Joyce G. Foster

Efficacy of an orange oil emulsion as an anthelmintic against Haemonchus contortus in gerbils (Meriones unguiculatus) and in sheep

Haemonchus contortus is a blood-sucking abomasal parasite responsible for major losses to small ruminant producers worldwide. The recent increase in populations of anthelmintic resistant parasites has produced a demand for alternative control methods. An orange oil emulsion that has shown activity against plant parasitic nematodes and H. contortus in vitro was assessed for activity against H. contortus in a gerbil model and in the natural ovine host. In gerbil experiments, animals were infected with 600 infective third stage (L3) H. contortus larvae. In one experiment, gerbils were treated with 600 milligrams per kilogram bodyweight (mg/kg BW) orange oil once or daily for 5 days. In a second experiment, gerbils were treated with 1200 mg/kg BW orange oil once or daily for 5 days. On Day 9 post-infection, gerbils were killed, their stomachs removed, and the worms counted. The 600 mg/kg BW dosage caused 7% and 62.6% parasite reduction compared to a control group when given once or daily for 5 days, respectively. The 1200 mg/kg BW dosage of orange oil caused 25% and 87.8% parasite reduction compared to a control group when given once or daily for 5 days, respectively. The difference between the multiple treatment and control group were significant at both dosages (P<0.005). In the sheep trial, 18 lambs were orally inoculated with 10,000 L3 H. contortus. One month later, two groups of six lambs each were dosed with 600 mg/kg BW orange oil either once or daily for 3 days. Fecal egg counts were monitored daily starting on the first day of treatment (Day 0) and continuing for 14 days. Results showed that a single dose of the product caused high fecal egg count reduction (97.4%) compared to control sheep. Egg counts were significantly reduced by Day 2 (P<0.0001). Thus, the orange oil emulsion may potentially be useful in the control of ovine haemonchosis.

Influence of drought on the concentration and distribution of 2,4-diaminobutyric acid and other free amino acids in tissues of flatpea (Lathyrus sylvestris L.)

2,4-Diaminobutyric acid (A2bu) may be responsible for the apparent toxicity of flatpea (Lathyrus sylvestris L.) forage to some livestock. To obtain information relative to environmental regulation of A2bu, 3-month old flatpea plants, cv. “Lathco”, were subjected to water-deficit stress for 1, 2, and 4 weeks. A2bu, the most abundant free amino acid in roots, stems, and leaves, increased nearly 100% in roots of stressed plants. Increases in the concentrations of asparagine (Asn), proline (Pro), and arginine (Arg) occurred in roots; Asn, Pro, and 4-aminobutyric acid (Abu) in stems; and Pro and homoserine (Hse) in leaves also occurred in response to drought stress. Proline was a minor constituent of the free amino acid pool, even under water-deficit stress. The distribution of A2bu and Pro in the stressed plants (roots > stems > leaves) was the reverse of that in plants supplied with adequate water (roots < stems < leaves). As concentrations of Asn and Abu decreased from roots to leaves in control tissues, concentrations of Hse and A2bu increased in roughly the same proportions. This observation suggests that Abu and Asn may be precursors of A2bu and Hse, respectively. The increase in A2bu levels in aerial parts of drought-stressed flatpea plants is probably not sufficient to lower the feed value of the forage.

Flatpea crossing methods and germplasm screening for reduced 2,4-diaminobutyric acid composition

SummaryFlatpea (Lathyrus sylvestris L.) is a potentially valuable forage legume, but it contains high levels of 2,4-diaminobutyric acid (A2bu), a compound that can have adverse effects on some animals, including rats and poultry. This study evaluated intercrossed pollination methodology needed for cultivar improvement and characterized intercrossed progeny for A2bu concentration. Pollen germination on an artificial medium, using pollen collected during different stages of flower development, was used to identify appropriate stages for flower emasculation. Pollen dehiscence occurred at an early-bud stage when petal color was first evident. Slightly more mature buds contained pollen with substantially higher in vitro germination than pollen from early-bud stage flowers. Lines that produced high numbers of seeds per pollination were identified from crosses between flatpea accessions. Cross-pollination resulted in significantly higher seed set than selfing. Pollination using caged honeybees was the most efficient method of hybridization, although the degree of inbreeding in bee-pollinated plants could not be determined. Intercrossed progeny produced by honeybee pollination contained a lower mean concentration of foliar A2bu than the mean for flatpea accessions.

Biochemical and microbiological aspects of conservation tillage: Important considerations for Appalachian agriculture a review

Abstract The role of microorganisms in legume performance in conservation tillage systems for hill land agriculture is reviewed. Discussion focuses on the significance of plant‐microbe symbioses in improving legume nutrient status and on the biochemical regulation of species interactions. Research imperatives are addressed.

Intercrossing methods, mutagenesis treatments, and tissue culture techniques for expanding the genetic diversity of flatpea (Lathyrus sylvestris L.)

Persistence on acidic soils makes flatpea (Lathyrus sylvestris L.) a potentially valuable crop species for many parts of the world. Use of this high yielding, perennial legume for forage, however, has been limited because of the large quantity of a neurotoxin, 2,4-diaminobutyric acid (DABA), in the plant. Cultivar development has been hindered by the narrow germplasm base and the lack of information about the breeding behavior of the plant and the applicability of mutagenesis treatments and tissue culture procedures for production of low-DABA variants. This study showed that pollen dehiscence occurs at early-bud stage when petal color is first evident. Mid- or late-stage flowers produced the highest levels of germinable pollen. Tripping of the stigma was required for pollination. Cross- pollination resulted in significantly higher seed set than selfing. Intercrossed progeny produced by honeybee pollination exhibited a lower mean concentration of foliar DABA than that of the accessions used as parents. Within the effective range of 10.0 to 17.5 kR for gamma irradiation of Lathco flatpea seeds, reduction of both seedling height and plant survival was a linear function of dose. A procedure was developed to regenerate flatpea plants from hypocotyl-derived callus cultures. Callus was initiated on a modified Schenk-Hildebrandt, low-ammonium medium containing 50 μM indole acetic acid (IAA) and 2.5 μM zeatin. After two subcultures on this medium, calli were transferred to morphogenesis medium containing 0.1 μM IAA and 1.0 μM zeatin. Although rhizogenesis was the primary morphogenetic response, infrequent and variable whole-plant regeneration was observed. Regenerated plants did not show substantial reduction in DABA concentration.

Flatpea organogenesis from callus cultures.

Abstract Flatpea (Lathyrus sylvestris L.) tissues originating from several European accessions were regeneration potential on several media formulations. Low-frequency, whole-plant regeneration of flatpea was obtained from hypocotyl-derived callus cultures, although the primary response of all accessions was root formation without shoots. Conditions for optimum whole plant-regeneration included callus initiation on a modified Schenk-Hildebrandt low-ammonium (SH-LA) medium containing 5.0 μM indoleacetic acid (IAA) and 2.5 μM zeatin followed by two subcultures and transfer of calli to morphogenesis medium, basal (SH-LA) medium containing 1.0 μM zeatin and 0.1 μM IAA. A medium containing 2.5 μM zeatin and 1.0 μM IAA was also effective for morphogenesis. Root and shoot primordia developed in several cultures, approximately 60 days after explant transfer to callus induction medium. 2,4-Diaminobutyric acid (DABA) content was not appreciably reduced in regenerated material.

Nonprotein amino acid composition of flatpea (Lathyrus sylvestris L.) as affected by ethephon seed treatments and seedling fertilization

Use of flatpea (Lathyrus sylvestris L.) as a forage is limited because of nonuniform seed germination and the potentially toxic effects of 2,4-diaminobutyric acid (A2bu), a nonprotein amino acid found in seeds and vegetative tissues. The effects of ethephon (2-chloroethyl phosphonic acid) on seed germination, amino acid leachates of seeds, and amino acid composition (particularly A2bu) of seedlings were investigated. Germination of flatpea seeds, imbibed for 16 h in 0, 100, 200, 400, 800, and 1600 mg/L ethephon, did not differ, but amino acid leachates tended to increase up to 200 mg/L ethephon and then decline at higher concentrations. The major amino acid constituents in leachates were A2bu, 4-aminobutyric acid (Abu), and homoserine (Hse). Dry matter accumulation of seedlings grown from ethephon-treated seeds was reduced for second cuttings grown from ethephon-treated seeds and high nitrogen grown plants. During regrowth, free amino acid accumulation was most pronounced in leaves of plants supplied with high nitrogen. The most abundant free amino acids in flatpea tissues were the same as those in seed leachates, but concentration and relative abundance varied with nitrogen level, plant part, and ethephon treatment. Results suggest that ethephon seed treatments can have persistent effects on the growth and amino acid composition of flatpea seedlings grown under different nitrogen regimes.