Analysis of pathogenicity, fungicide resistance and patulin production in strains of blue rot producer Penicillium sp

Abstract

The blue rot produced by Penicillium expansum is a post-harvest disease that causes significant economic losses in fruits and vegetables. The application of fungicides is the main way to combat this disease. However, there are strains resistant to them and added to this, public demand for reducing the use of pesticides has grown. On the other hand this fungus is a producer of patulin. This compound is a mycotoxin that causes acute and chronic diseases. The goal of this work was to analyze Penicillium sp strains in terms of their ability to produce blue rot in apples, resistance to fungicides and patulin production. In addition to select the best candidates for future studies using different control methods. We worked with 10 strains of Penicillium sp isolated of pear and apple rot from Alto Valle de Río Negro, 1 isolated from San Luis and 2 from references. The pathogenicity tests were performed on commercial Red delicious apples washed and then wounded to inoculate them with 20 L of a suspension of 106 conidia/mL. Apples were stored 7 days at 25°C and the diameter of the rots was measured (mm). The fungicide resistance at the doses recommended for standard postharvest treatments was evaluated ?in vitro?. A suspension of spores of the fungus was dispersed in plates with PDA. Then, holes were made, and there were inoculated with 5 fungicides Captan, Tecto (Thiabendazole), Carbendazim, Scholar (Fludioxonil), Penbotec (Pirymethanil) or water. Development or not of fungus was observed at 3 and 7 days of incubation at 25°C. Patulin determinations were performed by culturing the strains in PDA medium 7 days at 25°C. Then, the toxin was extracted and determined in HPLC-UV according to the modified AOAC technique. Regarding pathogenicity, INTA-1, INTA-2, INTA-6, INTA-10 strains developed rot diameters between 39-36 mm. On the other hand, the rest of the strains presented diameters smaller than 33mm. All the strains tested were resistant to Captan fungicide. Also, INTA-6 and INTA-10 strains showed total resistance to Tecto and Carbendazim and partial resistance to Penbotec and Scholar. On the other hand, the strain isolated in San Luis presented total resistance to Tecto, Carbendazim, Penbotec, and Captan. INTA-10 strain presented the highest production of patulin of 119.78μg/g PDA. However, the rest of the strains presented production below 45 μg/g PDA. From the results obtained, it is observed that all strains showed resistance at least one fungicide, several strain to 2 or 3 of them. The longer the fungicide was present, the greater resistance was observed. Strains also presented different capacities to generate blue rot in apples and to produce patulin. In addition, it was concluded that the INTA-10 strain is the best candidate to continue studying different control methods. It is highly pathogenic, resistant to fungicides and has the highest production of patulin.