Assessment of Genetic Variation in Hairy Vetch Using Canonical Discriminant Analysis

For improvement of these traits in hairy vetch, it is imperative to gain insight into the magnitude of variabilFor improvement of hairy vetch (Vicia villosa Roth) as a winter ity present in the species, as this will provide the basis cover crop, it is necessary to gain insight into the magnitude of variabilfor effective selection. Phenotypic variability is the obity present in the species. This study was conducted to assess the sources of genetic and phenotypic variability of V. villosa accessions. servable physical variation present in a population and Thirteen morphological and agronomic traits were measured on 42 includes both genotypic and environmental compopopulations of V. villosa and two populations of V. pannonica Crantz nents. Genotypic variability is the component of variain field studies at Urbana, IL, for 2 yr. These measurements include tion that is due to the genotypic differences among indiinitial seed weight, germination, stem length, stem width, leaf length, viduals within a population or among populations within and leaf width in the fall and spring, winter survival, biomass, and a a species, and is the main concern of a plant breeder. ratio of organic C to total N (C:N ratio) of the plants. The multivariate The phenotype is based on quantitative and qualitative data set was analyzed by canonical discriminant analysis (CDA) in characteristics by combining the genotypic basis and combination with a clustering procedure. In this analysis, the first two its interaction with the environment (Loos, 1993). If canonical variates were significant and accounted for 94% of the phenotypic observations are based on adequately large among-accession variability. The canonical variates indicated that fall and spring measurements of the leaf and stem, and C:N ratio are sample sizes and the physical traits measured show sigthe most differentiating traits among the accessions. The canonical nificant differences among populations, they can provariates were used to cluster the accessions into four subgroups on vide a reasonable representation of overall genetic perthe basis of the differentiating traits. Canonical discriminant analysis formance (Humphreys, 1991). was useful in identifying the genetic variation and the traits that better There are several methods to measure variation. With describe the variation among hairy vetch populations. Cluster analysis univariate analyses, each variable is analyzed separately was successful in differentiating the accessions into similar subgroups allowing for substantial overlapping of results to occur. on the basis of the measured traits. Plant breeders can use the informaUnivariariate statistical techniques such as analysis of tion on variation among Vicia accessions and focus on traits of particuvariance do not explain how accessions differ when all lar significance. measured variables are considered jointly. In CDA, a multivariate statistical technique, all variables are considered simultaneously in the differentiation of populaW cover crops have long been recognized as tions. This approach results in a more powerful comparipossible tools for maintaining and improving soil son of populations than can be achieved with univariate quality and consequently addressing production and enanalysis, provided the variables are correlated. Canonivironmental concerns in agriculture (Wagger et al., cal discriminant analysis can separate among-population 1998). Leguminous cover crops provide ground cover effects from within population effects by maximizing to reduce erosion potential and synthetic fertilizer N discrimination among populations when tested against inputs. In the central midwestern USA, hairy vetch is the variation within populations (Riggs, 1973). After reported to be the most beneficial leguminous winter determination of the among-population variability, the cover crop (Bollero and Bullock, 1994). Mahalanobis distance (D) statistic can be used as an Hairy vetch has performed well under a wide range indicator of the difference between populations (Loos, of growing conditions in several locations throughout 1993). The information obtained from CDA can then the USA. However, Smith et al. (1987) observed that additionally be used to group the accessions–populatemperature limitations are a likely occurrence north tions into smaller subgroups that are more similar to of the Ohio River. Frequent winterkill of fall-seeded each other (Khattree and Naik, 2000). Multivariate proplants is likely, and when plants do survive the winter, cedures based on phenotypic, morphologic, and agrothe accumulated biomass is variable and the subsequent nomic characteristics have been used in the assessment summer crop still requires additional N fertilizer appliof genetic diversity in soybean [Glycine max (L.) Merr] cations. According to Wagger et al. (1998), it is necessary (Bains and Sood, 1984), perennial ryegrass (Lolium perto select for the following important traits in cover–cropenne L.) (Humphreys, 1991), Lolium spp. (Loos, 1993), based production systems: chemical composition for enand tall fescue (Festuca arundinacea Schreb) (Vaylay hanced N dynamics and rate of dry matter accumulation and van Santen, 2002). in relation to winter hardiness. Hairy vetch is an annual, predominantly cross-fertilizing species. In recent literature, only two cultivars of K.M. Yeater, G.A. Bollero, D.G. Bullock, and A.L. Rayburn, Dep. hairy vetch have been registered. Plant introduction line of Crop Sciences, S. Rodriguez-Zas, Dep. of Animal Sciences, Univ. (PI) 383803, named ‘Americus’, is a result of a direct of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801. Received 28 increase from a wild population (Surrency et al., 1995). Oct. 2002. *Corresponding author ([email protected]). Abbreviations: C:N ratio, carbon to nitrogen ratio; CDA, canonical Published in Crop Sci. 44:185–189 (2004).  Crop Science Society of America discriminant analysis; NPGS, National Plant Germplasm System; PI, plant introduction. 677 S. Segoe Rd., Madison, WI 53711 USA