El INTA investiga la eficacia del funguicida azoxistrobin para el control del “moho verde”, una enfermedad de poscosecha producida por un hongo que ataca a los cítricos y produce importantes pérdidas económicas.

“Los problemas que trae aparejada la presencia de esta podredumbre es que la fruta estacionada madura en forma acelerada, los productores sufren pérdidas de lo invertido en cosecha, empaque y transporte y también existe la posibilidad de que pierdan confiabilidad como exportadores”, explicó el autor principal del estudio que fue presentado en las XIII Jornadas Fitosanitarias Argentinas, Pablo Velázquez.

Seguimiento:

Velázquez, investigador del INTA Famaillá –Tucumán–, sostuvo que en la década del 90 aparecieron cepas del hongo Penicillum digitatum resistentes a los imidazoles –entre ellos, el imazalil es el fungicida más usado–, lo que conlleva al problema de que para poder controlar el moho se necesitan aumentar las dosis con el consiguiente problema de los residuos en la fruta para exportar.

El equipo de investigación experimenta, entre otras alternativas, fungicidas como el azoxistrobin que inhibe el proceso respiratorio de los hongos y que controlaría las cepas resistentes al imazalil. En este sentido, las conclusiones del trabajo demostraron que el azoxistrobin fue tan eficaz en el control de esta podredumbre como los otros fungicidas empleados comúnmente.

Según afirmó Velázquez, Argentina es actualmente el primer productor mundial de limones y, dentro del país, Tucumán es el principal productor.

En la zona citrícola de esa provincia, el “moho verde” es la enfermedad de poscosecha más importante durante el período de exportación de limón como fruta fresca y el mayor daño se produce en los galpones de empaque, cuando la fruta permanece estacionada y sufrió alguna herida.

“Una sola fruta afectada sirve para que las frutas vecinas también se enfermen”, recalcó, al tiempo que explicó que las heridas o golpes que se producen desde el momento de la cosecha hasta su llegada al empaque, predisponen las infecciones.

Otros trabajos relacionados al tema:

Titre du document / Document title

Comparative efficacy of the new postharvest fungicides azoxystrobin, fludioxonil, and pyrimethanil for managing citrus green mold

Auteur(s) / Author(s)

KANETIS Loukas ⁽¹⁾ ; FORSTER Helga ⁽²⁾ ; ADASKAVEG James E. ⁽¹⁾

;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Department of Plant Pathology, University of California, Riverside 92521, ITALIE
⁽²⁾ Department of Plant Pathology, University of California, Davis 95616, ITALIE

Résumé / Abstract

Three new fungicides (i.e., azoxystrobin, fludioxonil, and pyrimethanil) are currently being introduced for postharvest management of citrus green mold in the United States. The effectiveness of each fungicide was evaluated when applied alone (at 1,000 to 1,200 mg/liter) or in mixtures (at 500 mg/liter each component) to lemon fruit that were wound-inoculated with imazalil/thiabendazole (TBZ)-sensitive or -resistant isolates of Penicillium digitatum. In laboratory studies when aqueous fungicide solutions were applied 9 to 21 h after inoculation, pyrimethanil showed the highest level of green mold control. The efficacy of fludioxonil and azoxystrobin was very high at the early timings, but decreased as time after inoculation increased. Differences in fungicide performance were not due to multiple fungicide resistance, but more likely due to differences in fungicide mobility in fruit tissue. Azoxystrobin-fludioxonil mixtures were significantly more effective when compared to single-fungicide treatments. Mixtures of imazalil with pyrimethanil were the most effective in controlling decay. The efficacy of all fungicides was significantly lower when mixed into a packing fruit coating as compared to aqueous or storage fruit coating applications. In laboratory and packingline studies, the lowest incidence of green mold decay was obtained when azoxystrobin-fludioxonil and imazalil-pyrimethanil were applied as aqueous solutions that were followed by a fruit coating. Among the new fungicides, azoxystrobin and fludioxonil applied in water or storage fruit coating, respectively, provided the best anti-sporulation activity. Storage fruit coating improved the activity of both fungicides. Pyrimethanil was the least effective fungicide in suppressing sporulation of the pathogen on decaying fruit. Overall, among the mixtures, azoxystrobin-fludioxonil and TBZ-fludioxonil had high anti-sporulation activity in aqueous and storage fruit coating applications. New integrated management programs should be based on monitoring of fungicide sensitivities in pathogen populations, rotating mixtures of products with different modes of action, and using appropriate fungicide application strategies.

Revue / Journal Title

Plant disease   ISSN 0191-2917   CODEN PLDIDE

Source / Source

2007, vol. 91, n^o11, pp. 1502-1511 [10 page(s) (article)] (34 ref.)

Fuente: http://cat.inist.fr/?aModele=afficheN&cpsidt=19190330

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Pre- and Postharvest Treatments to Control Green Mold of Citrus Fruit During Ethylene Degreening

Two approaches, fungicide applications to trees before harvest and drenching fruit after harvest,
were evaluated to minimize postharvest green mold, caused by Penicillium digitatum, particularly
among fruit subjected to ethylene gas after harvest, a practice termed “degreening” that
eliminates green rind color. Preharvest applications of thiophanate methyl (TM) controlled postharvest
green mold consistently. In five tests, green mold among degreened orange fruit was
16% when TM was applied 1 week before harvest; whereas, among fruit not treated, the incidence
was 89.5%. Thiabendazole (TBZ) applied to harvested fruit in bins before degreening also
was very effective. TBZ effectiveness was enhanced by mild heating (41ºC), adding sodium
bicarbonate, and immersing fruit, rather than drenching them, with the solution. With these
measures, an isolate of P. digitatum with a high level of TBZ resistance was significantly controlled.
In semicommercial tests with naturally inoculated fruit, TBZ and sodium bicarbonate
treatment reduced green mold incidence from 11% among untreated orange fruit to 2%. TBZ
residues in lemon fruit at 41ºC were about twice those treated at 24ºC. Neither TM before harvest
nor TBZ and sodium bicarbonate applied after harvest influenced green color removal during
degreening of orange fruit. Sodium bicarbonate slightly reduced the rate of lemon color
change.

Fuente Plant Disease / January 2006: http://ddr.nal.usda.gov/bitstream/10113/1310/1/IND43786138.pdf

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Titre du document / Document title

A molecular mechanism of azoxystrobin resistance in Penicillium digitatum UV mutants and a PCR-based assay for detection of azoxystrobin-resistant strains in packing- or store-house isolates

Auteur(s) / Author(s)

ZHIFANG ZHANG ^{(1 3)} ; ZENGRONG ZHU ^{(2 3)} ; ZHONGHUA MA ^{(1 3)} ; HONGYE LI ^{(1 3)}

;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Institute of Biotechnology, Zhejiang University, Hangzhou, Zhejiang 310029, CHINE
⁽²⁾ State Key Laboratory of Rice Biology, Institute of Insect Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, CHINE
⁽³⁾ Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Ministry of Agriculture, Zhejiang University, Hangzhou, Zhejiang 310029, CHINE

Résumé / Abstract

Sixty-five isolates of Pencillium digitatum (Pers.:Fr) Sacc., a causative agent of green mold of postharvest citrus, were collected from various locations in Zhejiang province in 2000, 2005 and 2006, and assayed for their sensitivity to the quinone outside inhibitor (QoI) fungicide azoxystrobin. The results showed that azoxystrobin is highly effective against P. digitatum, in vitro, and that the effective concentrations resulting in reduction of conidial germination and mycelial growth by 50% (EC₅₀) averaged 0.0426 μg/ml and 0.0250 μg/ml, respectively. Twenty-eight azoxystrobin-resistant mutants were obtained by UV mutagenesis and subsequent selection on medium amended with azoxystrobin (12 μg/ml) and salicylhydroxamic acid. All obtained mutants were highly resistant to azoxystrobin and their resistance was genetically stable. Analysis of the cytochrome b gene structure of P. digitatum (Pdcyt b) showed the absence of type I intron in the first hot spot region of mutation. These results indicate that P. digitatum is likely to evolve high levels of resistance to azoxystrobin after its application. Analysis of partial sequences of Pdcyt b from both the azoxystrobin-sensitive parental isolate and the 28 azoxystrobin-resistant mutants revealed that a point mutation, which leads to the substitution at code 143 of alanine for glycine (G143A), is responsible for the observed azoxystrobin resistance in the laboratory mutants. Based on this point mutation, two allele-specific PCR primers were designed and optimized for allele-specific PCR detection of azoxystrobin-resistant isolates of P. digitatum.

Revue / Journal Title

International journal of food microbiology   ISSN 0168-1605   CODEN IJFMDD

Source / Source

2009, vol. 131, n^o2-3, pp. 157-161 [5 page(s) (article)] (1/2 p.)

Fuente:  http://cat.inist.fr/?aModele=afficheN&cpsidt=21557019