Nine Cycles of Recurrent Selection for Increased Groat-Oil Content in Oat

and range from 0.50 to 0.93 (Baker and McKenzie, 1972; Branson and Frey, 1989b; Brown et al., 1974; Schipper Increases in the groat (caryopsis)-oil content of oat (Avena sativa and Frey, 1991b). Genotype 3 environment interaction L.) raise the energy value of oat grain. Nine cycles of recurrent phenotypic selection for high groat-oil content were conducted in a genetifor groat-oil content is not a major component of its cally broad-based oat population that included germplasm from the phenotypic variance (Branson and Frey, 1989b; Gullord, wild relative A. sterilis L. Our objectives in this experiment were to 1986; Thro and Frey, 1985). Genotypic variation for determine if selection for high groat-oil content was effective and if groat-oil content has been observed among adapted culselection reduced genetic variation for oil content; to identify agrotivars (Brown and Craddock, 1972) and among wild nomically acceptable lines with high groat-oil content; and to docurelatives, including the progenitor species, A. sterilis ment the indirect effects of selection on grain yield, groat fraction, (Frey and Hammond, 1975; Martens et al., 1979). Aland oil yield. We evaluated 100 random lines from the base (C0) though the groat-oil content of wild Avena species does population and each of the nine selection cycle populations in three not exceed the levels found in domesticated oat (Rezai, environments. Mean groat-oil content increased linearly during nine 1977), Thro and Frey (1985) reported that alleles for cycles of selection at a rate of 6.6 g kg21 cycle21 (equivalent to 6.7% of C0 population mean cycle21) from a mean of 98.2 g kg21 in C0 to higher oil content from A. sativa and A. sterilis are 158.5 g kg21 in C9. The rate of gain from selection did not decrease complementary. Thus, by combining alleles for higher in later cycles. Oil yield increased at a rate equivalent to 1.9% of C0 oil content from the two species, development of oat population mean cycle21, while mean groat fraction did not change genotypes with higher groat-oil contents than any preand mean grain yield decreased at a rate equivalent to 3.2% of C0 viously reported in either species was facilitated (Thro population mean cycle21. For all traits, genetic variation did not deand Frey, 1985). crease during selection cycles. Selected S0-derived lines from the popuThe abundance of genetic variation for oil content in lation with groat-oil contents .150 g kg21 exhibited lower yield, cultivated oat and interfertile wild hexaploid oat and greater lodging, and greater disease susceptibility compared with the the higher heritability of the trait permit relatively rapid best check cultivar. increases in groat-oil content from recurrent selection. Branson and Frey (1989b) developed a population from crosses among cultivated and wild oat germplasm with I in the groat (caryopsis) oil content of higher levels of groat-oil content. Three cycles of recuroat would be useful for producing a higher energy rent selection for increased groat-oil content in this popfeed grain (Price and Parsons, 1975). Oat oil also has ulation resulted in significantly elevated mean groat-oil excellent quality for human consumption, with relatively content in the third cycle population (Branson and Frey, low linolenate (18:3) and high oleate (18:1) and linoleate 1989b). Three further cycles of recurrent selection re(18:2) contents (Kalbasi-Ashtari and Hammond, 1977). sulted in continued gains in groat-oil content, achieved Oat oil from genotypes with elevated levels of oil tends at a reasonably constant, linear rate (Schipper and Frey, to be particularly favorable for human consumption, 1991b). Significant genetic variation for groat-oil conwith higher levels of antioxidants (Peterson and Wood, tent remained in the Cycle 6 population, suggesting that 1997) and higher ratios of unsaturated to saturated fatty continued gains in groat-oil content could be achieved acids than normal genotypes (Schipper et al., 1991). If in this population. Also, long-term recurrent selection oat cultivars with higher groat-oil contents and acceptfor increased seed oil content has been successful in able agronomic performance could be developed, the maize (Zea mays L.) (Dudley, 1977; Misevic and Alexuse of oat as an oilseed crop could become economically ander, 1989). The biological upper limit for groat-oil feasible (Frey and Hammond, 1975). content in oat is not known; oat lines developed from Groat-oil content in oat is quantitatively inherited six cycles of recurrent selection contained the highest (Frey et al., 1975). Gene action for groat-oil content levels of groat-oil content ever reported in the genus includes additive and nonadditive effects (Brown et al., Avena, 162.9 g kg21 (Schipper and Frey, 1991b). 1974), although additive gene action predominates Our objectives in this study were to determine if three (Thro and Frey, 1985). Consistently high estimates of additional cycles of recurrent selection would result in heritability of oil content in oats have been reported, continued increases in groat-oil content in this population; to evaluate the effects of nine cycles of recurrent Dep. of Agronomy, Iowa State Univ., Ames, IA 50011. Journal Paper selection for increased groat-oil content on grain yield, no. J-18123 of the Iowa Agric. Home Economics Exp Stn, Ames, IA. groat fraction, and oil yield; and to determine if genetic Project no. 3368 and supported by Hatch Act and State of Iowa funds. Received 9 Oct. 1998. *Corresponding author ([email protected]). Abbreviations: BYDV, barley yellow dwarf virus; NMR, nuclear magnetic resonance. Published in Crop Sci. 39:1636–1641 (1999).