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Rice (Oryza sativa L.) is a principle crop with great economic importance in Vietnam, providing daily food for over 90 million people in this country. However, a large rice growing areas and rice production are being seriously affected by the threats of devastation from climate change. The need to develop salinity tolerance rice varieties to cope with adverse climate change is very imperative. In this study, based on the genome sequence databases of 36 Vietnamese rice landraces, we have identified 9 Vietnamese rice landraces carrying nine SalT candidate gene with the sequence similarity to O. sativa SalT (the published GenBank: Z25811.1) which have shown salinity tolerance are: Te Nuong, Khau mac buoc, Chan thom, Khau giang, Tan ngan, Nang thom cho dao, OM5629, Hom rau and Thom Lai). Amongst them, 4 rice landraces including Nang thom cho dao, OM5629, Hom rau and Thom lai have shown 2 fragments of deletion with 6 and 7 nucleotides which were most identical to the reference SalT gene. Two primers has been successfully designed to identify the SalT candidate gene in Vietnamese rice landraces. This study provides useful information of salinity tolerance of some Vietnamese rice landraces for breeding programs.

Submergence stress regularly influences about 15 million hectares of rice growing areas in South and Southeast Asia. Vietnam is one of the most vulnerable countries affected by submergence stress in Asia. Submergence caused by typhoons and floods is one of the major reasons for rice production losses in this country. A majorquantitative trait locus (QTL) on chromosome 9, SUB1, has provided the opportunities to apply marker-assisted backcrossing (MABC) to develop submergence tolerant for an elite variety that is popularly grown in Vietnam. Improving rice tolerance with submergence is vital to minimize the risks from submergence stress. In this study, we reported a successful application of MABC method to select a line number 19 in BC2F1populations that has genetic background up to 89.8%. Key words: Bac Thom 7 (BC7), marker-assisted backcrossing (MABC), submergence tolerance.

This paper presents a method of using Cellular Neural Network (CNN) for solving hydraulic Navier-Stokes equations, which are a set of three partial differential equations with 3 functional variables and each function has three variables for time and space. The paper has 5 parts: part 1 is the introduction; Part 2 discusses the Navier-Stokes for flow through narrow slots; Part 3 analyzes and finds templates for designing CNN architecture; Part 4 provides some solutions for optimizing resources and speeding up computing; Part 5 sets up CNN chip for implementing and computing results; the last part is conclusion and developing trends.

A new QTL for spikelets per panicle (SPP) was detected on the long arm of chromosome 7 in an F2 population derived from a cross between the japonica cultivar Hwaseongbyeo and WH29001. WH29001, an advanced backcross line was developed by introgressing chromosomal segments from an accession of O. minuta (2n = 48, BBCC, Acc. no. 101141) into the O. sativa subsp. japonica cv. Hwaseongbyeo. The O. minuta allele increased SPP in the Hwaseongbyeo background despite the fact that O. minuta was the small panicle parent. Using F3 and F4 progenies, spp7 was validated and mapped to a 2.3 Mb region in the interval between the SSR markers RM445 and RM21615 based on the japonica genome sequence. A yield trial using F4 lines indicated that the lines carrying an O. minuta chromosome segment across the entire spp7 target region out-yielded its sister lines containing Hwaseongbyeo chromosome in the target region and Hwaseongbyeo by 14.3% and 15.9%, respectively. Increase in SPP in WH29001 was mainly because of the increase in primary branches per panicle. The locus, spp7 is of particular interest because of its independence from undesirable height and flowering time. SSR markers tightly linked to the spp7 will facilitate cloning of the gene underlying this QTL as well as marker-assisted selection for variation in SPP in an applied breeding program.

An advanced backcross line, WH29001, was produced from a single plant from BC5F3 families derived from a cross between Oryza minuta (2n = 48, BBCC, Acc. No. 101141) as a donor parent and the O. sativa subsp. japonica cv. Hwaseongbyeo as a recurrent parent. Although WH29001 resembled Hwaseongbyeo, several traits were different from those of Hwaseongbyeo, including awn length and heading date. These differences between Hwaseongbyeo and WH29001 could be attributed to the introgressed O. minuta chromosome segments into WH29001. SSR analysis enabled to identify thirteen O. minuta-specific chromosome segments in WH29001 genome. To map and characterize QTLs for awn length and heading date, an F2:3 population from the Hwaseongbyeo/WH29001 cross was developed. The 197 F2 plants and 197 F3 families were evaluated for the two traits and the genotypes of the 197 F2 plants were determined using eighteen SSR markers located in the introgressed segments from O. minuta. QTL analysis identified two QTLs each for days to heading and awn length on chromosomes 6 and 9, respectively. The total phenotypic variance explained by these four QTLs ranged from 8.1% to 51.0% in the F3 population. Interestingly, QTLs for heading date and awn length were colocalized on chromosomes 6 and 9, respectively. Among these QTLs identified, the QTLs for heading date (dth9) and awn length (awn6) had not been detected in previous QTL studies between Oryza cultivars, indicating the existence of potentially novel alleles from O. minuta. The QTLs detected in the present study could become a valuable source of natural genetic variation underlying the evolution of rice.

Rice is a stable food in Vietnam and plays a key role in the economy of the country. However, the production and the cultivating areas are adversely affected from the threats of devastation caused by the rise of sea level. Using marker-assisted backcrossing (MABC) to develop a new salt tolerance rice cultivar is one of the feasible methods to cope with these devastating changes. To improve rice salt tolerance in BT7 cultivar, FL478 was used as a donor parent to introgress the Saltol QTL conferring salt tolerance into BT7. Three backcrosses were conducted and successfully transferred positive alleles of Saltol from FL478 into BT7. The plants numbers IL-30 and IL-32 in BC3F1 population expected recurrent genome recovery of up to 99.2% and 100%, respectively. These selected lines that carried the Saltol alleles were screened in field for their agronomic traits. All improved lines had Saltol allele similar to the donor parent FL478, whereas their agronomic performances were the same as the original BT7. We show here the success of improving rice salt tolerance by MABC and the high efficiency of selection in early generations. In the present study, MABC has accelerated the development of superior qualities in the genetic background of BT7.