Resistance to powdery midew in pea germplasm

Abstract

Pea powdery mildew is an air-borne, worldwide-distributed disease caused mainly by Erysiphe pisi but can also be caused by other species like E. trifolii and E. baeumleri. Pea breeding is based largely on the use of er1 resistance gene, with little use of the second available gene er2. Even when er1 is regarded to provide a more durable type of resistance and today we know that in fact it is a mlo type; it is safer to have a broader battery of genes available to pre-event/delay resistance breakdown. For instance, It has been recently found that er1 is overcome by E. trifolii. In order to extend the availability of sources of resistance, we started by screening a germplasm collection resulting in the identification of quantitative and qualitative resistance to E. pisi. Particularly relevant was Pisum fulvum germplasm where we identified a new gene for resistance to E. pisi that we called Er3. Interspecific hybridization between P. fulvum and P. sativum is possible although hampered by low fertility and many other detrimental traits. We have been able to introduce Er3 into P. sativum background by backcrossing and selection for resistance and fertility, resulting in the release of a resistant pea cultivar (“Eritreo”) containing this gene. We have identified SCAR markers linked to this gene that will facilitate the early selection of individuals carrying the gene in breeding programs. The mode of action at the cellular level of the three resistance genes has been characterized, and genes and proteins involved in the resistance have been identified. At present we are approaching a deeper understanding of the molecular and biochemical mechanisms of response to E. pisi in pea and looking also for resistance to E. trifolii, and developing the tools and knowledge needed for the introgression of the resistance into pea cultivars.