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 hardshel l on cooking time and study the relationship between hardshell and oth er seed characteristics in bean genotypes grown in the semiarid highla nds 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 neg atively correlated with water absorption and increased cooking time in two of the three populations evaluated. The difference in cooking tim e and water absorption between scarified (hilum perforated) and unscar ified seed of different genotypes would indicate that the hardshell ch aracteristic plays a major role in extending the cooking time of beans . This study indicates that when seeds have an initial moisture conten t of 90 g kg(-1) seed or less, the hardshell problem is easily detecte d after soaking for 18 h, while the problem is rarely detected when in itial seed moisture levels are 120 g kg(-1) or higher. Selection again st the hardshell characteristic could be practised in bean germplasm u sing this information as part of a protocol to shorten the cooking tim e of beans grown in the Mexican highlands.