Phaseolorum Var Research Articles

Incidence of pod and seed infection in two soybean lines differing in resistance to Phomopsis seed decay

Two soybean (Glycine max) lines differing in resistance to Phomopsis seed decay were evaluated in field trials, over 3 yr, for time and incidence of pod and seed infection caused by Phomopsis longicolla, Diaporthe phaseolorum var. caulivora and D. p. var. sojae. Pod infection increased linearly with time but OX615 averaged 15% less than Coles at each sample date. Seed infection increased curvilinearly in conjunction with decreasing seed moisture with marked increases between the fifth and seventh weeks after flowering. At maturity, average seed infection was 69% in Coles and 28% in OX615. Key words:Glycine max, soybean, resistance to Phomopsis seed decay

Saprotrophic ability of Diaporthe phaseolorum var. caulivora on host and non-host plants, and on abiotic substrates

Four single-spore isolates of Diaporthe phaseolorum var. caulivora originating from diverse, soybean-growing locations in the United States were investigated for their saprotrophic ability and production of perithecia on host, non- host and abiotic substrates. Stem pieces of the host, Glycine max; non-hosts Triticum aestivum, Euphorbia heierophylla, Aeschynomene americana, Xanthium strumarium and Sesbania macrocarpa; toothpicks; and capillary glass tube were used as substrates. Autoclaved substrates were placed on acidified potato-dextrose agar and the medium was seeded with the four isolates of D. phaseolorum var. caulivora and incubated at 24 ± 1 °C. All isolates formed perithecia on substrates of plant origin. The pattern of perithecial arrangement was either clustered, solitary or both. Optimum carbon : nitrogen ratios for the production of perithecia were between 1:1 and 10:1. Ratios of 50:1, 100:1 and 500:1 supported either abundant, poor or no mycelial growth, respectively. Some isolates produced perithecia on acidified potato-dextrose agar without any plant substrates, suggesting that fertile isolates exist in the homothallic Diaporthe phaseolorum var. caulivora.

Effects of Induced Epidemics of Heterodera glycines, Diaporthe phaseolorum var. caulivora, and Pseudomonas syringae pv. glycinea in Single Inoculations or in Combinations on Soybean Yield and Other Agronomic Characters

The effects of induced epidemics of Heterodera glycines (Hg), Diaporthe phaseolorum var. caulivora (Dpc), and Pseudomonas syringae pv. glycinea (Psg) in single inoculations or in combinations on soybean yield and other agronomic characters were studied in the field for 3 planting dates from 1985–1987. Agronomic characters, such as size of nodules, number of pods, plant heights, yields, and disease ratings and infestations of soybean were noticeably influenced by the induced epidemics of the pathogens affecting soybeans. Similarly, the induced epidemics of these pathogens also produced either a negative or positive correlation coefficient of the various indicated agronomic characters. Synergistic-yield loss interaction between Dpc + Psg was positive. However, the synergistic-yield loss interactions between Dpc + Hg, Hg + Psg, and Dpc + Hg + Psg were negative. Based on the symptomatology of the diseases, there were no synergisms noted on soybean.

Influence of Soil Moisture on Formation of Perithecia and Pycnidia and Spore Release inDiaporthe phaseolorumvar.caulivora

The formation of perithecia and pycnidia and the release of ascospores and conidia, respectively, by Diaporthe phaseolorum var. caulivora was determined on soil at matric potentials (ψ m ) between 0 and -0.32 MPa. D. p. caulivora infected internodes of susceptible soybean cv. Bedford were incubated at 24 ± 1 C on the surface of soil samples adjusted to ψm = 0.0, -0.01, -0.02, -0.04, -0.08, -0.16, or -0.32 MPa. The number of perithecia and pycnidia formed and the number of sporulated perithecia and pycnidia that released ascospores and conidia, respectively, per square centimeter of soybean internode were counted at weekly intervals (...)

Analysis of Stem Canker Epidemics in Irrigated and Nonirrigated Conditions on Differentially Susceptible Soybean Cultivars

Incidence and severity of stem canker caused by Diaporthe phaseolorum var. caulivora were quantified from an inoculum point source in irrigated and nonirrigated plots of resistant, moderately resistant, and susceptible soybean cultivars (Bay, Wilstar 550, and Bedford, respectively) during the 1988-90 seasons. Steam canker severity at each disease assessment was higher on all cultivars in irrigated plots (...)

Soybean Cultivar Yield Response to Benomyl, Nitrogen, Phosphorus, and Irrigation Levels

AbstractSoybean [Glycine max (L.) Merr.] production for greatest yield involves intensive management of resource inputs. Proper cultivar selection, irrigation, and P application on P‐deficient soils have all been shown to increase yields. Nitrogen applications have resulted in variable yield effects. Under sprinkler irrigation, several diseases caused by species of Diaporthe [D. phaseolorum var. sojae (Lehman) Wehm., and D. phaseolorum var. caulivora Athow. G Caldwell.] and Phomopsis longicolla Hobbs, the Diaporthe/Phomopsis complex may also be yield limiting. This disease complex includes pod and stem blight (PSB), Phomopsis seed decay (PSD), and stem canker. In order to determine the combined influence of cultivar, irrigation level, fertility level, and disease control, field experiments were conducted in 1986, 1987, and 1988 at the South Central Research and Extension Center near Clay Center, NE to evaluate these possible soybean yield limiting factors. All combinations of two levels of benomyl [methyl‐l‐(butylcarlbamoyl)‐2‐benzimidazole carbamate] fungicide (0 and 1.12 kg ha−1 applied at R3 and R5), two levels of N (0 and 134.4 kg ha−1) and P (0 and 67.2 kg ha−1), and two cultivars (determinate Hoyt and indeterminate Zane) were tested at two nonreplicated levels of irrigation. Nitrogen and P application seldom increased seed yield. A yield increase (517 kg ha−1, 1986; 396 kg ha−1, 1987; 215 kg ba−1, 1988) occurred when benomyl was applied to Hoyt soybean under a high level of irrigation. Less of a yield response to benomyl was obtained with later‐maturing Zane, for both cultivars at the lower irrigation level, and during a year of below normal rainfall. Benomyl application decreased the incidence of PSB and increased seed size, but did not consistently affect PSD based on seed appearance. Stem canker was never observed during the course of this study. Yield increases were primarily the result of increased seed size associated with delayed maturity doe to PSB control and increased number of seeds per pod due to benomyl's possible growth regulatory properties. This research indicates that, contrary to previous reports in the northern USA, pod and stem blight can be a yield‐limiting factor with or without the development of Phomopsis seed decay under high‐yield environments.

Spatial and Temporal Spread of Soybean Stem Canker from an Inoculum Point Source

Incidence and severity of stem canker arising from inoculum point sources of Diaporthe phaseolorum var. caulivora was quantified on resistant (Bay), intermediate (DPL105, W550) and susceptible (Bedford) soybean cultivars in the field during 1986 and 1987. Disease progress was described by the Weibull model. The shape parameter (c) of the model was equal to the idealized c value of a monocyclic disease for Bedford (...)

Effect of Date of Planting, Genotype and Source of Seed on Disease Incidence, Yield, and Agronomic Performance of Soybean

AbstractFour soybean genotypes chosen from four seed sources were planted in a factorial arrangement on four dates in a split‐plot design at the Alabama A & M Experimental Station on a Decatur silt clay loam soil. The highest vigor index was recorded from seeds harvested from the 4th date of planting. These seeds had the lowest level of Diaporthe phaseolorum var. caulivora infection, indicating that vigor index, as a measurement of seed quality, was negatively correlated with the level of infection by soybean stem canker pathogen. Seed yield was highest at the 2nd date of planting and lowest at the 4th date of planting. Tracy‐M and Bedford confirmed previous reports on their resistance and susceptibility, respectively, to soybean stem canker. All the genotypes performed their best at the 2nd date of planting. Source of seeds appeared to have little effect on the performance of the plant in the field.

Comparison of possible phytotoxic metabolites in culture filtrates of the Diaporthe/Phomopsis complex of soybeans

Filter-sterile culture filtrates of isolates of Diaporthe phaseolorum var. caulivora, Diaporthe phaseolorum var. sojae (anamorph Phomopsis sojae), and Phomopsis longicolla, causal agents of stem canker, pod and stem blight, and seed decay, respectively, on soybeans (Glycine max), grown on Czapek-Dox broth inhibited germination of soybean seeds (significant at P=0.05). Wilting and necrosis of excised soybean seedlings was significantly greater than the controls when treated with culture filtrates of P. longicolla and P. sojae. Soybean seedling radicle growth inhibited significantly when culture filtrates of P. longicolla were added.

Severity of Soybean Stem Canker Disease Affected by Insect-Induced Defoliation

Greenhouse studies using the soybean (Glycine max) cultivar Bragg showed a significant (P<0.0001) negative relationship (Y=102.636−1.066X+0.006X 2 ) between lengths of stem cankers incited by Diaporthe phaseolorum var. caulivora and defoliation caused by larvae of the soybean looper, Pseudoplusia includens. Reductions in length were greatest when cankers developed at times when defoliation was just completed. (…)

Measurement of Soybean Resistance to Stem Canker Caused by Diaporthe phaseolorum var. caulivora

Measurement of Soybean Resistance to Stem Canker Caused by Diaporthe phaseolorum var. caulivora

Influence of Temperature on Growth and Pathogenicity of Geographic Isolates of Diaporthe phaseolorum var. caulivora

Influence of Temperature on Growth and Pathogenicity of Geographic Isolates of Diaporthe phaseolorum var. caulivora

Possible phytotoxic metabolites in culture filtrates of Diaporthe phaseolorum var. sojae

Filter-sterile culture filtrates of an isolate of Diaporthe phaseolorum var. sojae (Phomopsis sojae), causal agent of pod and stem blight and seed decay of soybeans (Glycine max), grown on Czapeks-dox broth significantly (P = 0.05) inhibited germination of cabbage (Brassica oleracea), cantaloupe (Cucumis melo), onion (Allium cepa), soybean, and wheat (Triticum vulgare) seeds and wilted soybean seedling cuttings within 24 hr. Inhibition of seed germination and severity of soybean seedling wilt increased with increased concentrations of culture filtrates and increased incubation time of the cultures.

Seedborne Diaporthe phaseolorum var. caulivora in Iowa and Its Relationship to Soybean Stem Canker in the Southern United States

Seedborne Diaporthe phaseolorum var. caulivora in Iowa and Its Relationship to Soybean Stem Canker in the Southern United States

Physiologic Specialization of Diaporthe phaseolorum var. caulivora in Soybean

Physiologic Specialization of Diaporthe phaseolorum var. caulivora in Soybean

Yield Reductions Caused by Stem Canker in Soybean1

Stem canker (caused by Diaporthe phaseolorum var. caulivora Athow &amp; Caldwell) was first observed in Louisiana on soybean [Glycine max (L.) Merr.] near Rosa in 1981. In 1982, several thousand hectares of soybeans were damaged in the southern part of Louisiana, some of which were heavily damaged. The objective of this study was to assess the extent of yield reductions of soybean cultivars caused by stem canker in Louisiana. Thirty‐two cultivars were field grown in Olivier silt loam (fine‐silty, mixed, thermic Aquic Fragiudalfs) soil. They were grown in a randomized complete block design with four replications. A wide range of responses was observed; several cultivars from Maturity Groups V through VIII were resistant to the disease. Significant negative correlations occurred between yield and disease ratings among cultivars and maturity groups. This study indicated several cultivars that should not be grown in soil where the stem canker organism is known to be present and identified other cultivars that could possibly be grown in the presence of the stem canker organism.

A New Phomopsis Species from Soybean

A new species of Phomopsis isolated from soybean is described. The species, P. longicolla, differs from P. sojae, the anamorph of Diaporthe phaseolorum var. sojae, in several morphological characte...

Seed molds of soybean in Ontario and the influence of production area on the incidence ofDiaporthe phaseolorumvar.caulivoraandPhomopsissp.

Diaporthe phaseolorum var. caulivora (Dpc) and Phomopsis sp. (Ps) were the predominant pathogens isolated from 328 pedigreed seed lots of soybean (Glycine max) produced in Ontario in 1980, 1981, and 1982. Dpc and/or Ps were present in 89% of the seed lots. Mean incidence of Ps in 1981 and 1982 was higher in seed of the cultivar Harcor produced in an area having a longer growing season than required for cultivar maturity, but mean incidence of Ps in seed lots of the cultivar Hodgson was similar in all production areas. Incidence of Dpc was not affected by area of production. Sclerotinia sclerotiorum was isolated from surface sterilized seed of one seed lot in 1982. Ten other fungi were found infrequently in seed lots.

Symptomless Infection, Persistence, and Production of Pycnidia in Host and Non-Host Plants by Phomopsis batatae, Phomopsis phaseoli, and Phomopsis sojae, and the Taxonomic Implications

Phomopsis batatae, P. phaseoli, and P. sojae were able to infect, without production of obvious symptoms, seedlings of sweet potato and of 16 legumes inoculated in the greenhouse. These fungi produced pycnidia on inoculated seedlings incubated in laboratory moist chambers. Under conditions of natural infection in the field, P. sojae was recovered from stems of 14 of 21 legumes. This fungus was also isolated from seeds of cowpea and lima bean as well as from soybean, its usual host. The interpretation of these results questions the validity of regarding these anamorphs as three distinct species. Taken with the close similarity in morphology reported for these taxa in the literature and observed in my own isolates and in herbarium specimens, I conclude that these taxa are all one species, the valid name of which is Phomopsis phaseoli (Desm.) Sacc. For similar reasons, I consider the teleomorphs Diaporthe phaseolorum var. batatatis, var. phaseolorum, and var. sojae to be one and the same taxon, D. phaseolorum (Cooke & Ellis) Sacc. I believe that teleomorphic and anamorphic isolates from stem cankers and blighted tops of soybean should be provisionally called D. phaseolorum f. sp. caulivora and P. phaseoli f. sp. caulivora, respectively, until it can be demonstrated by a non-wounding technique that they can cause these pathological conditions when re-introduced into the host.

The Development of Diaporthe phaseolorum Variety Sojae in Culture

The development of the Phomopsis state of Diaporthephaseolorum var. sojae is described briefly. Both a and J conidia are produced from similar phialides. The isolate studied is homothallic but has trichogynes or trichogyne-like hyphae in early developmental stages. Perithecia develop from initials that include an ascogonial coil surrounded by enveloping hyphae. Perithecial initials ultimately differentiate into an outer peridium, a prominent centrum pseudoparenchyma layer, and paraphyses. Peridial and centrum hyphae in the apical region proliferate early in development to produce an elongate, periphysis-lined neck. The ascogenous system develops from the terminal portion of the ascogonial coil by septation of coil cells and subsequent production of short, ascogenous hyphae. The ascogenous hyphae proliferate to form a hemispherical basal hymenium. Asci are produced from croziers. The asci become detached from the hymenium and fill the centrum, compressing paraphyses and pseudoparenchyma. Development of D. phaseolorum var. sojae is believed to be a variation of the basic developmental pattern known in some other Pyrenomycetes. Data obtained from developmental studies of perithecia play an important role in current systematic concepts of pyrenomycetous fungi. The major source of this emphasis comes from Luttrell's comprehensive review (26) of perithecial development where developmental patterns were conceived as centrum types characteristic of various taxonomic groups. The present study is the third in a series of investigations of perithecial development in representative Pyrenomycetes. Previous studies on Hypoxylon serpens (Pers. : Fr.) Kickx (17) and Gelasinospora reticulospora (Greis & Greis-Dengler) Moreau & Moreau (18) revealed that perithecial development in these fungi could be viewed as a variation on the same basic ontogenetic pattern. Nonetheless, these two fungi belong to different families and represent the Xylaria and Sordaria perithecial centrum types, respectively. An additional centrum type believed to represent the Diaporthales has received little detailed study. The Diaporthe type centrum has traditionally been depicted as lacking paraphyses in the perithecium, although Luttrell himself has questioned the universality of this concept (27). More recently, studies in the genus Gnomonia by Fayret and Parguey-Leduc (10) and Huang and Luttrell (16) have provided evidence that paraphyses exist in fungi that are unquestionably members of the Diaporthales. There have been, however, no comprehensive developmental studies on Diaporthe, the type genus of the Diaporthales. The present study was therefore undertaken.