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Indigenous upland rice is a staple food for local people in the North and Northeast regions of Thailand. As a result, variations of grain yield and GxE interactions have been utilized for wider adaptability of upland rice varieties. A high yielding genotype that performs well under a good yielding environment as well as in poor environments is greatly needed. Our experiment, therefore, aimed to identify high potential indigenous upland rice varieties for grain yield and yield stability under rainfed conditions. Fifty upland rice genotypes were evaluated from 2013 to 2015, in which a randomized complete block design with three replications was laid out over the three years. Based on grain yield, eight indigenous upland rice varieties, including ULR026, ULR042, ULR075, ULR078, ULR080, ULR081, ULR089 and ULR105; demonstrated superior performance, high yield stability, and greater adaptability over the other varieties, including the Sew Mae Jan check variety. Additional qualities of the superior varieties included high amylose content (ULR081 and ULR075), high aroma (ULR078), and intermediate gelatinization temperature test (GT) (ULR078, ULR026, and ULR105). The participatory varietal selection (PVS) test for farmer(s) acceptance, and promotion of these varieties under rainfed conditions will be further studied.

The soybean (Glycine max (L.) Merrill) is one of the world’s most important sources of food, feed, and fuel due to its high protein value and oil content. However, there exists a lack of soybean genotypes suitable for growth in diverse conditions as soybean breeders have developed their own varieties for specific purposes within their own unique environments. This, therefore, creates the need for soybean genotypes for different environments. The objectives of the experiment described herein were to determine the genotype magnitude through the environment interaction (GxE) of new soybean breeding lines, thereby identifying widely and/or specifically adapted genotypes under ten of Northeast Thailand’s typical environmental conditions from 2017 to 2019. Analyses of the environment (E) and GxE captured a large portion of the total sum of squares of grain yield and related traits, which demonstrated the influence of the two factors in evaluating soybean genotypes, thereby identifying the need for response analysis to identify superior genotypes in each environment. Based on the grain yields of three environments, four genotype groups were clustered. Within the high grain yield environment (EG1), we identified five genotypes with higher yield performance (35*sj-32 (3356 kg/ha), 38D*a-16 (3138 kg/ha), 42*Ly-50-2 (3122 kg/ha), 35*Lh-7 (3116 kg/ha), and 223*Lh-85 (3073 kg/ha)) of KK (3132 kg/ha), the recommended soybean variety for Northeast Thailand, than that of the CM60 (2606 kg/ha). These five top-yielding genotypes, however, produced unstable grain yields through varied environments as they were each narrowly adapted to a specific environment. Moreover, those genotypes may be grown within a rotational cropping system in a duo-environment (wet and dry season) of soybean production in Thailand’s northeast region.

RD6 is one of the most favorable glutinous rice varieties consumed throughout the north and northeast of Thailand because of its aroma and softness. However, blast disease and salt stress cause decreases in both yield quantity and quality during cultivation. Here, gene pyramiding via marker-assisted backcrossing (MAB) using combined blast resistance QTLs (qBl 1, 2, 11, and 12) and Saltol QTL was employed in solving the problem. To pursue our goal, the RD6 introgression line (RGD07005-12-165-1), containing four blast-resistant QTLs, were crossed with the Pokkali salt tolerant variety. Blast resistance evaluation was thoroughly carried out in the fields, from BC2F2:3 to BC4F4, using the upland short-row and natural field infection methods. Additionally, salt tolerance was validated in both greenhouse and field conditions. We found that the RD6 &ldquo, BC4F4 132-12-61&rdquo, resulting from our breeding programme successfully resisted blast disease and tolerated salt stress, while it maintained the desirable agronomic traits of the original RD6 variety. This finding may provide a new improved rice variety to overcome blast disease and salt stress in Northeast Thailand.

Bacterial blight (BB) has caused significant reductions in yield and quality of rice. The use of genetically resistant cultivars has proven to be one of the most effective methods used to address this problem. This study screened a total of 333 Thai lowland indigenous rice germplasms against four Xanthomonas oryzae pv. oryzae (Xoo) isolates under greenhouse conditions in the rainy and dry seasons of 2017. The ten varieties demonstrating the greatest BB resistance in the lower five centimeters of the lesion lengths in both experiment years were further investigated and validated for their agronomic performances in field conditions at the Udon Thani Rice Research Center in 2018. Our findings revealed that of the ten BB resistant lowland rice varieties, five varieties; LLR023, LLR134, LLR137, LLR205 and LLR207, exhibited high performances of agronomic traits in field conditions; as found in the plant height, tiller number, panicle number, panicle length, seeds per panicle, grain yield and harvest index when compared with the KDML105 check varieties. These five selected rice varieties may further serve as new genetic resources for future BB resistance and agronomic trait improvement programs.

Vegetable corn with an excellent, balance proportion of kernel carbohydrates in relation to good eating quality appeals to consumers. Sweet-waxy corn hybrid is proposed to improve palatability of traditional cooked waxy corn, well known as synergistic corn. We determined genetic effects of sugars, phytoglycogen, total starch, and amylopectin and estimated general combining ability of parents for these traits. Three sweet corn lines assigned as female were crossed with eight waxy corn lines as male following the North Carolina II. About 11 parents, 24 F1 progenies, and 3 checks were evaluated in randomized complete block design with three replications in two seasons between 2017-2018. Then, entry means of 38 genotypes was clustered with dendogram. Additive effect was important for favored kernel carbohydrates except for phytoglycogen. Two sweet corn lines 101LBW and 101LTSC-10 were proposed as broad-based testers for total sugar and sugar fractions, whereas a waxy corn line KVMON for total starch and amylopectin. Cluster analysis based on amylopectin, total sugar, and phytoglycogen was reliable to discriminate corn genotypes into seven major groups, and two sweet-waxy corn F1 hybrids 101LTSC-10/C13-1 and 101LTSC-10/KV3473 corresponding to our selection criteria were identified. Implications in plant breeding and suggestions for further investigations are discussed.

Rainfed lowland rice is the most common crop ecosystem in Northeast Thailand and varieties well adapted to drought-prone environments are required. On-farm multi-location experiments were conducted for 3 years to determine the drought type commonly developed, to identify genotype by environment interaction for rainfed lowland rice and to examine whether genotypic variation in these experiments was related to that in on-station controlled water- environment screening experiments conducted previously ( Monkham et al., 2015 ). Among 32 on-farm experiments, 4 experienced continuous drought with no standing water during the whole growing season, and 3 of them all in high toposequence positions died before maturity. For the remaining experiments, both intermittent and terminal droughts were common, while some experiments developed early season drought and delayed transplanting but resulted in no apparent yield penalty. The first set of multi-location experiments consisted of 14 experiments in 6 provinces in Northeast Thailand across 2 years with 24 common genotypes. Mean grain yield of 13 environments that were harvested was 2300–3900 kg ha −1 and no severe drought developed at any environment. While main effect of genotype was not significant for grain yield, genotype by environment interaction was significant, and the results of clustering analysis identified 3 environmental groups and 3 genotype groups that explained the main source of the genotype by environment interaction. The genotypic variation obtained in the on-farm multi-location experiments in one environmental group of low yielding environments was correlated with that obtained under earlier intermittent drought selection experiments on-station. The results also indicate the usefulness of screening genotypes based on short delays in the intermittent drought conditions on-station. A second set of multi-location experiments conducted throughout Northeast Thailand to test the performance of four genotypes selected from the first set of multi-location experiments confirmed that these genotypes outperformed the popular variety KDML105. The present study confirmed the usefulness of initial screening under intermittent drought conditions conducted on research stations followed by further on-farm selection. It is suggested that on-station selection experiments should target yield levels representative of on-farm yield levels.

Many of the economically important rice cultivars including ‘Khao Dawk Mali 105’ (KDML105) or jasmine rice, one of the world’s famous rice exported from Thailand suffers from drought due to erratic rainfalls and limited irrigation. To improve drought tolerance and reserve genetic background of KDML105, chromosome segment substitution lines (CSSL) containing drought tolerant quantitative trait loci (DT-QTL) has been previously developed by backcrossing between KDML105 and drought tolerant donor, IR58586-F2-CA-143 (DH212). To understand the physiological responses related to drought tolerance in CSSL lines compared to parents, two CSSLs namely CSSL1-16 and CSSL1-18, respectively were used in this study. Twenty-one-d-old hydroponically grown plants were subjected to 20% PEG for 0, 7, 14 d and then recovered from stress for 3 d. The results indicated that CSSL lines especially, CSSL1-16 showed better performance under drought stress compared to their recurrent parent. Drought tolerance superior CSSL1-16 line was indicated by high water status (high relative water content and leaf water potential), good osmotic adjustment, high proline and greater membrane stability. Moreover, this line was able to resume growth after stress recovery whereas other lines/cultivar could not recover. Similarly, drought tolerant donor showed high water status suggesting that well-maintained plant water status was associated with drought tolerant trait. It could be concluded that the highest drought tolerant line was CSSL1-16 followed by DH212, CSSL1-18 and KDML105. It would be interesting to go further into introgressed section in CSSL1-16 to identify potential candidate genes in DT-QTL for breeding drought tolerant rice in the future.

Waxy corn is a popular, alternative staple food in most Asian countries including Thailand. The availability of small-ear waxy corn genotypes with prolific ears and a high level of carotenoids is expected to benefit growers and consumers. Integrated evaluation among source germplasm is essential before performing further breeding efforts for enhancing prolific ears and high-carotenoid content. Thus, the present study explored the variability of ear prolificacy, total carotenoids, lutein, zeaxanthin, and beta-carotene among yellow small-ear waxy corn accessions. About 44 corn accessions and 4 check varieties were evaluated for agronomic traits and yield components under multienvironment trials in a randomized complete block design (RCBD). The immature seed sample of these genotypes was analyzed to quantify the content of total carotenoids and some carotenoid fractions. All traits showed that low GXE interaction and significant genotypic diversity existed among all tested accessions with the predominant contribution of genotype to total phenotypic variation and beta-carotene. Accessions were clustered into four major groups based on the similarity of multiple carotenoids profiles. Three selected accessions (UT121001, KKU-WX112087, and KKU-WX212001) had higher values of total carotenoids, lutein, zeaxanthin, and beta-carotene than those of all check varieties. High and positive correlations among second-emerged ears, marketable second-emerged ears, and total ear number indicate that a higher chance of secondary ears becomes marketable ears with an increase of total ears per plant per hectare. Lutein and zeaxanthin had positive, strong correlations with total carotenoids. The implications and breeding strategies are discussed prior to promoting yellow small-ear waxy corn as a biofortified crop.

This research paper aims to evaluate the performance of DSSAT CERES-Rice model in simulating the impact of different (28 °C, 30 °C and 32 °C) increased temperatures change with the relations of five upland rice genotypes (Dawk Pa-yawm, Mai Tahk, Bow Leb Nahng, Dawk Kha 50 and Dawk Kahm) on grain yield for future crop management. Results showed that temperature significantly affected grain yields, harvest index, flowering and maturity date which indicate that medium temperature (30 °C) gave highest grain yield bearing genotype Dawk Kahm (6,700 kg/ ha) whereas at maximum temperature (32 °C), simulated grain yields varied from 3094 to 6460 kg/ ha. Root Mean Square Error (RMSE) values of simulated and observed data less than 10% indicated that grain weight, leaf area index, tillers number and harvest index had more consistency agreement with the yield. Thus, it was proved that the CERES-Rice crop simulation model was more useful as a tool for different phenological traits under changing temperature conditions. And the model approximated grain yields at different temperatures with reasonable accuracy.

Upland rice production plays an important role in both household consumption and crop rotation. Until now, a blast resistant upland variety has not been released in Thailand. The bimodal pattern of rain distribution in Thailand’s upland rice production areas create a favorable environment for the outbreak of leaf blast when seedling-tillering, and neck blast within the heading stage. The use of genetically resistant cultivars has proven to be an effective way to cope with this problem. In this study, 256 indigenous upland rice plants were screened for blast resistance under greenhouse and field conditions. Ten indigenous upland rice varieties, ULR292, ULR242, ULR219, ULR162, ULR161, ULR134, ULR109, ULR098, ULR081, and ULR066, were identified as resistant to leaf blast disease in both natural infection and artificial inoculation, under greenhouse conditions. Additionally, six of the ten varieties, ULR162, ULR161, ULR134, ULR109, ULR098, and ULR081, were found to be resistant to neck blast under field conditions. These new sources of blast resistance identified from indigenous upland rice varieties proved more resistant than the check varieties, depicting their potential for further use in Thailand’s rice blast resistance improvement program.

Drought remains the most important factor that affects rice productivity, especially in rainfed areas, worldwide. Upland rice is one of the crop choices of farmers in the rainfed environment. Although upland rice varieties require less water than lowland rice varieties, yields often remain limited by drought, particularly in the period of early growth. The aims of this study were to identify the traits related to early drought tolerance in upland rice varieties, and to identify the potential sources of germplasm for early drought tolerance. A total of sixty upland rice varieties were planted in a factorial experiment with a randomized complete block design with 3 replications in the rainy seasons of 2011 and 2012, under greenhouse conditions. Based on the drought tolerance index (DTI), the test germplasm sources were classified into three groups: (i) susceptible; (ii) moderately tolerant; (iii) tolerant to drought stress. Grain yield (GY) showed significant negative correlations with the leaf rolling score (r= − 0.623, Pr= − 0.673, Pr= − 0.746, Pr= 0.698, Pr= 0.618, P

Rainfed lowland rice in the Mekong region is mostly grown in drought-prone areas, and drought resistant varieties could be selected using either terminal drought (severe water stress after flowering) or intermittent drought (frequent mild stress) screening. Delay in flowering is considered as a putative trait for selection of drought resistant genotypes, and its effectiveness as an indirect selection trait and its association with genotype's flowering duration, i.e. the time taken from the first to last flower in a plot, was evaluated under the two drought screening methods. These screening methods together with flood control were used at two locations, Chum Phae and Ubon in north-east Thailand using a total of 70 genotypes with different growing duration. Delay in flowering was estimated for the two drought screening methods and flowering of individual panicles within a plot was recorded to determine flowering duration of each genotype in the flood and terminal drought conditions. Mean reduction in grain yield was 52–55% under the terminal drought screening while it was 10–19% for the whole population and 23–33% for early flowering genotypes in the intermittent drought. Delay in flowering under intermittent drought condition at both locations was associated with yield reduction; genotypes that exhibited shorter delay in flowering had smaller yield reduction percentage and larger number of panicles. At Chum Phae, where grain yield reduction was associated with flowering time, genotypes with longer flowering duration under terminal drought had smaller yield reduction, and this was found even among genotypes that flowered about the same time under flood condition. However, there was no association between delay in flowering and flowering duration. It is concluded that delay in flowering appears promising as a selection criterion under intermittent drought conditions, provided a higher yield reduction can be achieved for example by using an increased irrigation interval.

Estimation methods and evaluation of ethanol yield from sweet sorghum ( Sorghum bicolor (L.) Moench) based on agronomic production traits and juice characteristics is important for developing parents and inbred lines of sweet sorghum that can be used by the bio-ethanol industry. The objectives of this study were to compare published indirect methods for the calculation of ethanol yields from sweet sorghum and test them against direct ethanol production in laboratory, as well as to determine the relationships among total soluble sugar and juice traits with ethanol concentrations over time. Four sorghum varieties (KKU40, Theis, BJ248 and SPV1411) were compared for juice characters and ethanol yield in a randomized complete block design with four replications. Agronomic and juice traits of sweet sorghum were recorded during flowering and at harvest. Juice of sweet sorghum was fermented by yeast ( Saccharomyces cerevisiae ) to obtain ethanol yields in the laboratory, which were then compared with ethanol yields calculated based upon five calculation methods from the literature. Ethanol yield estimates calculated from published methods were generally higher than laboratory values. However, estimates based upon Somani and Taylor (2003) and on Smith et al. (1987) when multiplying theoretical yields by 80% were not significantly different from laboratory results. Though ethanol yield are strongly correlated with sugar yields, juice traits influenced the rate of fermentation of sugars over time. For example, glucose, fructose and nitrogen content in the juice had a positive effect on ethanol concentration after 12 h of fermentation while multiple juice traits were significantly associated with ethanol concentrations after 24, 36 and 48 h of fermentation.

Pigmented rice is receiving much attention due to the large amounts of bioactive compounds and various health benefits.However, little information is available on its agronomic and physiological aspects. This research aimed to explore the effects of salinity on yield and grain quality of pigmented rice and the modulation of salinity responses by exogenous application of spermidine (Spd). Four cultivars of rice were grown in pots until the early booting stage. Thereafter, the plants were sprayed with 1 mM Spd for 7 successive days before being irrigated with 25 mM NaCl instead of tap water until maturity. Grain yield, yield components and harvest index in all rice cultivars were negatively affected by this salinity stress. Pretreatment with Spd dramatically improved yield and yield components of salt-treated plants, particularly the salt-sensitive cultivar. The major yield components which were improved and contributed most to the dramatic increase in seed yield were the number of filled grains per panicle and panicle fertility. Moreover, Spd pretreatment resulted in an increase in K+/Na+ ratio in rice grains. Salt stress increased nutritional quality of mature grains, i.e., total phenolic content, anthocyanins, proanthocyanins and antioxidant activities (evaluated by FRAP, DPPH and ABTS assays) in all rice cultivars. Furthermore, all aspects of health-promoting nutritional characters were further enhanced by Spd pretreatment. Thus foliar spraying of Spd to rice plants prior to salt application improved grain yield as well as nutritional quality of colored rice grains in relation to total phenolics, flavonoid pigments and antioxidant capacities.

Bacterial leaf blight (BLB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most serious diseases in rice production. Breeding varieties specifically for their resistance to BLB disease is therefore an efficient and cost-effective strategy. However, the resistance gene for BLB can be race and non-race specific, meaning it is often overcome by the pathogen. The identification of new sources of resistance genes for Xoo is crucial in rice breeding programmes. In this study, six rice varieties were assessed using six Xoo isolates in multiple screening conditions. The GGE biplot analysis considers both genotype (G) and genotype environment (GE) interaction effects and demonstrates GE interaction. The first two principal components (PCs) accounted for 95.46% of the total GE variation in the data. Based on lesion length and stability performance, Phaladum was the most ideal genotype against all Xoo isolates in the four screening conditions. The results relayed that Phaladum indigenous rice varieties could be considered as new sources of bacterial leaf blight resistance in Thailand. In the future, the BLB resistance gene in this variety will be identified in regard to mode of inheritance and used as parental line in rice breeding programmes for resistance to BLB.

To investigate the changes in physiological parameters in leaves of field-grown rice genotypes differing in their salt tolerance. Thirty rice cultivars classified as tolerant (T; 11), moderately tolerant (MT; 5), moderately sensitive (MS; 7) and sensitive (S; 7) based on the previous screening at the seedling stage were established in a greenhouse. Thirty-day-old seedlings were then transplanted to a rice field, situated in a moderately saline area in northeastern Thailand, where EC slowly increased from 2.03 to 6.46 dS m−1 from the transplanting date to harvest. Leaf samples (the third leaves from the top or the flag leaves during the vegetative or the reproductive phase, respectively) were collected, at 1 month intervals, when the plants were 60-, 90-, 120- and 150-day-old corresponding to active tillering, early reproductive, late reproductive and harvest stage, respectively. Leaf samples were analyzed for changes in proline, chlorophyll and malondialdehyde (MDA). The harvested panicles were evaluated for the percentage of filled grain weight and the concentration of Na+ and K+ in the top internode. The patterns of change and the mean concentrations of most physiological parameters in rice leaves during the course of development were strikingly similar for the four classes of salt tolerance. Proline concentration remained relatively constant throughout the development and finally showed a dramatic increase in the flag leaves at harvest. MDA concentration tended to increase with age reaching the maximum in the flag leaves at harvest. The chlorophyll concentration was higher during the vegetative stage than the reproductive stages. At harvest corresponding to the time of maximum salinity, the T group tended to contain higher proline and stayed green longer than the other groups. Moreover, the T group showed higher percentage filled grain weight which was associated with lower Na+/K+ ratio in the top internode. The percentage filled grain weight was negatively correlated with Na+ concentration and Na+/K+ ratio in the top internode and proline concentration in flag leaves, but did not correlate with chlorophyll and MDA in flag leaves. Rice cultivars which are tolerant at the seedling stage also showed higher tolerance in the field condition as shown by higher percentage filled grain weight and lower Na+ uptake to the panicles. Tolerant cultivars tended to accumulate less proline in their leaves similar to that found at the seedling stage.

Aims The objectives of this study were to evaluate salt tolerance level of rice genotypes using the well-established screening criteria; the salt injury score, survival percentage and ratio between Na+ and K+, as well as the contents of proline and chlorophyll, and to identify the relationship between salt tolerance and physiological characters.

The Sakon Nakhon (SKN) rice cultivar is non-photosensitive, rich in aroma, and an excellent choice for cooking quality, which adapts well to both upland and lowland conditions. Furthermore, it has been adopted by Thailand’s sugarcane growers, as it has proved fit for an upland crop preceding the sugarcane cropping system. However, SKN is very susceptible to blast disease caused by Pyricularia oryzae. The purpose of this study was to breed SKN for blast resistance, using marker-assisted backcrossing, together with phenotypic selection. The breeding population was constructed by crossing the SKN (recurrent) with the RD6 introgression line (donor), which contained four blast resistant quantitative trait loci (QTLs). Franking microsatellite markers for blast resistance QTLs on chromosomes 1, 2, 11 and 12 were used for selection through BC2F2. Thirteen BC2F3 selected lines were evaluated under greenhouse conditions, and seven lines of BC2F4 were evaluated against blast, along with their agronomic traits, under field conditions (upland and lowland). SKN 39-10-19-29-12 and SKN 39-10-19-29-13 presented high resistance to leaf and neck blast, and were non-photosensitive, with the same agronomic traits as the SKN. This study successfully demonstrates the improvement of the recommended SKN variety blast resistance, while maintaining similar agronomic traits.

Appropriate canopy management and proper application of fertilizer under different growing conditions and agronomic practices can obtain reliable yield of physic nut (Jatropha curcas L.). The objective of this study was to determine the effects of pruning level in first year and fertilizer rate of combined NPK in the first and second years on growth and yield of three-year old physic. A split plot design with four replications was used. Three pruning levels of 50, 75 and 90 cm from the ground were assigned in main plots and combinations of NPK fertilizers at the rates of 0, 312.5 and 625 kg ha-1 were arranged randomly in subplots. All pruning levels from the ground did not have significant effects on branch number and branch length (cm), whereas application of fertilizer did increase branch number and branch length especially at the rate of 312.5 kg ha-1. Harvest in the second year gave higher yield (1,559 kg ha-1) than did in the first year (1,180 kg ha-1) for all treatments, suggesting that it is not necessary to prune physic nut every year in commercial plantations. It is recommended to prune the three-year old physic nut at 70 cm from the ground. Pruning at 90 cm from the ground is possible but not at 50 cm. it is also recommended to apply fertilizer to the three-year old physic nut under rainfed conditions at the rate not exceeding 312.5 kg ha-1 and this should be based on soil analysis. Application of higher rates depressed yield

Salinity tolerance levels and physiological changes were evaluated for twelve rice cultivars, including four white rice and eight black glutinous rice cultivars, during their seedling stage in response to salinity stress at 100 mM NaCl. All the rice cultivars evaluated showed an apparent decrease in growth characteristics and chlorophyll accumulation under salinity stress. By contrast an increase in proline, hydrogen peroxide, peroxidase (POX) activity and anthocyanins were observed for all cultivars. The K(+)/Na(+) ratios evaluated for all rice cultivars were noted to be highly correlated with the salinity scores thus indicating that the K(+)/Na(+) ratio serves as a reliable indicator of salt stress tolerance in rice. Principal component analysis (PCA) based on physiological salt tolerance indexes could clearly distinguish rice cultivars into 4 salt tolerance clusters. Noteworthy, in comparison to the salt-sensitive ones, rice cultivars that possessed higher degrees of salt tolerance displayed more enhanced activity of catalase (CAT), a smaller increase in anthocyanin, hydrogen peroxide and proline content but a smaller drop in the K(+)/Na(+) ratio and chlorophyll accumulation.

This study was carried out to elucidate the spermidine (Spd) and gibberellic acid (GA3) priming-induced physiological and biochemical changes responsible for induction of salinity tolerance in two rice (Oryza sativa L.) cultivars, namely ‘Niewdam Gs. no. 00621’ (salt tolerant) and ‘KKU-LLR-039’ (salt sensitive). The seeds of the two cultivars were primed separately with distilled water, 1 mM Spd or 0.43 mM GA3. Primed seeds were germinated and the resultant seedlings were hydroponically grown for 14 days before being exposed to salinity stress (150 mM NaCl) for 10 days. Seed priming with Spd or GA3 slightly improved salt-induced reductions in growth, anthocyanin and chlorophyll contents of the seedlings. Salt stress induced pronounced increases in Na+/K+ ratio, proline and H2O2 contents, particularly in the sensitive cultivar. The levels of these salt-sensitivity physiological indicators tended to be mitigated by priming with Spd and GA3. Salt-stressed seedlings grown from seeds primed with these growth regulators also possessed higher phenolic contents and greater antioxidant capacity than the control seedlings. Based on all growth and physiological data, Spd tended to be more effective than A3 in improving salt tolerance in both rice cultivars.

Improvements in its political and tourism sectors have encouraged Lao PDR to explore export options for its traditional waxy rice varieties. As such, farmers and agriculturists are exploring ways to enhance yield and capture high-quality traits into improved varieties such as Thasano1 (TSN1) and Thadokkham1 (TDK1). In this study, the effects of nitrogen (N) on yield and quality traits were investigated in two traditional varieties, Hom Nang Nouane (HNN) and Kai Noy Leuang (KNL), and in two popular improved varieties, TDK1 and TSN1. The plants were cultivated during the 2006 wet season at the Rice and Cash Crop Research Centre, NAFRI, Lao PDR, and were subjected to four N rates. Results showed that while increased N rates enhanced yields and yield components in TDK1 and TSN1, the two traditional varieties, HNN and KNL, were not as responsive. In contrast, the quality traits assessed in this study of the four varieties were not affected by N. Yield and textural attributes further suggest that TSN1 is a better candidate than TDK1 for breeding programs aimed at combining quality traits from HNN and KNL into improved varieties.