This paper reviews the adaption to heat and drought stresses inPhaseolus vulgaris, a grain and vegetable crop widely grown in both the Old and New World. Substantial genotypic differences are found in morphophysiological characteristics such as phenology, partitioning, plant-water relations, photosynthetic parameters, and shoot growth, which are related to reproductive responses. The associations between (a) days to podding and leaf water content and (b) the number of pods per plant and seed yield are consistent across different environments and experiments. Leaf water content is maintained by reductions in leaf water potential and shoot extension in response to heat and drought stress. Heat-tolerant cultivars have higher biomass allocation to pods and higher pod set in branches. These traits can be used as a marker to screen germplasm for heat and drought tolerance. In this paper, we briefly review the results of our studies carried out on heat and drought tolerance in the common bean at the Tropical Agriculture Research Front, Ishigaki, Japan.

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The fertility of sandy soils in the Sahelian zone (SZ) is extremely low. This poor soil fertility is one of the limiting factors of crop production in the SZ. Therefore, it is imperative to improve or to maintain soil fertility through various agricultural management methods. Further, it is well known that soil organic matter plays an important role in improving the physicochemical properties of these sandy infertile soils. Therefore, it is essential to develop a suitable tool for the appropriate evaluation of soil organic carbon (SOC) dynamics in the SZ. Therefore, the Rothamsted carbon model (Roth-C) was verified in 32 treatments of two long-term field experiments with and without crop residue application. These experiments were performed by ICRISAT. The performance of the model was evaluated by statistical methods using four indices (RMSE: root mean square error, LOFIT: lack of fit, r: correlation coefficient, and M: mean difference). As a result, the predicted SOC values in the case without crop residue management decreased with time in approximately 10 cultivated years. In contrast, in the case with crop residue application, the predicted SOC remained roughly equal to the initial SOC value during the term observed. Mostly, the Roth-C-modelled values agreed well with the actual value. RMSE and LOFIT, the statistical indicators of agreement between predicted and observed values, showed a significant conformity between the predicted and observed SOC values in all the 32 treatments. This fact means that Roth-C can estimate long-term SOC dynamics of several technical options that developed with short-term trials. Moreover the annual carbon requirement for SOC maintaining can be calculate if enough number of cases was estimated. And also analysis of regional carbon dynamics was made possible with using Roth-C model. It will contribute to show the sustainable development in SZ against global warming and other climatic changes.

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This study was conducted to clarify the genotypic differences in diurnal variations in leaf gas exchange characteristics and the effect of irrigation levels, growth stages and cultivars on leaf water status, gas exchange characteristics and seed yields. Associations of leaf water status with photosynthetic rate in five cultivars of snap bean were also determined. Diurnally, leaf gas exchange was highest at 9:30 h, decreased but remained constant between 11:30 to 14:15 h and then decreased up to 16:15 h. Cultivars Haibushi and Ishigaki-2 displayed higher photosynthetic activity throughout the day. The cultivars having higher seed yield showed higher leaf conductance, transpiration rate and leaf vapor pressure deficit at floral bud initiation stage and higher leaf water potential and relative water content in the irrigated plot at flowering stage. The cultivars with slow development of leaf water deficit displayed higher rates of photosynthesis and vice versa. The results showed that midday hours showed large genotypic differences in leaf gas exchange characteristics with constancy of photosynthetically active radiation. Therefore, screening of snap bean cultivars can be made during midday hours for gas exchange characteristics irrespective of growth stages and irrigation levels. Cultivars maintaining higher leaf water content with increasing water deficit can be selected for higher rates of photosynthesis. Disciplines:Agricultural environment / Crop production Additional key words: heat tolerance, leaf water content, leaf water potential, photosynthesis, water deficit JARQ 41 (3), 201 -206 (2007)