Hybrid vigor in sorghums

The grain yields, stover yields, percentage of lodging, plant height, number of leaves of the main stalk, weight of 100 kernels, and the date of heading of 19 F1 hybrids and nine parental varieties are reported. The experiments were conducted at University Farm, Tucson Ariz., in 1941 and at Salt River Valley Experiment Station, Mesa. Ariz., in 1942 and 1943. Silage yields of the most promising hybrids and their parents also were obtained in 1942 and 1943. The silage was analyzed for total sugars, protein, fat, ash, and crude fiber. All of the possible F1 hybrid combinations between hegari, Ajax, Atlas, Kalo, Grohoma, and Double Dwarf milo 38 were grown in 1942 and 1943. All but three of the 19 hybrids had grain yields in excess of the means of the parents. Grohoma X Double Dwarf milo 38 and Ajax X Double Dwarf milo 38 produced the highest yields. Fifteen of the 19 hybrids yielded more stover than the means of the parents. Crosses involving hegari or Double Dwarf milo 38 gave the largest increases in stover yield. All of the hybrids had increases in plant height over the means of the parents, ranging from 6.2% to 113.8%. All of the hybrids with either hegari or Double Dwarf milo 38 as one of the parents had increases in the number of leaves of the main stalk. Many of the hybrids were so tall that they lodged excessively. The Ajax hybrids showed the least inclination to lodge. In the F1 hybrids, the average seed size was intermediate or was as large as or larger than that of the larger-seeded parent. The hegari-Atlas hybrid yielded 30.7 tons of silage per acre in comparison with 18.7 tons of the heavy producing Atlas variety. Such large yields are difficult to harvest mechanically. Most of the hybrids tested were too tall for ready machine harvesting of the grain crop, and had brown seeds, an undesirable color from the market standpoint. The commercial production of hybrid sorghum seed awaits the development of economical methods of hybrid seed production.