<i>Phomopsis</i> sp. ocurrence in <i>Carya illinoinensis</i> (Wangenh) K. Koch seedlings

Abstract

Pecan seedlings production has increased in recent decades, especially in southern Brazil, consequently, intensifies studies in crop phytosanitary problems in this region. Sanitary quality is an important factor in the production of forest seedlings, considering the occurrence of diseases in all stages of the production process. In April 2021, dark and irregular leaf spots were observed in pecan seedlings under nursery conditions. The evolution of symptoms caused leaf drop and compromised plant development, due to the reduction of their photosynthetic area. It was verified that it was a fungus, which was isolated on potato-dextrose-agar (PDA) medium, and later had its pathogenicity verified in detached pecan leaflets. Four-mm disks of the pure culture of the Phomopsis sp. were placed on the surface of healthy leaflets, previously injuredwith a sterilized histological needle. After inoculation, the leaflets were placed in gerbox boxes lined with two sheets of sterilized filter paper and moistened with sterilized distilled water and kept in an incubation chamber for seven days at 25 ± 2ºC and 12 h photoperiod. Eight healthy leaflets were used as controls, which were subjected to the same conditions, except for fungus inoculation, using only disks of PDA culture medium. The isolate proved to be pathogenic, with the first symptoms after 6 days of inoculation, the initially circular and necrotic lesions coalesced and at 10 days reached 16 mm. The re-isolation was carried out as soon as the reproductive structures of the fungus appeared, these were transferred to Petri dishes with PDA culture medium. The fungus causing the symptoms was identified as Phomopsis sp. and, this work presents the first report of the occurrence of Phomopsis sp. in Carya illinoinensis under nursery conditions in Brazil.