Richard C. Johnson

Oil and meal characteristics of core and non-core safflower accessions from the USDA collection

Germplasm evaluation of ex situ collections is needed to document collection characteristics, enhance utilization, and to determine collection needs. The objectives of this study were to (1) provide oil and meal evaluation information for a major portion of the United States Department of Agriculture (USDA) safflower (Carthamus tinctorius L.) collection, (2) compare ranges, variances and means between 203 core and 797 non-core accessions, and (3) determine if region of origin could be differentiated based on accession oil and meal characteristics. Means of the core and non-core accessions differed for % oil, palmitic acid, stearic acid, α-tocopherols, and phenolic glucosides (both bitter and cathartic) (P<0.05). Differences between linoleic acid, oleic acid and β-tocopherol means were not significant, and the variance between core and non-core accessions differed only for palmitic acid. Thus the core was not fully representative of the non-core accessions, but did capture a large fraction of the diversity in oil and meal factors present. Accessions from the Americas, China, South-West Asia, and South-Central Asia were differentiated using canonical discriminate analysis, but these regions overlapped to varying degrees with the E. European, Mediterranean, and E. African regions. Variation in % oil and fatty acids were generally more important than tocopherols and phenolic glucosides in differentiating accessions on a regional basis. The check cultivars Montola 2001 (high oleic) and Morlin (high linoleic) had oil and fatty acid content comparable to the maximums found in the collection. The ranges for tocopherols and phenolic glucosides among collection accessions, however, exceeded those of the cultivars, suggesting that collection accessions could be useful for genetic manipulation of these factors.

Relationship between relative water content during reproductive development and winter wheat grain yield.

SummaryWater is often the most limiting factor to winter wheat (Triticum aestivum L.) production in the southern Great Plains of the U.S.A., yet the lack of reliable screening criteria has precluded direct selection for drought resistance in breeding programs. Previous work showed that leaf relative water content (RWC) was highly heritable when measured under field-drought conditions, but its adoption as a screening tool for yield improvement requires further investigation of the genetic relationship between grain yield and RWC. Plants representing high and low yield potential under drought stress, and a random group of plants, were selected from an F2 population having the pedigree, TAM W-101/Sturdy. Two sets of entries, each comprised of the two parents and 24 F2-derived lines, were evaluated under a rainshelter in the F3 (1986) and F4 (1987) generations to determine differences in leaf RWC during reproductive development. One set of entries did not receive any water after the jointing stage, and the other set was grown under well-watered conditions. A positive relationship was observed between grain yield and RWC measured during anthesis and mid-grain fill, as the high-yield selections maintained a significantly higher RWC than the low-yield selections. Grain yield and RWC were also positively associated among random selections segregating for both traits. Subsequent adjustment of genotype means for differences in reproductive development at time of sampling underscored the need to consider differences in maturity when RWC is the selection criterion.

Characterization of the USDA Poa pratensis collection usingRAPD markers and agronomic descriptors

Characterization of germplasm collections is critical to assesscollection diversity and enhance utilization. A Poapratensis L. germplasm collection of 228 accessionsrepresenting 26 countries, along with 17 commercial check cultivars,was characterized using 86 random amplified polymorphic DNA(RAPD) markers and 17 agronomic descriptors. The Dicesimilarity coefficient used for RAPD data ranged from 0.56 to 0.95and average Euclidean distance used for agronomic data ranged from0.28 to 2.52. No two accessions had a similarity of one or a distanceof zero, showing there were no duplicate entries. Cluster analysis ofRAPD data using the unweighted pair-group method usingarithmetic averages (UPGMA) revealed 11 accessions withparticularly low similarity values. These were subsequently found tobe misidentified Poa species (one each ofP. alpina,P. compressa,P. glauca,P. urssulensis and sevenP. trivialis). ForRAPD data, 62% of the entries were in one large cluster with46 additional clusters containing one to 13 accessions. For agronomicdata, 89% of the entries were in four main clusters. Thisclustering pattern for RAPD and agronomic data suggested uniquegenotypes were generally under represented in the collection. Theagronomic-based clusters showed some broad separation byaccession origin, but in general, origin did not correspond closelywith the clustering pattern. The correlation between the RAPD andagronomic-based distance matrices, excluding misidentifiedaccessions, was highly significant (P<0.01) (n= 234, r = − 0.14). However, the correlationrepresented a relatively small fraction of the total variation,indicating that both molecular and agronomic characterizations wereneeded to assess overall diversity.

Characterization of a USDA Kentucky Bluegrass (Poa pratensis L.) Core Collection for Reproductive Mode and DNA Content by Flow Cytometry

Kentucky bluegrass (Poa pratensis L.) is an important turf and forage grass species with a facultative apomictic breeding behavior. In this study, mature seed and leaf tissue from 38 accessions of a USDA core collection of Kentucky bluegrass were analyzed with flow cytometry to characterize the reproductive mode and DNA content for each accession. Major reproductive pathways for each accession were determined based upon the presence and the position of the peaks observed and the known methods of reproduction for Kentucky bluegrass. While the majority of the accessions exhibited facultative apomictic reproductive behavior with a combination of reduced, zygotic and unreduced, parthenogenic embryo production, obligate sexual or obligate apomictic accessions were also found to be present in this core collection. In addition, reduced, parthenogenic and unreduced zygotic embryos were also detected in several accessions. Flow cytometric analysis of somatic tissue revealed a large range of DNA variation within this core collection. We also examined the sensitivity of flow cytometry in analyzing bulked samples containing a large number of plants with varied DNA content and determined that flow cytometry can effectively detect a plant having a different DNA content within a 15-plant bulk sample. Overall the combination of mature seed and somatic tissue analysis generated important information for the Kentucky bluegrass core collection and can be an effective and affordable tool to characterize even greater numbers of Kentucky bluegrass accessions.