Abstract
Key messageDefence responses of cyst nematode and/or wheat curl mite infested barley engage the altered reactive oxygen species production, antioxidant machinery, carbon dioxide assimilation and photosynthesis efficiency.The primary aim of this study was to determine how barley responds to two pests infesting separately or at once; thus barley was inoculated with Heterodera filipjevi (Madzhidov) Stelter (cereal cyst nematode; CCN) and Aceria tosichella Keifer (wheat curl mite; WCM). To verify hypothesis about the involvement of redox metabolism and photosynthesis in barley defence responses, biochemical, photosynthesis efficiency and chlorophyll a fluorescence measurements as well as transmission electron microscopy were implemented. Inoculation with WCM (apart from or with CCN) brought about a significant suppression in the efficiency of electron transport outside photosystem II reaction centres. This limitation was an effect of diminished pool of rapidly reducing plastoquinone and decreased total electron carriers. Infestation with WCM (apart from or with CCN) also significantly restricted the electron transport on the photosystem I acceptor side, therefore produced reactive oxygen species oxidized lipids in cells of WCM and double infested plants and proteins in cells of WCM-infested plants. The level of hydrogen peroxide was significantly decreased in double infested plants because of glutathione–ascorbate cycle involvement. The inhibition of nitrosoglutathione reductase promoted the accumulation of S-nitrosoglutathione increasing antioxidant capacity in cells of double infested plants. Moreover, enhanced arginase activity in WCM-infested plants could stimulate synthesis of polyamines participating in plant antioxidant response. Infestation with WCM (apart from or with CCN) significantly reduced the efficiency of carbon dioxide assimilation by barley leaves, whereas infection only with CCN expanded photosynthesis efficiency. These were accompanied with the ultrastructural changes in chloroplasts during CCN and WCM infestation.
Highlights
The changing climatic conditions, for example long, warm spring, hot summer, lack of the frost during winter and changed rainfall patterns in the temperate climate zone, are conducive to pests and pathogens gradation on crop plants
Plants are equipped with sophisticated defence apparatus involving non-enzymatic and enzymatic antioxidants to cope with oxidative stress and to promote photosynthesis efficiency
Kinetic of chl a fluorescence revealed that rice plants sensitive to mite feeding had a significantly lower number of open photosystem II (PSII) reaction centres (RCs) (F0) among all PSII RC (Vj) as well as significantly lower efficiency of trapped energy flux (TRo/ CSo) compared to resistant plants (Buffon et al 2018)
Summary
The changing climatic conditions, for example long, warm spring, hot summer, lack of the frost during winter and changed rainfall patterns in the temperate climate zone, are conducive to pests and pathogens gradation on crop plants. All these circumstances can contribute to a decrease in crop productivity (Gregory et al 2009). WCM can effectively spread plant pathogenic viruses such as the wheat streak mosaic virus (WSMV) from the family Potyviridae. This is the most significant economic impact of WCM on cereal yielding. As a result of WCM feeding or WSMV transmission on cereal leaves, the grain yield losses may reach up to 40% (Skoracka et al 2017, 2018a; Aguirre-Rojas et al 2019)
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