Detecção de Xylella fastidiosa e quantificação da clorose variegada dos citros em pomares no Amazonas

Abstract

Citrus variegated chlorosis (CVC) is a disease caused by Xylella fastidiosa subsp. pauca, a gram-negative bacterium limited to the xylem and spread by vectors and infected propagation material. In the mid-1980s and early 2000s, CVC was considered the most serious disease of citrus in Brazil, causing production losses and millionaire losses to producers. The pathogen was detected for the first time in Amazonas in 2007, where visual assessment studies of the disease were carried out, as well as the detection and isolation of the pathogen. In 2021, another study was carried out focusing only on detecting the bacteria. In this sense, this work sought to quantify the intensity of the disease, isolate and detect the pathogen in orchards from the metropolitan region of Manaus (AM). The disease intensity was quantified using incidence and severity measures in plants with different ages and scion-rootstock combinations, such as 'Pêra' and 'Natal' orange tree scions and 'Rangpur' lemon and 'Cleopatra' tangerine scions. '. Bacterial isolation was performed using serial dilution techniques and “prints” or stamps in BCYE culture medium. Molecular detection was performed by conventional PCR with specific primers for X. fastidiosa, RST31/RST33, using plant and bacterial genomic DNA as a template. The highest incidences were observed in Iranduba and Manaus, with 100% of the disease in the inspected plants, followed by Rio Preto da Eva, with 68%, the highest levels of severity in orchards of these municipalities were in level 4, all quadrants with symptoms. Bacterial isolation resulted in the growth of 21 isolates from Rio Preto da Eva and 14 isolates from Manaus. The presence of the disease was detected in four of the eight.