Regional Plant Introduction Station Research Articles

Evaluation of Selected Corn Plant Introductions for Silk-feeding Resistance to Corn Earworm (Lepidoptera: Noctuidae)1

Corn breeders have previously obtained silk-feeding resistance to larval feeding by Heliothis zea (Boddie) predominantly from one main source: a corn originally collected in Mexico named ‘Zapalote Chico’ (PI 217413). Herein is reported a search for other sources of resistance from plant introduction corn maintained at the North Central Regional Plant Introduction Station, Ames, Iowa. From 1981 to 1984, 325 lines were evaluated in the laboratory for H. zea silk-feeding resistance. Twenty-four lines were selected from the 325 lines and retested in 1985. Three lines (PI 213705, PI 340856, and PI 369361) produced 6-d larval weights that did not differ significantly from those from the resistant check, ‘Zapalote Chico.’ These lines may provide new sources of resistance for corn breeders to use in development of resistant cultivars.

Nitrogen Fixation Capabilities of Plant Introduction Accessions of Pasture and Range Forage Legumes1

AbstractMany legume species provide excellent quality forage, although the extent to which non‐cultivated species are able to fix N symbiotically is generally unknown. In this report 91 accessions of legumes from the genera Astragalus, Onobrychis, Lupinus, Hedysarum, and Oxytropis were tested for their ability to nodulate and fix N effectively. All accessions were obtained from the USDA Western Regional Plant Introduction Station at Pullman, Wash. Accessions were first screened by evaluating them in small plastic growth tubes. Eighty‐two accessions were nodulated by at least one Rhizobium strain and 53% of the accessions tested were judged to be effectively nodulated based on yield. All accessions that were identified as effective were then grown in Leonard jars and inoculated with single strains of rhizobia. Dry matter yield and nitrogen content were determined for all entries. Twenty‐seven accessions which were tested in Leonard jars were considered to have potential as effective N2‐fixing forage legumes based on comparison with N‐fertilized controls. The highest yielding entries were several A. cicer L. (cicer milkvetch) accessions and a single accession of H. coronarium L. (sulla). This survey has identified a number of accessions of each genus that may have potential for use in forage legume breeding programs.

Crude Protein, Crude Fiber, Tannin, and Oxalate Concentrations of 33 Astragalus Species

Piant introduction collections grown at the Western Regional Plant Introduction Station for preliminary evaluation and seed increase were evaluated for crude protein, crude fiber, tannin, oxaiates, and readily detectable alkaloids. Sixty-eight Astrugalus accessions representing 33 species and 1 unidentifled accession had a range of 8.2 to 24.2% crude protein, 113 to 28.6% crude fiber, 4.2 to 10.0 mg/g tannin,and 0.15 to 1.10% oxalntes. Species with more than 18% crude protein and less than 28% crude fiber (i.e., comparable to good quahty alfalfa (Medicago sativa) bay) and acceptable levels of tannin and oxaiate were A. canadensis, P.I. 19978 and A. siliquosus, PI. 330696. None of the accessions tested gave a positive Dragendorff reagent color test for alkaloids. Some of the species reported are known to be selenium accumulators and/or contain toxic nitro-compounds that may be damaging to grazing animals. A. siliquosus is a species that contains nitro-compounds and will accumulate selenium.

Evaluation of maize plant introductions for cold tolerance

We evaluated cold-tolerance responses of 144 plant introductions (PI) of maize (Zea mays L.), attempting to include in our sample at least one PI adapted to each of the countries or ecological zones respresented in the maize germplasm collection at the North Central Regional Plant Introduction Station at Ames, Iowa, USA. Plant introductions were grown for 42 days in plastic boxes (26 cm long × 19 cm wide × 10 cm deep) in a growth chamber maintained at 10±1 °C. Cold-tolerance responses of each PI were evaluated by three traits: 1) percentage emergence (recorded 30 days after planting), 2) emergence index, an estimate of rate of emergence, and 3) seedling dry weight (sampled 42 days after planting). Estimates of variances and heritabilities for these three traits were large, suggesting that genotypic variation for cold tolerance in the maize germplasm collection would be sufficient to permit selection advance. Furthermore, genotypic correlations among the three traits were high: therefore, improvement by index selection should be possible. Correlations between the cold-tolerance traits and days from planting to 50% silk emergence (an estimate of maturity obtained at Ames. Iowa, USA) were low. Days from planting to 50% silking emergence for the 25 most cold-tolerant PI's ranged from 46 for PI 214279 from Canada to 106 for PI 331440 from Ethiopia. It should be possible, therefore, to develop cold-tolerant genotypes adapted to all latitudes.

Breeding Procedures for Panicum maximum Jacq. Suggested by Plant Variability and Mode of Reproduction1

In 1970, spaced plants of 158 accessions of guineagrass (Panicum maximum Jacq.), supplied by the USDA Regional Plant Introduction Station, Experiment, Ga., were studied in detail at Tifton, Ga. Great variation was observed in all 12 characters studied. Plant height ranged from 53 to 248 cm and single green plant weight ranged from 0.09 to 6.13 kg. The in vitro dry matter digestibility (IVDMD) of complete culms at the early‐full‐head stage ranged from 41 to 72%. Most accessions set seed well when selfed under bag. Only 1.3% of the spaced plants survived the 1970‐71 winter (–8 C minimum), but 80% of the plants of PI 284764 from the Union of South Africa survived. A study of spaced‐plant progenies from 295 plants in the 1970 planting revealed that 87.8% were highly apomictic (showed no segregation). Facultative apomixis was present in 11.6% of the progenies. These carried 5 to 20% of offtype plants.Two sexual plants, discovered in facultative apomictic introductions PI 277946 and 277922, gave fertile hybrids when crossed with giant short‐day types. Seed shattering was heavy and similar in some 6,000 plants studied. Suggested breeding procedures include screening extensive ecotype collections from Africa and recombining in one or more genotypes (fixed by apomixis) the desirable genes currently available. Suggested procedures for obtaining genes for shatter resistance include mutation breeding, screening selfed progenies of sexual plants and advanced generations of sexual ✕ apomictic hybrids that may release shatter resistance genes hidden in the germplasm, and transferring shatter resistance from other Panicum species by interspecific hybridization.

TRIUMPH FIELD PEA

not available

Selenium Accumulation in Astragalus Species

AbstractSome Astragalus species are known to be Se accumulators and are toxic to grazing animals. The Western Regional Plant Introduction Station, Pullman, Wash., had 108 accessions representing 49 species of Astragalus, mostly of non‐North American origin, available for this study. The Se accumulation characteristics of these had not been determined and therefore their potential as forage in areas of seleniferous soil was open to question.Plants were greenhouse grown in soil containing 18 ppm Se. The forage was dried and analyzed for total Se by AOAC methods.Selenium content varied from a high of 213 ppm in Astragalus tephrosoides Boiss. to a low of no detectable Se in 45 accessions. Sixty accessions, representing 26 species, accumulated 5 ppm Se or more and could be poisonous to grazing animals.

Collecting Wild Fruits in the U.S.S.R.

Abstract Under the auspices of the Agreement Between the United States of America and the Union of Soviet Socialist Republics on Exchanges in the Scientific, Technical, Educational, Cultural, and Other Fields in 1966-67, I collected wild fruits in the Union of Soviet Socialist Republics in the summer of 1967. I travelled with Dr. Willis Skrdla, Research Agronomist, U.S. Regional Plant Introduction Station, Ames, Iowa, who collected seed of legume and forage crops. We arrived in Moscow August 15 and departed October 1.

Collecting Wild Fruits in the U.S.S.R.

Abstract Under the auspices of the Agreement Between the United States of America and the Union of Soviet Socialist Republics on Exchanges in the Scientific, Technical, Educational, Cultural, and Other Fields in 1966-67, I collected wild fruits in the Union of Soviet Socialist Republics in the summer of 1967. I travelled with Dr. Willis Skrdla, Research Agronomist, U.S. Regional Plant Introduction Station, Ames, Iowa, who collected seed of legume and forage crops. We arrived in Moscow August 15 and departed October 1.