The Physiological and Biochemical Effects on Napier Grass Plants FollowingNapier Grass Stunt Phytoplasma Infection
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Date
2021
Authors
Asudi, George O.
Omenge, Keziah M.
Paulmann, Maria K.
Reichelt, Michael
Grabe, Veit
Mith ̈ofer, Axel
Oelm ̈uller, Ralf
Furch, Alexandra C. U.
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Abstract
Napier grass stunt (NGS) phytoplasma, a phloem-limited bacterium,
infects Napier grass leading to severe yield losses in East Africa. The
infected plants are strongly inhibited in growth and biomass production.
In this study, phytoplasma-induced morphological changes of the vascular
system and physiological changes were analyzed and compared with
uninfected plants. The study showed that the phytoplasmas are more
abundant in source leaves and range from 103 bacteria/µg total DNA in
infected roots to 106 in mature Napier grass leaves. Using microscopical,
biochemical, and physiological tools, we demonstrated that the
ultrastructure of the phloem and sieve elements is severely altered in
the infected plants, which results in the reduction of both the mass flow
and the translocation of photoassimilates in the infected leaves. The
reduced transport rate inhibits the photochemistry of photosystem II in the
infected plants, which is accompanied by loss of chloroplastic pigments
in response to the phytoplasma infection stress eventually resulting in
yellowing of diseased plants. The phytoplasma infection stress also
causes imbalances in the levels of defense-related antioxidants,
glutathione, ascorbic acid, reactive oxygen species (ROS), and—in
particular—hydrogen peroxide. This study shows that the infection of
NGS phytoplasma in the phloem of Napier grass has an impact on the
primary metabolism and activates a ROS-dependent defense response.
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article
Keywords
bacterial pathogens, etiology, host parasite interactions, Napier grass stunt phytoplasma, pathogen detection, phloem mass flow, photoinhibition, plant immune responses, plant stress and abiotic disorders, H2O2
Citation
Asudi, G. O., Omenge, K. M., Paulmann, M. K., Reichelt, M., Grabe, V., Mithöfer, A., ... & Furch, A. C. (2021). The physiological and biochemical effects on Napier grass plants following Napier grass stunt phytoplasma infection. Phytopathology®, 111(4), 703-712.