The powdery mildew ofcucurbits caused by Sphaerotheca fusco Blumer (syn. S.fuliginea) is the most common and severe disease of this crops in the Mediterranean areas. The controI of the pathogen is usually carried out by several sprays with synthetic and specific fungicides which cause detrimental effects to the environment as weU as risks for resistance development in the fungus populations. These aspects and the contemporary development ofmore sustainable agricu1tural systems have increased the research of suitable alternatives such as bìological control. Several microorganisms bave been found to be effective against S.fusca, but their survival and effectiveness, particu1arly in open field, is frequent1y influenced by the variability ofclirnatic conditions. Therefore, it ìs necessary 10 evaluate also the influence of enviromnentaJ parameters on the both survival and performance of biocontrol agents. The aim ofthis study was to evaluate both the survival and activity against powdery mildew ofthe yeast Cryptococcus lauremii (LS-28) and the yeast-like fungus Aureobasidium pullulans (Au34/2) in fields ofmelon in Southem ItaJy. The antagonists were applied on leaves weekly, from the second half oflune (before ofpowdery mildew symptorns appearance) 10 the end ofJuly (at full development offruits), in 2000 and 200 l. The fungicide penconazole (Topas 10Ee'), at intervals of 14 days, as weU as the biofungicide AQlO~ (Ampelomyces quisqualis), applied weekly, were also included as controls. Both powdery mildew severity and totaJ yeasts (yeasts and yeast Iike fungi) population were periodica1ly assessed. The disease severity was evaluated on allleaves using an empirical scale with 5 degree of disease, from O(no infection) to 5 (lOOO/c, of leaf surfaee covered by the pathogen) and data were processed using the disease index ofMcKinney. Yeasts population was assessed on surface of leaves randomly taken from each plot. Daily temperature, RH and rainfall were also recorded during all the trials time. In the year 2000, LS28 and Au34/2 reduced the disease severity over 56% and 49%, respectively, while in the year 2001 it was reduced over 35% and 27%, respectively. In both years the yeasts aetivity resu1ted comparable to that of chemical control. Wrth respect to AQIO, the yeasts activity was higher in the fìrst year when the disease pressure was stronger, while resulted not different in the second year. The 10taJ yeasts population was significantly higher on leaves treated with antagonists than on leaves ofuntreatedcontrol, fungicide and AQIO. In the fìrst year the applied yeasts induced higher population levels (up to about lO fold) than those observed during the second year; this resu1t could partially explain the higher effectiveness showed by antagonists in the fìrst year. In both years, the climate resuhed very hot and dry with max temperatures frequently above 30 0e and RH under 40%. In each year it rained only one time in the second half of July, drastica1ly reducing T max, increasing RH and inducing an appreciable increment ofyeasts population. This pointed outas T max and RH are crucial factors in the establishmentandsurvivalofLS-28 and Au34/2 on cucwbits leaves under field conditions. The resu1tsofthis study encourage further investigations in order 10 optimise the new proposed bìological means and to verify ifsome modes ofaction already expressed by LS-28 and Au34/2 agaìnst necrotrophic fungi are also involved in their activity against the biotrophic fungus S.fusca.

Survival and activity ofbiocontrol yeasts against powdery mildew of cucurbits in the field

LIMA, Giuseppe;DE CURTIS, Filippo;
2002-01-01

Abstract

The powdery mildew ofcucurbits caused by Sphaerotheca fusco Blumer (syn. S.fuliginea) is the most common and severe disease of this crops in the Mediterranean areas. The controI of the pathogen is usually carried out by several sprays with synthetic and specific fungicides which cause detrimental effects to the environment as weU as risks for resistance development in the fungus populations. These aspects and the contemporary development ofmore sustainable agricu1tural systems have increased the research of suitable alternatives such as bìological control. Several microorganisms bave been found to be effective against S.fusca, but their survival and effectiveness, particu1arly in open field, is frequent1y influenced by the variability ofclirnatic conditions. Therefore, it ìs necessary 10 evaluate also the influence of enviromnentaJ parameters on the both survival and performance of biocontrol agents. The aim ofthis study was to evaluate both the survival and activity against powdery mildew ofthe yeast Cryptococcus lauremii (LS-28) and the yeast-like fungus Aureobasidium pullulans (Au34/2) in fields ofmelon in Southem ItaJy. The antagonists were applied on leaves weekly, from the second half oflune (before ofpowdery mildew symptorns appearance) 10 the end ofJuly (at full development offruits), in 2000 and 200 l. The fungicide penconazole (Topas 10Ee'), at intervals of 14 days, as weU as the biofungicide AQlO~ (Ampelomyces quisqualis), applied weekly, were also included as controls. Both powdery mildew severity and totaJ yeasts (yeasts and yeast Iike fungi) population were periodica1ly assessed. The disease severity was evaluated on allleaves using an empirical scale with 5 degree of disease, from O(no infection) to 5 (lOOO/c, of leaf surfaee covered by the pathogen) and data were processed using the disease index ofMcKinney. Yeasts population was assessed on surface of leaves randomly taken from each plot. Daily temperature, RH and rainfall were also recorded during all the trials time. In the year 2000, LS28 and Au34/2 reduced the disease severity over 56% and 49%, respectively, while in the year 2001 it was reduced over 35% and 27%, respectively. In both years the yeasts aetivity resu1ted comparable to that of chemical control. Wrth respect to AQIO, the yeasts activity was higher in the fìrst year when the disease pressure was stronger, while resulted not different in the second year. The 10taJ yeasts population was significantly higher on leaves treated with antagonists than on leaves ofuntreatedcontrol, fungicide and AQIO. In the fìrst year the applied yeasts induced higher population levels (up to about lO fold) than those observed during the second year; this resu1t could partially explain the higher effectiveness showed by antagonists in the fìrst year. In both years, the climate resuhed very hot and dry with max temperatures frequently above 30 0e and RH under 40%. In each year it rained only one time in the second half of July, drastica1ly reducing T max, increasing RH and inducing an appreciable increment ofyeasts population. This pointed outas T max and RH are crucial factors in the establishmentandsurvivalofLS-28 and Au34/2 on cucwbits leaves under field conditions. The resu1tsofthis study encourage further investigations in order 10 optimise the new proposed bìological means and to verify ifsome modes ofaction already expressed by LS-28 and Au34/2 agaìnst necrotrophic fungi are also involved in their activity against the biotrophic fungus S.fusca.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11695/18611
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