the Key to Fight NCDs and Farmer Poverty

Prevalence of chronic noncommunicable diseases(NCDs)is rapidly increasing and has become a global problem in modern day.Over consumption of simple,processed carbohydrate foods is considered one of the main causes of NCD in young and elderly populations.Whole grain rice is an important source of a complex carbohydrate,dietary fiber,enriched with vitamins,minerals,and antioxidants.However,palatability of brown rice is the key success factor among white-rice-addicted communities.In the initial phase,we successfully breed rice strains with aromatic,soft-whole grain,white rice contains high grain-Fe/Zn density and intermediate glycemic index(GI).The most successful variety was uniquely soft-textured black purple rice named Riceberry,depicting rice enriched with blueberry nutritional characteristics.Product development for fiber-rich,high antioxidant has been extremely active from academia,real sectors,and SMEs.In total,39 patent applications(18 granted patents),12 international publications,and 18,700 Youtubes related to Riceberry.From 2017,Riceberry has become the most popular choice for product development surpassing Thai Hommali Rice.More than 200 food and non-food products were commercialized as dairy replacement,side dishes,meals,hot beverages,bakery,and breakfast cereals.In the second phase,we successfully breed low GI rice strains named Pink+4 equipped with farmers’preferred resistance to flash flooding,bacterial leaf blight,leaf blast,and devastating brown planthopper adapted to organic rice production.Innovative products combined of low GI rice flour with purple Riceberry have been the next trend for functional ingredients and foods.These healthy rice products have high potential globally as healthy foods,gluten-free,fiber-rich,complex carbohydrate,and nutrient-dense from sustainable organic farming.

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.

Morphological and molecular identification of Neopestalotiopsis clavispora causing flower blight on Anthurium andraeanum in Thailand

Flower blight on anthurium(Anthurium andraeanum)was observed during August 2018 on an anthurium cultivation farm in the Songkhla Province of southern Thailand.The fungal isolate was identified as Neopestalotiopsis clavispora based on the morphology and DNA sequence of the internal transcribed spacer(ITS),translation elongation factor 1-α(tef1-α),andβ-tubulin(tub)genes.The phylogenetic tree,based on the combined sequences of ITS,tef1-α,and tub,confirmed this pathogen as N.clavispora.Pathogenicity of the species was confirmed according to Koch’s postulate:N.clavispora could infect anthurium.To the best of our knowledge,this is the first report of N.clavispora as a pathogen of anthurium.

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.

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.