Erwinia persicina Causing Chlorosis and Necrotic Spots in Leaves and Tendrils of Pisum sativum in Southeastern Spain

Abstract

In 2003, symptoms of generalized chlorosis as well as necrosis in leaves and tendrils were observed in Pisum sativum L. cv Tirabeque grown in green fields in southeastern Spain (Granada Province), and by 2004, the disease affected approximately 12 ha. Bacteria isolated from symptomatic samples were gram negative, rod shaped, motile, oxidase negative, facultatively anaerobic, and fermentative, which coincided with the general characteristics of the family Enterobacteriaceae. The gene encoding the 16S rRNA from two isolates (LPPA 406 and LPPA 408) was sequenced after PCR amplification (1). The two sequences were identical (EMBL Accession No. AM294946 for LPPA 408) and showed 99% similarity with several strains of Erwinia persicina (including the type strain ATCC 35998, LPPA 373, LMG 11254, GS04, and LMG 2691). Additional biochemical tests were performed using E. persicina ATCC 49742 as a control. The three strains were negative for arginine dihydrolase activity, indol production, hydrolysis of casein, and hydrolysis of gelatin. In contrast, they were positive for assimilation of adonitol, l-lactate, mannitol, m-inositol, erythritol, sorbitol, sucrose, nitrate reduction, hydrolysis of aesculin, and growth in 5% NaCl at 36°C. Nevertheless, E. persicina ATTC 49742, but not the isolates from P. sativum, produced a pink pigment. The latter isolates were also tested for pathogenicity. Bacterial suspensions (108 CFU/ml) were spray inoculated on 10 pea seedlings of cv. Tirabeque. Seedlings were covered with transparent plastic bags for 2 days and held in an incubation chamber at 22°C and 80% relative humidity with a 12-h photoperiod. Assays were conducted twice. Symptoms that developed were similar to those originally observed in the field, whereas symptoms did not occur on control seedlings sprayed with sterile distilled water. Bacteria sharing the characteristics of the inoculated isolates were recovered from symptomatic plants, hence fulfilling Koch's postulates. E. persicina has been isolated previously from bean in the United States (3) and southeastern Spain (1) and from tomato, banana, and cucumber in Japan (2). To our knowledge, this is the first report of the bacterium on P. sativum. References: (1) A. J. González et al. Plant Dis. 89:109, 2005. (2) M. V. Hao et al. Int. J. Syst. Bacteriol. 40:379, 1990. (3) M. L. Schuster et al. Fitopatol. Bras. 6:345, 1990.