Development of natural late blight epidemics in pure and mixed plots of potato cultivars with different levels of partial resistance

Abstract

Late blight, caused by Phytophthora infestans , is the most severe disease of potato worldwide. Controlling late blight epidemics is difficult, and resistance of host cultivars is either not effective enough, or too easily overcome by the pathogen to be used alone. In field trials conducted for 3 years under natural epidemics, late blight severity was significantly lower in a susceptible cultivar growing in rows alternating with partially resistant cultivars (mixtures) than in unmixed plots of the susceptible cultivar alone. Partially resistant cultivars behaved similarly in unmixed and mixed plots. Mixtures of cultivars reduced disease progress rates and sometimes delayed disease onset over unmixed plots, but did so significantly only for the slowest epidemic. This suggests that reduction of area under the disease progress curve (AUDPC) in mixtures resulted from the cumulative action of minor effects. Disease distribution was focal in all plots at all dates, as shown by Morisita's index values significantly exceeding 1. Significant yield increases for the susceptible cultivar, and occasionally for the partially resistant ones, were observed in mixed-cultivar plots compared with single-cultivar plots. These results show that cultivar mixtures can significantly reduce natural, polycyclic epidemics in broadleaved plants attacked by pathogens causing rapidly expanding lesions.

Resistance to Phytophthora infestans in Solanum tuberosum landraces in Southern Chile

“…Finally, the AUDPCr values observed in the present study are lower than those reported by Mendoza (2010) in Cameroon, who reported AUDPCr values of 0.39 and 0.49 for resistant and moderately resistant material, respectively. Andrivon et al (2003) reported that the severity of late blight disease was significantly lower in susceptible cultivars when they were planted in rows alternating with cultivars which had partial resistance. Mixing cultivars produced a large reduction in the disease progress rate.…”

The effect of potato variety mixtures on epidemics of late blight in relation to plot size and level of resistance

“…Andrivon et al (2003) found that late blight severity on a susceptible cultivar was significantly lower when the cultivar was grown in rows alternating with partially resistant cultivars than when it was grown alone. They showed that this was the result of cumulative effects over the course of the epidemic.…”

“…An improved understanding of the effect of potato variety mixtures on late blight is important because such mixtures may have a role to play in a durable 'systems approach' to disease management in low input agricultural systems . Variety diversification may also help to reduce pesticide input in conventional systems (Andrivon et al, 2003).…”

Intraspecific functional diversity in hosts and its effect on disease risk across a climatic gradient

“…The use of potato genotype mixtures has shown potential as a management component for late blight in the United States (Garrett and Mundt 2000b) and France (Andrivon et al 2003), but did not have as important an effect near Quito, Ecuador, except at a site distant from other potato production (Garrett et al 2001) or when combined with fungicide use (Pilet et al 2006). Environmental differences between the sites where potato mixtures were evaluated for late blight management may be important for explaining the relative utility across the sites.…”