Etiología de la necrosis apical, cancros y muerte de ramas en naranja (Citrus sinensis (L.) Osbeck) en los cantones Chone y Flavio Alfaro

Abstract

The orange is a tropical species belonging to the Rutaceae family, whose fruits are in demand throughout the world due to their high nutritional value; however, the yield of this crop is commonly affected by the incidence of diseases. The objective of this research was to identify the causal agent of apical necrosis, cankers and death of branches in orange (Citrus sinensis (L.) Osbeck) in the Chone and Flavio Alfaro cantons. 45 samples were collected in seven localities belonging to two orange-producing cantons in the province of Manabí and in each of them 135 trees were randomly selected in which four branches of 15 cm length were collected, transferred to the Phytopathology laboratory and the sections with the presence of the disease were sown in triplicate in potato dextrose agar (PDA) culture medium. Once mycelial growth was observed, two sowings were carried out by isolation in water agar (AA) medium. To induce the formation of reproductive structures (pycnidia), the isolates were sown on water agar (AA) medium with autoclaved pine branches at a rate of three sowings per isolate. Observations of mature conidia (n = 10) were performed with a binocular light microscope coupled to a camera with software. For pathogenicity tests, 3 8-month-old plants were used for each isolate. The inoculated plants were evaluated weekly for one month. Of the 70 isolations carried out, 54 were pathogenic. Lasiodiplodia sp. It was the only gender that was identified. The colonies developed white, brown, black and brown cottony mycelium. The conidia were observed to be hyaline in the immature state and brown when mature, septate and oval with longitudinal striae. Based on the morphological and cultural characteristics of the isolates obtained, it was determined that the genus responsible for apical necrosis, cankers and death of branches in orange is Lasiodiplodia sp.