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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.

Rice (Oryza sativa L.) ‘KDML105’ is the most popular aromatic rice originating in Thailand. This cultivar is highly susceptible to abiotic stresses, especially drought and salt stress during the seedling stage. The objective of this study was to investigate the photosynthetic performance in response to drought and salt stress of four improved breeding lines, specifically CSSL94 and CSSL103 (containing drought-tolerant quantitative trait loci: DT-QTLs) and RGD1 and RGD4 (containing a salt-tolerance gene, SKC1), with ‘KDML105’ (susceptible) and DH103 (tolerant to drought and salt stress) as the controls. Rice seedlings were grown for 21 days in hydroponic solutions and then exposed to salt stress (150 mM NaCl) or drought stress (20% PEG6000) for 10 days. The results indicated that when subjected to drought and salt stress, all rice lines/cultivar exhibited significant reductions in net photosynthesis rate (PN), stomatal conductance (gs), transpiration rate (E), the maximal quantum yield of PSII photochemistry (Fv/Fm), the effective quantum yield of PSII photochemistry (Fv’/Fm’), photosynthetic pigments, and SPAD readings, whereas water use efficiency (WUE) and non-photochemical quenching (NPQ) increased. Compared with ‘KDML105’, CSSL94, and CSSL103 were more tolerant to both drought and salinity, showing less reduction in all photosynthetic parameters. For RGD1 and RGD4, it was confirmed that these lines had a higher level of salt tolerance than ‘KDML105’ based on better photosynthetic performance under salt stress, demonstrating that these lines were also more tolerant to drought stress.

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.

This study focused on the transferred xa5 gene from the rice cultivar IR62266 into the genome of the RD6 cultivar for bacterial leaf blight (BLB) resistance using the marker-assisted backcrossing method. Ten RD6 introgression lines were selected from the BC2F2:3 population. The RD6 introgression lines and their parents were evaluated for BLB resistance using 15 isolates of Xanthomonas oryzae pv. oryzae (Xoo) collected from northeastern Thailand. The Xoo isolates were artificially inoculated onto the leaves of the rice cultivars for validation of BLB resistance at the seedling stage. The results showed that there were statistically significant differences in the BLB lesion length among the test cultivars in most of the Xoo isolates. The broad-spectrum resistance values of introgression lines BC2F2:3 1-13-17-52 and BC2F2:3 1-28-8-37 were the same (0.6) and close to that of the resistant cultivar IR62266 (0.67). In further application, the new rice lines (RD6 resistance to BLB) can be used for pyramiding with other traits for blast resistance and drought tolerance combined with desirable agronomic attributes, for the development of an RD6 rice variety. Keywords: Marker assisted selection, Recessive gene, Resistance, Rice, xa5

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.

Taeng-Thai is the Thai name for oriental pickling melon or muskmelon (Cucumis melo L.) which is a Cucumis species. Based on consumption as Thai traditional dessert, fruit characters at ripening stage are very important to improve the muskmelon cultivar. Understanding the genetic control of fruit traits is the key to a successful for crop improvement. Research aimed to determine the genetic effects, number of genes and heritability of fruit characters in muskmelon. The results have shown that both additive and dominant effects governed for fruit weight, fruit length, fruit width and fruit thickness with the number of gene as 40.26, 1.55, 10.70 and 11.10 genes, respectively. Simple phenotypic correlation coefficients shown, had a significant positive correlation among the four fruit traits. Due to the quantitative inheritance of fruit characters, quantitative traits loci (QTL) mapping of those traits were necessary to identify all controlling genes of fruit traits in further muskmelon improvement.

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.

Phosphorus (P) deficiency is a major factor limiting rice yield throughout the world. Fortunately, some rice accessions are tolerant and can thrive well, even in soils with low P content. The ability to uptake P is heritable, and thus can be incorporated into rice cultivars through standard breeding methods. The objective of this study was to screen for tolerance to phosphorus deficiency and validate the tolerant accessions with phosphorus uptake 1 (Pup1) gene-linked markers in Thai indigenous upland rice germplasm. One hundred sixty-eight rice varieties were screened in a solution culture and assigned a phosphorus deficiency tolerance index and plant symptom score. Eleven upland rice accessions (ULR026, ULR031, ULR124, ULR145, ULR180, ULR183, ULR185, ULR186, ULR213, ULR260, and ULR305), together with the lowland rice cultivar (PLD), were classified as tolerant. They were each validated by nine markers linked to the Pup1 locus and observed for the expected polymerase chain reaction (PCR) product of 0 to 9 markers. The presence or absence of the tolerant allele at the Pup1 locus showed only a slight relationship with the tolerance. Moreover, some lines such as ULR183 and ULR213 expressed high tolerance without the Pup1-linked gene product. Both accessions are useful for the exploration of novel genes conferring tolerance to phosphorus deficiency.

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

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.

Limited labor, cost, and time regarding hybrid formation and yield trials encourages corn breeders to identify potential F1 hybrids without crossing all possible combinations by line screening based SSR-genetic distance. Therefore, this study aimed to (i) determine combining ability and heterosis of 24 hybrids, (ii) group 11 parental lines employing both phenotypic and SSR markers, and (iii) study the association between SSR based-genetic distance and hybrid performance on agronomic traits and yields. 11 parental lines, 3 waxy and 8 sweet corns, were crossed following North Carolina Design II and were genotyped applying 30 SSR markers. 24 hybrids, 11 parents, and 3 check varieties were evaluated in two seasons (2017/2018) at Khon Kaen University, Thailand. Among eleven lines, 101 L/TSC-10, KV/mon, and KV/3473 were good combiners for developing early maturity (46 DAP,-1.43**; 49 DAP,-2.51**; 52 DAP,-0.73**, respectively) and lodging resistance (102.3 cm,-16.34**; 140.5 cm,-5.89*; 125.1 cm,-11.10**, respectively) hybrids meanwhile 101 LBW (6.8 ton ha−1; 1.10**) and Y.18 (6.9 ton ha−1; 1.08**) were suitable parents for high-yielding hybrids. High heterosis estimates with lack of SCA effects for certain traits revealed an essential role of parental adaptation. SSR based-genetic distance between sweet and waxy lines was wide enough ranging from 0.67 to 0.92. Contrasting dendogram pattern and insignificantly poor correlation between SSR and phenotypic based-genetic distances indicated that agreement between SSR and phenotypic markers was lacking. SSR based-genetic distance failed to predict hybrid performance, heterosis, and SCA as poor correlation was revealed. Absence of dominance effects and relatively high genetic distance among parental lines were possible explanations for the poor predictions.

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.

1, 21, KKU Research Journal

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.