Correlated Responses to Selection for Greater -Glucan Content in Two Oat Populations

Kibite and Edney, 1998; Cervantes-Martinez et al., 2001). Cervantes-Martinez et al. (2001) conducted one cycle Oat (Avena sativa L.) -glucan lowers serum cholesterol in huof phenotypic selection of individual S0 plants for greater mans. Thus, enhancing its content in oat cultivars for human consumption is desirable. Phenotypic selection for greater -glucan content -glucan content in two genetically broad-based oat was effective in two broad-based oat populations, BG1 and BG2. The populations. They found that mean -glucan content initial and selected cycles of each of these populations were evaluated increased 5.9 and 2.6 g kg 1, and the genetic variance in 1996 and 1997 at two Iowa locations to determine the correlated decreased by 9 and 22% in the two populations, respecresponses of agronomic and grain quality traits to selection for greater tively. Rankings of oat lines for -glucan were generally -glucan content. Correlated responses were generally unfavorable consistent across environments. These findings indicate for agronomic performance, but favorable in terms of human nutrithat phenotypic selection for greater -glucan content tional value of oat grain. Mean protein content increased by 5% in will be effective to develop cultivars with elevated -gluone population while mean oil content and heading date did not can content. change. Mean grain yield, biomass, and test weight were reduced by The potential association of oat -glucan content with 25, 23, and 2%, respectively, in one population and not affected in the other. Plant height decreased by 5% in one population only. agronomic characteristics and other grain quality traits Genotypic variances were unchanged by selection, except the genetic is important to consider because selection for greater variance for plant height in BG2 increased. Selection strengthened -glucan content might also change other traits as a negative genotypic correlations between -glucan content and grain correlated response. Correlated responses may cause yield, biomass, and oil content in both populations, and between changes in favorable or unfavorable directions in agro-glucan content and test weight, heading date, and height in one nomically important traits when direct selection for a population. -Glucan yield (the product of -glucan content and grain single trait is practiced. For example, Payne et al. (1986) yield) was positively genotypically correlated with both grain yield reported that three cycles of recurrent selection for grain (r 0.92 in both populations) and -glucan content (r 0.66 and yield in spring oats increased grain yield, kernel number, r 0.26 in the two populations). Selection for greater -glucan yield kernel weight, and rate of grain filling, whereas heading could be used to improve -glucan content and grain yield simultaneously. date and maturity were delayed. Schipper and Frey (1992) found that five cycles of recurrent selection for greater groat oil content in oat did not affect groat protein content, but four cycles of recurrent selection H serum cholesterol level is a major risk factor for greater groat protein increased groat oil content. of premature heart disease in humans (Phillips et Correlated responses to selection depend in part on al., 1978; Mayes, 1990). Oat soluble fiber lowers blood the genotypic correlation between the selected trait and cholesterol levels when consumed in the daily diet, parother traits. Genotypic correlations are caused by either ticularly in those individuals with initially high blood chopleiotropy, in which the same gene affects different lesterol level (Kurtzweil, 1994; Welch, 1995). Dietary contraits, or linkage, when traits are controlled by different trol of serum cholesterol may, therefore, have a major genes but the loci are genetically linked (Falconer and impact on human health. The component responsible for Mackay, 1996). Phenotypic correlations between traits lowering serum cholesterol is (1→3)(1→4)-D-glucan, can be due to genetic or environmental effects or both. or -glucan, a cell wall polysaccharide found in the en-Glucan content is not strongly correlated with grain dosperm and subaleurone layers of cereal seeds (Davidyield (Holthaus et al., 1996; Kibite and Edney, 1998). son et al., 1991; Behall et al., 1997). Oat cultivars with However, Holthaus et al. (1996) reported a low positive greater -glucan concentrations are desirable for huphenotypic correlation, Kibite and Edney (1998) found man consumption. a low negative phenotypic correlation, and Peterson Oat -glucan content is a polygenic trait controlled et al. (1995) reported both low positive and negative by genes with mainly additive effects and no intergenic correlations of -glucan with grain yield. Phenotypic interaction, with heritability estimated on a single plot correlations of -glucan with yield also can change from basis ranging from 0.45 to 0.58 (Holthaus et al., 1996; positive to negative depending on the environment (Brunner and Freed, 1994). -Glucan content also has C.T. Cervantes-Martinez, Univ. Autonoma Chapingo, Carretera Mexico-Texcoco km 38.5, Texcoco, Edo. de Mex., Mexico 56230; K.J. exhibited positive or nonsignificant correlations with Frey, Dep. of Agronomy, and P.J. White, Dep. of Food Science and test weight (Peterson et al., 1995), protein content Human Nutrition, Iowa State Univ., Ames, IA 50011; D.M. Wesenb(Brunner and Freed, 1994), and groat percentage (Holerg, USDA-ARS, National Small Grains Germplasm Research Facilthaus et al., 1996). However, Saastamoinen et al. (1992) ity, P.O. Box 307, Aberdeen, ID 83210; and J.B. Holland, USDAARS Plant Science Research Unit, Dep. of Crop Science, Box 7620, Abbreviations: BLUP, best linear unbiased predictor; h2, heritability; North Carolina State Univ., Raleigh, NC 27695-7620. Received 25 NIRS, near-infrared reflectance spectroscopy; NMR, nuclear magMay 2001. *Corresponding author ([email protected]). netic resonance; PI, plant introduction; REML, restricted maximum likelihood; SEC, standard error of calibration. Published in Crop Sci. 42:730–738 (2002).