Ana Moral

Prehaustorial Resistance against Alfalfa Rust (Uromyces striatus) in Medicago truncatula

The legume species Medicago truncatula is gaining interests as a plant for structural and functional genomics that can be used to identify agronomically important genes in crop legumes. Resistance to the alfalfa rust (Uromyces striatus) was studied in a germplasm collection of M. truncatula. Accessions varied in resistance, as expressed by disease severity, but none showed macroscopically visible necrosis. Histological investigations, in selected lines covering the whole range of resistance reactions, revealed little difference in spore germination and none in orientation of germtubes on the leaf surface. However, appressorium formation on the stoma was significantly reduced in some accessions. Differences in resistance among accessions were more evident once the stoma were penetrated by the infection structures. Resistance was mainly due to a restriction of haustorium formation with varying levels of early abortion of the colonies, a reduction in the number of haustoria per colony, and hampered colony growth. In addition, necrosis of the host cells associated with infection hyphae was detectable in some accessions from the beginning of colony development. This information will be useful for eventual mapping and cloning analyses of resistance genes in M. truncatula that will in turn be useful for understanding other legume/rust interactions.

Resistance against broomrapes (Orobanche and Phelipanche spp.) in faba bean (Vicia faba) based in low induction of broomrape seed germination

Broomrapes are weedy root parasitic plants that severely constraint faba bean production. After long and extensive breeding efforts made in several countries only moderately resistant cultivars are available to farmers, being their resistance based on a combination of avoidance and resistance mechanisms. In this work we characterize the resistance mechanism of two faba bean breeding lines selected for resistance to Orobanche crenata. Mini-rhizotron experiments showed that low induction of seed germination is a major component of resistance in these lines against O. crenata, O. foetida and P. aegyptiaca. This is confirmed by in vitro experiments with root exudates. The fact that low induction of germination is similarly operative against O. crenata, O. foetida and P. aegyptiaca reinforce the value of this resistance.

Resistance reaction to powdery mildew (Erysiphe pisi) in a germplasm collection of Lathyrus cicera from Iberian origin

Several Lathyrus species have a considerable potential as alternative pulses in sustainable dryland farming systems mainly due to their high tolerance to drought and disease resistance. Powdery mildew is a serious disease affecting several Lathyrus species. Little is known on the availability of resistance and the underlying resistance mechanisms against powdery mildew in the Lathyrus genus. The present study assessed and characterized the resistance reaction to powdery mildew, Erysiphe pisi, in a collection of Iberian Lathyrus cicera accessions. In general, a compatible reaction with no macroscopically visible necrosis was observed but accessions with reduced disease severity despite of a high infection type have also been identified. This Partial Resistance was in some accessions only expressed in the adult plant stage. The controlling genes of the Lathyrus resistance mechanisms can be of great interest not only for the Lathyrus improvement per se but also for related legume species, like field pea.