หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Nodule Growth and Nitrogen Fixation of Selected Soybean Cultivars under Different Soil Water Regimes) ผู้เขียน:Aung Moe Myo Tint, ดร.เอ็จ สโรบล, ศาสตราจารย์, Sutkhet Nakasathein, Witith Chai-aree สื่อสิ่งพิมพ์:pdf AbstractSensitivity of N2 fixation to soil-drying has been considered as a major limiting factor to improving soybean yield. Seven soybean cultivars derived from various parents—namely, Nakhon Sawan 1 (NS-1), SJ.4, Sukhothai 1 (ST-1), Sukhothai 2, (ST-2), Sukhothai 3 (ST-3), Chiang Mai 60 (CM-60) and Chakkrabandhu 1 (CK-1) were evaluated for their nodulation and growth and yield in the first experiment. They were derived from various parents and their maturity differed from 90 to 110 d. Cultivars NS-1, ST-2 and ST-3 were selected to examine their nodule growth and N2 fixation capability under different water regimes in the second experiment. Nitrogenease activity (NA) of the nodulated roots of soybean increased with an increase in nodule dry matter (NDM) until 15 d after vegetative stage 4 (15 DAV4; R4) and then declined at 22 DAV4 (R5) under the well-watered regime. Under a water regime with progressive soil drying, the NA of the nodulated roots significantly decreased by 17.73% of the control from 7 DAV4 (R3). Among the soybean cultivars, NS-1 showed higher nodulation and N2 fixation capacity under both water regimes. The NA of nodulated roots severely diminished by 87.10% of control at 12 DAV4 (R4) under progressive soil drying and did not recover well after rewatering; nodule growth was similarly affected. There was a greater and significant correlation between NDM and other observed physiological parameters at the R4 stage. NDM is the most fundamental parameter for selecting better soybean cultivars for N2 fixation under both water regimes. The soil plant analysis development (SPAD:M-502) reading showed a highly significant correlation (r=0.84) with NA and other physiological parameters. SPAD readings could be used as a rapid assessment technique for the identification of potential cultivars with greater N2 fixation for both water regimes by measuring the accumulated total N in the shoot biomass at harvest. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Differential Responses of Selected Soybean Cultivars to Drought Stress and Their Drought Tolerant Attributions) ผู้เขียน:Aung Moe Myo Tint, ดร.เอ็จ สโรบล, ศาสตราจารย์, Sutkhet Nakasathein, Witith Chai-aree สื่อสิ่งพิมพ์:pdf AbstractSeven soybean cultivars in Thailand were evaluated under well-watered and drought- stressed regimes. A randomized complete block design with three replications in greenhouses was used. Control pots were kept well watered. Imposing drought stress commenced at the vegetative growth stage 3 (V3) for 15 d and then pots were re-watered. Shoot dry matter (SDM), root dry matter (RDM), nodule dry matter (NDM), shoot tissue moisture content (STM%) and electrolyte leakage from leaf tissue (EL%) of each tested cultivar under both water regimes were investigated. Physiological responses of the cultivars and their relationship were identified. Their drought tolerances were examined using a stress susceptibility index (SSI), mean productivity (MP), geometric mean productivity (GMP), stress tolerance (TOL) and a stress tolerance index (STI). SDM, RDM and NDM decreased with increasing water stress. SDM, NDM, STM%, and EL% showed significant correlations with seed yield. On the basis of the physiological responses and drought tolerance attributes of the cultivars studied, SJ-4 was the most drought tolerant cultivar indicating that SJ-4 is not only the appropriate genotype for cultivar improvement but also for cultivation in drought-prone areas. STI had a highly significant correlation with seed yield (r=0.66) and could distinguish better yielding genotypes under the drought-stress environment. The results also showed that STI was the most appropriate index to attain better yielding cultivars for a drought-stress environment, followed by GMP. |