Characterization of field pea (Pisum sativum) resistance against Peyronellaea pinodes and Didymella pinodella that cause ascochyta blight

Abstract

Ascochyta blight is one of the most destructive diseases in field pea and is caused by either individual or combined infections by the necrotrophic pathogens Peyronellaea pinodes, Didymella pinodella, Ascochyta pisi and Ascochyta koolunga. Knowledge of disease epidemiology will help in understanding the resistance mechanisms, which, in turn, is beneficial in breeding for disease resistance. A pool of breeding lines and cultivars were inoculated with P. pinodes and D. pinodella to study the resistance responses and to characterize the underlying resistance reactions. In general, phenotypic analysis of controlled environment disease assays showed clear differential responses among genotypes against the two pathogens. The released variety PBA Wharton and the breeding line 11HP302-12HO-1 showed high levels of resistance against both pathogens whereas PBA Twilight and 10HP249-11HO-7 showed differential responses between the two pathogens, showing higher resistance against D. pinodella as compared to P. pinodes. OZP1604 had high infection levels against both pathogens. Histochemical analysis of leaves using diamino benzidine (DAB) showed the more resistant genotypes had lower accumulation of hydrogen peroxide compared to susceptible genotypes. The digital images of DAB staining were analyzed using ImageJ, an image analysis software. The image analysis results showed that quantification of leaf disease infection through image analysis is a useful tool in estimating the level of cell death in biotic stress studies. The qRT-PCR analysis of defense related genes showed that partially resistant genotypes had significantly higher expression of PsOXII and Pshmm6 in the P. pinodes treated plants, whereas expression of PsOXII, PsAPX1, PsCHS3 and PsOPR1 increased in partially resistant plants inoculated with D. pinodella. The differential timing and intensity of expression of a range of genes between resistant lines challenged with the same pathogen, or challenged with different pathogens, suggests that there are multiple pathways that restrict infection in this complex pathogen-host interaction. The combination of phenotypic, histochemical and molecular approaches provide a comprehensive picture of the infection process and resistance mechanism of pea plants against these pathogens.

Antifungal Properties of Bio-AgNPs against D. pinodes and F. avenaceum Infection of Pea (Pisum sativum L.) Seedlings

“…Plant responses to pathogen infection involve a series of reactions associated with the reinforcement of cell walls, oxidative burst, the activation of the antioxidative system, hormonal adjustment, the synthesis of stress-related biomolecules (e.g., phytoalexins), and proteins related to both secondary [70] and primary metabolism [71], which are common to various fungal infections [72][73][74]. Up to now, the changes in the transcriptome and proteome of pea plants infected with D. pinodes or F. oxysporum have revealed an increase in the levels of various proteins, i.e., those involved in energy and amino acid metabolism, redox response, the synthesis of pisatin or pathogenesis-related (PR) proteins, and proteins involved in changes in the structures of the cell walls (e.g., lignin biosynthesis, the modification of the degree of methyl esterification of pectins) [2,28,[75][76][77][78][79]. However, data on the metabolic responses of pea to fungal infections are scarce.…”

“…Pea is also cultivated as a rotation and disease-breaking crop. These special attributes make pea important for both natural and agricultural ecosystems [1,2]. Pea seeds have high nutritional value owing to their high-quality protein content (15-30%), high amino acid availability (such as arginine, phenylalanine, leucine, isoleucine, tryptophan, lysine, and threonine), and energy (carbohydrate content 24-49%) and mineral element content (such as potassium, phosphorous, magnesium, and calcium) [3,4].…”

“…The main limitation in the cultivation of peas is the lack of yield stability caused by abiotic and biotic stresses [6]. The most devastating fungal diseases of pea are Ascochyta blight and root rot [2,7].…”

“…Ascochyta blight, also known as "black spot" disease, is a major foliar pea disease that occurs in Europe and other countries, such as Canada, Australia, the USA, and China, and causes a loss that can reach 75% [2,8,9]. The disease causes dark-brownish necrotic lesions on the aboveground parts of the plant, including pods and seeds, which affect their quantity and quality [8,10].…”

“…Ascochyta blight pathogens can coexist as a fungal complex or infect plants individually, and their prevalence varies worldwide. However, D. pinodes is considered to be the most pathogenic and damaging pathogen associated with the disease, regardless of the region-dominant species [2,8]. Moreover, D. pinodes is also associated with pea root rot [15].…”