SELECTION FOR AGRONOMICALLY ACCEPTABLE INBRED LINES IN ADAPTED X EXOTIC SORGHUM BACKCROSS POPULATIONS

The correlation between yield and other undesirable agronomic traits i n sorghum (Sorghum bicolor (L.) Moench) may limit the isolation of sui table inbred lines from adapted x exotic backcrosses. The objective of this study was to compare use of a rank summation index with independ ent culling when trying to select agronomically acceptable lines from progeny of matings between three exotic accessions and two adapted par ents, an inbred Line, and a broad-based population. Phenotypic correla tions among yield, plant height, days to flowering, and seed weight we re generally low (r < +/-0.50). Selection for yield alone resulted in Lines with increased height and days to flowering. The number of agron omically acceptable lines derived from two of the three matings of the adapted population (KP9B) by using independent culling levels was gre ater than the number derived from the corresponding matings of the ada pted inbred line (CK60). Also, with the use of rank summation index sc ores, KP9B matings gave a higher number of acceptable lines than did c orresponding CK60 matings. Mean yields and seed weights of the top-sco ring 10 lines selected by using the rank summation index were either c omparable with or better than the means of their respective adapted pa rent. In most instances, selections were earlier flowering and slightl y taller than their adapted parent. Overall, backcrossing to an adapte d population enhanced the utilization of exotic accessions more than b ackcrossing to an adapted inbred line. Selection for agronomic accepta bility within introgressed populations was effective by using rank sum mation index and independent culling.