EFFECTS OF HARDSHELL CHARACTER ON COOKING TIME OF COMMON BEANS GROWN IN THE SEMIARID HIGHLANDS OF MEXICO

The present study was undertaken to develop a protocol to screen bean germplasm for the hardshell character, evaluate the effect of hardshell on cooking time and study the relationship between hardshell and other seed characteristics in bean genotypes grown in the semiarid highlands of Mexico. Between 50 and 75% of the variation in cooking time of recently harvested beans was explained by differences in the degree of water absorption after soaking for 18 h. Seed coat brightness was negatively correlated with water absorption and increased cooking time in two of the three populations evaluated. The difference in cooking time and water absorption between scarified (hilum perforated) and unscarified seed of different genotypes would indicate that the hardshell characteristic plays a major role in extending the cooking time of beans. This study indicates that when seeds have an initial moisture content of 90 g kg(-1) seed or less, the hardshell problem is easily detected after soaking for 18 h, while the problem is rarely detected when initial seed moisture levels are 120 g kg(-1) or higher. Selection against the hardshell characteristic could be practised in bean germplasm using this information as part of a protocol to shorten the cooking time of beans grown in the Mexican highlands.