|
Disease Note Bacterial Leaf Spot and Stem Collapse of Mung Bean Caused by Pseudomonas syringae pv. syringae. M. W. George, Plant Science Division, University of Idaho, Moscow 83843-4196. R. R. Tripepi, Plant Science Division, University of Idaho, Moscow 83843-4196. Plant Dis. 74:394. Accepted for publication 15 February 1990. DOI: 10.1094/PD-74-0394E. Collapsed upper stems and necrotic spots on leaves were observed
on mung bean (Vigna radiata (L.) R. Wilczek 'Berken') seedlings grown
for rooting bioassays. A gram-negative, rod-shaped bacterium was
consistently isolated from symptomatic stem tissue. The bacterium
was identified as Pseudomonas syringae pv. syringae van Hall based
on: 1) production of levan, a hypersensitive reaction in tobacco, a
green diffusible fluorescent pigment on King's medium B, and syringomycin
as determined by the inhibition of Geotrichum candidum Link
ex Pers. growth (1); 2) use of mannitol, inositol, sorbitol, and L-lactate
as sole carbon sources; and 3) negative responses for oxidase
production, soft rot in potato, and halo blight on bean pods. To
fulfill Koch's postulates, lO-day-old mung bean seedlings were stab-inoculated
with a 104 cfu/ml bacterial suspension. At 28 C, typical
symptoms developed within 3 days after inoculation, and the same
bacteria were reisolated from diseased seedlings. The pathogen was
seedborne, because approximately 10% of seedlings that grew from
surface-sterilized seeds became diseased within 9 days. This is the
first report of a disease in mung bean caused by P. s. pv. syringae. |