Resistance reaction of Medicago truncatula genotypes to Fusarium oxysporum: effect of plant age, substrate and inoculation method

Abstract

Fusarium wilt, caused by several formae speciales of Fusarium oxysporum, is an important disease of most crop and pasture legumes, including field pea (Pisum sativum), chickpea (Cicer arietinum), lucerne (alfalfa, Medicago sativa) and barrel medic (M. truncatula). Medicago truncatula is an important pasture legume and a model legume species. Hence, it can be used to increase our knowledge of resistance mechanisms efficient to block F. oxysporum infection if its response to the disease is characterised. We evaluated the physiological and susceptibility responses to the disease of two contrasting M. truncatula genotypes, and the effect of several cultural conditions known to affect the disease incidence, such as plant age at infection time, growth substrate and the method of inoculation. Our results indicated that the A17 accession harbours a moderate level of resistance to the disease. We also showed that the method of inoculation strongly affected development of fusarium wilt disease in this model species, whereas it was not significantly altered by plant age or the inorganic growth substrate tested. In addition, we describe a rapid change in leaf temperature after infection, which can be used as an indirect parameter to confirm fungal infection at a very early stage of the interaction.