ABSTRACT
Biotic and abiotic factors have an effect on rice production all around the world. Diseases are regarded as major restrictions among the biotic stressors, and rice sheath blight (Rhizoctonia solani Kühn) is one of the most calamitous diseases that significantly damage the crop. Lately, biocontrol of fungal plant pathogens has appeared as an appealing approach. The present investigation was undertaken to evaluate different biocontrol agents like Talaromyces flavus, Chaetomium globosum, Pseudomonas fluorescens and Aspergillus niger against sheath blight disease. Prior to sowing, seeds were bioprimed with each isolate and sown in the nursery. After 21 days, seedlings were transplanted in-vivo and were inoculated with a virulent isolate of Rhizoctonia solani at maximum tillering stage. Observations on biochemical parameters and gene expression studies were carried out at 24, 48, 72, and 96 hpi. Enzymatic activity viz., chitinase, ?-1,3-glucanase, catalase, and PAL was observed maximum in Chaetomium globosum. PR-genes viz., IPT, BrD, HmPr, AMP, AldD, NIC and LisH showed up-regulation at 96 hpi. Chaetomium globosum had the highest yield, maximum number of tillers with least RLH% as compared to other treatments. However, results indicated biocontrol agents are helpful and they induce multitude of defence responses against R. solani in rice.
ABSTRACT
Phytophthora spp. are the most serious threat to citrus industry worldwide. Being a soil borne problem, use of tolerant rootstocks is the most ecofriendly approach to manage the deadly diseases caused by this fungus. Here, we assessed the reaction of eight citrus rootstock genotypes including sour orange, Troyer citrange and six variants of C. jambhiri Lush. viz., RLC-5, RLC-6, RLC-7, Grambiri, rough lemon and Italian rough lemon against the inoculation of Phytophthora nicotianae. Inoculation of P. nicotianae infected the feeder roots of tested rootstocks to varying degree, expressing higher disease incidence (81.25%) and number of infected feeder roots (54.25-60.62%) depending on the rootstock. Troyer citrange and sour orange proved most tolerant rootstocks against the inoculated fungus. Phytophthora inoculation tended to increase the levels of reactive oxygen species (H2O2 and O2-), antioxidant enzymes (catalase, peroxidase, glutathione reductase, superoxide dismutase and β-1,3-glucanase) and protein content. However, it significantly reduced the levels of macro- (N, P, K Ca and Mg) and micro- (Cu and Zn) nutrients, although the extent of variation was rootstock specific. Overall, Troyer citrange and sour orange expressed the lowest variation in the levels of ROS, peroxidase (POX), superoxide dismutase (SOD) and β-1,3-glucanase, protein and nutrient contents, while rough lemon proved most strongly affected. Of the various variants of Citrus jambhiri, RLC-5 and Italian rough lemon proved more tolerant for Phytophthora nicotianae than rest of the clones tested.
ABSTRACT
A total of 75 isolates belonging to five different species of Trichoderma viz., T. asperellum, T. harzianum, T. longibrachiatum, T. pseudokoningii and T. virens were screened for the production of silver nanoparticles. Although all the isolates produced nanoparticles, T. virens VN-11 could produce maximum nanoparticles as evident from the UV-Vis study. The highest Plasmon band was observed at 420 nm at every 24 h that attained maximum intensity at 120 h (0.543). The high resolution transmission electron microscopy (HRTEM) further provided the morphology of the nanoparticles. These nanoparticles were found single or aggregated with round and uniform in shape and 8-60 nm in size. The nitrate reductase activity of VN-11 was found to be 150 nmol/h/mL which confirmed the production of silver nanoparticles through reduction of Ag+ to Ag0.