Exploiting heterosis is one method to increase cotton yields that have stagnated in recent years. We produced 120 F2 cotton (Gossypium hirsutum L.) hybrids from a half diallel of 15 cultivars and one strain. The parents and their F2s (136 genotypes) were evaluated in three Mississippi Delta locations in 1990. Total and first harvest lint yields were taken from four replications per location. Yield components and fiber properties were determined from two replications. The primary objective of this study was to determine if parental region of origin was related to midparent and useful heterosis. We also explored the use of molecular markers (restriction fragment length polymorphisms, RFLPs) and coefficients of parentage in identifying heterotic effects. Significant heterosis over all crosses for total and first harvest yield, lint percentage, boll weight, and 50% span length were detected. For total yield, the specific combining ability and specific combining ability by location interaction components accounted for 79% of the total genetic variance components. General combining ability effects accounted for the remaining 21%. Four of the highest six general combiners for yield were from the Delta region. One each came from the East and West regions. The F2s derived from the West’s cultivar, Prema, were not only high in yield, but also resulted in the highest bundle strength. The correlation of genetic distance (calculated from RFLP data) and heterosis was 0.08, and that for coefficient of parentage and heterosis was 0.05. Region of origin for one parent of a cross was an important factor in the expression of F2 heterosis from crosses among Delta cultivars. But, a similar relationship with F2 heterosis in crosses between Delta cultivars and those from other regions was not observed. General approaches to producing high yielding F2s are: (i) choose at least one parent well adapted to the targeted region; (ii) the second parent may come from any region or country; and (iii) if fiber quality is a breeding objective, at least one parent must have above average fiber quality as well as be a good yield combiner.
