Plant Introduction Lines Research Articles

Settling and Feeding Responses of Pea Weevil (Coleoptera: Bruchidae) to Flowers of Selected Pea Lines

This study characterized the settling and feeding responses of female pea weevils, Bruchus pisorum (L.), to flowers of pea lines varying in their susceptibility to pea weevil oviposition and, in so doing, sought to examine the potential of using weevil responses to flowers to screen pea germplasm for antixenosis resistance. In dual-choice laboratory tests, weevils were less frequently observed settling and feeding on flowers of plant introduction lines (PI 196027, PI 263026) with pod antixenosis to ovipositing weevils than on flowers of 2 cultivars ('Alaska', 'Garfield') susceptible to oviposition. Weevils did not discriminate when exposed to 2 flowers from susceptible lines or 2 flowers from resistant lines. These results suggest it may be possible to use a flower assay to screen pea germplasm for antixenosis resistance to pea weevil. This study also demonstrates the application of Markov chain models for the analysis of data in which repeated categorical responses of test insects are observed.

Interaction Between Russian Wheat Aphid (Homoptera: Aphididae) and Resistant and Susceptible Genotypes of Wheat

Interaction between the Russian wheat aphid, Diuraphis noxia (Mordvilko), and the resistant wheat, Triticum aestivum L., plant introduction lines PI 137739, PI 140207, and PI 262660 and the susceptible wheat cultivar ‘Stephens’ were studied. D. noxia reproductive rate and population development were higher when fed on Stephens compared with the resistant genotypes. Reproductive rate of D. noxia decreased as aphid density and length of aphid time on plant increased. Whereas, D. noxia populations increased with increasing aphid densities and length of aphid time on plant. Although the populations of D. noxia were lower when fed resistant genotypes. total chlorophyll content was reduced compared with the susceptible genotype. This could have been caused by increased aphid probing activity on resistant genotypes. There was no significant difference between the antibiotic line PI 140207 and the tolerant line PI 262660 in aphid reproductive rate, population density or reduction in leaf chlorophyll content. Expression of several polypeptides were altered by D. noxia feeding on PI 137739 and Stephens. Three polypeptides of sizes ≈32, 33, and 35 k were enhanced in PI 137739 but not in Stephens. Involvement of these proteins in plant defense is discussed.

Susceptibility to Clover Yellow Vein Potyvirus in the United States Germ Plasm Collection of Subterranean Clover

In spring 1991, natural infections of clover yellow vein virus (CYVV) caused severe disease in 60% of experimental accessions of subterranean clover (Trifolium subterraneum) grown in field trials at Mississippi State, Mississippi. A search for resistance to CYVV was initiated within the United States collection of subterranean clover germ plasm. Plants of each of 261 plant introduction (PI) lines and three cultivars were grown in the greenhouse during the winter and spring of 1991-1992. Seedlings were mechanically inoculated with CYVV-Pratt and evaluated 21-28 days later. Initial DAS-ELISA confirmed an absolute correlation of symptoms with infection [...]

Evaluation of screening methods and search for resistance in muskmelon, Cucumis melo L., to the twospotted spider mite, Tetranychus urticae Koch

Three techniques of screening for resistance in muskmelon, Cucumis melo L., to the twospotted spider mite, Tetranychus urticae Koch, were compared in a laboratory test. Coefficient of variation values were approximately equal for a whole-leaf and floating-disc technique in terms of mean number of mobile mites and eggs, whereas both were substantially lower than that associated with a clip cage. Therefore, both the floating-disc and whole-leaf technique are indicated as superior techniques for isolating mites on melon leaves in screening trials. In greenhouse mass screening trials (using a whole-leaf technique), many lines exhibited lower densities of adult twospotted spider mites compared with a standard commercial variety ‘Perlita’. Melon lines ‘BUS’, ‘CHI’, Plant Introduction (PI) 164343 and PI 17895 exhibited resistance in greenhouse mass screenings and had significantly lower numbers of female mites per leaf in more intensive greenhouse screenings. PI lines 124101, 124431, 125896 and 125956, which expressed resistance in greenhouse mass screenings, also had low densities of mites in field screening.

Relationship of Endogenous Abscisic Acid to Sucrose Level and Seed Growth Rate of Soybeans

It has been proposed that abscisic acid (ABA) may stimulate sucrose transport into filling seeds of legumes, potentially regulating seed growth rate. The objective of this study was to determine whether the rate of dry matter accumulation in seeds of soybeans (Glycine max L.) is correlated with the endogenous levels of ABA and sucrose in those sinks. The levels of ABA and sucrose in seed tissues were compared in nine diverse Plant Introduction lines having seed growth rates ranging from 2.5 to 10.0 milligrams dry weight per seed per day. At 14 days after anthesis (DAA), seeds of all genotypes contained less than 2 micrograms of ABA per gram fresh weight. Levels of ABA increased rapidly, however, reaching maxima at 20 to 30 DAA, depending upon tissue type and genotype. ABA accumulated first in seed coats and then in embryos, and ABA maxima were higher in seed coats (8 to 20 micrograms per gram fresh weight) than in embryos (4 to 9 micrograms per gram fresh weight. From 30 to 50 DAA, ABA levels in both tissues decreased to less than 2 micrograms per gram fresh weight. Levels of sucrose were also low early in development, less than 10 milligrams per gram fresh weight at 14 DAA. However, by 30 DAA, sucrose levels in seed coats had increased to 20 milligrams per gram fresh weight and remained fairly constant for the remainder of the filling period. In contrast, sucrose accumulated in embryos throughout the filling period, reaching levels greater than 40 milligrams per gram fresh weight by 50 DAA. Correlation analyses indicated that the level of ABA in seed coats and embryos was not directly correlated to the level of sucrose measured in those tissues or to the rate of seed dry matter accumulation during the linear filling period. Rather, the ubiquitous pattern of ABA accumulation early in development appeared to coincide with water uptake and the rapid expansion of cotyledons occurring at that time. Whole tissue sucrose levels in embryos and seed coats, as well as sucrose levels in the embryo apoplast, were generally not correlated with the rate of dry matter accumulation. Thus, it appears that, in this set of diverse soybean genotypes, seed growth rate was not limited by endogenous concentrations of ABA or sucrose in reproductive tissues.

Hydrogen Oxidation by the Host-Controlled Uptake Hydrogenase Phenotype of Bradyrhizobium japonicum in Symbiosis with Soybean Host Plants

Symbioses between uptake hydrogenase host-regulated (Hup-hr) phenotypes of Bradyrhizobium japonicum and exotic, agronomically unadapted soybean germ plasm were examined for expression of uptake hydrogenase activity. Determinations for hydrogen evolution and uptake hydrogenase activity identified five plant introduction (PI) lines which formed hydrogen-oxidizing symbioses with strains USDA 61 and PA3 6c. Hup-hr strains belonging to serogroup 94 expressed uptake hydrogenase activity in symbioses with PI 181696 and PI 219655 at rates sufficient to prevent hydrogen from escaping the nodules. The identification of soybean germ plasm forming hydrogen-oxidizing symbioses with Hup-hr bradyrhizobia potentially has implications for enhancing nitrogen fixation efficiency in soybean production.

Improvement of Levels of Bacterial Wilt Resistance in Eggplant Through Breeding

Significant differences in Kaplan-Meier survival curves were calculated by the log-rank test for root-dip inoculated parental lines and their corresponding S3 families in five of seven eggplant (Solanum melongena) accessions. The accessions from The U.S. Department of Agriculture's Plant Introduction (PI) Collection had been selected based on resistance to bacterial wilt. Resistance in one of these seven S3 families was significantly greater than that of the parents. The survival curves were plotted for 21 days after inoculation of 3-wk-old seedlings with a broth culture of Pseudomonas solanacearum, based on time from inoculation to initial wilt symptoms for plants grown in a greenhouse at temperatures of 33-37 C in daytime and 24-27 C at night. Significant differences were found in the survival curves of parental PI lines and their corresponding F3 families of all four crosses in the hybridization program. Resistance in three of the four families was significantly improved over levels expressed by the parents. Levels of resistance that equalled the most resistant parent were found in the fourth family. Both crossing and selfing of resistant eggplants offer promise in developing lines with improved bacterial wilt resistance.

Mendelian and Non-Mendelian Inheritance of Three Isozymes in Peanut (Arachis hypogaea L.)1

Abstract Because of the importance of peanut (Arachis hypogaea L.) as an oil, food, and feed source worldwide and the contributions of breeding and genetics to yield and quality improvement, it is desirable to understand the genetic structure of the plant. Isozymes have been used to gain an understanding of the genetic structure of several plant species. However, we found no literature on the inheritance of isozymes in peanut. The F1 and F2 seed of several crosses between cultivars and plant introduction lines of three botantical types of peanut were used to investigate the inheritance of three isozymes by horizontal starch gel electrophoresis: phosphohexose isomerase (PHI), isocitrate dehydrogenase (IDH), and glutamate oxaloacetate transaminase (GOT). Each of the three enzymes displayed two different banding patterns, the difference being the presence vs. the absence of either one (IDH) or two (PHI, GOT) bands. Chi-square analysis for goodness of fit of the observed F2 segregation ratios to ratios expected from genetic models indicated that the polymorphisms for both PHI and IDH are controlled by single genes. Two loci, Phi-1 and Idh-1, respectively, are proposed. Sixty-five of 71 F1 progeny monitored for GOT showed the banding pattern of the male parent. The F2 progeny segregated into the two parental types, but the ratios did not fit a simple genetic model. Possible explanations for the observed paternal inheritance of GOT include biparental transmission of plastids, prezygotic RNA synthesis and genomic imprinting.

Effect of Abscisic Acid on Amino Acid Uptake and Effiux in Developing Soybean Seeds1

The role of abscisic acid (ABA) in regulating growth of developing soybean [Glycine max (L.) Merr.] seeds is not fully understood. The objectives of this study were to characterize the effect of ABA on the in vitro uptake of asparagine and glutamine by isolated immature cotyledons in three soybean plant introduction (PI) lines with genotypic differences in seed growth rate and final seed weight. Cotyledons were incubated in uptake buffer solutions plus 14C‐asparagine or 14C‐glutamine and treatment concentrations of ABA. The ABA levels in the uptake solutions were 0, 10‐7, 10‐6, and 10‐5 M. The uptake rate of glutamine was approximately three times that of asparagine. Among PI lines, the heavy seeded line had a greater rate of asparagine uptake while the light seeded line had a greater rate of glutamine uptake. For asparagine, 10‐6 M ABA depressed uptake compared to the control. For glutamine, ABA enhanced uptake compared to the control at both 10‐6 and 10‐5 M. In an additional experiment, we observed no effect of ABA and K+ on the release of labeled asparagine from excised soybean seed coats. These data indicate that amino acid uptake rates are genotypically dependent and may be influenced by ABA concentration.

Relationship of Tissue Water Relations to Asparagine Uptake in Developing Soybean Seeds1

Amino acids play an important role in the N nutrition of developing soybean [Glycine max (L.) Merr.] seeds. Factors affecting cotyledonary amino acid uptake within those seeds are not well understood. The objectives of this study were to investigate the effects of altered soybean cotyledon water relations on in vitro asparagine uptake by those cotyledons. Two experimental plant introduction (PI) lines with genotypic differences in seed growth rate and final seed weight were grown in the field. They were PI 416.845 (heavy seeded), and PI 361.058 (light seeded). Cotyledons were sampled at 32 days after anthesis for the light seeded line, and 32 and 45 days after anthesis for the heavy seeded line. Cultivar Evans was used for the studies involving plants grown in the growth chamber. Cotyledons were incubated in uptake buffer solutions containing 10 mmol kg‐1 14C‐asparagine and adjusted to various water potential levels with mannitol (a slowly penetrating osmoticum) or ethylene glycol (a rapidly penetrating osmoticum). Solution water potential levels were approximately 0, −0.5, −1.0, −1.5, and −2.0 MPa. The rate of asparagine uptake for the heavy seeded genotype was greater than that for the light seeded genotype. Uptake was greater at −0.5 and −1.0 MPa than at 0 and −2.0 MPa in the experiments using plants grown in the growth chamber. In the study using field‐grown plants, asparagine uptake was similar in mannitol solutions of 0, −0.5, and −1.0 MPa, but declined in mannitol solutions of −1.5 and −2.0 MPa. Results for ethylene glycol as osmoticum were similar at 32 days after anthesis although reductions of uptake at −1.5 and −2.0 MPa were not as great. Our results indicate that asparagine uptake by excised cotyledons is influenced by the water potential components of their cells, specifically the cell turgor.

Effect of Early and Late Flowering on Agronomic Traits of Soybean at Different Planting Dates1

Double‐cropping soybean [Glycine max (L.) Merr.] after a winter small grain crop often forces planting to be delayed beyond the date when maximum yield, plant height, and vegetative mass can be attained. The objective of this study was to evaluate soybean plant introduction (PI) lines selected for differing flowering dates, but with a constant maturity, for differences in vegetative size and yield reduction due to delayed planting. Two groups, each consisting of 12 PI lines, were compared in the field at Lexington, KY for 3 yr (1982–1984) in early (15 May) and late (21 June) planting on a Maury silt loam (fine, mixed, mesic Typic Paleudalf) soil. The early flowering group (group EF) flowered 10 days and matured 1 day earlier than the late flowering group (group LF). Group LF was taller with more nodes at Rl, R4, and R7 in both planting dates. The flowering and pod initiation (R1–R4) and seed filling (R4–R7) periods were shorter in group LF than in group EF. Yields averaged over all 3 yr were 1510, 1520, 1370, and 1380 kg ha−1 for group EF early planting, group LF early planting, group EF late planting, and group LF late planting, respectively. Both groups showed a 9% decrease in yield due to delayed planting. The planting date effect was highly significant, while the group effect and the planting date ✕ group interaction were nonsignificant for yield. In 1983 and 1984, group LF had smaller yield reductions in delayed plantings than group EF (6 and 17% reductions for each group, respectively). Although the planting date ✕ flowering group interaction for yield was highly significant in 1983 and 1984, group LF did not yield significantly more in late plantings. In 1982, the two groups did not differ in yield in late plantings. Thus, in this sample of soybean Pis, delayed flowering increased height and vegetative size but did not provide a yield benefit in late plantings.

Mexican Bean Beetle (Coleoptera: Coccinellidae) Development on Resistant and Susceptible Soybean Lines in the Laboratory and Relationship to Field Selection

Laboratory investigations were conducted to study development and mortality of Mexican bean beetle, Epilachna varivestis Mulsant, larvae reared on resistant plant introduction lines, released field-screened resistant breeding lines, and susceptible soybean cultivars. Mortality was low and development normal on susceptible cultivars, indicating an absence of any antibiotic mechanisms. Conversely, high mortality and slower developmental rates of larvae on the various resistant lines indicated presence of antibiotic mechanisms. Antibiosis was apparent as three relative levels: low resistance (L76-0328, L76-0049), medium resistance (L76-0272, L76-0038, L78-608), and high resistance (L76-0132, PI 227687, PI 171451, PI 229358). Results also suggest that a larval screening technique conducted specifically for an antibiotic reaction could be as effective as using existing field-screening techniques to develop resistant soybeans with high levels of antibiosis.

Recurrent Phenotypic Selection for Resistance to Brown Leaf Spot in Smooth Bromegrass1

Smooth bromegrass (Bromus inermis Leyss.) cultivars are susceptible to brown leaf spot [caused by Pyrenophora bromi (Died.) Drechs.]; however, there is variation among plants within cultivars for lesion size. The objective of this research was to determine the effectiveness of recurrent phenotj pic selection as a method of breeding for resistance to brown leaf spot. The source population (Cycle 0) was 93 plant introduction lines and five cultivars. Four cycles of selection for reduced lesion size were conducted using artificial inoculation in the greenhouse. A test comparing the four cycles and the check cultivars Saratoga and Baylor was conducted in the greenhouse. Mean lesion size, lesion frequency, and overall disease severity were significantly lower for Cycle 4 than for previous cycles. The percentage of plants in each severity class shifted to higher percentages in lower rating classes in Cycle 4 compared to previous cycles and check cultivars. However, even in Cycle 4 some plants were rated as moderately susceptible. The correlations between lesion size and lesion frequency, lesion size and overall severity, and lesion frequency and overall severity (476 df) were 0.64, 0.90, and 0.83, respectively (P<0.01). Methods of inoculation and incubation have been developed that were effective and reliable in screening for resistance to brown leaf spot. Four cycles of selection resulted in a significant increase in the level of resistance to brown leaf spot in smooth bromegrass.

Relationship of Cotyledon Cell Number and Seed Respiration to Soybean Seed Growth1

Seed Growth rate in soybean [Glycine max (L.) Merr.] is known to be important in determining final yield. Factors influencing growth rate, however, are less well understood. The objectives of this study were to investigate the relationship of cotyledonary cell number and seed component (cotyledons, seed coat, and embryonic axis) respiration to seed growth rate and final seed weight for three field‐grown soybean Plant Introduction (PI) lines with genetic differences in seed weight. They were PI 361.058 (light seeded, 92 mg seed−1), PI 317.336( medium seeded, 225 mg seed−1), and PI 416.845 (heavy seeded, 316 mg seed−1). Seed growth rate varied from 2.6 to 10.0 mg seed−1 day−1, and the number of cells in the cotyledons varied from 4.6 ✕ 106 to 10.3 ✕ 106. The three PI lines examined differed in both rates and duration of cell division in the developing seeds. Seed growth rate and final seed weight were related to number of cells in the cotyledons. However, the relationship was not linear. Growth rate per cell for the heavy seeded line was approximately 67% greater than that for the light seeded line. No relationship was observed between seed growth rate or final seed weight and respiration rates. Respiration rates among PI lines for each seed component decreased similarly during seedfill. Within each PI line, respiration rates decreased faster in cotyledon tissue than in either seed coat or embryonic axis tissue. Our results indicate that seeds having a relatively high number of cells per cotyledon have greater rates of dry matter accumulation and final dry weights, and that these growth characteristics are not associated with increased seed respiration.

Nodulation of Soybean Plant Introduction Lines with the Fast‐Growing Rhizobial Strain USDA 2051

The domesticated soybean, Glycine max (L.) Merr., had been thought until recently to nodulate only with rhizobia of the slow‐growing species R. japonicum. However, in 1982, the soybean cultivar Peking was reported to nodulate effectively and fix N2 with newly isolated fast‐growing rhizobial species (as yet unnamed) from China. In the present study, 285 plant introductions of G. max, from nine Asian countries representing maturity groups 00 to ✕ were tested for nodulation with the fast‐growing Rhizobium sp. strain USDA 205. Five seeds of each soybean line were surface sterilized, planted in vermiculite in growth trays, and inoculated with a broth culture of strain USDA 205. After growth for 5 weeks in the greenhouse, plants were removed from the planting medium and the roots were evaluated visually for nodulation response. Fifty‐six percent of the G. max introductions tested formed normal‐appearing nodules (effective). Effectively nodulated lines occurred in all maturity groups. A higher frequency (more than 80%) of nodulation‐compatible lines was found in the southeast Asian nations of Thailand, Malaysia and Indonesia. G. max introductions nodulated by strain USDA 205 varied in apparent efficiency of fixation, as evidenced by relative differences in both plant growth and green color of foliage when grown in N‐free media.

Abscisic Acid and Its Relationship to Seed Filling in Soybeans

The effect of exogenous abscisic acid (ABA) on the rate of sucrose uptake by soybean (Glycine max L. Merr.) embryos was evaluated in an in vitro system. In addition, the concentrations of endogenous ABA in seeds of three soybean Plant Introduction (PI) lines, differing in seed size, were commpared to their seed growth rates. ABA (10(-7) molar) stimulated in vitro sucrose uptake in soybean (cv ;Clay') embryos removed from plants grown in a controlled environment chamber, but not in embryos removed from field-grown plants of the three PI lines. However, the concentration of ABA in seeds of the three field-grown PI lines correlated well with their in situ seed growth rates and in vitro [(14)C] sucrose uptake rates.Across genotypes, the concentration of ABA in seeds peaked at 8.5 micrograms per gram fresh weight, corresponding to the time of most rapid seed growth rate, and declined to 1.2 micrograms per gram at physiological maturity. Seeds of the large-seeded genotype maintained an ABA concentration at least 50% greater than that of the small-seeded genotype throughout the latter half of seed filling. A higher concentration of ABA was found in seed coats and cotyledons than in embryonic axes. Seed coats of the large-seeded genotype always had a higher concentration of ABA than seed coats of the small-seeded line. It is suggested that this higher concentration of ABA in seed coats of the large-seeded genotype stimulates sucrose unloading into the seed coat apoplast and that ABA in cotyledons may enhance sucrose uptake by the cotyledons.

SCREENING WORLD ONION GERMPLASM COLLECTION AND COMMERCIAL CULTIVARS FOR RESISTANCE TO SMUT

Two hundred and fifty-five accessions to the USDA world onion germplasm collection and 66 commercial cultivars of Allium cepa were screened for resistance to Urocystis magica, the causal agent of onion smut. The trial was conducted in Cloverdale, British Columbia on a muck soil heavily infested with U. magica. Percent smut infection in bulbs at harvest was measured and significant differences (P = 0.01) among the accessions and cultivars occurred. Three plant introduction lines and one commercial cultivar were completely resistant to U. magica in the trial and significant levels of resistance were found in six other plant introduction lines and one commercial cultivar.

Glycoalkaloids in tissue culture of Solanum species. Dehydrocommersonine from cultured roots of Solanum chacoense

Dehydrocommersonine, a newly described glycoalkaloid, was isolated from root tissue initiated from a callus culture of Solanum chacoense. Tuber tissue of this plant introduction line did not contain commersonine or its dehydro compound. Callus of S. chacoense and three cultivars of Solanum tuberosum that failed to initiate roots were devoid of glydoalkaloids. Callus of S. tuberosum varieties Merrimack and Wauseon which had developed some roots were found to contain solanine and chaconine.

Título en español.

Rojas de habichuelas con síntomas parecidos a los del virus del mosaico común de la habichuela CBCMV) se recolectaron de una planta originada de semilla de una línea de habichuela introducida en Puerto Rico. La transmisión a dos cultivares de habichuelas (Stringless Bean Refugee y Topcrop) inoculados con extracto de las hojas, revelaron que la planta estaba infecta con BCMV y el virus del mosaico del pepinillo (CMV), designado como estirpe PR. La estirpe CMV-PR mostró dos tipos de síntomas: un leve bandeado de las nerviaciones en algunos cultivares y necrosis del ápice en otros. Las plantas hospederas representaban 8 géneros y 12 especies de leguminosas y 16 especies de otras familias. Las propiedades físicas son similares a las de las estirpes corrientes de CMV. La estirpe CMV-PR reaccionó serológicamente con los antisueros de CMV-C y CMV-S en pruebas de difusión en gel. Los viriones midieron de 25 a 27 manómetros. La estirpe CMV-PR fue transmitida a la habichuela y al frijol por el áfido Myzus persicae y por semilla recolectada de plantas infectas de esas dos especies. La supervivencia del virus en semillas de habichuela y frijol almacenadas por 6 meses y 1 año, respectivamente, agravan la posibilidad de una amplia diseminación geográfica por medio de semilla infecta.

Screening Peppers (Capsicum annuum L.) for Resistance to Curly Top Virus1

Abstract Fifty plant introduction lines of pepper were screened for resistance to curly top virus using the vector Circulifer tenellus Baker and a strain of virus known to be pathogenic on peppers Inoculations were done by caging either 3 or 15 viruliferous leafhoppers onto a leaf at the 4-true-leaf stage of growth. Four lines (PI 257053, PI 281297, PI 288938, and PI 357522) showed apparent resistance when inoculated by 3 leafhoppers, but non appeared resistant for more than a few days when inoculated by 15 leafhoppers. No correlation was found between leafhopper longevity on a plant and that plant’s resistance to the virus.