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Screening for Drought Resistance with the Use of Some Morpho-Physiological Characters in Soybean [Glycine max (L.) Merr.].
Abstract:
Drought experiments in soybean were carried out using 100 soybean genotypes in the first experiment and 20 selected soybean genotypes in the second experiment under controlled greenhouse condition. The objectives of the study were to (1) test the morpho-physiological responses of soybean genotypes to drought and determine the morpho-physiological characters that can be used as indices in screening for drought resistance; and (2) identify the resistant, moderately resistant, and susceptible genotypes that can be used in soybean breeding programs.
Experiment 1 showed that leaf relative water content (RWC) was highly correlated to seed yield. Transpiration rate was also positively correlated to seed yield but the degree of correlation was lower than that of leaf RWC. Leaf RWC was used as the basis for determining the degree of resistance in Experiment 1 since it showed the most significant correlation to seed yield.
Experiment 2 made use of eight resistant, four moderately resistant, and eight susceptible soybean genotypes selected from the first experiment based on leaf RWC and seed yield data, planted under well-watered and drought conditions. Experiment 2 confirmed that leaf RWC had a significant contribution to seed yield. The experiment also showed that improved seed yield was associated with high shoot-root ratio and harvest index. Poor seed yield was associated with high root weight, reduction in total green leaf area, and low stomatal resistance. High leaf RWC was associated with high proline content and low reduction in total green leaf area.
This experiment consistently showed that genotypes having a high leaf RWC under drought condition can be expected to produce a high seed yield. Considering seed yield as an important aspect in any breeding program, high seed yield and related characters like high leaf RWC, high free proline content, high harvest index, high shoot-root ratio, low root dry weight, and low reduction in total green leaf area were characters important in screening for drought resistance.
Emgopa 19, GC 841027, UPL Sy-2, SJ-5, Willis and Tampomas consistently showed a high leaf RWC and a high seed yield in two successive experiments; therefore they are classified as drought resistant genotypes. On the other hand, IPBSy91-04-25-08-02, ACC 868, IPBSy92-07-04-01, and Kipas Putih were categorized as susceptible genotypes because of their low leaf RWC and low seed yields in both experiments. Likewise, Dourados, MTBR 45, AGS 314, LB 79, BR 38, AGS 314, and B3613 had inconsistent leaf RWC and low seed yield in Experiment 1 and Experiment 2. Together with other genotypes like Embrapa 4, Cikuray, Pangrango, and Co1, which were categorized as moderately resistant in the first experiment, Dourados, MTBR 45, AGS 314, LB 79, BR 38, AGS 314, and B3613 were classified as moderately resistant.