Ascochyta pisi is a fungal plant pathogen that causes A scochyta blight on pea leaf blight or pea blight and lesions of stems, leaves, and pods pea leaf spot and pea pod spot. Ascochyta pisi hardly survives in the soil or on crop residues because of its poor saprophytic competitiveness and because chlamydospores are rare. Primary infection is purely seed-borne. Conidia and other fungal structures are transmitted on the outside of the seed coat and cause primary infection.
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Advances in Ascochyta research View all 16 Articles. The role of seed infection with Ascochyta pisi using naturally infected seeds with an incidence from 0. A significant effect of A. The level of seed infection at planting had no impact on A. Results suggest that the disease did not progress significantly from seeds to seedlings, hence did not contribute to infection of aerial parts of the plants, and therefore infected seeds cannot be regarded as a source of inoculum in the epidemiology of this pathogen under western Canadian growing conditions.
Assessing seed components of seeds with varying levels of A. This indicates that infected seeds may be an important way for the pathogen to survive in nature. Ascochyta blight, also referred to as the ascochyta blight complex, is one of the major diseases affecting field pea production and can be caused by several pathogens with anamorphs in the genus Ascochyta Tivoli and Banniza, Worldwide, Peyronellaea pinodes syn.
Mycosphaerella pinodes , Ascochyta pisi , and Phoma pinodella have been associated with this disease. In Australia other species of Phoma including Phoma koolunga Davidson et al. Among the causal agents of ascochyta blight, P. Symptoms of P. Pycnidia are easily visible in mature lesions of A. Infection of pea seed is one of the major survival mechanisms of Ascochyta spp.
Infection reduces seed germination, and seedlings that do develop from infected seeds may be diseased resulting in poor plant development and stands Jones, ; Maude, ; Moussart et al.
Higher severity of seed staining could be correlated with deeper penetration of P. The impact of seed-borne inoculum is influenced by factors including rainfall and temperature, and areas with low rainfall often produce disease-free seeds in the field Bathgate et al. Surface sterilization of pea seeds results in a reduction of seed infection with P. Seed infection levels with P.
Seed-borne infection of other species of the ascochyta blight complex such as Phoma spp. Ascochyta spp. Until , A. In , the pea variety Century originally released as Creamette [ Gfeller and Wallen, ] was introduced and quickly gained in acreage due to its high level of resistance to A. Simultaneously, P. In the early s, a resurgence of A. In response to this, experiments were conducted to reassess the impact of seed infection in the epidemiology of A.
It was hypothesized that pea plants developing from seeds infected with A. It was also hypothesized that low levels of seed coat staining would be indicative of no or a low incidence of embryo infection with A. Seeds of CDC Patrick, a green cotyledon field pea cultivar, were used for this experiment. Two commercial seed lots with an incidence of natural A.
Samples were combined to obtain A. Field experiments were established in the Canadian province of Saskatchewan in May at Outlook, Saskatoon, and Milden where levels of A. Detailed dates and general agronomic practices are presented in Supplementary Table S1. Experiments were designed as randomized complete block designs with four replicates. Plot size was 1. During the growing season, plant emergence was assessed by counting the number of seedlings per one meter plant row in four arbitrarily selected rows or row segments of each plot.
The severity of symptoms caused by A. Five arbitrarily selected plants were rated in each plot and data were transformed to percentage disease severity using the class mid points. The averages per plot were calculated for further data analyses. At harvest, seed yields were determined for each plot, seeds were assessed for thousand seed weight TSW and the incidence of seed infection with pathogens. For seed testing, seeds per plot were surface-sterilized by soaking in 0.
Each seed was assessed for infection by A. The latter also included a small number of underdeveloped and shriveled seeds assumed to be caused by A. For each category, seven replicates of 50 seeds were soaked in sterile distilled water for 2 h to soften the seed coat. Seeds were dissected into seed coat, cotyledon, and embryo.
Seed components were surface-sterilized by soaking in 0. Each Petri dish was assessed for infection and fungal growth was morphologically identified to the species level for A. All data were analyzed using in SAS Version 9. All data were tested for normality and heterogeneity of variances of residuals.
Data of emergence, yield, TSW, disease severity and the incidence of A. Incidence data for A. Initially, other pathogens detected in seed samples were used as covariates. Final modeling of A. Seedling emergence ranged from 10 to 24 seedlings per meter row in plots, with an overall average of 16 seedlings per meter row. Emergence was lowest at Milden in and highest at the same location in , which was most likely associated with soil moisture conditions during emergence.
CDC Patrick grown from seeds with incidence levels of A. The average severity of A. Overall, disease development on peas was higher at Saskatoon and Outlook in than in other years and locations because of higher precipitation and mm, respectively, compared to to mm in other years and locations during the growing season May to August.
Seed infection with A. The severity of P. There were no significant differences in P. The incidence of P. Except for Outlook and Milden , harvested seeds had more A. Seed components without staining of the seed coat were not infected with A. Seed coats, cotyledons, and embryos of all other four seed staining categories were infected with A. In addition to A. Only incidence data of Epicoccum spp. Seed staining category, seed components, and their interaction had significant effects on the incidence of A.
TABLE 1. CDC Patrick seeds that were separated into four seed coat staining categories. CDC Patrick that were separated into four seed coat staining categories. Bars indicate standard errors of the mean. Letters above columns indicate significant differences: columns of each series with a letter in common are not significantly different.
Pea seedling emergence was slightly, but statistically significantly affected by the incidence of A. This indicates that even an incidence of A much more significant impact of A.
In contrast, assessments of seed samples from several years and locations with A. When comparing these numbers it is important to keep in mind that the earlier reports used pea varieties that are now 60 to more than years old, and were most likely more susceptible to A. Even though the first highly A. A negligible impact of A. Precipitation during the growing seasons of to at experimental locations was average or above average, so conditions generally were conducive for the initiation of epidemics.
Very low levels of seedling infections and no effect of A. There was also no effect on seed yield, seed size or the infection levels with this pathogen of harvested seeds. In general, A. In four of the six field experiments seed infection of harvested seeds with A.
Wallen et al. A higher incidence of A. When assessing seed components for infection, the embryo of all seeds were infected with A. This is distinctly different from seed infection by P. Seeds with higher seed coat staining always showed evidence of necrosis caused by P.
This positive correlation between increasing outer seed coat staining and infection of inner seed components suggests that P. The relatively high incidence of A. The lack of correlation between foliar infection, from which water-splashed conidia could infect flowers, and the incidence or depth of seed infection indicates that airborne ascospores of A.
Little is known about the life cycle of A. The latter is homothallic and readily produces sexual fruiting structures pseudothecia which are thought to overwinter on pea stubble generating airborne ascospores that represent the initial inoculum for the new pea crop in the following season reviewed in Roger and Tivoli, Studies in France showed that ascospores of P.
The teleomorph of the heterothallic species A. To date, no studies have been conducted to determine whether pseudothecia develop under field conditions, nor have there been attempts to trap ascospores of this species.
EPPO Global Database
The role of seed infection with Ascochyta pisi using naturally infected seeds with an incidence from 0. A significant effect of A. The level of seed infection at planting had no impact on A. Results suggest that the disease did not progress significantly from seeds to seedlings, hence did not contribute to infection of aerial parts of the plants, and therefore infected seeds cannot be regarded as a source of inoculum in the epidemiology of this pathogen under western Canadian growing conditions.
List of symptoms / signs
Pea blight, leaf and pod spot
Ascochyta pisi is a fungal plant pathogen that causes ascochyta blight on pea , causing lesions of stems, leaves, and pods. These same symptoms can also be caused by Ascochyta pinodes , and the two fungi are not easily distinguishable. The host of Ascochyta pisi is the field pea Pisum sativum L. Ascochyta pisi also infects 20 genera of plants and more than 50 plant species including soybean, sweet pea, lentil, alfalfa, common bean, clover, black-eyed-pea, and broad bean. Field pea is an annual, cool season legume that is native to northwest and southwest Asia.