Characteristics of deep root system of drought tolerance in cowpea (Vigna unguiculata (L.) Walp) were evaluated by using 'basket' method and gene analysis. The ratio of the deep root number and dry weight per total lateral roots in drought tolerant cultivar '205' was significantly higher than those of drought sensitive '555'. These results suggested that drought tolerant cultivar has deeper rooting traits than the sensitive one. The drought tolerance of each cultivar was mainly regulated by

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... lated gene, BZR1, which relates to lateral root development. Furthermore, the expression of genes such as MSBP1 and Hy5 as well as BZR1 of lateral roots was significantly enhanced in the deep roots compared to the shallow roots in the drought tolerant cultivar. Taken together, the deep root system in cowpea may contribute to its drought tolerance through enhanced water uptake from deep soil layer.