Abstract
Sugarcane smut is a significant fungal disease that causes a major loss in sugar yield and quality. In this study, we isolated an endophytic strain B18 from a sugarcane root, which showed plant growth-promotion, hydrolytic enzyme production, antifungal activity against sugarcane pathogens (Sporisorium scitamineum, Ceratocystis paradoxa, Fusarium verticillioides), and the presence of nifH, acdS, and antibiotic genes (hcn, prn, and phCA) under in vitro conditions. BIOLOG(R) phenotypic profiling of B18 established its ability to use various carbon and nitrogen sources and tolerate a range of pH and osmotic and temperature stresses. Whole-genome analysis of B18, identified as Pseudomonas aeruginosa, showed that it consists of a single circular chromosome of 6,490,014 bp with 66.33% GC content. Genome annotation has identified 5,919 protein-coding genes, and 65 tRNA, and 12 rRNA genes. The P. aeruginosa B18 genome encodes genes related to ethylene, nitrogen (nifU, norBCDERQ, gltBDPS, and aatJMPQ), and phosphate (pstABCS and phoBDHRU) metabolism and produce indole-3-acetic acid and siderophores. This also includes genes encoding hydrolases and oxidoreductases, those associated with biocontrol mechanisms (hcnABC, phzA_B, phzDEFGMS, and pchA), colonization (minCDE and lysC), and biofilm formation (efp, hfq, flgBCDEFGHI, and motAB), and those associated with metabolism of secondary metabolites. Collectively, these results suggest a role for P. aeruginosa B18 in plant growth enhancement and biocontrol mechanisms. The P. aeruginosa B18 strain was found to be an efficient colonizer in sugarcane; it can improve growth through modulation of plant hormone production and enhanced host-plant resistance to smut pathogen S. scitamineum in a smut-susceptible sugarcane variety (Yacheng71-374). These biocontrol and plant growth promotion properties of P. aeruginosa B18 area are discussed in this report.
Highlights
Sugarcane (Saccharum spp. interspecific hybrids) is the most prominent economic crop in tropical and sub-tropical countries and the world’s main source of sugar
We focused on the endophytic P. aeruginosa B18 strain isolated from sugarcane roots, which promotes sugarcane growth and tolerance to smut
We aimed to study the P. aeruginosa B18 endophyte isolated from sugarcane root in relation to (i) plant-growth-promoting and antifungal activities, (ii) functional genes, (iii) production of cell wall degrading enzymes, (iv) metabolic profiling, (v) host colonization pattern, (vi) whole-genome analysis, and (v) improvement of sugarcane growth under smut pathogen stress in the greenhouse condition
Summary
Sugarcane (Saccharum spp. interspecific hybrids) is the most prominent economic crop in tropical and sub-tropical countries and the world’s main source of sugar. In China, sugarcane is a key agricultural crop, and it contributes to about 90% of sugar production nationally. Besides a limited water supply, the occurrence of various diseases and insect pests and the overuse of fertilization adversely affect Chinese sugarcane production (Li and Yang, 2015). More than 60 sugarcane diseases have been reported in China (Huang and Li, 2016). Sugarcane smut, caused by the fungal pathogen Sporisorium scitamineum, is a major disease. It is wide-spread in all the major sugarcane production areas in China, such as Guangxi, Yunnan, Guangdong, and Hainan. Sugarcane smut disease control currently relies primarily on breeding resistant cultivars (Shen et al, 2014), which is constrained by long, expensive breeding procedures and limited success (Liu et al, 2017). The disease can be managed by chemical fungicides (Bhuiyan et al, 2012) but is neither advised nor practiced to prevent environmental degradation (Pandin et al, 2017)
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