Heritability of Lipase Activity of Oat Caryopses

Selection for oat cultivars with lower lipase activity may be important for other purposes. Lipase may have Oat (Avena sativa L.) is a potentially economically viable source a role in the initiation of oxidative rancidity by some of lipase, an enzyme used in foods, chemicals, and pharmaceuticals, which occurs on the surface of oat caryopses (groats). The objectives lipoxygenases that cause off-flavors in malt and beers of this study were to: (i) estimate the broad-sense heritability of and spoilage of wholemeal flour (O’Connor et al., 1992). the lipase activity of oat caryopses, (ii) determine the genetic and Lipase activity is significantly higher in oat than in both phenotypic correlations between lipase activity and other important barley (Hordeum vulgare L.) and wheat (Triticum aestiagronomic traits, and (iii) test whether five cycles of recurrent selection vum L.). Higher oil content increases feeding value of for test weight caused a correlated response in lipase activity. Entries oat (Stothers, 1977), and selection for increased groatincluded 10 check cultivars, 95 randomly chosen S0-derived lines from oil percentage has been successful (Schipper and Frey, the initial cycle (C0), and 19 S0-derived lines from C5 of a population 1991). Low lipase activity may be particularly important developed by randomly mating oat cultivars and lines adapted to the for high-oil oat cultivars. midwestern USA. Entries were grown at three Iowa locations in 1996 Parmar et al. (1994) detected significant differences and 1997. Broad-sense heritability estimates for lipase activity were 0.22 on a sample basis in the population, and 0.63 on a line-mean basis. for lipase activity among early and midseason oat cultiLipase activity had positive genetic correlations with total biomass (r 5 vars. After a 5-d reaction period, the mean lipase activity 0.31), heading date (r 5 0.53), and plant height (r 5 0.58), positive for early oat lines ranged from 28.7 to 52.7% hydrolysis phenotypic correlations with heading date (r 5 0.18) and plant height and that for midseason oat lines ranged from 32.3 to (r 5 0.26), and negative phenotypic correlations with biomass (r 5 61.3%. Both the groat percentage and the groat weight 20.13), test weight (r 5 20.30), weight of 50 seeds (r 5 20.18), weight had significantly negative correlations with lipase activof 50 groats (r 5 20.40), and groat percentage (r 5 20.34). The C0 ity. Groat weight and groat percentage, among other and C5 populations did not differ for mean lipase activity, indicating seed traits, affect test weight; therefore, selection for that selection for increased test weight did not affect lipase activity. test weight may cause changes in groat weight and groat We suggest that selection for cultivars with higher lipase activity and percentage, which may affect lipase activity. Test weight acceptable grain quality is possible. is the primary indicator of oat grain quality, so it is important to determine if test weight and lipase activity have a genetic correlation. The objectives of this study were to: (i) estimate the H of fats and oils to free fatty acids is imbroad-sense heritability of lipase activity of oat caryopportant in the production of detergents and a numses; (ii) determine the genetic and phenotypic correlaber of other industrial products (Vulfson, 1994). Curtions between lipase activity and other important agrorently, the energyand capital-intensive Colgate-Emery nomic traits; and (iii) test whether five cycles of process is employed to achieve commercial hydrolysis recurrent selection for test weight caused a correlated of fats and oils (Sonntag, 1982). The surfaces of oat response in lipase activity in a population developed by caryopses (groats) are rich in lipase, an enzyme which randomly mating oat cultivars and genotypes adapted hydrolyzes esters and lipids at a lipid-water interface. to the midwestern USA. Results from this study will Oat has the potential to be an economical source of allow predictions of the effectiveness of direct and indilipase for industrial hydrolysis under mild conditions rect selection for altered levels of lipase activity. and with relatively simple equipment (Shahani, 1975; Lee and Hammond, 1990; Parmar and Hammond, MATERIALS AND METHODS 1994). Oat lipase does not have obvious substrate specificity (O’Connor et al., 1992). Parmar and Hammond Plant Materials (1994) suggested that higher lipolytic activity of oat We estimated the heritability of lipase activity in an oat groats can be achieved by (i) using an impact-type depopulation originally developed from crosses between huller instead of a wringer-type dehuller, (ii) using cultiadapted lines and cultivars. Klein et al. (1993) conducted recurvars specifically selected for high lipase activity, (iii) rent selection for higher test weight in this population. We exposing the fats to two to three lots of moist caryopses, randomly selected 95 lines (K475-K557) from the initial popuand (iv) dilution of the substrate with hexane. Developlation (C0) and 19 lines (P171-P270) from the fifth cycle of ment of oat cultivars with increased lipase activity may selection (C5) for higher test weight. The seeds of each line attract new market uses for oat. planted in 1996 represented progeny derived from two generations of self-fertilization (S2 generation) from a non-inbred S.W. Hoi and J.B. Holland, Dep. of Agronomy; E.G. Hammond, parent (S0 generation). Therefore, we refer to the lines tested Dep. of Food Science and Human Nutrition and Center for Crops Utilization Research, Iowa State Univ., Ames, IA 50011. Journal Abbreviations: CRx 5 correlated response of Trait X obtained by Paper no. J-17869 of the Iowa Agric. and Home Econ. Exp. Stn., indirect selection for Trait Y; Rx 5 response of Trait X obtained by Ames, IA 50011. Project 3368. *Corresponding author (jbhollan@ direct selection for Trait X; ix, iy 5 selection intensity for traits X and iastate.edu). Trait Y, respectively; hx, hy 5 square root of narrow-sense heritability of traits X and Trait Y, respectively. Published in Crop Sci. 39:1055–1059 (1999).