Sensibilidade à fungicidas de espécies de Lasiodiplodia associadas à fruteiras no nordeste brasileiro e adaptabilidade de isolados

Abstract

The Northeast region of Brazil is an important producer and exporter of tropical fruits. In this region, diseases caused by Lasiodiplodia species significantly impact crops, particularly grapevine, mango, papaya, and red mombin. While L. theobromae is the dominant species, others such as L. brasiliensis, L. euphorbiaceicola, L. hormozganensis, L. iraniensis, and L. pseudotheobromae are also linked to these diseases. However, there is limited information on the fungicide sensitivity of these lesser-known Lasiodiplodia species. This study aimed to assess the sensitivity and fitness of isolates from five Lasiodiplodia species collected from fruit orchards in Northeast Brazil to the fungicides imazalil, tebuconazole, thiabendazole, and thiophanate-methyl. The sensitivity of 153 Lasiodiplodia isolates from grape, mango, papaya, and red mombin to the fungicides was assessed by measuring the effective concentration (EC50) needed to inhibit 50% of mycelial growth. Subsequently, five isolates with the lowest (sensitive-S) and highest (less sensitive-LS) EC50 values for the fungicides were examined for sensitivity stability, fungicide effectiveness in controlling the isolates on detached fruits, and fitness components, including mycelial growth, osmotic sensitivity, and virulence. The sensitivity to tebuconazole (mean EC50 = 0.15 μg/mL) was greater than to thiophanate-methyl (mean EC50 = 0.34 μg/mL), thiabendazole (mean EC50 = 1.15 μg/mL), and imazalil (mean EC50 = 2.36 μg/mL). Cross-sensitivity was observed exclusively between imazalil and tebuconazole. Low-sensitive isolates to imazalil showed increased sensitivity after successive subcultures, whereas the other isolates maintained stable sensitivity levels. The control efficacy of LS isolates to imazalil and tebuconazole on mango, papaya and seriguela was significantly lower than that of S isolates. Fitness costs were observed only in LS isolates to thiabendazole, as they exhibited lower virulence on papaya fruits compared to S isolates. Isolates classified as LS to imazalil, tebuconazole, and thiophanate-methyl demonstrated a greater ability to grow under salt stress compared to S isolates. The findings of this study suggest the potential presence of Lasiodiplodia isolates from grape, mango, papaya, and red mombin orchards in Northeastern Brazil that are resistant to imazalil, tebuconazole, thiabendazole, and thiophanate-methyl. Keywords: Botryosphaeriaceae; Tropical fruit diseases; Chemical control; DMI fungicide; MBC fungicide; Fungicide resistance; Fitness.