Abstract
Endophytic fungi play an important role in plant survival and reproduction, but the role of their metabolites in plant growth and immunity, as well as in crop quality formation, is poorly understood. Zhinengcong (ZNC) is a crude ethanol extract from the endophytic fungus Paecilomyces variotii, and previous studies have shown that it can improve the growth and immunity in Arabidopsis thaliana. The aim of the study was to reveal the trade-off balance between plant growth and immunity by evaluating the mechanisms of ZNC on potato growth, yield, and priming immunity against the oomycete Phytophthora infestans indoors and in the field. ZNC maintained a good balance between plant growth and resistance against P. infestans with high activity. It induced the reactive oxygen species (ROS) production, promoted plant growth, yield and quality parameters, enhanced the expression of indoleacetic acid (IAA) related genes, and increased the absorption of nitrogen from the soil. Moreover, the plant endophytic fungus extract ZNC stimulated the pathogen-associated molecular pattern (PAMP) triggered immunity (PTI) pathway and contributed to the ZNC-mediated defense response. Two years of field trials have shown that irrigation with ZNC at one of two optimal concentrations of 1 or 10ng/ml could significantly increase the output by 18.83% or more. The quality of potato tubers was also greatly improved, in which the contents of vitamin C, protein, and starch were significantly increased, especially the sugar content was increased by 125%. Spray application of ZNC onto potato plants significantly reduced the occurrence of potato blight disease with 66.49% of control efficacy at 200ng/ml and increased the potato yield by 66.68% or more in the field. In summary, plant endophytic fungus extract ZNC promoted potato immunity, yield, and quality and presented excellent potential in agricultural applications.
Highlights
Potato (Solanum tuberosum L.) is one of the most important staple crops worldwide, preceded only by rice and wheat, playing an essential role in the sustainable food supply and decreasing poverty and malnutrition (Robertson et al, 2018)
1 and 10 ng/ml ZNC significantly increased the potato root length and root weight, which were measured at day 80, especially for the 1 ng/ml ZNC treatment (Figures 1E–H). These results showed that low concentrations (10−8–10−9) of ZNC could promote potato growth parameters, including height, leaf area, stem diameter, root length, and root weight
For the MAPK signaling pathway and plant-pathogen interaction, we found that some genes were induced at the transcriptional level with p < 0.05, including 19 probable leucine-rich repeat receptor like kinase (LRRRLK) FLAGELLIN-SENSING 2 (FLS2) proteins, two PHLOEW PROTEIN 2-LIKE A8-like proteins belonging to the mitogenactivated protein kinase kinase (MEKK1) protein catalog, four transcription factors, two pathogenesis leaf protein 4-like proteins (LOC102598474 and LOC102598598), one 1-aminocyclopropane−1-carboxylic acid synthase (ACS) 1/2/6like protein and three substances of chitin signaling (Figure 2A)
Summary
Potato (Solanum tuberosum L.) is one of the most important staple crops worldwide, preceded only by rice and wheat, playing an essential role in the sustainable food supply and decreasing poverty and malnutrition (Robertson et al, 2018). Potato late blight, caused by the oomycete Phytophthora infestans, is a devastating disease (Jiang et al, 2018). Despite the large amounts of chemical pesticides used by growers, this disease is still a major cause of potato yield loss. An increasing number of growers and consumers around the world have raised awareness on the importance of effective and sustainable food production (Guyer et al, 2015). It is essential to find environment-friendly agro-chemicals with dual functions in crop nutrient uptake and disease resistance management, which ensures the sustainable development of agricultural products
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