Occurrence of black rot in Jatropha curcas L. plantations in India caused by Botryosphaeria dothidea

摘要

A new disease in Jatropha curcas L. plants was observed during the summer season in 2009 and 2010 in plantations in several Indian states, including Andhra Pradesh, Assam, Chhattisgarh and Madhya Pradesh. The outbreak of the disease coincided with the leaf-dropping (dormant) stage of the crop, which sets in with the increasing moisture stress. Affected J. curcas plants showed drying along with shrivelling, and discoloration of the stem with sticky reddish-brown exudation at the base of the plants. Black lesions (soft and rotting) on the stem under the bark and cambium layer were also observed. From the affected stem parts, fungal cultures were isolated and tested for their pathogenicity on pot-grown plants. The fungal isolates caused symptoms on J. curcas leaves and petioles (black spots, 1-3 mm in diameter). Then they spread to the stems causing shrivelling and gummosis of hard-wood stems, and finally led to the death of the infected plant. The causal fungus was identified as Botryosphaeria dothidea using microscopic observations of hyphae and spores, and internally transcribed spacers (ITS) sequencing technique. In addition, four other fungal isolates were also isolated from the affected tissues, which were identified as Macrophomina phaceolina, Phomosis longicolla, Fusarium oxysporum and Alternaria alternata using the ITS sequencing technique. The role of these fungal cultures, i.e. whether they grow as saprophytes on the affected dead tissues or have any role in causing the black rot disease, needs further study. Spraying J. curcas plants showing early symptoms of this disease with Bavistin (carbendazim 50% WP) at the rate of 2 g l(-1) water controlled the spread of the symptoms and led to the recovery of plants with new leaf growth after the rains.