Influence of phytopathogenic bacteria on the activity of soy photosynthetic apparatus

Abstract

Goal. To determine the differences in the impact of artificial infection with different in spread and harmfulness strains of bacterial pathogens — Pseudomonas savastanoi pv. glycinea (angular spot) and Hanthomonas fuscans pv. fuscans (small black spot) on the parameters of photochemical activity of the photosynthetic apparatus of soybean (Glycine max). Methods. Classical microbiological, biophysical, statistical. The biophysical method of induction of chlorophyll fluorescence was used to assess the condition and activity of the photosynthetic apparatus of soybean plants under artificial infection with bacterial strains. Results. The tendency was fixed to increase the minimum fluorescence (F0) of soybean leaves infected with P. savastanoi pv. glycinea B9190, as well as its reduction by lesions of X. fuscans pv. fuscans B9283. In the leaves of the affected plants, the suppression of the fluorescence maximum (Fm) by 16.2% was detected at infection with P. savastanoi pv. glycinea B9190 and its increase by 14.1% under the influence of X. fuscans pv. fuscans B9283. Quantum efficiency of photosystem II (FSII) — Fv/Fm parameter — decreased by 11.5% in leaves affected by P. savastanoi pv. glycinea B9190, while infection with X. fuscans pv. fuscans B9283 — increased that parameter by 7.1%. Indicator “decrease in chlorophyll fluorescence” (Rfd value), which is closely correlated with photosynthetic activity by inoculation of soybean plants with strains of P. savastanoi pv. glycinea B9190 and X. fuscans pv. fuscans B9283, was suppressed almost equally — by 6.7 and 6.1%, respectively. Conclusions. Artificial infection with the most common and harmful pathogen P. savastanoi pv. glycinea B9190 significantly adversely affected the fast “light” and slow “dark” reactions of photosynthesis by reducing the content of active chlorophyll, inhibiting its resynthesis, deteriorating the maximum quantum efficiency of FSII, and reducing carbon assimilation. The photosynthetic apparatus of soybeans proved to be more resistant to X. fuscans pv. fuscans B9283. The pathogen suppressed only the “dark” processes of photosynthesis, which can affect plant productivity. The potential efficiency of carbon assimilation (Rfd value) was suppressed almost equally — by 6.7 and 6.1% in the case of artificial infection of soybean plants with phytopathogenic strains — P. savastanoi pv. glycine B9190 and X. fuscans pv. fuscans B9283, respectively. Thus, the ability of the bacterial pathogen to have a more destructive and rapid effect on the plant organism gives it advantages to spread, scale and capture certain ecological niches and increase the manifestation of harmfulness.