Heterosis for Grain Yield and Other Agronomic Traits in Foxtail Millet

varietal crosses or selfed selections from planned crosses have not been widely used is that foxtail millet is one Foxtail millet [Setaria italica (L.) P. Beauv.] is a largely selfof the most difficult species to cross-pollinate (Baltenpollinating species that is used as a warm-season annual in the USA. Nearly all cultivars of this species grown in the USA are selections sperger, 1996). The flowers are small (about 1 mm in from land races. This research was undertaken to determine whether length), and anthesis generally occurs near midnight and sufficient high-parent heterosis is expressed in foxtail millet for grain in the morning but varies greatly with the environment yield and other key traits to justify the development and use of varietal (Malm and Rachie, 1971). However, Siles et al. (2001) crosses. Seven diverse parents and 21 F2s and 21 F3s produced from described an artificial technique of hybridization that biparental crosses were evaluated in five environments in 1996. resulted in 67.5% hybrid seed set per flower crossed. Genotype environment interaction was highly significant for grain Also, Wang (1991) reported the discovery of male-steryield, but the highest yielding entries were high-yielding in each enviile varieties of foxtail millet. The ability to hybridize ronment. High-parent heterosis for grain yield was detected in 18 of foxtail millet opens other options to breeders besides 21 F2s. On the basis of the estimate of average heterosis, which was selecting from land races. If nonadditive gene action is highly significant in every environment, the expected yield of the F1 important, then either midand/or high-parent heterosis generation was 68% greater than the average yield of the parental cultivars. This high level of heterosis for grain yield suggested that may be sufficient to justify the production and use of varietal crosses or other types of cultivars in which there exists a varietal crosses. relatively high amount of heterozygosity would provide a significant Information on the inheritance of important agroyield benefit over nonhybrid cultivars. Although significant heterotic nomic traits of foxtail millet, including susceptibility to effects were observed for each of the other traits, additive effects key diseases, is limited. Most of the previous work has were more important. Significant correlations between traits of the focused on estimating broad-sense heritabilities and reestimates of additive and/or variety heterosis effects suggested that alized genetic gains, with little attention directed to meaat least some of the genes controlling grain yield, plant height, and suring levels of heterosis or to assessing the relative imspike length were either the same or in coupling phase linkage. portance of different types of gene action (Athwal and Singh, 1966; Singh and Athwal, 1966; Gill and Randhawa, 1975; Vishwanatha et al., 1981; Gurunadha Rao I the great plains of the USA, foxtail millet is et al., 1984; Prasada Rao et al., 1985). Darmency et used primarily as a warm-season annual forage. The al. (1987) reported that most of 19 morphological and USDA has not released any estimates of land area reproductive traits were probably under the control of planted to foxtail millet. However, it is often included nonadditive genetic components, but this research was in wheat–continuous crop rotations, which in some enviconducted on an interspecific cross between foxtail milronments have been shown to be superior to the more let and its wild relative S. viridis (L.) P. Veauv. Also, traditional wheat–fallow rotations (Senft 1998). The information on the importance of genotype environgrain of foxtail millet also is harvested for pet birdseed, ment interaction for this species when grown in environand in China, India, and other parts of East Asia this ments of the Great Plains is lacking. species has been an important food crop for centuries. Important agronomic traits in foxtail millet include Foxtail millet is largely a self-pollinating species. Outnot only grain yield, days to heading, days to maturity, crossing rates have been estimated from 0.0 to only and plant height, but also number of tillers and spike 1.4% for plants separated by 0.30 m (Till-Bottraud et length. When foxtail millet is used as a forage, tillering al., 1992), although Li et al. (1935) reported rates as is a desirable trait. However, nontillering cultivars are high as 5.6% for some varieties under certain conditions. preferred for use in producing birdseed because the Nearly all foxtail millet cultivars grown in the USA seeds typically are larger. Spike length also is correlated are selections from land races. A primary reason that with seed size. One of the more important diseases affecting foxtail millet is leaf spot, which is caused by at M.M. Siles, D.D. Baltensperger, and G. Hein, Panhandle Research least three species of Helminthosporium spp., H. setariae and Extension Center, Univ. of Nebraska-Lincoln, Scottsbluff, NE Sawada, H. turcicum Pass., and H. carbonum Ullstrup 69361-4939; W.K. Russell and L.A. Nelson, Dep. of Agronomy and (Haenseler, 1941; Robert, 1962). Horticulture, Univ. of Nebraska-Lincoln, Lincoln, NE 68583-0915; B. Johnson, Pioneer Hi-Bred Int., 19456 State Hwy. 22, Mankato, MN The objective of this research was to determine the 56001; L.D. Van Vleck, Dep. of Animal Science, Univ. of Nebraskapresence and importance of heterosis for grain yield Lincoln, Lincoln, NE 68583-0908; S.G. Jensen, Dep. of Plant Pathand other important agronomic traits of foxtail millet. ology, Univ. of Nebraska-Lincoln, Lincoln, NE 68583-0722. A contriAlso, the relative importance of genotype environbution of the Univ. of Nebraska Agricultural Research Division, Lincoln, NE 68583. Received 20 Aug. 2003. *Corresponding author mental effects and the interaction of heterosis with these ([email protected]). effects were measured. This information is needed by breeders to determine the best types of cultivars to Published in Crop Sci. 44:1960–1965 (2004). develop and to design testing programs with appropriate © Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA numbers and types of environments.