Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Effect of temperature and air humidity on multiplication of Xanthomonas campestris pv. undulosa and symptom expression in susceptible and field-tolerant wheat genotypes.

Abstract

Multiplication of X. c. pv. undulosa in the leaf tissues of susceptible and field-tolerant wheat genotypes was determined at the seedling stage under different incubation conditions. Dry air did not inhibit the bacterial multiplication, while temp. had a direct effect on the population density. Symptoms were not observed at 15°C. Lesion development occurred when bacterial concn reached an estimated threshold of 108 c.f.u./leaf. Differences in population densities between wheat genotypes Alondra and Pavon were only noticeable at 25° and dry air conditions, without correlation to differences in symptom expression. It is concluded that for the 2 genotypes tested, resistance did not seem to operate at the seedling stage when plants were inoculated by infiltration. It is suggested that an active temp.-dependent mechanism or saturation of the target sites appears to be involved in the bacterial inhibition process. It is concluded that temp. had a major effect on disease development, confirming the risk of bacterial leaf streak in warmer, non-traditional wheat growing areas, and that different types of resistance are likely to exist in the X. c. pv. undulosa/wheat system.