Peanut (Arachis hypogaea L.) has the potential to become a major source of biodiesel, but for market viability, peanut oil yields must increase. Oil yield in peanut is influenced by many different components, including oil concentration, seed mass, and mean oil produced per seed. All of these traits can potentially be improved through selection as long as there is sufficient genetic variation. To assess the variation for these traits, a diallel mating design was used to estimate general combining ability, specific combining ability, and heritability. General combining ability estimates were significant for oil concentration, weight of 50 sound mature kernels (50？SMK), and mean milligrams oil produced per SMK (OPS). Specific combining ability was significant for oil concentration. Reciprocal effects were detected for OPS. Narrow-sense heritability estimates were very high for oil concentration and 50？SMK and low for OPS. The low OPS heritability estimate was caused by the negative correlation between oil concentration and seed size. Consequently, oil concentration and seed mass alone can be improved through early generation selection, but large segregating populations from high oil crosses will be needed to identify progeny with elevated oil concentrations that maintain acceptable seed sizes. 1. Introduction The cultivated peanut (Arachis hypogaea L.) is an important annual oilseed crop planted as a food group throughout the world. In the USA, over one million acres of peanut were planted in 2012 [1]. Peanut has potential as a source of biofuel, but because it must compete for food use, increases in oil production on a per acre basis are essential if the crop is to be used as a source of oil for biofuel conversion. Previous studies conducted with peanut indicate that selectable genetic variation exists for oil content. Additive effects (general combining ability (GCA)) were more important than nonadditive effects (specific combining ability (SCA)) for determining oil content in studies measuring populations [2, 3] and an population [4]. The performance of parental lines was generally a good predictor of hybrid oil content [3, 4]. Cytoplasmic (maternal) effects were significant in the generation in a study by Isleib et al. [3] but were much less pronounced in a study using s [4]. Layrisse et al. [4] observed a significant positive correlation between oil content and yield based on GCA effects. Correlations between oil content and seed mass, pod weight, and pod length were not significant. Dwivedi et al. [5] determined that high oil content can be
E. E. Sykes and T. E. Michaels, “Combining ability of Ontario-grown peanuts (Arachis hypogaea L.) for oil, fatty acid, and taxonomic characters,” Peanut Science, vol. 13, no. 2, pp. 93–97, 1986.
T. G. Isleib, H. E. Pattee, and F. G. Giesbrecht, “Oil, sugar, and starch characteristics in peanut breeding lines selected for low and high oil content and their combining ability,” Journal of Agricultural and Food Chemistry, vol. 52, no. 10, pp. 3165–3168, 2004.
A. Layrisse, J. C. Wynne, and T. G. Isleib, “Combining ability for yield, protein and oil of peanut lines from South American centers of diversity,” Euphytica, vol. 29, no. 3, pp. 561–570, 1980.
S. L. Dwivedi, R. Jambunathan, S. N. Nigam, K. Raghunath, K. R. Shankar, and G. V. S. Nagabhushanam, “Relationship of seed mass to oil and protein contents in peanut (Arachis hypogaea L.),” Peanut Science, vol. 17, no. 2, pp. 48–52, 1990.
K. T. Holley and R. O. Hammons, Strain and Seasonal Effects on Peanut Characteristics, vol. 32 of Georgia Agriculture Experiment Station Research Bulletin, University of Georgia, 1968.
S. H. Patil, “Induced mutations for improving quantitative characters of groundnut,” Indian Journal of Genetics and Plant Breeding, vol. 32, no. 3, pp. 451–459, 1972.
Z. Y. Hu, W. Hua, L. Zang et al., “Seed structure characteristics to form ultrahigh oil content in rapeseed,” PLoS ONE, vol. 8, no. 4, Article ID e62009, 2013.
K. Liu, F. Orthoefer, and E. A. Brown, “Association of seed size with genotypic variation in the chemical constituents of soybeans,” Journal of the American Oil Chemists' Society, vol. 72, no. 2, pp. 189–192, 1995.
V. R. Pantalone, G. J. Rebetzke, R. F. Wilson, and J. W. Burton, “Relationship between seed mass and linolenic acid in progeny of crosses between cultivated and wild soybean,” Journal of the American Oil Chemists' Society, vol. 74, no. 5, pp. 563–568, 1997.
C. E. Simpson, J. L. Starr, S. C. Nelson, K. E. Woodward, and O. D. Smith, “Registration of TxAG-6 and TxAG-7 peanut germplasm,” Crop Science, vol. 33, no. 6, article 1418, 1993.
B. Griffing, “Concept of general and specific combining ability in relation to diallel crossing systems,” Australian Journal of Biological Science, vol. 9, no. 4, pp. 462–493, 1956.
M. D. Burow and J. G. Coors, “DIALLEL: a microcomputer program for the simulation and analysis of diallel crosses,” Agronomy Journal, vol. 86, no. 1, pp. 154–158, 1994.
H. D. Upadhyaya and S. N. Nigam, “Detection of epistasis for protein and oil contents and oil quality parameters in peanut,” Crop Science, vol. 39, no. 1, pp. 115–118, 1999.
J. N. Wilson, M. R. Baring, M. D. Burow, W. L. Rooney, and C. E. Simpson, “Generation means analysis of oil concentration in peanut,” Journal of Crop Improvement, vol. 27, no. 1, pp. 85–95, 2013.
N. D. Wilson, D. E. Weibel, and R. W. McNew, “Diallel analyses of grain yield, percent protein, and protein yield in grain sorghum,” Crop Science, vol. 18, no. 3, pp. 491–495, 1978.
S. L. Dwivedi, K. Thendapani, and S. N. Nigam, “Heterosis and combining ability studies and relationship among fruit and seed characters in peanut,” Peanut Science, vol. 16, no. 1, pp. 14–20, 1989.
H. T. Stalker and C. E. Simpson, “Germplasm resources in Arachis,” in Advances in Peanut Science, H. E. Pattee and H. T. Stalker, Eds., pp. 14–53, American Peanut Research and Education Society, Stillwater, Okla, USA, 1995.
