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PLANT GENETIC RESOURCES

Patterns of Variation in a Collection of Meadow Fescue Accessions

^a Dep. of Agronomy, Univ. of Wisconsin-Madison, Madison, WI 53706-1597 USA
^b Dep. of Agronomy, Auburn Univ., Auburn, AL 36849-5412 USA

mdcasler{at}facstaff.wisc.edu

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 
Meadow fescue (Festuca pratensis Huds.) is a pasture grass that has been little used in North America since the introduction of its higher yielding relative tall fescue (F. arundinacea Schreb.). The objectives of this study were to quantify genotypic variation for agronomic traits within the USDA National Plant Germplasm System (NPGS) collection of meadow fescue accessions and to relate that variation to the geographic source of the accessions. Seedlings of 213 accessions were transplanted to Ashland and Marshfield, WI, and to Crossville, AL, in 1991. Four spaced plants per accession, overseeded with white clover (Trifolium repens L.), were established at each location. Forage yield, disease reaction, morphological traits, maturity, and survival were determined in 1992 and 1993. For most traits, accessions responded similarly at the two Wisconsin locations, but differently between Wisconsin and Alabama. Phenotypic correlations between the two states were positive, but very low. Between 18 and 36% of the sum of squares for accessions was due to country or region source of each accession. Romanian and Hungarian accessions had the highest mean forage yield, with superior survival in both Wisconsin and Alabama. Several accessions had short, narrow leaf blades, thin stems, wide crowns, and high survival, suggesting potential use as turf-type germplasm. A core collection of 55 accessions was proposed on the basis of cluster analysis classification.

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 
MEADOW FESCUE is a diploid (2n = 2x = 14) forage grass widely adapted to lowlands of central and northern Europe. It is used primarily for grazing or in a frequent-cutting hay management system. Cytogenetic studies suggest it is the source of the P genome of tall fescue (Sleper, 1985). It is partially sympatric with tall fescue in the southern portion of its distribution. Molecular marker analysis suggests that it is also closely related to perennial ryegrass, Lolium perenne L. (Xu and Sleper, 1994). It hybridizes with both perennial and Italian ryegrass (L. multiflorum Lam.), but produces male-sterile hybrids with these species (Thomas and Humphreys, 1991).

There is a tetraploid cytotype of meadow fescue [F. pratensis var. apennina (De Not.) Hack.] which is adapted to altitudes above 1100 m in the Alpine massif, the Carpathian Mountains, and the Apennini Mountains (Tyler, 1988). The natural distributions of tetraploid and diploid cytotypes overlap between 1100 and 1800 m of the Alpine massif and the Apennini Mtns. (Tyler et al., 1978). Triploid plants have been found in these meadows, suggesting the possibility of natural hybrids between diploid pratense and tetraploid apennina, and a mechanism for gene flow between cytotypes (Tyler, 1988).

Meadow fescue was first introduced into North America before 1800 (Kennedy, 1900) and spread throughout the USA during the 19th century (Buckner et al., 1979). Extensive forage yield testing in the late 19th and early 20th centuries led to the conclusion that tall fescue had vigor and resistance to crown rust, caused by Puccinia coronata Corda, superior to that of meadow fescue (Buckner et al., 1979). As a result, meadow fescue has not been cultivated in significant or measurable quantities in the USA since the early 20th century.

Numerous cultivars of meadow fescue have been developed by European breeding programs where meadow fescue is highly adapted and widely utilized. Of 233 F. pratensis accessions listed by the Germplasm Resources Information Network (internet address: http://www.ars-grin.gov/npgs/; verified August 17, 1999), 79 either have a cultivar name or otherwise appear to be derived from breeding programs. Meadow fescue germplasm has also been used extensively in the improvement of Lolium x Festuca hybrids (Thomas and Humphreys, 1991). Thus, it is highly likely that considerable progress has been made in breeding meadow fescue for crown rust resistance and other important agronomic traits. Four improved cultivars, two developed in Canada, were described by Alderson and Sharp (1994).

Genetic variation has been documented within numerous meadow fescue populations for forage yield, in vitro digestibility, relative maturity, and resistance to Drechslera dictyoides (Drechs.) Shoemaker (Aastveit and Aastveit, 1990; Frandsen and Fritsen, 1982; Frandsen et al., 1978, 1981). The presence of large amounts of additive genetic variation for crown rust resistance in closely related species (Mansat and Betin, 1979; Wilkins, 1978; Wofford and Watson, 1982) implies that crown rust resistance also exists within meadow fescue. Both additive and non-additive sources of genetic variation appear to be important for agronomic traits of meadow fescue (Aastveit and Aastveit, 1989; Frandsen et al., 1981).

An evaluation of seven meadow fescue cultivars and 15 tall fescue cultivars under a free-choice management-intensive grazing system on three dairy farms showed meadow fescue to have 11% lower forage yield potential than tall fescue (Casler et al., 1998). However, mean intake, estimated as the difference between pre- and post-grazing forage yield, was similar for meadow and tall fescue. These results suggest that meadow fescue may have had higher palatability to lactating dairy cows (Bos taurus) than tall fescue. Meadow fescue cultivars varied for both pasture yield and forage intake. Thus, some meadow fescue germplasm may be useful in developing cultivars for use in intensive grazing management systems in North America.

The objectives of this study were to quantify genotypic variation for agronomic traits within the USDA-NPGS collection of meadow fescue accessions and to relate that variation to the geographic source of the accessions.

	Materials and methods

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 
This study consisted of an evaluation of 221 meadow fescue accessions from the USDA National Plant Germplasm System (NPGS) collection. Seeds were germinated in a greenhouse at Madison, WI, in January 1991 and raised as individual seedlings. Of the 221 accessions, seven did not germinate and one was incorrectly classified as F. pratensis. Seed originating from a collection site, stored at 3 to 4°C and 30 to 35% relative humidity, was used to represent as many accessions as possible (75 accessions). Accessions were otherwise represented by a first- or second-generation seed increase, which was conducted at Pullman, WA, mostly in 1986.

Wisconsin Locations
Seedlings of the remaining 213 accessions were transplanted to field sites near Ashland and Marshfield, WI, in May 1991. Soil types were Ontonagon silty clay loam [very-fine, mixed Glossic Eutroboralf] at Ashland (46°35'N, 90°54'W) and Withee silt loam [fine-loamy, mixed, frigid Aeric Glossoboralf] at Marshfield (44°40'N, 91°53'W). The experimental design at each site was a randomized complete block with two replicates. Plots consisted of a row of four plants, spaced 30 cm apart. Plots were 90 cm apart and organized into six columns within each block; columns were also 90 cm apart. Immediately after planting, the entire experimental area was broadcast seeded with a prostrate form of Dutch white clover at a rate of 7 kg ha^-1 to provide weed control and simulated sward conditions.

Plots were mowed twice in 1991, but no data were collected. Plots were managed for three cuttings in 1992 and 1993 — early June, late July, and early October. Fertilization with P and K was done according to recommendations derived from soil tests.

Data were collected immediately prior to the first cutting in 1992, in early to mid-June, when the earliest plants at each location were in mid-anthesis. Plant height was measured to the top of the highest panicle. Relative maturity of each whole plant was rated on a 0-to-8 scale: 1 = vegetative, 2 = early boot, 3 = initial panicle emergence, 4 = complete panicle emergence, 5 = full peduncle elongation, 6 = spikelet opening, 7 = anthesis, and 8 = post-anthesis. The mean maturity stages at the time of rating for the two locations were 4.2 and 4.4 (between complete panicle emergence and fully elongated peduncle). Length and maximum width of the flag leaf blade was measured on two of the most reproductively advanced tillers per plant. Stem diameter was measured on the lowermost above-ground internode of those two tillers per plant. Forage yield was rated on a visual scale of 0 = missing plant to 20 = most vigorous plant. Following the rating, 40 plants (two from each nonzero numerical rating category) were harvested at a 5-cm stubble height. These plants were dried at 60°C and weighed.

Immediately prior to the second and third cuttings, crown rust reaction was rated on a scale of 0 = no visible symptoms, 1 = 10% of youngest leaves covered with pustules, ... , 10 = 100% of youngest leaves covered with pustules. Forage yield ratings and 40-plant harvests were made for the second and third cuttings as described for the first cutting.

In 1993, forage yield, maturity, and crown rust reaction were determined as described above. The mean maturity stages for each location was 4.3 (between complete panicle emergence and fully elongated peduncle). Plant diameter was measured immediately following third harvest in 1993. Survival was computed as the percentage of plants alive in the fall of 1993.

Each set of 40 harvested plants was divided into two sets of 20, each set including one plant of each size class. A linear regression calibration was computed between forage yield ratings and dry matter yield of the 20 harvested plants for each of the 24 sets (two sets x three cuttings x 2 yr x two locations). The 24 regression data sets were paired according to cutting x year x location. Data from each member of a pair were used to validate the calibration developed in the alternate member of the pair. Regressions were judged adequate for predicting forage yield from visual ratings, with calibration R² ranging from 0.75 to 0.94 and validation r² ranging from 0.72 to 0.88. Based on these results, a single linear regression was computed from the 40 harvested plants of each cutting and used to predict forage yield of that cutting for all plants. Forage yield estimates were summed over three cuttings in each year prior to any statistical analysis. Previous work has shown that visual ratings of forage yield made by an experienced researcher had high genetic correlations (r = 0.93–0.97) with forage yield of meadow fescue (Aastveit and Aastveit, 1989).

Alabama Location
Seeds were also germinated in a greenhouse at Auburn, AL, in July 1991. Seedlings were transplanted to the field near Crossville, AL, in October 1991. The soil type was a Hartsells fine sandy loam (fine-loamy, siliceous, thermic Typic Hapludult). The latitude and longitude were 34°17'N, 85°43'W. The experimental design was the same as that used in Wisconsin, including the Dutch white clover overseeding. Plots were clipped or grazed between December 1991 and February 1993, to facilitate tillering and weed control, but no data were collected during this time. Fertilization with P and K was done according to recommendations derived from soil tests.

Plant height, relative maturity, and flag leaf blade length and width were determined on reproductive plants in April 1993, when the earliest plants were in mid-anthesis. The mean maturity stage was 5.6 (between full peduncle extension and spikelet opening). Survival was computed as the percentage of plants alive at this stage. Leaf spot reaction (most likely caused by a Bipolaris spp. or Drechslera spp.) was rated on a scale of 0 = no symptoms, ... , 10 = leaves completely covered with lesions.

Statistical Analysis
All variables were analyzed in a random-effects model by generalized least squares (Searle, 1971) to handle missing and unbalanced data. Analyses of variance were computed for each variable at each location and across locations. Variance components for accessions and accession x state and accession x location(state) interactions were computed by equating mean squares to their expectations. Phenotypic correlation coefficients between locations for each variable were used to interpret accession x location interactions.

Accession means were computed for each variable, averaged across both Wisconsin locations and both years, and separate for the Alabama location. This resulted in 15 variables, nine from Wisconsin and six from Alabama. Each of these 15 variables were subjected to a nested analysis of variance to estimate components of variance due to regions, countries within regions, and accessions with countries. Regions were defined as (i) Central and Northern Europe, (ii) Mediterranean, (iii) North America, (iv) Australia, (v) Russia–Afghanistan, (vi) Scandinavia, and (vii) Southeastern Europe.

The 15 variables were standardized and organized into 15 principal components. The principal component scores were subjected to cluster analysis using Ward's method (Milligan, 1980). Organizing the variables into principal components prior to clustering avoided inadvertent weighting that would have resulted from groups of highly correlated variables (Gnanadesikan, 1977), which were common in this data set. Instead, the principal components were weighted by their variance percentages during the cluster analysis. Use of principal components for clustering ensured that each of the 15 metric variables contributed equally, in both variance and weight, to the cluster formation.

Because of differential survival between Alabama and Wisconsin, only 186 accessions, which were observed in both states, could be used in the cluster analysis. The full cluster dendrogram was truncated at the point for which the accession sums of squares for the principal components was divided into 70% among clusters and 30% within clusters. This was judged to be a reasonable compromise between the conflicting goals of a high among-cluster variance and a low number of clusters.

	Results and discussion

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 
Of the 213 accessions transplanted to the field in 1991, nine did not survive the first winter in Wisconsin and six did not survive the first summer in Alabama. Of the nine that did not survive in Wisconsin, one was from Poland, one from Spain, five from Morocco, and two from Russia. Of the six that did not survive in Alabama, two were from Afghanistan, one from Switzerland, and three from Russia.

Genotypic Variation and Accession x Environment Interactions
Variation among accessions was significant (P < 0.05) for all variables measured at all locations. Combined analyses of variance for leaf blade length and width, plant height, maturity, and survival showed that accession x location interaction within Wisconsin was not significant, while accession x state interaction was significant (P < 0.01) for all five variables (Table 1) . Accession x state variance components were always considerably larger than accession x location(state) variance components, and equal to or larger than the experimental error variance component for all variables except survival.

Variation among Region and Country Germplasm Sources
Regions and countries within regions accounted for 17 to 36% of the sum of squares for accessions (Table 3) . Region and country sources of variation were both significant (P < 0.05) for leaf blade length, plant height, maturity, and forage yield in Wisconsin. Either the region or the country source of variation was significant for all of the other variables. These results are similar to those from evaluations of the USDA-NPGS collections of orchardgrass, Dactylis glomerata L., and perennial ryegrass (Casler, 1991, 1995).

Country means for seven of the 15 variables are shown in Table 4 ; the others were not shown because of redundancy or lack of significance. The Moroccan accession PI 347577 was the most unique, with a wide crown, narrow stems (2.0 vs. 2.2 mm; P < 0.01), short leaves, and relatively low forage yield (Table 4). Three other accessions had similarly wide crowns: two from the former Yugoslavia (PIs 277842 and 277843) and one from Bulgaria (PI 294724). The Bulgarian accession was unique among this group in having a forage yield mean higher than the overall mean (124 vs. 105 g plant^-1; P < 0.01). The Moroccan and two Yugoslavian accessions appeared to be more useful as turfgrass germplasm than as forage grass germplasm.

The Hungarian accessions had the highest mean forage yield, being significantly greater, or nearly so, than the mean for all other countries (Table 4). Hungarian accessions had mean forage yield ranging from 105 to 146 g plant^-1, all equal to or greater than the overall mean, nine of 14 significantly so (P < 0.05). For all other variables, these accessions were unremarkable, having means near the mean of all other accessions. Their high forage yield in Wisconsin and above-average survival in Alabama suggest that they have a broad range of adaptation and may be valuable germplasm for cultivar development in both regions of the USA.

There were some large differences among country sources in relative adaptation to Wisconsin and Alabama. Among the most extreme, Afghani and Finnish accessions were well adapted to Wisconsin, but highly unadapted to Alabama. Less extreme, but still preferentially adapted to Wisconsin over Alabama, were accessions from Canada, the Czech Republic, Denmark, Germany, the Netherlands, and Switzerland. These countries represent climates much more similar to Wisconsin than to Alabama. Individual accessions from three countries (Belgium, Morocco, and Norway) appeared to be more adapted to Alabama than to Wisconsin, as indicated by low survival and/or forage yield in Wisconsin. One additional accession from Bulgaria (PI 294706) had a similar adaptation response. The Moroccan germplasm would represent an adaptation zone more similar to Alabama than Wisconsin, with winter growth and summer dormancy. The apparent preferential adaptation of the single Belgian, Bulgarian, and Norwegian accessions could not be explained.

The Australian accession and all five Turkish accessions were unadapted to both states, as indicated by low survival or forage yield in Wisconsin and low survival in Alabama. Conversely, the most broadly adapted germplasm, came from Hungary and Romania. Among the 24 Hungarian and Romanian accessions, 13 exceeded the overall means for Wisconsin forage yield, Wisconsin survival, and Alabama survival. Only 24 additional accessions met each of these three criteria [Bulgaria (1), Denmark (5), Germany (1), Great Britain (1), Italy (1), Netherlands (3), Russia (8), Sweden (1), and the former Yugoslavia (3)]. The means of these 37 accessions, compared with the overall means were 92 vs. 85% survival in Wisconsin, 86 vs. 70% survival in Alabama, and 118 vs. 105 g plant^-1 in Wisconsin (all P < 0.01). These 37 accessions were generally unremarkable for all other variables. Of these 37 accessions, 28 were named cultivars or were directly derived from European breeding programs. Thus, the greatest short-term benefit for use of meadow fescue germplasm in Wisconsin or Alabama appears to be from cultivars developed in other regions. The presence of nine accessions collected from wild or naturalized sites suggests that additional plant exploration may benefit the meadow fescue collection. However, the extreme geographic diversity among these nine accessions [Romania (1), Russia (6), and the former Yugoslavia (2)] suggests that extensive exploration may be necessary to collect additional valuable germplasm as identified in this study.

Cluster Analysis
Thirty-five clusters were required to describe 70% of the variation among accession means (Fig. 1) . The clusters were highly unbalanced with respect to number of accessions (Tables 5 and 6) . Eleven of 35 clusters contained only one accession, suggesting phenotypic uniqueness of these accessions. For the 24 multi-accession clusters, their pooled within-cluster variances among principal component scores were somewhat uniform, ranging from 0.26 to 0.65, and were not associated with cluster size. Thus, any multi-accession clusters identified as phenotypically desirable should contain phenotypic variation upon which to base further selection.

View larger version (20K): [in this window] [in a new window]   Fig. 1 Cluster dendrogram for 35 clusters of 186 meadow fescue accessions, accounting for 70% of the phenotypic variation among accessions (number of accessions per cluster are in parentheses)

The cluster dendrogram was unbalanced with respect to cluster size (Fig. 1, Table 5). The upper 17 clusters (A1 through F3) contained 140 accessions, while the lower 18 clusters (G1 through L2) contained only 46 accessions. There were distinct and significant (P < 0.01) differences between these two groups of accessions (Table 6). Those accessions in the upper 17 clusters had shorter leaf blades (by 25 mm in Wisconsin and 23 mm in Alabama), narrower leaf blades (by 0.4 mm in Wisconsin and 0.8 mm in Alabama), taller plants (by 10 cm in Wisconsin and 4 cm in Alabama), earlier maturity (4.4 vs. 3.6 in Wisconsin and 5.8 vs. 4.8 in Alabama), greater survival (by 8% in Wisconsin and 15% in Alabama), 0.2 mm thicker stems, and 15 g plant^-1 higher forage yield compared with the accessions in the lower 18 clusters.

The 18 clusters in the lower portion of the dendrogram fell into two categories (Fig. 1, Table 6). Clusters G1 through G5 and J1 through L2 contained 29 accessions that tended to be relatively photoperiod sensitive. Their mean maturity rating was 3.5 in Wisconsin and 5.6 in Alabama. Only five of these 29 accessions had acceptable levels of forage yield and survival in Wisconsin, averaging 120 g plant^-1 and 90%, respectively. Of these five accessions, three (PIs 315441 and 502376 from Russia and PI 317425 from Afghanistan) were moderately adapted to Alabama, with mean survival of 67%. The other two (PI 182855 from the Czech Republic and PI 372624 from Denmark) were unadapted to Alabama, with mean survival of 31%. The other seven clusters, H1 through I5, contained 17 accessions that tended to be relatively photoperiod insensitive, with mean maturity ratings of 3.6 in Wisconsin and 3.5 in Alabama. Only three of these 17 accessions (PI 294712 from Bulgaria and PIs 314528 and 315438 from Russia) had acceptable means for forage yield and survival in both states, averaging 106 g plant^-1 in forage yield, 83% survival in Wisconsin, and 58% survival in Alabama.

Six clusters (A1, B3, C3, D3, K1, and L2) had mean forage yield significantly higher than the overall mean (Table 6; 120 vs. 105 g plant^-1; P < 0.01). Only one of these clusters (D3 with one accession, PI 295670 from Russia) had an unacceptable mean disease rating for either state. Because most of the 49 accessions in Clusters A1, B3, C3, K1, and L2 had average to high levels of survival in both states, this collective group of accessions probably represents the most valuable germplasm for developing improved and broadly adapted meadow fescue germplasm for sites similar to Wisconsin and Alabama.

In addition to the Moroccan accession, the cluster analysis identified six additional accessions in Clusters B1 and B2 that might be useful in developing a turf-type meadow fescue. These accessions (PIs 233820 and 233821 from Italy, PI 237271 from Denmark, PI 249823 from Russia, PI 272115 from Poland, and PI 311047) had mean leaf blade length shorter than average (by 30 cm in Wisconsin and 43 cm in Alabama) and narrower than average (by 0.8 mm in Wisconsin and 1.5 mm in Alabama). All six potential turf-type accessions, except PI 233821, had low disease reactions in both states. An additional accession (PI 383656 from Turkey) had extremely short and narrow leaf blades and a wide crown, but had low survival in both states.

Core Subset
Finally, the 35 clusters provide a basis for developing a core subset of meadow fescue accessions. The use of variables measured in two climatically different states broadens the applicability of the cluster analysis for use in developing the core subset. The perennial ryegrass core subset was created by drawing a random sample of two accessions each from 17 clusters similarly derived (Casler, 1995). The existence of some highly unique accessions in the meadow fescue collection led to a high frequency of clusters containing only one accession (11 of 35). Extensive use of a core subset based on a single accession per cluster will tend to overemphasize evaluation of these 11 accessions to the exclusion of a large number of more representative accessions. The unbalanced nature of the cluster dendrogram, with respect to variable means and accession frequencies between its upper and lower halves, will further exaggerate this problem. For this collection, it might be wiser to draw a frequency-dependent core subset. For example, consider s_i = n_i/5 (rounded upwards for non-integers), where s_i = the number of core subset accessions from Cluster i and n_i = the total number of accessions in Cluster i. This formula would provide a core subset of 55 accessions (30% of those tested), preserving a more representative portion of accessions from Clusters A1 through F3 (64% of the core subset compared to 78% of the entire collection from these clusters).

	ACKNOWLEDGMENTS

 
We thank Mike Mlynarek (Ashland) and Dan Wiersma (Marshfield) of the Department of Agricultural Experiment Stations, University of Wisconsin-Madison, for their willingness to provide land and to assist with plot maintenance. We thank Vicki Bradley, Richard Johnson, and Dave Stout of the USDA-ARS-NPGS Western Region Plant Introduction Station, Pullman, WA, for supplying seeds, answers to many questions, and moral support. We thank the members of the Forage and Turf Grass Crop Germplasm Committee for approving our funding request and for their intellectual support. We thank Kay Asay, Kevin Jensen, and Jerry Chatterton of the USDA-ARS Forage and Range Unit, Logan, UT, for financial support of this project from their CRIS. We also thank Richard R. Smith, USDA-ARS Dairy Forage Research Center, Madison, for assisting in the transfer of funds from Logan, UT, to Madison.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion REFERENCES

 
This research was supported by the USDA-ARS, Forage and Range Research Lab., Logan, UT, and CRIS Project No. 5428 21000 005 00D, "Evaluation and Enhancement of Cool-Season Forages."

Received for publication January 7, 1999.

	REFERENCES

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