Pod Stage Research Articles

Infection of Soybean with Soybean mosaic virus Increases Susceptibility to Phomopsis spp. Seed Infection

Infection of soybean [Glycine max (L.) Merr.] plants with Soybean mosaic virus (SMV) has been reported to enhance Phomopsis spp. seed infection, which reduces seed quality. The objective of this study was to determine the influence of SMV on Phomopsis spp. seed infection and seed germination and vigor. During 1995 to 1997, plants of two SMV‐susceptible cultivars (Clark and Williams) and their SMV‐resistant isolines (L78‐434 and L78‐379, resistant to SMV strains G1‐G6) were mechanically inoculated with SMV (G2 strain) at growth stages V4, V8 or R2, and Phomopsis spp. inocula were applied to all plants. Seeds harvested from SMV‐resistant isolines were consistently SMV free, whereas seeds from SMV‐inoculated susceptible cultivars accumulated SMV in seedcoats. Although environmental conditions were favorable, the incidence of Phomopsis spp. seed infection was consistently less than 12% in SMV‐resistant plants, and up to 14‐times greater in SMV‐inoculated susceptible plants, with primary infection occurring after seeds reached physiological maturity (at or after yellow pod stage). Seeds from SMV‐resistant isolines had high average standard germination (88%) and higher vigor (67% accelerated aging; 7 mS m−1 g−1 conductivity), whereas seeds from SMV‐inoculated susceptible cultivars had low standard germination (48%), low vigor (30% accelerated aging; 13 mS m−1 g−1 conductivity). Thus, infection by SMV at or before growth stage R2 increased the susceptibility of soybean seed to Phomopsis spp. infection, and resulted in poor seed quality and low vigor.

Crop losses in cowpea due to the pod-sucking bugs Riptortus dentipes, Mirperus jaculus, Anoplocnemis curvipes and Nezara viridula

The effects of increasing population densities of the cowpea pod-sucking bugs (PSB) Riptortus dentipes, Mirperus jaculus, Anoplocnemis curvipes and Nezara viridula were studied in caged potted cowpea (Vigna unguiculata) plants with infestation levels from 0 (control) to 12 adult bugs per cage. Generally, there was an increase in damage to cowpea (measured as damage to pods and seeds) with increasing in insect density. There was also a highly significant correlation between the number of infesting adult bugs and damage to pods and seeds, and a significant negative correlation between bug numbers and cowpea yield. The results suggest that control measures should be initiated at: 4 bugs (fourth instar and above) per 10 plants for R. dentipes and M. jaculus ; 2 bugs per 10 plants for A. curvipes and 6 bugs per 10 plants for N. viridula at podding stage.

Hypersensitive response of beans to Apion godmani (Coleoptera: Curculionidae).

High levels of resistance to Apion godinani Wagner have been reported in bean, Phaseolus vulgaris L., landraces from Mexico. We report on the role of hypersensitivity to A. godmani in five resistant and three susceptible bean genotypes. In susceptible genotypes (cultivars 'Canario 107','Jamapa', and 'Zacatecas 45'), the eggs and first instars of A. godmani were embedded in the pod mesocarp and usually were surrounded by healthy tissue. In contrast, in resistant landraces ('Amarillo 154', 'Amarillo 155', 'J-117', 'Puebla 36', and 'Pinto 168'), necrotic tissues developed concentrically around the oviposition site, encapsulating eggs and dead larvae. An inverse relationship between percentage egg and larval encapsulation at the early immature pod stages and percentage of damaged seeds at harvest was found. Results indicate that hypersensitivity in developing pods plays an important role in antibiosis to A. godmani in beans. This information will facilitate future genetic and biochemical research and provide much needed information concerning the phenotypic basis of resistance to A. godmani in bean.

Research Observation: Cattle Preference for Lambert Locoweed over White Locoweed

White (Oxytropis sericea Nutt. in T.& G.) and Lambert (O. lambertii var. biglovii Pursh) locoweed grow adjacent to each other on the foothills of the Rocky Mountains from southeastern Wyoming to northeastern New Mexico. Lambert locoweed matures later and flowers about 3‐4 weeks after white locoweed, thus potentially increasing the critical period of poisoning when livestock graze areas infested by both species. The objective of this study was to evaluate cattle consumption of these 2 species as they progress phenologically. In 1998, 15 Hereford cows grazed a 32 ha pasture infested with both species from the time white locoweed flowered in mid June until both species were mature and senesced in August. In 1999, 4 cows were placed in a 5 ha pasture infested with both species for 4 days in each of the following periods: (1) flower stage of white locoweed, (2) flower stage of Lambert locoweed, immature pod at white locoweed, (3) immature pod stage of Lambert locoweed, mature pod while (4) mature pod and seed shatter stage respectively. Diets were estimated by bite-count. Lambert locoweed was preferred over white locoweed in the season-long grazing trial in 1998, and in each of the 4 intensive grazing trials in 1999. The cows consumed white locoweed as availability of Lambert locoweed declined in 1998, but little white locoweed was consumed in the 4 intensive grazing trials in 1999. The toxic locoweed alkaloid swainsonine ranged from 0.04 to 0.06% in white locoweed, but was not detected in Lambert locoweed in this study.

Cattle preferences for Lambert locoweed over white locoweed

White (Oxytropis sericea Nutt. in T. G.) and Lambert (O. lambertii var. biglovii Pursh) locoweed grow adjacent to each other on the foothills of the Rocky Mountains from southeastern Wyoming to northeastern New Mexico. Lambert locoweed matures later and flowers about 3-4 weeks after white locoweed, thus potentially increasing the critical period of poisoning when livestock graze areas infested by both species. The objective of this study was to evaluate cattle consumption of these 2 species as they progress phenologically. In 1998, 15 Hereford cows grazed a 32 ha pasture infested with both species from the time white locoweed flowered in mid June until both species were mature and senesced in August. In 1999, 4 cows were placed in a 5 ha pasture infested with both species for 4 days in each of the following periods: (1) flower stage of white locoweed, (2) flower stage of Lambert locoweed, immature pod at white locoweed, (3) immature pod stage of Lambert locoweed, mature pod while (4) mature pod and seed shatter stage respectively. Diets were estimated by bite-count. Lambert locoweed was preferred over white locoweed in the season-long grazing trial in 1998, and in each of the 4 intensive grazing trials in 1999. The cows consumed white locoweed as availability of Lambert locoweed declined in 1998, but little white locoweed was consumed in the 4 intensive grazing trials in 1999. The toxic locoweed alkaloid swainsonine ranged from 0.04 to 0.06% in white locoweed, but was not detected in Lambert locoweed in this study.

Relationship of physiological characters to yield parameters in oilseed rape (Brassica napus L.)

The physiological basis of seed yield in oilseed rape (Brassica napus L.) still remains unclear, and conclusions on the contribution of such traits to seed yield are difficult to make. Nine cultivars, classified into three yield groups (high, medium and low) based on significant differences in seed yield from previous trials, were tested over two locations and years. Leaf chlorophyll content, net photosynthetic rate per unit leaf area (PA), per unit leaf dry matter (PDM) and per unit leaf chlorophyll (PC), transpiration rate (TR) and water use efficiency (WUE) were investigated on fully expanded leaf numbers 4 (vegetative), 6 (early flowering) and 8 (early podding stage) on the main stem and related to seed yield, total dry matter (TDM) and harvest index (HI) of each yield group. Differences among yield groups for seed yield, TDM and HI were significant. Chlorophyll content was lowest on leaf 4, but increased with leaf age. Correlations between net photosynthetic rate and seed yield were not found. However, cultivars in the high yield group maximized their net photosynthetic rates (PA, PDM, and PC) on leaf 6 during early flowering at the time when TR was lowest and WUE at its highest. In the medium and low groups, photosynthetic rates were highest on leaf 4, but decreased to lowest values on leaf 8, together with the high yield group. In general, the results indicate that the largest contribution to net photosynthesis by oilseed rape leaves occurred during the vegetative and early flowering stages compared with the early pod-filling stage. Key words: Total dry matter, harvest index, photosynthesis, chlorophyll

Natural incidence of endophytic bacteria in pea cultivars under field conditions.

Pea plants grown in the field were used to study the natural incidence of endophytic bacteria in the stem. Eleven pea cultivars at the flowering stage were screened for the presence of endophytic bacteria using a printing technique with surface disinfested stem cross-sections on 5% Trypticase Soy Agar (TSA). Five cultivars showed colonization. Cultivar Twiggy showed the highest and most consistent colonization and was further investigated. Stems of cv. Twiggy at the pod stage were analyzed for endophytic bacterial types and populations. Cross-sections of surface disinfested stems were printed on 5% TSA. Endophytic bacterial populations decreased from the lower to the upper part of the stem. One section from the third and the fourth internode was surface disinfested, homogenized, and spiral plated on the media 5% TSA, R2A, and SC (Davis et al. 1980). Over a series of 30 samples, 5% TSA gave significantly better recovery of bacterial endophytes compared with R2A and SC media. For most stems, populations ranged from 10(4) to 10(5) CFU/g except in one of the field blocks in which endophyte populations were uniformly higher. Comparison of colony counts by spiral plating and printing showed a positive correlation. The most frequently recovered bacterial types were Pantoea agglomerans and Pseudomonas fluorescens. Less frequently isolated were Pseudomonas viridiflava and Bacillus megaterium.

Physiological responses of argentine peanut varieties to water stress. Water uptake and water use efficiency

The water extraction capability and water use efficiency (WUE) of two argentine peanut varieties Florman INTA and Manfredi 393 INTA, respectively classed as drought-sensitive and drought-tolerant were compared. The experiment was grown at two different regimes of water supply. Between 47 and 113 days after sowing (DAS) half of the crop was irrigated, while the other half received no water. Soil water contents, canopy temperature, above ground dry matter and root length density (RLD) were measured periodically during the drought period. Water use (WU), stress degree day (SDD), extraction front velocity (EFV), uptake coefficient, shoot and pod water use efficiency corrected (WUE c) by vapor pressure deficit, and soil resistance were calculated from the measurements. Manfredi 393 INTA had a higher WU than Florman INTA in both irrigated (IRR) and water-stressed (WS) treatments. This was linked to a higher transpiration rate as demonstrated by SDD time course values. The EFV obtained from lineal and logistic fitted models showed a similar pattern for both varieties. However, the logistic function fitted better than the linear model. The observed differences in WU under drought were explained by slightly but consistently higher uptake coefficient values in Manfredi 393 INTA. Uptake coefficient differences between varieties were not associated with RLD; thus, it was not useful as an indicator of the genotypic ability to extract soil water. Florman INTA possessed higher WUE c than Manfredi 393 INTA in both IRR and WS treatments. On the other hand, these differences between varieties were not observed for pod WUE c. Both varieties showed similar values under the irrigated regime because the higher WU on Manfredi 393 INTA was compensated for a higher pod production due to an enhanced partitioning of assimilates to pods. Under WS regime, pod WUE c was significantively reduced in both varieties. The mechanical impedance in the soil upper layer contributed to this reduction. Although critical soil resistance was similar for the two varieties under study, its effect was remarkable on Florman INTA due to a delay in the onset of the beginning pod stage and non-synchronous reproductive development. Manfredi 393 INTA demonstrated an adaptative advantage to drought, expressed in its higher pod production, due to either an earlier onset of beginning peg stage that affected differentially peg penetration into the dry soil upper layer, and an enhanced partitioning of assimilates to pods.

Rhizobial inoculant formulations and soil pH influence field pea nodulation and nitrogen fixation

Crop production systems that include field pea (Pisum sativum L.) in rotation are important for sustainable agriculture on acid soils in northwestern Canada. Greenhouse experiments were conducted to compare the ability of liquid inoculant applied to the seed, powdered peat inoculant applied to the seed, and granular inoculant applied in a band with the seed to establish effective nodulation on field pea grown at soil pH(H2O) 4.4, 5.4 and 6.6. Plants were grown to the flat pod stage, and then total plant biomass dry weight, dry weight of nodules, number of nodules, plant nitrogen content, and proportion of plant nitrogen derived from the atmosphere (%Ndfa) were measured. Granular and powdered peat inoculants produced greater nodule numbers and weight, plant nitrogen content, %Ndfa and total biomass than liquid inoculant in at least two of the three experiments. Only granular inoculant was effective in establishing nodules at soil pH 4.4, but granular and powdered peat inoculants were effective at pH 5.4, and all three formulations were effective at pH 6.6. The results showed that granular inoculant has potential for effective nodulation of field pea grown on acid soil. Key words: Rhizobium, inoculant formulations, field pea, nodulation, acid soil

Pest management in cowpea. Part 2. Integrating planting time, plant density and insecticide application for management of cowpea field insect pests in eastern Uganda

The focus of this study was to formulate a cost-effective pest management strategy for cowpea growers in Uganda. An initial experiment examined the influence of different times of planting and plant densities on infestation levels of the major field pests of cowpea. Results indicated that planting at the on-set of rains, at 30×20 cm 2 or 60×20 cm 2 gave better yields. Here, we studied the effect of time and frequency of insecticide application on the field pests infestations. Results showed that a single spray at budding, flowering and podding had the highest marginal returns (3.12) in comparison to spraying throughout the season (1.77) and at seedling, flowering and podding stages (2.18). The best treatments from these two experiments were combined and compared to the single control measures, and the untreated control. Cowpea grain yields and marginal returns from plots receiving combined control measures were higher than those from plots receiving only cultural or chemical control measures. Our study provides evidence that a few well-timed sprays in combination with cultural practices are not only effective but also very profitable.

Late Season Toxic Alkaloid Concentrations in Tall Larkspur (Delphinium spp.)

Tall larkspurs [Delphinium barbeyi (L. Huth), D. occidentale (Wats.), D. glaucescens (Rydb.), D. glaucum (Wats.)] pose a serious poisoning threat to cattle on many summer ranges. Livestock producers often defer grazing until larkspur is mature, but spe cific information is lacking on toxic alkaloid concentrations in larkspur from pod stage to senescence. Tall larkspur leaves and seed pods were collected about every 2 weeks during the pod stage to senescence from marked plants in locations in Utah (Logan and Salina), Idaho (Ashton, Humphrey, and Oakley), Colorado (Yampa and Montrose), and California (Carson Pass) from 1995 to 1997. Toxic alkaloid concentions in pods (x ‐ = 2.9 mg/g) exceeded leaf alkaloid concentrations (x = 1.5 mg/g in all species, but the magnitude of the difference varied among the 4 species. Leaves showed a more rapid decrease in toxic alkaloid concentration with plant maturity compared to pods. Seed pods did not begin to lose substantial amounts of toxic alkaloid until larkspur matured and pods began to dessicate. At seed shatter, D. glaucescens pods retained more toxic alkaloid than the other species, and alkaloid concentration was sufficiently high after pods had shattered (3.5 mg/g) to pose a moderate grazing risk. After seed shatter, the toxic alkaloid concentrations in leaves and pods of D. barbeyi, D. occidentale , and D. glaucum were generally less than 2 mg/g; thus, risk of losing cattle would be low for the remainder of the grazing season.

Stylet Penetration Activities by <I>Aphis craccivora</I> (Homoptera: Aphididae) on Plants and Excised Plant Parts of Resistant and Susceptible Cultivars of Cowpea (Leguminosae)

Direct current electrical penetration graphs (DC-EPGs) were used to analyze the stylet penetration activities of cowpea aphid, Aphis craccivora Koch, on plants of aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cultivars of cowpea, Vigna unguiculata (L.) Walpers. Aphid stylet penetration on whole plants at seedling, flowering, and podding stages were studied in one experiment, and in another experiment excised leaves from seedling plants, excised flowers, and excised pods were tested. Electrical signals depicting the aphid stylet penetration activities on their host plants were amplified, recorded onto a paper chart recorder, and scored for specific waveform patterns. Compared with similar tissues of ICV-1, intact leaves and excised seedling foliage of ICV-12 plants caused severe disruption of aphid stylet penetration activities. This was manifested in frequent penetration attempts that were abruptly terminated or unsustained, and in shorter penetration times, signifying antixenosis resistance in ICV-12. There was reduced occurrence of E waveforms, which represent stylet activity in plant vascular tissues. Also, prior exposure of test aphids to plants of one cultivar did not significantly influence the expected stylet penetration activities on plants of the other cultivar. Overall, ICV-12 exhibited high levels of resistance against A. craccivora.

Late season toxic alkaloid concentrations in tall larkspur (Delphinium spp.)

Tall larkspurs [Delphinium barbeyi (L. Huth), D. occidentale (Wats.), D. glaucescens (Rydb.), D. glaucum (Wats.)] pose a serious poisoning threat to cattle on many summer ranges. Livestock producers often defer grazing until larkspur is mature, but specific information is lacking on toxic alkaloid concentrations in larkspur from pod stage to senescence. Tall larkspur leaves and seed pods were collected about every 2 weeks during the pod stage to senescence from marked plants in locations in Utah (Logan and Salina), Idaho (Ashton, Humphrey, and Oakley), Colorado (Yampa and Montrose), and California (Carson Pass) from 1995 to 1997. Toxic alkaloid concentions in pods (average= 2.9mg/g) exceeded leaf alkaloid concentrations (average= 1.5 mg/g in all species, but the magnitude of the difference varied among the 4 species. Leaves showed a more rapid decrease in toxic alkaloid concentration with plant maturity compared to pods. Seed pods did not begin to lose substantial amounts of toxic alkaloid until larkspur matured and pods began to dessicate. At seed shatter, D. glaucescens pods retained more toxic alkaloid than the other species, and alkaloid concentration was sufficiently high after pods had shattered (3.5 mg/g) to pose a moderate grazing risk. After seed shatter, the toxic alkaloid concentrations in leaves and pods of D. barbeyi, D. occidentale, and D. glaucum were generallyless than 2 mg/g; thus, risk of losing cattle would be low for the remainder of the grazing season

Effects of the multiple leaflet gene on agronomical and physiological characters of mungbean (Vigna radiata)

Near-isogenic lines of mungbean (Vigna radiata) were produced from backcrossing two Thai recommended cultivars, KPS 1 and CN 36, with the multiple leaflet line, V 5926, until BC9. The isogenic lines were evaluated against the two recipients at Kasetsart University, Thailand, in the rainy season of 1996 and the dry season of 1997. The effect of the gene controlling the multiple leaflet on physiological and agronomical characters was investigated. Seed yield, plant height, and number of pods per plant were greater in the trifoliate leaflet cultivars than in the multiple leaflet near-isogenic lines, whereas the numbers of seeds per pod and 1000-seed weights were not significantly different. Light saturation and photosynthetic rate did not differ, while light interception and dry matter accumulation were greater in the trifoliate leaflet cultivars than in the multifoliate lines. The leaf area index (LAI) of the trifoliate parents was greater at the vegetative stage but lower at the flowering and young pod stages, due to the greater number of leaflets per plant of the multifoliate lines. After the beginning of the podding stage, the LAI of the multifoliate lines was less than that of the parents, as the number of leaflets per plant of these lines hardly changed while that of the trifoliate parents increased.

Effect of water stress during floral initiation, flowering and podding on the growth and yield of faba bean (Vicia faba L.)

Faba bean (Vicia faba L.) is currently being adopted as a useful rotation crop on fine-textured or duplex, neutral to alkaline soils in the low rainfall Mediterranean-type environments of south-western Australia. However, seed yields in these environments are often limited by water stress. The aims of this study were to investigate the effect of water stress on growth and yield of three contrasting faba bean genotypes (ACC286, Fiord and Icarus) under glasshouse conditions and to identify any critical stages of development when faba bean is particularly sensitive to water deficits. The stress treatments were imposed by withholding water at floral initiation, 50% flowering and 50% podding, while monitoring the levels of photosynthesis, stomatal conductance, leaf water potential and leaf extension. A well-watered unstressed control was also included.The early podding stage of development was the most sensitive to water deficit in faba bean, causing a reduction in harvest indices and seed yields of at least 50% in all three genotypes. In contrast, genotypes showed a better ability to recover from stress at floral initiation and first flower stages than at early podding. As water deficits developed, leaf water potential decreased, leaves lost turgor and leaf area was reduced dramatically due to wilting. Leaflets were unable to expand and stomatal conductance and photosynthesis declined to about 50mmolm−2s−1 and 6μmolm−2s−1, respectively. While stomatal conductance and photosynthesis recovered after rewatering, leaf size was reduced permanently, especially with the stress treatment at podding. In addition, some lower leaves failed to recover turgor after rewatering in the stress treatment at podding, and this advanced leaf senescence, especially in Icarus. The genotype ACC286 appeared to cope better with moisture stress at floral initiation, first flowering and early pod set, than the other genotypes. ACC286 produced more than twice the seed yield of Fiord and Icarus in the stress treatment at podding, partly because total dry matter was not reduced as severely and there was no reduction in the number of seeds per pod. This study suggests there is considerable variation amongst faba bean genotypes in tolerance to water stress, and that maximising the number of flowers, pods and seeds is among the most important traits for maintaining stable and high seed yields under water deficit conditions.

Evaluation of pigeonpea pod borer and pod fly tolerant lines at Kabete and Kiboko in Kenya

Pigeonpea lines which have shown tolerance to pod borer and pod fly damage at ICRISAT, Patancheru, India, were tested in the field at Kabete and Kiboko, Kenya, and compared with five local checks. There were sprayed and unsprayed plots for each line. Endosulfan 35 E.C. was applied at 0.07% active ingredient (a.i.) starting at flower bud expansion stage, at 50% flowering, early podding, and full podding stages. At crop maturity, all pods from three plants plot -1 were sampled and seed damage by different insect pests determined. The results showed that seeds from all lines were damaged by pod borers and pod sucking bugs. Pod fly incidence was greater at Kabete than at Kiboko, and damage was lower on test lines than on checks. Spraying reduced seed damage from 57.6% to 9.3% and from 59.9% to 4.5% on pod borer lines and pod fly lines, respectively, at Kiboko, and from 19.9% to 5.4% on pod fly lines at Kabete. At Kiboko seed damage in unsprayed pod borer (57.6%) and pod fly (59.9%) lines was similar. Seed damage on pod fly lines at Kiboko (59.9%) was significantly higher than at Kabete (19.9%). Positive significant correlations were observed between seed mass and pod fly damage at Kabete (r = 0.31*) and Kiboko (r = 0.30*). The results indicated that although some lines showed tolerance to pod borer and pod fly damage, they were highly susceptible to pod sucking bugs, suggesting that such tolerance does not hold against other insect groups.

Characterization and management of bud blight disease of soybean in India

Bud blight disease (BBD) of soybean ( Glycine max L. Merr.) showed little or no transmission via seeds from naturally infected plants. This is consistent with the presence of Peanut Bud Necrosis Tospovirus (PBNV) which has been investigated recently in the Chhattisgarh region of India and is not seed-borne. Various host species were tested in host range studies. Of these, the bud blight pathogen infected only four species, producing chlorotic/necrotic rings/spots on Chenopodium amaranticolor Coste & Reyn, Nicotiana glutinosa L., Vigna unguiculata (L.) Walp. cv. C 152 and systemic infection in Arachis hypogea . Parts of the seed from diseased soybean examined by transmission electron microscopy and immunosorbent electron microscopy revealed no virus particles. Extracts from the first trifoliate leaf were more infectious (14.7 local lesions) on local lesion hosts than those from the second trifoliate leaf (1.33 local lesions) and the extracts from the third trifoliate leaf were not infectious. Soybean germplasm lines/cultivars, namely KHJB 1, JS 84-1 and JS 71-05, were not infected, whereas JS 81-227, ES 5, JS 2, JS 79-81 and JS 340 were highly resistant to bud blight under natural field conditions with location severity indices of 3.91 out of 9.00. The number of plants with bud blight infections was significantly high when the crop was at the flowering and pod initiation stages. However, the number of infected plants was significantly lower when the crop was at the pre-bloom and podding stages. Similarly, infected plants were significantly more common in JS 75-46 than in JS 335.

Observations of Lupinus Sulphureus-Induced "Crooked Calf Disease"

Lupin-induced crooked calf disease occurred in a fall calving herd of cows in Northeastern Oregon. Sixty-seven calves from a herd of 131 cows (51%) were born with congenital skeletal malformations primarily of the front limbs, neck, or spine and a few had cleft palates. Because of the nature of the malformations, lupine was suspected, and investigation of the ranch and pastures where cows grazed revealed 2 species of lupine (Lupinus sulphureus; Douglas ex. Lindl. and Lupinus leucophyllus; Douglas ex. Hooker) and poison-hemlock (Conium maculatum). Poison-hemlock was not grazed and therefore eliminated as the teratogenic plant. Extensive grazing of the Lupinus sulphureus especially the seed pods was evident. Chemical analysis of the 2 lupine species demonstrated that L. sulphureus was likely the cause of the birth defects because it contained high levels of the quinolizidine alkaloid anagyrine, a known teratogen. Lupinus sulphureus is a yellow-flowered lupine and contained 1.84% anagyrine in the seed, whereas Lupinus leucophyllus, a purple flowered lupine, contained other quinolizidine alkaloids but no anagyrine. The seed pods of L. sulphureus were high in total alkaloids (42 mg/g of dry seed), of which 45% was anagyrine. After a review of breeding records, grazing patterns and growth stage of plants, it was determined cattle probably ingested L. sulphureus in the seed pod stage during critical fetal developmental periods of gestation. Epidemiologic studies suggested the critical gestational period included day 21 to day 100; 70% of the malformed calves were born to cows that were exposed to the plant during gestation days 60 to 80. The risk of deformities was markedly increased in fetuses exposed during this interval. A few malformations occurred in cows exposed to the lupine as early as gestation day 21 and as late as day 100. We conclude that L. sulphureus was the teratogenic species, and producers should prevent cows from grazing L. sulphureus during gestation days 40 to 100 and consider herbicide control of this lupine species.

Toxic Alkaloid Concentration in Tall Larkspur Species in the Western U.S.

Larkspur (Delphinium spp.) kills more cattle on mountain rangelands in the western U.S. than any other plant, disease or predator. The concentration of toxic alkaloids was measured in 4 larkspur species, at 10 locations, at 2-week intervals during the growing season. In addition, multi-year samples from previous studies were analyzed to determine year-to-year variation in toxic alkaloids. Mountain larkspur (D. glaucum Wats.) had the highest concentration of toxic alkaloids averaged over growth stages (1.01% of dry weight), tall, (D. barbeyi (L.) Huth) and waxy larkspur (D. glaucesens Rydb) were intermediate (0.65 and 0.49% respectively), and duncecap (D. occidentale S. Watts) was lowest (0.29%). Toxic alkaloid concentration generally declined as the plants matured. However, toxic alkaloids in tall larkspur at Yampa, Colo. increased slightly in the pod stage, and toxic alkaloids in waxy larkspur increased from the vegetative to the bud stage. Concentration of toxic alkaloids in tall and duncecap larkspur leaves were higher in plants growing in open sunlight than those shaded under aspen or conifer canopy. Toxic alkaloid concentration varied among individual plants (C.V. 20-60%). Knowledge of the toxic alkaloid concentration of larkspur populations can be used to predict the risk of larkspur poisoning.

Roles of Oxalic and Malic Acids in Chickpea Trichome Exudate in Host-Plant Resistance to Helicoverpa armigera

Effects of malic acid and oxalic acid on oviposition of Helicoverpa armigera were investigated in a laboratory cage choice experiment. Malic acid stimulated oviposition at a concentration of 0.6 μmol/cm2 but inhibited it at 3.4 μmol/cm2. Oxalic acid showed neither stimulation nor inhibition of oviposition at 0.25–1.7 μmol/cm2. Correlations between the amount of these acids in trichome exudate on leaf and pod surface and H. armigera populations and pod damage were investigated in a field experiment using 14 chickpea genotypes. Malic acid on the leaves stimulated oviposition during the vegetative and flowering stages, when its concentration was 0.1–0.7 μmol/cm2. Later, during the podding stage there was no significant correlation between either egg density or pod damage and malic acid levels. However, there was a significant negative correlation between pod damage and oxalic acid levels. Oxalic acid, which had been reported to have an antibiotic effect on H. armigera larvae, has an important role in resistance to this pest in chickpea. The length of the podding period was also a factor influencing the extent of pod damage; a longer podding period resulted in prolonged exposure to H. armigera attack and more pod damage.