Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: An Improved Infiltration Technique to Test the Pathogenicity of Xanthomonasoryzae Pv. Oryzae in Rice Seedlings

Authors
item Schaad, Norman
item Wang, Z - VISITING SCIENTIST USDA
item Di, M - U OF ALASKA,FAIRBANKS
item Mcbeath, J - U ALASKA, FAIRBANKS
item Peterson, Gary
item Bonde, Morris

Submitted to: Seed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 1996
Publication Date: N/A

Interpretive Summary: A simple, reliable technique to test for the pathogenicity of Xanthomonas oryzae pv. oryzae was developed. A plastic disposable 1.0-ml syringe was modified by attaching a rubber ring to the blunt end of the syringe. Using an inoculum containing 10**6-7 cfu viable cells of the pathogen, the bacteria were infiltrated into the leaf with the syringe. After 10-14 days in a lighted dew chamber, dark green water-soaked lesions resulted. In contrast, when the standard leaf clipping method was used only bleached or tan-colored lesions developed. The method should be useful as a rapid reliable method for testing for pathogenicity and breeding for resistance.

Technical Abstract: Pathogenicity testing of Xanthomonas oryzae pv. oryzae by the standard leaf clipping technique resulted in a bleached, hypersensitive-like reaction preceding a general yellowing or browning of the tissue. Water-soaked lesions were never observed and the pathogen could not be isolated. Using a plastic disposable 1.0-ml syringe modified to infiltrate rice leaves, water-soaked lesions developed in leaves of 4- to 5-leaf stage plants growing in a lighted dew chamber, 10-14 days after infiltration with an inoculum containing 10**6-7 cfu X. o. pv. oryzae/ml. Exudate was often evident. The newly developed infiltration technique was to compare the standard leaf clipping technique by inoculating plants of rice cv IR-24 with three strains of X. o. pv. oryzae from China, three strains of X. o. pv. oryzae (X1-5, X1-8, and X37-2) from Texas, two strains of X. o. pv. oryzicola from China, and two unknown yellow- pigmented bacteria isolated from California rice seeds in a commercial, lighted dew chamber. Inoculation by the clipping technique usually resulted in bleached or tan-colored lesions regardless of the organism used. Using the infiltration technique, dark green water-soaked lesions consistently developed with all strains of X. o. pv. oryzae and X. o. pv. oryzicola from China, but not with the Texas strains or the unknown bacteria

Last Modified: 12/25/2014
Footer Content Back to Top of Page