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United States Department of Agriculture

Agricultural Research Service

Title: Comparison of the Virulence of Isolates of Tilletia Indica, Causal Agent of Karnal Bunt of Wheat, from India, Pakistan, and Mexico

item Bonde, Morris
item Peterson, Gary
item Fuentes-Davila, G - CIMMYT, MEXICO
item Phillips, John

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 9, 1996
Publication Date: N/A

Interpretive Summary: Karnal bunt is a serious disease affecting wheat in India, Pakistan, Afganistan, and Mexico. Although never having been found in the United States, the increasing presence of the disease in northwest Mexico suggests that it is only a matter of time before spreading to the United States. The International Maize and Wheat Improvement Center (Centro Internacional de Mejoramiento de Maiz y Trigo [CIMMYT]), Mexico, in field tests in Mexico has screened for disease resistance in approximately 20,000 wheat lines. Likewise, the Punjab Agricultural University in India has screened 20,000 lines. Our study in Frederick, MD, demonstrates that the genes for Karnal bunt resistance in Mexican wheat lines is effective against Asian cultures of the pathogen and that genes in the Indian lines are effective against cultures of the pathogen from Mexico. The results suggest that incorporation of these sources of Karnal bunt resistance into U.S. cultivars should help protect the United States from the disease when it enters

Technical Abstract: The virulence of four T. indica teliospore field populations, two from Mexico and one each from India and Pakistan, were tested for virulence on five resistant, one moderately susceptible, and two susceptible wheat genotypes. The five resistant lines represented the most Karnal bunt resistant genotypes in the breeding programs at the International Maize and Wheat Improvement Center (CIMMYT), Mexico, and Department of Plant Breeding, Punjab Agricultural University, Ludhiana, India. Plants at the boot stage were inoculated by injecting into the boot a water suspension of sporidia. At maturity, all inoculated and control wheat spikes were harvested individually and percentages of T. indica-infected seeds determined. Infected seeds from 10 randomly selected spikes per treatment were examined to estimate the proportion of each infected seed converted to a sorus. Although there were differences in pathogen aggressiveness, there was no evidence of the existence of races. Wheat lines resistant to the Mexican fungal populations also were resistant to those from Asia, and vice versa; there was a significant direct correlation (P ó 0.05) between percentage of seeds infected and extent of fungal colonization of infected seeds with all but one pathogen population when comparing resistant vs other wheat genotypes

Last Modified: 4/22/2015
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