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The present study aimed to determine the effect of different organic and inorganic source of fertilizers on growth and performance of rice. The experiment was conducted at two locations: Tinh Bien and Tri Ton AnGiang province with two varieties of landrace rice with AG3 and AG4. Each experiment has seven treatment. Treatments included a combination of organic and inorganic nutrients at sevenrates (F1:80-40-40+ organic manures 10 t ha-1;F2:60-40-40+ organic manures 10 t ha-1;F3: 40+40+40+ organic manures 10 t ha-1;F4: 20-40-40+ organic manures 10 t ha-1. F5:only organic manures 12 t ha-1; F6: control no dose of NPK;F7: farmers used: 120-40-60+ organic manures 12 t ha-1). The experiment is arranged on the farmer's field, a split-plot in a randomized complete block design with three replications. Treatments produced significant results for plant height. Panicle length and grain yield but thousands grains weight was not significant. Result showed that application of half of recommended 60-40-40 + organic manures 10 t ha-1 produced significantly higher value for grain yield and good for quality lance rice.

Landrace rice genotypes AG4 were evaluated inTri Ton, Tinh Bien, AnGiang Province with three replications in a field experiment during 2019 to 2020. The analysis revealed significant differences among the genotypes against all the characters studied. In general, phenotypic variance is higher than the corresponding genotypic variance for all the characters studied. AG4 rice is considered as the unique landrace varietal group because of its aroma and superior grain quality.To confirm the presence or absence of fragrance in AG 4,a set of 11 lines was phenotypedby using gas chromatographic separation to quantify 2AP content in milled rice samples. KOH tested and PCR method with two directives RM223 and FMU1-2 are recorded to select the lines with the best fragrance followed by line7, 10 ,14 and 20.The shape is determined by the length and width ratio.From shape evaluation, length and width ratio of AG4 are high. Level of chalkiness is. There are mostly low contents on AG4, when doing rice quality analysing. It is the evidence for the deliciousness on rice. Milling quality determines the final yield and fracture rate of milled rice. Recorded line 7 for high milling rate is over 50%. Protein content of rice varieties ranges from 6.9 to 8.6%. Lines 7 and 56 have the highest protein content (8.5-8.6%). Characters like number of panicles per plant, panicle weightg, number of grains per panicle, and grain yield recorded are high. Grain yield analysis revealed significant differences among lines. Selected AG4, lines number 7 can be used in breed selection program in the nearest future to provide the local need.

BackgroundOryza sativa L. contains two cultivated subspecies, indica and japonica, which are considered to be derived from wild rice relative, O. rufipogon. Although domestication cinario of O. sativa has been extensively studied, it is still inconclusive and contradictory. Moreover, it remains to be revealed why O. rufipogon had acquired wide range of genetic diversity to fit various habitat and life cycle of plant from annual to perennial.ResultsAlthough O. rufipogon distributes in southeast Asia from Indonesia to India, perennial wild rice strains were distributed in deep-water area of the Mekong Delta in Southern Vietnam. Some of wild rice strains collected in Dong Thap were heterologous in the length of intron 20 sequence of single-copy nuclear PolA1 gene, encoding for the largest subunit of RNA polymerase I. Thus, these wild rice strains were probably considered as interspecific hybrids, because the S-type (0.14 kb) intron 20 was found in O. rufipogon, O. glumaepatula, and O. barthii while L-type (1.5 kb) was shared by O. longistaminata and O. meridionalis. Therefore, we identified two wild rice strains that contained homologous L-type intron 20 of PolA1 gene in the CLRRI collection. These two strains, named as MD1 and MD2, had fertile spikelet with long anthers which were typical feature of African O. longistaminata. In addition, MD1 strain and O. longistaminata shared the same protein tag (Ptag) sequence, which was different to that of O. rufipogon and O. sativa. Interestingly, MD1 strain contained plastid DNA with a 69-bp deletion in ORF100 which was shared with indica and annual O. rufipogon, but not with japonica and perennial O. rufipogon. ConclusionWe have identified that MD strains found in the Mekong Delta were probably O. longistaminata-like cryptic species and contributed to enlarge genetic diversity of O. rufipogon, and is probably involved in the origin of O. rufipogon indica ancestor of as the maternal lineage.

Oryza rufipogon Griff. is a perennial species of wild rice widely distributed along the channels and rivers of the Mekong Delta, Vietnam. This study attempted to find centers of diversity among wild rice populations in this area and their inter‐relationships. The highest genetic diversity was found in the Dong Thap population and the lowest in the Can Tho population. Maternal diversity evaluated using chloroplast INDELs detected ten plastid types, five of which were novel relative to other Asian countries. The mitochondrial genome suggested two unique deletions. One 699‐bp deletion via short tandem repeats was accompanied by another deletion including orf153. All accessions carrying the mitochondrial type were found in a particular plastid type. This unique maternal lineage was confined to specific channels where it showed vigorous vegetative growth in comparison to upstream areas where various maternal lineages and maximum genetic diversity occurred. This area along the Mekong Delta is a center of not only nuclear but also maternal diversity.

Chalkiness is a major constraint on rice production because it is one of the key factors determining grain quality (appearance, processing, milling, storing, eating, and cooking quality) and price. In this study, we conducted grain chalkiness gene identification using co-dominant insertion/deletion (INDEL) markers and SSR marker combination on 50 different varieties. The application results in 7 InDel markers and SSR marker on chromosome 7 were recorded. Three primers, InDel 5, InDel 14 and RM21938, associated with grain chalkiness. For the InDel 5 primer, the amplification product was 100%. Use of primer InDel 5 in detection and evaluation of genotype to the chalkiness trait of rice grain on 50 rice varieties indicated the suitability level with phenotypic evaluation was 86% and the unsuitability level was 14%. For the InDel 14 primer, the amplification products were 100%. The suitability with phenotypic assessment was 84% and the unsuitability was 16%. For the RM21938 primer, the amplification product was 94%. The suitability with phenotypic assessment was 76% and the unsuitability was 24%. Thirteen of the selected varieties had grain chalkiness gene both InDel 5, InDel 14 and RM21938. Total 13 varieties were detected from InDel 5, InDel 14 and RM12938 primer combinations also showed high efficiency of the InDel technique in identifying chalkiness gene in rice grain. A cluster analysis was performed and a dendrogram was constructed which evinced the nature of phylogenetic classification among the genotypes of the varieties. These markers could be used for developing quality of rice in breeding program.

Salinity affects rice growth in all growth stages, with the seedling and reproductive stages being the most sensitive. Genetically improving salt tolerance of rice is an important objective of rice breeding programs. Hence, mapping quantitative trait loci (QTL) will be useful for marker-assisted selection in rice breeding programs. An advanced backcross population (BC2F2) was developed with the parents included OM5629 as a donor of salt tolerance and OM7347 as a recurrent parent with good quality traits and drought tolerance. Molecular markers associated with both qualitative and quantitative trait loci (QTL) salt tolerance were identified by using 416 polymorphic SSR markers. QTLs, associated with stress tolerance at EC = 15 dS/m at seedling stage, detected from the BC2F2 population of OM7347/OM5629, were located on chromosomes 1 and 3. Three QTLs were identified at the intervals of RM3252-S1-1 - RM10694, RM3740-RM5336 and RM11125-RM9 with genetic distance of 4.4, 4.5 and 18 cM on chromosome 1, respectively. Two QTLs at the intervals of RM3867-RM6959 and RM6876-RM4425 with genetic distance of 4.5 and 18.0 cM on chromosome 3, respectively. One QTL on chromosome 5 was detected at the interval of RM874 - RM10359, it was associated with salt stress tolerance under EC = 8dS/m at vegetative stage. Three QTLs at the regions of RM1324-RM2412, RM1185-RM24, and RM1282-RM2560 on chromosome 1, and one QTL of RM453-RM511 on chromosome 12, were related to salt tolerance under EC = 8dS/m at reproductive stage. Two tightly linked markers as RM3252-S1-1 and RM3867, were exhibited their effectiveness in identification of salt tolerance genotypes in BC3F6 population of OMCS2000/ Pokkali. The identification of new QTLs associated with salt tolerance will provide important information for the functional analysis of rice salinity stress.

Development of drought tolerant high-yielding varieties is essential because increased areas are subject to drought in the Mekong delta, Vietnam. The purpose of this experiment was developed using IR75499-73-1-B as drought tolerant donor and OMCS2000 as a recipient parent basis of a phenotypic and molecular marker for BC2F2 generation. Seven markers (RM219, RM201 RM105, RM23602, RM23877, RM24103 and RM328) were used for a idifying to drought tolerant. Primer RM23877 detected the highest number of lines as homozygous donor alleles (11 lines), followed by RM105 and RM201 (9 lines). The drought gene was introgressed into the new breeding lines. The plant height, number of tillers, and filled grain had positive correlation with yield/hill under drought stress. The lines BC2F2-45 and BC2F2-54 developed as drought tolerant, and gave high yield. This is an opportunity to improve breeding for high yield and drought tolerant rice varieties in Vietnam.

In this study, the correlation coefficients among agro-morphological variation, genetic diversity, and drought tolerance in 44 rice cultivars were analyzed. The drought tolerance at seeding stage (DTS) was significantly proportional to drought tolerance at vegetative stage (DTV) (r = 0.60). In addition, DTS and DTV had strong significant positive correlation to leaf roll (r = 0.87 and 0.54, respectively). Means of unfilled grains and tilling per panicle were proportionally correlated to DTS (r = 0.22 and 0.25, respectively), and DTV (r = 0.20 and 0.36, respectively). However, weight of 1000 grains and filled grains recorded no correlation to DTS and DTV. At a homologous coefficient of 16.85 integrated from cluster analysis of agro-morphological, quantitative characteristics and drought tolerant scores, the rice was divided into five groups. Maximum PIC (polymorphic information content) values were detected in three markers including RM11125, RM21, and RM5629, which were between 0.78-0.79. Cluster analysis of microsatellite markers revealed that by a genetic distance of 0.63, the rice varieties were separated into three clusters. The results provide valuable information for rice breeders to select donors in breeding rice integrated with drought tolerance and good agronomic characteristics.

Present study was performed to analysis both physical and chemical properties of rice germplasm and heritability for yield components in combinations. A total of 44 lines/varieties obtained from Cuu Long Rice Research Institute genebank, and 30 F1 generation combinations were evaluated. The results showed that the rice line IR79008-B-11-B-B-1 showed overall good physical characters (head rice, grain length, grain width, chalkiness). In terms of chemical characteristics, three varieties IR75499-73-1-B, OM6162, and OM4900 were found to have good amylose content, gel consistency, protein content, gelatinization temperature, and aroma. A very notable finding was that the cross between OM6162/SwarnaSub1 that low amylose content (20.2%), high gel consistency (78.2 mm), high protein content (8.1%), appropriate gelatinization temperature (scale 5), low chalkiness (level 0), high heritability (0.9) for grain yield trait/cluster, and (0.84) for the number of panicles/cluster. Moreover these characters consist of plant height, panicles lenght, number of panicles/cluster, number of filled grains/panicle, number of unfilled/panicle, and grain yield/ cluster showed moderate to high heritability of mean for combination OM6162/SwarnaSub1. The results suggest that the grain yield trait/cluster and the number of panicles/cluster are important yield contributing traits to rice breeders for selecting ideal combinations for higher yield and quality of next generations.

Soybean production in Vietnam has recently been threatened by the widespread dissemination of soybean rust (SBR) caused by the fungus Phakopsora pachyrhizi. Application of molecular breeding is considered as a feasible method to improve soybean rust resistance and minimize the adverse effects from overuse fungicides in this country. In this study, we have successfully applied molecular markers in a backcross breeding program to introgress the Rpp5 gene of SBR resistance into HL203, an elite Vietnamese soybean variety, from two donor lines of DT2000 and Stuart 99084B-28. The plants in BC4F1 generation had maximum contribution from the recurrent parents and retained SBR resistance gene.

This article 'Combining Ability and Heterosis for Some Physiological Traits in Rice' appeared in the International Rice Research Notes series, created by the International Rice Research Institute (IRRI) to expedite communication among scientists concerned with the development of improved technology for rice and rice-based systems. The series is a mechanism to help scientists keep each other informed of current rice research findings. The concise scientific notes are meant to encourage rice scientists to communicate with one another to obtain details on the research reported.

This article 'Genetic Nature of Some Agronomic Traits in Two Elite Lines of Rice' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.

This article 'Genetic Studies in the F2 of Crosses for High Grain Quality' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.

This article 'Genetic Studies of Seed Dormancy in High Grain Quality Cultivars' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.

This article 'Yield Evaluation of Major Indigenous Rice Varieties Grown on Cuu Long Delta' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.

This article 'Deep Water Rice Yield Trials on the Cuu Long Delta' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.

This article 'Path Analysis of Rice Grain Yield Under Saline Conditions' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.

This article 'Genetic Diversity in Rice Oryza sativa L' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.