Inheritance of groat-oil content and high-oil selection in oats (Avena sativa L.)

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<ul><li><p>Euphytica 34 ( 1985) 25 I~-263 </p><p>INHERITANCE OF GROAT-OIL CONTENT AND HIGH-OIL SELECTION IN OATS </p><p>(A VENA SATIVA L.) </p><p>A. M. TH RO and K. J. FREY </p><p>Department of Agronomy, Iowa State University, Ames. Iowa 50011. USA </p><p>Rrwived 1 MLIJ, 1984 </p><p>IYVEX WOKVS </p><p>Avena sativa, oats. groat-oil content, high-oil selection. lipids, gene action, transgressive segregation. recur- rent selection. SUMMARY </p><p>The potential for breeding for high groat-oil content in oats was investigated by (a) conducting generation means analyses on data from three matings among adapted Avenu sutiva L. cultivars, (b) practicing one cycle of phenotypic recurrent selection in a segregating population derived from eight species backcrosses (Avencr sativn x (A. sativa x A. sterilis)) among 24 parents. and (c) identifying transgressive segregates from interspecific (A. satiny x A. sterilis) matings, </p><p>Additive gene action was the most important component in explaining the variation among generation means for groat-oil content. Dominance and epistatic interactions involving dominance were not significant in any mating. Significant residual genetic variation occurred in one mating, even after additive, dominance. and three digenic interactions were fitted. The importance of additive genes action implies that desired allelic combinations for high groat-oil content can be obtained in pure-line cultivars. </p><p>One cycle of phenotypic recurrent selection using single plants as the selection units resulted in a genetic gain of 1.7 to 2.1% in groat-oil content. Individual plants selected for initiating the second cycle had from 9.5 to 12.6% groat oil. </p><p>Over all 12 interspecific matings, the Fz progeny means were similar to the midparent values. Only two were significantly deviant. Transgressive segregates for high and low groat-oil content from these matings provided evidence that A. sterilis possesses alleles for high and low groat-oil content that are different from those in the gene pool of cultivated oats. </p><p>INTRODUCTION </p><p>The energy content of oat grain is lower than that of other cereals (HUTCHINSON &amp; MARTIN, 1955; BROWN &amp; CRADDOCK, 1972). An increase in groat (caryopsis)-oil con- tent, however, could improve the energy content of oats because lipid digestion gives 2.25 times greater energy equivalent than does protein or carbohydrate (PRICE &amp; PAR- SONS, 1974). STOTHERS (1977) found that high-oil (9%) oats approached barley in feeding value for hogs. One way to increase the energy value of oats, therefore, is </p><p> Journal Paper Nb. J-l 1340 of the Iowa Agric. and Home ECon. Exp. Sm., Ames, Iowa 5001 I. Project 2447. This study was supported in parts by grants from the Iowa Committee for Agricultural Development and the International Harvester Company. Present address: Agron. Dep.. Louisiana State University. Baton Rouge. LA 70803, USA. </p><p>251 </p></li><li><p>A.M. THRO AND K. J. FREY </p><p>to develop oat cultivars with high groat-oil content(BRowN et al., 1966; FORSBERG ET AL., 1974; FREY &amp; HAMMOND, 1975). FREY &amp; HAMMOND (1975) calculated that if oats had 17% groat oil combined with present levels of grain yield and protein content they might compete as an oilseed crop for producing high quality culinary oil (KALBA- SI-ASHTARI &amp; HAMMOND, 1977). HAMMOND (1983) calculated that extraction of oil from oats with 10% groat oil would add 2 4 net per kilogram. </p><p>A wide range in groat-oil content is typical of hexaploid oats. BROWN et al. (1966) observed a range of 3.9 to 9.0% oil in 169 USA cultivars grown in Illinois, and SAHAS- RABIJDHE (1979) found 4.2 to 11.3% oil in USA and Canadian cultivars grown in Ontar- io. Most strains in recent USA Uniform Early and Midseason Oat Performance Nur- series have from 5 to 8% groat oil]. Groat-oil contents among A. sterilis L. collections vary from 2.0 to 11.6% (BROWN &amp; CRADDOCK, 1972; FREY ; HAMMOND, 1975; REZAI, 1977). These values seem relatively low when compared with oilseed crops, but oats have the highest seed-oil content of any cereal (WEBER, 1973; PRICE &amp; PARSONS, 1975). </p><p>The genotype is the major source of variation for groat-oil content in oats, and genotypic and environmental effects on this trait are additive (HUTCHINSON &amp; MARTIN, 1955; STUKE, 1960; BAKER &amp; MCKENZIE, 1972). BAKER &amp; MCKENZIE (1972) reported that progeny mean heritability ranged from 68 to 93%. Single plant heritabilities were reported by STUKE (1960) to be from 83 to 98%, and BROWN et al. (1974) obtained values of 59 to 79%. BAKER &amp; MCKENZIE (1972) and BROWN et al. (1974) found additive gene action for groat-oil content and that general combining ability (gca) effects were larger than those for specific combining ability and gca effects were correlated with parent groat-oil content. </p><p>Groat-oil content is determined largely by the genotype of the maternal plant, and this control is due to nuclear and not plasmagenes (BROWN &amp; ARYEETEY, 1973; BROWN et al. 1974). Thus the oil content of the groats from a plant estimates the capacity of the maternal genotype for oil production. </p><p>This paper reports on (a) the gene action involved in the inheritance of groat oil of oats, (b) the effectiveness of phenotypic recurrent selection for high groat-oil content in segregating populations, and (c) transgressive segregates from interspecific oat mat- ings. This information is pertinent to choosing an optimum breeding procedure for increasing oat oil yield. </p><p>MATERIALS AND METHODS </p><p>Generation means analysis. Three intraspecific matings of A. sativa were used to study gene action for total groat-oil content (Table 1). L x H and H x L matings were genetically equivalent because groat oil content does not exhibit cytoplasmic inheri- tance. Nine generations were produced for each mating: P,, P,, F,, F,, F,, BC,F,, BC2FI, BC,F,, and BC2F2 (BC, and BC2 refer to backcrosses made to P, and P2, respec- tively). The designated generation refers to the plants on which the groats used for analysis were produced. These materials were grown in the field in 1980 in a rando- mized complete block experiment with 25 entries (the seven progeny generations in </p><p> H. W. RINES &amp; R. P. HALSTEAD. Unpublished data. </p><p>252 Euphyiica 34 (I 985) </p></li><li><p>Table I. Designations of levels (i.e., H = high and 1. = low) of groat-oil content in parents of three oat matings. </p><p>Mating Groat-oil level designation </p><p>M I: Garland x Pettis LxH M2: Jaycee x Richland HxL M3: Garland x Richland LXL </p><p>each mating, plus the four cultivars used as parents) and eight replicates. Four repli- cates were sown at the Agronomy Field Research Center, Ames, and four at the North- ern Iowa Experimental Farm, Kanawha, Iowa. A plot was a hill sown with 15 seeds. and hills were spaced 30 cm apart in perpendicular directions. Experimental areas were fertilized with 28-45-45 kg/ha of N, PzO,, and KzO, respectively, and hoed as necessary to keep the experiments weed-free. Plants were sprayed with a fungicide (Dithane) at weekly intervals from anthesis to maturity to prevent foliar diseases. When the plants were mature, they were harvested, dried, and threshed. </p><p>Chemical analysis were performed on a sample of oat seeds, dehulled to provide a 3.5 to 5 g lot of groats, from each plot. The nuclear magnetic resonance method (NMR) described by CONWAY &amp; EARLE (1963) was used to analyze for oil content of the groats. For statistical analyses, for each mating a data set was constructed that contained values for seven progeny generations and the parents, and each mating was analyzed separately. </p><p>The generation-means analysis (HAYMAN, 1958) was used to estimate the contribu- tions of several genetic effects to the variation among generation means. GAMBLES notation (1962) for the genetic parameters was used, i.e. m equals the mean of the Fz, a and d are pooled additive and pooled dominance effects, respectively, over all loci, and aa, ad, and dd represent the pooled additive x additive, additive x dom- inance, and dominance x dominance digenic interaction effects, respectively. The in- verse of the variance of a generation mean was used as the weighting factor for that generation, and a weighted analysis of variance was performed on the data to obtain a weighted sum of squares for generations. Next, genetic parameters, beginning with m, were fitted sequentially. A model was judged adequate to describe the variation among generation means when the mean square for lack of fit was no longer significant when tested against the mean square for generations x environment interaction from the overall analysis of variance. Genetic effects were estimated for each trait in each mating via weighted least squares analysis, and standard errors of the estimates were calculated by using the method of DARnAH (1970). </p><p>Selection for high groat-oil content. Selection was initiated among and within the pro- genies of eight three-way matings (species backcrosses). Initially, eight interspecific single-cross matings were made by crossing each one of eight A. sterilis accessions with a different one of eight A. sativa cultivars (Table 2). All 16 parents used in the interspecific matings had high groat-oil content. Parents of both species were chosen from geographically separate regions so as to include as much genetic diversity as possible. A. sativa parents mated with the interspecific single-cross matings to produce </p></li><li><p>A.M. THRO AND K. J. FREY </p><p>Table 2. Geographic origin and groat-oil content for parents of eight three-way matings (Avena sativq~ x (A. sativq x A. sterilis)) of oats. </p><p>Parent Geographic origin </p><p>Avena sativa I. High-oil group CI 6857 Florida, USA Lodi Wisconsin, USA MO-0-5499 Missouri, USA wright Wisconsin, USA MO-0-205 Missouri, USA Orbit New York, USA CI 3445 India Dal Wisconsin, USA </p><p>A. sterilis PI 28273 1 Israel PI 296247 Israel PI 309193 Israel PI 309430 Israel PI 324806 Algeria PI411540 Algeria PI411971 Iraq PI 412443 Sicily </p><p>A. sativa II. Agronomic group Noble Indiana, USA Otee Wisconsin, USA Spear South Dakota, USA Lang Illinois, USA stout Indiana, USA CI 9273 Iowa, USA Pettis Missouri, USA PI 469112 Iowa, USA </p><p>x </p><p>Groat oil content (%I </p><p>10.7 8.2 9.2 8.6 8.9 7.2 </p><p>11.0 8.5 </p><p>9.1 9.7 </p><p>10.0 9.1 9.3 </p><p>10.2 9.4 9.7 </p><p>6.8 7.3 8.8 7.0 5.9 9.3 9.0 9.3 </p><p>8.8 </p><p>three-way matings were eight cultivars and breeding lines (Table 2) chosen for excel- lence of grain yield, groat-oil content, test weight, and lodging resistance. </p><p>F, seeds within three-way matings were heterogeneous, so to adequately sample the variation within a three-way mating, 20-25 F, seeds of each three-way mating were sown in the greenhouse, and ca. 100 selfed seeds were harvested from each of 10 plants per mating. The 8000 F, seeds from the three-way matings (100 seeds from each of 10 F, plants from each of the eight three-way crosses) were space-sown in the field in April, 1979, at the Agronomy Field Research Center near Ames, Iowa, on a Webster loam soil (line loamy, mixed, mesic Typic Haplaquodoll). Spacing was 15 cm within rows and 0.9 m between rows. Cultural practices were the same as those described for the generation-means experiment. </p><p>When plants were mature, the surviving 4447 plants were harvested and threshed individually. Threshed seed lots from individual plants were examined for agronomic </p><p>254 Euphytica 34 (1985) </p></li><li><p>GROAT-OIL COUTENT IN OATS </p><p>Table 3. Parents, their geographic origin, and means of groat-oil content for parents and Fz progenies from Avenn sativa x A. sterilis matings. </p><p>Female parent (A. sativa) </p><p>Groat-oil Male parent (A. strrilis) x content (7;) </p><p>PI PI PI PI 411540 412443 411971 324819 (Algeria) (Turkey) (Iraq) (Algeria) 9.3 8.5 8.5 9.3 x.9 </p><p>Dal (Wisconsin, USA) 7.7 8.8 8.5 7.6 8.7 8.4 Orbit (New York, USA) 6.1 7.9 7.4 7.9 8.3 7.9 CI 3445 (India) 9.7 9.6 8.5 9.1 10.0 9.3 </p><p>X 8.0 8.8 8.1 8.2 9.0 8.5 </p><p>quality, and 667 lots that had white or yellow hulls and were awnless were used for oil analyses. A 3.5 to 5.0 g sample of groats from each of the 667 F2 plants was analysed for oil content by using the NMR method (CONWAY &amp; EARLE, 1963). Next, 72 F, lines derived from 72 F, plants that bore seed with groat-oil content of 7.5:: or greater were selected as parents for the first cycle of recurrent selection. </p><p>Remnant seeds from the 72 F, plants were sown in the greenhouse, and 36 biparental matings were made with each mating involving parent lines derived from different three-way matings. F,s from the 36 matings were sown in the greenhouse, and when mature approximately 100 F, seeds were harvested from one or more F, plants from each mating. About 2500 F, seeds were space-sown in the field in 1981 at the Agron- omy Field Research Center, Ames, utilizing cultural conditions similar to those de- scribed before. Drought was severe at Ames in 1981, and only 286 plants produced sufficient seed for groat oil analysis. Ninety lines derived from F, plants with groat-oil content of 9.5% or greater in their seeds were selected to continue this project. This 90-line sample included at least one line from each of 25 of the 36 biparental matings. </p><p>Factorial interspecific matings. A factorial set of 12 interspecific matings was made among four A. sterilis accessions and three A. sativa cultivars (Table 3). All parents were chosen for high groat-oil content. As far as possible, parents were chosen from geographically separated regions. Seeds from the exact plants used as parents and F1 seeds of the matings were space sown in a split-plot randomized block design with two replicates at the Agronomy Field Research Center, Ames, Iowa. Whole plots were matings and subplots were generations within a mating (P, or A. sativa parent, PJ or A. sterilis parent, and F,). Rows within plots were 3 m long with 0.9 m between rows, and 20 seeds were sown per row at 15-cm intervals. In each whole plot, parents were represented by one row (20 seeds) each and the F, progeny by five rows (100 seeds). Soil type and cultural practices for this experiment were as described earlier. </p><p>Panicles of A. sterilis parents and of Fz segregates that shattered were covered when panicles were completely emerged with bags made of Delnet PQ 218 high density polyethylene nonwoven fabric (Hercules, Inc., Wilmington, DE 19899). Light intensity under the bags was reduced by 9.5%. At maturity, 10 random plants were harvested from each row. Plants were threshed separately, and a 3.5 to 5 g groat sample from </p><p>Euphyrica 34 (1985) 255 </p></li><li><p>A. M. THRO AND K. J. FREY </p><p>each plant was analyzed for oil content by the NMR method (CONWAY &amp; EARLE, 1963). </p><p>Oil percentages from individual plants in a plot were averaged to give a plot mean, and plot means were used to compute analyses of variance according to the model for a split-plot design. Next, F, progeny data were analyzed as a cross-classification design to permit the computation of components of variance for effects of males, ef- fects of females, and interaction of males and females. Components for males and female equate to variance due to general combining ability ($&amp;, and the interaction component equates to specific combining abi...</p></li></ul>