A detailed evaluation method to identify sources of quantitative resistance to Fusarium oxysporum f. sp. pisi race 2 within a Pisum spp. germplasm collection

Abstract

Fusarium oxysporum f. sp. pisi (Fop) is an important pathogen of field pea (Pisum sativum) worldwide. The constant evolution of the pathogen drives the necessity to broaden the genetic basis of resistance to Fop. To achieve this, it is important to have a large germplasm collection available and an accurate and efficient method for disease assessment. Here, a detailed evaluation method coupling disease incidence, disease rating over time and its related area under the disease progression curve (AUDPC) was established and used to screen a Pisum spp. germplasm collection against one isolate of Fop race 2. A large variation in the disease response of specific pea accessions ranging from highly resistant to susceptible was observed within the collection, indicating the quantitative expression of the resistance. The repetition of the inoculation experiments on a subset of 19 accessions, including two susceptible accessions, indicated that the scoring method was robust and reproducible and confirmed the highly resistant phenotypes of 11 accessions. To initiate the characterization of resistance mechanisms within these accessions, the external and internal stem symptoms were compared between these selected pea accessions, together with the extent of fungal colonization within plants. All these tests indicated that, in all resistant accessions, the resistance mechanisms efficiently stopped pathogen progression at the crown. Incorporation of these sources of resistance to breeding programmes will contribute to improved Fop resistance in pea cultivars.

Understanding pea resistance mechanisms in response to Fusarium oxysporum through proteomic analysis

“…We selected 3 genotypes showing different levels of resistance based on a previous work where a Pisum spp. germplasm collection was screened against Fop race 2 (Bani et al, 2012). Our results of the disease symptoms evaluation corroborate those obtained by Bani et al (2012), supporting the significant differences in the resistance level observed between these three genotypes.…”

“…However, we also found two redox homeostasis proteins increased in both partially and resistant genotypes in response to inoculation (aldo/keto reductase and 12-oxophytodienoic acid 10,11-reductase). This could be explained because Fop also colonizes the basal region of the plant of both genotypes, such as has been detected on the screening made by Bani et al (2012) for detection of Fop within plant tissue. Another defense related proteins were identified to be more represented in S and P genotypes.…”

“…It is no strange to find these proteins more represented in S infected plants, with more significance at 72 hai as signal of the fast colonization of the root by Fop. Bani et al (2012) described that only 7 days after inoculation Fop had already colonized the whole plant in the susceptible genotypes. However, we also found two redox homeostasis proteins increased in both partially and resistant genotypes in response to inoculation (aldo/keto reductase and 12-oxophytodienoic acid 10,11-reductase).…”

“…Disease was evaluated by estimating the percentage of leaves with symptoms and the area under the disease progression curve (AUDPC) as described (Bani et al, 2012). Symptoms were also measured from control (non-inoculated) plants to counteract those symptoms due to the inoculation procedure.…”

“…Resistance to Fop race 1, 5 and 6 is conferred by single dominant gene while resistance to race 2 have been recently shown to be quantitative (Bani et al, 2012(Bani et al, , 2014McPhee et al, 2012). Nevertheless, the constant evolution of the pathogen drives the necessity to broaden the molecular basis of resistance to Fop.…”