Classification, Distribution and Biology

Abstract Sorghum ( Sorghum bicolor L. Moench) is a highly versatile crop of African origin with multiple uses as food, feed, fodder, fuel, and fiber. The grain is used as food or feed; the stem can be used as a source of fiber, fuel, and lately as feedstock for cellulosic ethanol. The crop is grown throughout the tropics, semitropics, arid, and semiarid regions of the world, and according to the Food and Agriculture Organization, India, Nigeria, Mexico, United States, Argentina, and Ethiopia are the major producers. Ethiopia is the primary and India is the secondary center of its diversity. Immense morphological diversity of the cultivated types has emerged because of variable climate and geographical exposures in which its wild ancestors evolved, coupled with selection pressures imposed by the environment and by man for domestication (Doggett, 1988). The immense variation in the genus is currently conscribed to 22 species distributed in five sections, viz., Eusorghum , Chaetosorghum , Heterosorghum , Parasorghum, and Stiposorghum . Only one species, S. bicolor, is cultivated, while all the other 21 are wild or weedy. Profitable utilization of genetic resources, however, demands an interdisciplinary, multipronged approach to increase the probability of achieving the desired genetic improvement. To this end, this chapter presents a review of the current knowledge on (1) biosystematic aspects such as taxonomy, classification, and biology; (2) distribution, genetic resources, working groups, and gene pools; (3) utilization aspects including the specific potential of the wild species in crop improvement; and (4) strategies to maximize utilization of wild germplasm resources, including direct hybridization, reproductive barriers, and their circumvention.