Biochemical changes, antioxidative profile, and efficacy of the bio-stimulant in plant defense response against Sclerotinia sclerotiorum in common bean (Phasaeolus vulgaris L.).

Sclerotinia sclerotiorum, is a highly destructive pathogen with widespread impact on common bean (Phasaeolus vulgaris L.) worldwide. In this work, we investigated the efficacy of microbial consortia in bolstering host defense against sclerotinia rot. Specifically, we evaluated the performance of a microbial consortia comprising of Trichoderma erinaceum (T51) and Trichoderma viride (T52) (referred to as the T4 treatment) in terms of biochemical parameters, alleviation of the ROS induced cellular toxicity, membrane integrity (measured as MDA content), nutrient profiling, and the host defense-related antioxidative enzyme activities. Our findings demonstrate a notable enhancement in thiamine content, exhibiting 1.887 and 1.513-fold higher in the T4 compared to the un-inoculated control and the T1 treatment (only S. sclerotiorum treated). Similarly, the total proline content exhibited 3.46 and 1.24-fold higher and the total phenol content was 4.083 and 2.625-fold higher in the T4 compared to the un-inoculated control and the T1 treatment, respectively. Likewise, a general trend was found for other antioxidative and non-oxidative enzyme activities. However, results found were approximately similar in T2 treatment (bioprimed with T51) or T3 treatments (bioprimed with T52). Further, host defense attribute (survival rate) under the pathogen challenged condition was maximum in the T4 (15.55 % disease incidence) compared to others. Therefore, bio priming with consortia could be useful in reducing the economic losses incited by S. sclerotiorum in common beans.

Plant growth promotion and differential expression of defense genes in chilli pepper against Colletotrichum truncatum induced by Trichoderma asperellum and T. harzianum.

BACKGROUND: Trichoderma asperellum and T. harzianum were assessed in this study as a potential biological control against Colletotrichum truncatum. C. truncatum is a hemibiotrophic fungus that causes anthracnose disease in chilli thereby affecting plant growth and fruit yield. Scanning electron microscope (SEM) technique showed the beneficial interaction between chilli root-Trichoderma spp. inducing the plant growth promotion, mechanical barrier, and defense network under C. truncatum challenged conditions. METHODS: Seeds bio-primed with T. asperellum, T. harzianum, and T. asperellum + T. harzianum promoted the plant growth parameters and strengthening of physical barrier via lignification on the wall of vascular tissues. Seed primed with bioagents were used for exploring the molecular mechanism of defense response in pepper against anthracnose to assess the temporal expression of six defense genes in the Surajmukhi variety of Capsicum annuum. QRT-PCR demonstrated induction of defense responsive genes in chilli pepper bioprimed with Trichoderma spp. such as plant defensin 1.2 (CaPDF1.2), superoxide dismutase (SOD), ascorbate peroxidase (APx), guaiacol peroxidase (GPx), pathogenesis related proteins PR-2 and PR-5. RESULTS: The results showed that bioprimed seeds were assessed for T. asperellum, T. harzianum, and T. asperellum + T. harzianum-chilli root colonization interaction under in vivo conditions. The results of the scanning electron microscope revealed that T. asperellum, T. harzianum and T. asperellum + T. harzianum interact with chilli roots directly via the development of plant-Trichoderma interaction system. Seeds bio-primed with bioagents promoted the plant growth parameters, fresh and dry weight of shoot and root, plant height, leaf area index, number of leaves, stem diameter and strengthening of physical barrier via lignification on the wall of vascular tissues and expression of six defense related genes in pepper against anthracnose. CONCLUSIONS: Application of T. asperellum and T. harzianum and in combination of treatments enhanced the plant growth. Further, as seeds bioprimed with T. asperellum, T. harzianum and in combination with treatment of T. asperellum + T. harzianum induced the strengthening of the cell wall by lignification and expression of six defense related genes CaPDF1.2, SOD, APx, GPx, PR-2 and PR-5 in pepper against C. truncatum. Our study contributed for better disease management through biopriming with T. asperellum, T. harzianum and T. asperellum + T. harzianum. The biopriming possess enormous potential to promote plant growth, modulate the physical barrier, and induced the defense related genes in chilli pepper against anthracnose.

PGPR-mediated induction of systemic resistance and physiochemical alterations in plants against the pathogens: Current perspectives.

Plant growth-promoting rhizobacteria (PGPR) are diverse groups of plant-associated microorganisms, which can reduce the severity or incidence of disease during antagonism among bacteria and soil-borne pathogens, as well as by influencing a systemic resistance to elicit defense response in host plants. An amalgamation of various strains of PGPR has improved the efficacy by enhancing the systemic resistance opposed to various pathogens affecting the crop. Many PGPR used with seed treatment causes structural improvement of the cell wall and physiological/biochemical changes leading to the synthesis of proteins, peptides, and chemicals occupied in plant defense mechanisms. The major determinants of PGPR-mediated induced systemic resistance (ISR) are lipopolysaccharides, lipopeptides, siderophores, pyocyanin, antibiotics 2,4-diacetylphoroglucinol, the volatile 2,3-butanediol, N-alkylated benzylamine, and iron-regulated compounds. Many PGPR inoculants have been commercialized and these inoculants consequently aid in the improvement of crop growth yield and provide effective reinforcement to the crop from disease, whereas other inoculants are used as biofertilizers for native as well as crops growing at diverse extreme habitat and exhibit multifunctional plant growth-promoting attributes. A number of applications of PGPR formulation are needed to maintain the resistance levels in crop plants. Several microarray-based studies have been done to identify the genes, which are associated with PGPR-induced systemic resistance. Identification of these genes associated with ISR-mediating disease suppression and biochemical changes in the crop plant is one of the essential steps in understanding the disease resistance mechanisms in crops. Therefore, in this review, we discuss the PGPR-mediated innovative methods, focusing on the mode of action of compounds authorized that may be significant in the development contributing to enhance plant growth, disease resistance, and serve as an efficient bioinoculants for sustainable agriculture. The review also highlights current research progress in this field with a special emphasis on challenges, limitations, and their environmental and economic advantages.

Regulation of L-proline biosynthesis, signal transduction, transport, accumulation and its vital role in plants during variable environmental conditions.

BACKGROUND: In response to various environmental stresses, many plant species synthesize L-proline in the cytosol and accumulates in the chloroplasts. L-Proline accumulation in plants is a well-recognized physiological reaction to osmotic stress prompted by salinity, drought and other abiotic stresses. L-Proline plays several protective functions such as osmoprotectant, stabilizing cellular structures, enzymes, and scavenging reactive oxygen species (ROS), and keeps up redox balance in adverse situations. In addition, ample-studied osmoprotective capacity, L-proline has been also ensnared in the regulation of plant improvement, including flowering, pollen, embryo, and leaf enlargement. SCOPE AND CONCLUSIONS: Albeit, ample is now well-known about L-proline metabolism, but certain characteristics of its biological roles are still indistinct. In the present review, we discuss the L-proline accumulation, metabolism, signaling, transport and regulation in the plants. We also discuss the effects of exogenous L-proline during different environmental conditions. L-Proline biosynthesis and catabolism are controlled by several cellular mechanisms, of which we identify only very fewer mechanisms. So, in the future, there is a requirement to identify such types of cellular mechanisms.