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Background: Powdery mildew (PM) possesses a wide range of host plants, including mungbean that causes severe yield reductions. Using resistant varieties is an economically and environmentally effective approach in controlling the disease. Methods: In this study, the genetic basis of inheritance and marker loci for PM resistance were investigated using 126 F2:9 recombinant inbred lines (RILs) raised from resistant and susceptible parents, V4785 and CN72, respectively. PM reaction in these RILs was visually scored from natural infection in the field and the segregation pattern was determined by the chi-square test (χ2). Result: The results revealed the segregation ration of 1:1, indicative of a dominantly inherited resistance gene controlling resistance against PM in V4785. Observation of potential polymorphism in two parents and two different bulks, each containing 10 RIL individuals showing either the highest resistance or susceptibility, identified 2 and 37 putatively linked inter-simple sequence repeat (ISSR) and ISSR-anchored resistance gene analog (ISSR-RGA) markers, respectively. Of these, 1 ISSR and 3 ISSR-RGA markers were stably inherited and linked to PM resistance (P less than 0.01). These linked marker systems may prove useful for facilitating the improvement of a durable resistant variety through marker-assisted selection in mungbean breeding programs.

The effects of culture media on growth and proliferation of ‘Earsakul’ dendrobium (Dendrobium) protocorm-like bodies (PLBs) were evaluated in a two-step culture. After culturing on each of the four first step media for 4 months and on each of the four second step media for 4 months, the greatest total PLB fresh weight, increase in number of PLBs and growth rates were obtained when using Vacin and Went medium 1 (VW1) in both culture steps compared with those in 15 other medium combinations. Starting from 0.5 g of PLBs, culturing on VW1 for 8 months achieved a total of 415.25 g of PLBs, a multiplication rate of 830-fold. The supplementation of tomato (Solanum lycopersicum) and substitution of ‘Hom Thong’ banana [Musa acuminata (AAA group)] with ‘Khai’ banana [M. acuminata (AA group)] in this new medium promoted growth and proliferation of dendrobium PLBs 2.4-fold over the control medium, suggesting its usefulness in commercial micropropagation.

Cercospora leaf spot (CLS) resistance is a highly desirable trait for mungbean (Vigna radiata [L.] Wilczek) production in Thailand. ‘V4718’ is a vital resistance source that shows high and stable resistance to CLS disease. A previous study identified a major quantitative trait locus (QTL) (qCLSC72V18-1) controlling CLS resistance and found the marker (I16274) that was located closest to the resistance gene by using F2:9 and F2:10 recombinant inbred line populations derived through a cross between ‘V4718’ and the susceptible variety ‘Chai Nat 72’ (‘CN72’). Here, we evaluated three newly reported simple sequence repeat (SSR) markers and one InDel marker together with six previously identified markers that were linked to qCLSC72V18-1 to further identify the markers that were located close to this QTL. By performing bulk segregant analysis on two validation populations, we found that two SSR markers (Vr6gCLS037 and Vr6gCLS133) and one InDel marker (VrTAF5_indel) were putatively associated with CLS resistance. Of these markers, only the VrTAF5_indel marker showed a significant association with the CLS resistance gene with a logarithm of odds score > 3 across the phenotypic data for 2016 and 2018. QTL analysis with inclusive composite interval mapping revealed that the VrTAF5_indel marker was integrated into the genetic map with other previously identified markers. The I16274 and VrTAF5_indel markers flanking the QTL of interest accounted for 41.56%-60.38% of the phenotypic variation with genetic distances of 4.0 and 5.0 cM from the resistance gene, respectively. Both markers together permitted only 0.40% recombination with the CLS resistance gene in marker-assisted selection and thus could be useful in future breeding efforts for CLS resistance in mungbean.

Mungbean (Vigna radiata (L.) R. Wilczek var. radiata) yield is dramatically constrained by powdery mildew (PM) caused by Sphaerotheca phaseoli (Z.Y. Zhao) U. Braun (1985), which is considerably prevalent in the cool-dry season of production in South, East, and Southeast Asia countries including Thailand. Exploitation of varieties resistant to the disease is crucial to meet sustainable production. A population of 64 F2:9 and F2:10 recombinant inbred lines (RILs) generated by hybridization of the susceptible parent 'Chai Nat 72' (CN72) with the resistant parent 'V4758' was used to assess genetic resistance and identify inter simple sequence repeat-anchored resistance gene analog (ISSR-RGA) markers linked to the PM resistance gene. The PM response in these RILs was visually scored in the field during the winter seasons, twice in 2015 and 2018, and the segregation pattern was determined by the chi-square test (χ 2 ). The resulting segregation ratios of 1:1 indicated a qualitative nature with a dominantly inherited resistance gene conferring PM resistance. When bulk segregant analysis (BSA) was undertaken using 378 ISSR-RGA primer combinations among both parents and DNA bulks of resistant and susceptible F2:9 individuals, 11 of these exhibited polymorphisms, and one marker I41tP379 was closest to the PM resistance gene which revealed a highly significant correlation with PM resistance (R 2 (%) = 26; P < 0.001) with a logarithm of odd (LOD) score of 5.85. The closest marker I41tP379 could trace the PM resistance gene in molecular marker assisted breeding for mungbean improvement.