Abstract
Asian grapevine rust (Phakopsora euvitis) is a serious disease, which causes severe leaf necrosis and early plant defoliation. These symptoms are unusual for a strict biotrophic pathogen. This work was performed to quantify the effects of P. euvitis on photosynthesis, carbohydrates, and biomass accumulation of grapevine. The reduction in photosynthetic efficiency of the green leaf tissue surrounding the lesions was quantified using the virtual lesion concept (β parameter). Gas exchange and responses of CO2 assimilation to increasing intercellular CO2 concentration were analyzed. Histopathological analyses and quantification of starch were also performed on diseased leaves. Biomass and carbohydrate accumulation were quantified in different organs of diseased and healthy plants. Rust reduced the photosynthetic rate, and β was estimated at 5.78, indicating a large virtual lesion. Mesophyll conductance, maximum rubisco carboxylation rate, and regeneration of ribulose-1,5-bisphosphate dependent on electron transport rate were reduced, causing diffusive and biochemical limitations to photosynthesis. Hypertrophy, chloroplast degeneration of mesophyll cells, and starch accumulation in cells close to lesions were observed. Root carbohydrate concentration was reduced, even at low rust severity. Asian grapevine rust dramatically reduced photosynthesis and altered the dynamics of production and accumulation of carbohydrates, unlike strict biotrophic pathogens. The reduction in carbohydrate reserves in roots would support polyetic damage on grapevine, caused by a polycyclic disease.
Highlights
Rusts have always been considered important threats to crops due to the damage they incite in the host plant
Damage caused by Phakopsora euvitis in grapevine has not been quantitatively assessed; the aim of this work was to quantify the effects of the disease on photosynthetic rates and carbohydrate dynamics
Colonization by P. euvitis caused a significant reduction in CO2 assimilation rate in leaves of V. labrusca
Summary
Rusts have always been considered important threats to crops due to the damage they incite in the host plant. Causal agents of rusts are biotrophic pathogens which have highly developed infection structures, such as, haustoria, and limited lytic enzymes. In addition these pathogens induce long-term suppression in host defense (Mendgen and Hahn, 2002). They are highly specialized parasites, rust pathogens reduce host growth by diverting photoassimilates to their own development and reducing the host photosynthetic area (Helfer, 2014). Recent rust epidemics in wheat, coffee and soybean caused negative economic (Hodson, 2011; Sikora et al, 2014), social (Avelino et al, 2015), and environmental (Godoy et al, 2016) impacts around the world
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call