The influence of Aphanomyces cochlioides on selected physiological processes in sugar beet leaves and yield parameters

Abstract

Alterations in some physiological processes in source leaves of sugar beet-such as chlorophyll and carbohydrate concentrations, stomatal conductance, rate of net photosynthesis and transpiration, and activity of the photosynthetic apparatus during root interaction with Aphanomyces cochlioides, were investigated. The influence of time of infection on plant health, yield quality and quantity was also examined. Plants were infected at different times of their growth period: on the sowing day and 4 or 8 weeks after sowing. A variation treatment, with nonpelleted seeds infected on the sowing day, was also analyzed. The experiment showed that development of disease symptoms depends on the time of infection and seed protection. A significant root yield decrease was observed in case of late infection, as compared to the yield of plants infected on the sowing day. The fresh weight of leaves was significantly increased where there was late infection. The infected plants showed a lower content of K + , Na + and α-amino-N than did the controls. Infection by A. cochlioides induced chlorophyll degradation mostly in older leaves with the occurrence of natural senescence processes. Chlorophyll fluorescence parameters indicated that the photosynthetic apparatus of younger leaves was more sensitive to pathogen infection, when compared to older ones. The photochemical efficiency of photosystem II was reduced in young leaves mainly due to disturbance of the water-splitting system. In plants grown from non-pelleted seeds a strong impairment of PSII was observed only in those leaves which developed during early pathogen infection. In young leaves of plants infected in the fourth week after sowing, inhibition of the rate of net photosynthesis was correlated with the increase in intercellular CO 2 concentration, indicating some disturbance in the carbon assimilation phase. In mature leaves of late infected plants the reduction of photosynthesis net rate was associated with a decrease of stomatal conductance and an increase of diffusion resistance to CO 2 and H 2 O, which was also the cause of the transpiration rate inhibition. When the leaves developed during early infection, an increase of specific leaf weight and accumulation of carbohydrates was observed. In mature leaves of nonprotected plants infected on the sowing day, the recovery of all physiological processes was observed together with a diminution of disease symptoms.

The role of sugar signaling in plant defense responses against fungal pathogens

“…A decrease in photosynthesis has been reported in compatible interactions with biotrophic fungi, i.e., Albugo candida, Puccinia coronata and Blumeria graminis (Chou et al 2000;Scholes and Rolfe 1996;Swarbrick et al 2006) as well as necrotrophic pathogens such as Botrytis cinerea (Berger et al 2004(Berger et al , 2007. The photosynthetic organs of young leaves of sugar beet are particularly sensitive to the infection by Aphanomyces cochlioides (oomycetes) (Chołuj and Moliszewska 2012).…”

Proteomic Analysis of Aphid-Resistant and -Sensitive Rose (Rosa Hybrida) Cultivars at Two Developmental Stages

“…Simultaneously the levels of sugar and carbohydrate were significantly lowest in -sensitive cultivars of cut roses at both developmental stages. Although many reports have suggested that sugars act a prime sensing mechanism to pathogen attack [ 51 , 52 , 53 , 54 ]. However, our results indicate that sugars and carbohydrates act a prime inducing precursor to aphid tolerance only in resistant cultivars compared to sensitive cultivars.…”

Differentiation of the disease caused by Aphanomyces cochlioides and girth scab on sugar beet roots - a review

“…Symptoms of Aphanomyces root rot (1, 2) and of girth scab given by (A) Benada et al (1984), (B) by Hinfner and Homonnay (1966), and (C) symptoms of seedling damping-off given by Benada et al (1984) showed different susceptibility to the damage caused by a. cochlioides (Moliszewska 2009). Chołuj and Moliszewska (2012) proved that the severity of the disease increases in conditions favourable for the pathogen (hot and wet conditions, the experiment was realised in a greenhouse). The disease develops if the pathogen inoculum is at an appropriate level in a period of about one month after sowing, even if the seed protection was applied.…”

“…Like in other soil-borne diseases, its control is difficult. Crop protection should usually be based on seed treatment with fungicides, use of cultivars with higher levels of resistance, management of soil moisture, long rotations with non-host crops and weed control (Szymczak-Nowak 1987;Asher 1992;Beale et al 2002;Pearsson & Olsson 2005;Chołuj & Moliszewska 2012;Nechwatal et al 2012). Moliszewska (2009) experiments in 2003, which started from the investigation of seedling diseases.…”

“…The disease develops if the pathogen inoculum is at an appropriate level in a period of about one month after sowing, even if the seed protection was applied. Pathogens can affect the photosynthetic apparatus even if the disease symptoms are not visible; and in mature leaves, a. cochlioides causes chlorophyll degradation (Chołuj & Moliszewska 2012).…”