Changes of Pectin Content in Alfalfa Plants after Inoculation with Different Isolates of Corynebacterium michiganenense pv. insidiosum

Abstract

Summary Susceptible alfalfa plants were inoculated with cell suspension of Corynebacterium michiganense pv. insidiosum, a highly virulent or slightly virulent isolate, through their overground parts. 11 weeks after inoculation the plants were sampled and divided according to symptoms observed on the traverse cuts of roots (degrees of disease severity). The pectin content was determined in the roots and in the overground parts. The majority of the control plants were found at the zero degree of disease severity. The plants, inoculated with highly virulent isolate of the pathogen, were characterized by degrees of disease severity 0, 1,2, and 3–4. The plants inoculated with a slightly virulent isolate were characterized only by the low degrees of disease severity (0 and 1). Pectin content in the overground parts and in the roots was practically the same in the control plants and inoculated plants with degree of disease severity 0. However, the content of pectins in the plants inoculated with the highly virulent pathogen, having the degree of disease severity 1, was much less than both in the controls and in the plants with the degree of disease severity 0. The pectin content in such plants with the degrees of disease severity 2 and 3–4 was also decreased, but this decrease was much smaller than in the previous case (at the degree of disease severity 1). In the case of inoculation with a slightly virulent pathogen, the content of pectins in the overground parts was almost the same in the control and inoculated plants with the degrees of disease severity 0 and 1. As for the roots, the pectin content in the roots exhibited a smaller reduction in plants with the degree of disease severity 1 than in the control plants. The possibility of a relationship between the biochemical changes, resistant mechanisms of host against the pathogen, and the symptoms of disease is discussed.