Abstract

CONTRERAS, Nancy; JIMENEZ, Odaliz; BONILLA, Marianela  and  NASS, Herman. Identification and characterization of  Leifsonia xyli subsp. xyli  as sugarcane pathogen (Saccharum sp.) in the Centro Occidental region of Venezuela. Bioagro [online]. 2008, vol.20, n.2, pp.111-118x. ISSN 1316-3361.

Given that in experimental and commercial sugarcane fields in Lara and Yaracuy states, thin stalks with rachitic appearance were observed, the objectic of this paper was to identify and characterize the causal agent from isolations made in yeast extract, dextrose, and calcium carbonate (YDC). For the pathogenicity tests, healthy budwood were inoculated by injection of the bacterial suspension at the shaft at the nodal region. The isolations originated colonies white cream color, mucoid, and round shape, with whole borders, gelatinous consistency and brilliant aspect. Under optical microscopy were seen bacillary simple form with a slight swelling in the ends, wedge shaped, frecuently V-curved. From the pathogenicity tests, symptoms including a salmon pink discoloration just below the growing point of young cane and an orange red discoloration of the nodal vascular bundles in mature cane stalk developed. The symptoms were evidenced at fifteen days after inoculation and in the re-isolation identical colonies like the original ones were obtained.  The isolate grew in the cultures YDC, NBY and D2 of Kado and Heskett. The bacterium was Gram positive, aerobic, acid reaction in red phenol dextrose agar, negative oxidase, and positive catalase. Negative nitrate reduction, indol production, starch hydrolysis, H₂S from cysteine, gelatin liquefaction, urease production, casein hydrolysis and positive growth at 37 ºC. Negative carbohidrate reduction of sorbitol and mamnose. According to morphological, cultural, physiological and biochemical characteristics it was identified as Leifsonia xyli subsp xyli, coryneform bacterium causal agent of  ratoon stunting disease of  sugarcane.

Keywords : Plant pathology; bacteria; stunting disease.