​Antagonistic Activity of Panchagavya and Trichoderma spp. against Wilt Complex causing Pathogens of Chickpea (Cicer arietinum L.)

Background: Chickpea wilt complex caused by several soil-borne pathogens is the major yield-reducing malady worldwide. Biological control is one of the best, low-cost and ecologically sustainable method for managing plant diseases caused by soil-borne pathogens. Methods: In this present investigation Panchagavya and Trichoderma spp. were evaluated by following poisoned food technique and dual culture technique against wilt complex causing pathogens i.e. Fusarium oxysporum f. sp. ciceri, Fusarium solani and Macrophomina phaseolina. Result: Among the different isolates of Trichoderma spp. evaluated, Trichoderma viride (AAU isolate) was highly antagonistic to F. oxysporum f. sp. ciceri (52.78%) and F. solani (65.37%) whereas, Trichoderma asperellum (AAU isolate) was highly antagonistic to M. phaseolina (65.93%). Panchagavya at the highest concentration (50%) showed significantly higher efficacy (80.74, 66.62 and 49.67%) in inhibiting the mycelial growth of all three pathogens and at the lowest concentration it was moderately effective.

A cell-free approach to identify binding hotspots in plant immune receptors

Plant immune receptors are often difficult to express heterologously, hindering study of direct interactions between these receptors and their targets with traditional biochemical approaches. The cell-free method ribosome display (RD) enables expression of such recalcitrant proteins by keeping each nascent polypeptide chain tethered to its ribosome, which can enhance protein folding by virtue of its size and solubility. Moreover, in contrast to an in planta readout of receptor activity such as a hypersensitive response that conflates binding and signaling, RD enables direct probing of the interaction between plant immune receptors and their targets. Here, we demonstrate the utility of this approach using tomato recognition of Trichoderma viride ethylene-inducing xylanase (EIX) as a case study. Leveraging the modular nature of the tomato LeEIX2 and LeEIX1 leucine-rich repeat (LRR) receptors, we applied an entropy-informed algorithm to maximize the information content in our receptor segmentation RD experiments to identify segments implicated in EIX binding. Unexpectedly, two distinct EIX-binding hotspots were discovered on LeEIX2 and both hotspots are shared with decoy LeEIX1, suggesting that their contrasting receptor functions are not due to differential modes of ligand binding. Given that most plant immune receptors are thought to engage targets via their LRR sequences, this approach should be of broad utility in rapidly identifying their binding hotspots.

Management of Deleterious Effect of Fusarium oxysporum Associated with Red Palm Weevil Infestation of Date Palm Trees

Red palm weevil (RPW) is a dangerous pest that infects the date palm tree and makes tunnels in the tree’s trunk. RPW infection is followed by secondary invaders of microorganisms that cause degradation of the trunk tissues leading to toppling the crown and death of the tree in a short time. This study showed that Fusarium oxysporum Schlecht. was the common fungal species isolated from the root and trunk tissues of the date trees infested with RPW, which recorded 100% of frequency. Pathogenicity of 4 isolates of F. oxysporum was confirmed on date palm seeds and seedlings. The results confirmed that all isolates involved in rot of the germinated seeds (40–100% incidence), root rot, and death of palm seedlings (20–100%) under artificial infection as well as degradation of date palm petioles. Application of 20 L/palm of systemic fungicide (Topsin) at 1% as foliar and soil drench of date palm for successive three times successfully reduced development of the deterioration and suppressed the growth of F. oxysporum. Interestingly this fungicide did not suppress the growth of Trichoderma viride Pers. So, our results recommend this fungicide to suppress the pathological and degradable activities of F. oxysporum during the integrated pest management of RPW on date palm trees.

PHYTOCHMICAL ANALYSIS AND ANTIFUNGAL POTENTIAL OF SORGHUM HELEPENSE L. FOR THE MANAGEMENT OF OCHRATOXIGENIC FUNGI

Ochratoxigenic fungal species are a major cause of various infections in plants and posed a serious threat to their consumers,including humans and animals. In the current study the objective was to examine the in vitro efficacy of different concentrations of leaves methanolic extract of S. helepense L. (Pers.) against target pathogenic ochratoxin producing fungal species (Trichoderma viride Pers., Trichoderma harzianum Rifai. and Cladosporium cladosporioides (Fresen.) G.A. de Vries).For this purpose, different concentrations viz. 2%, 4%, 6%, 8% and 10% of leaf methanolic extract were prepared and tested for antifungal potential in a completely randomized design (CRD). Results revealed that all the applied concentrations of S. helepense inhibited the growth of all the tested fungal strain. Maximum growth inhibition was observed in 2% of concentration of methanolic extract of S. helepense in case of C. cladosporoides i.e. 84%. On the other hand minimum reduction was observed in 4% of concentration of methanolic extract of S. helepense against T. viride as compared to control. The phytochemical analysis was also conducted to evaluate that which chemical entities were present that account for antifungal potency of methanolic extract of S. helepense. Results of phytochemical analysis revealed the occurrence of saponins, alkaloids, coumarins, flavonoids and tannins while the plant is devoid of terpenoids, phlobatanins and glycosides respectively. Hence it can be concluded that the methanolic leaf extract of the tested plant proved to be beneficial for inhibiting the growth of test ochratoxigenic fungi.

Interrelationship Among Seed Quality Parameters and Fungi Associated with Seeds of Cotton (Gossypium Hirsutum L.)

A total of twenty nine species of fungi namely Aspergillus aculeatus Lizuka, A. flavus Link, A. fumigatus Fresenius, A. niger Van Tiegh, A. nidulans Eidam, A. subramanianii Visagie, Frisvad & Samson, A. tamariiKita G., A. toxicarius Murak, A. wentii Wehmer, Curvularial unata (Wakker) Boedijn, Colletotrichum gloeosporioides (Penz.) Sacc., C. gossypii Southw., Chaetomium globosum Kunze., Fusarium moniliforme J. Shelden, F. nivale (Fr.) Sorauer, F. oxysporum Schlechtendal, F. fujikuroi Nirenberg, F. solani(Mart.) Sacc., Lasiodiplodiatheobromae (Pat.) Griffon & Maubl., Meyerozyma guilliermondii (Wick.) Kurtzman & M. Suzuki., Mucor sp. P. Micheli ex L., Penicillium aculeatum Raper& Fennell, Penicillium citrinum Thom, Rhizoctonia solani Khun., Rhizopus stolonifer (Ehrenb.) Vuill., Rhizopus oryzae Went & Prins. Geerl., Rhizo mucor sp. Luce t & Costantin, Syncephalastrum racemosum Cohn and Trichoderma viride Pers. were found to be associated with the seeds of 14 varieties viz. CB-1 to CB-14 of cotton. Seed quality analysis showed that percentage of pure seeds, germination, moisture, seedling mortality and associated fungi with different varieties of cotton seeds varies from 97.08-99.92%, 80-93%, 10-11.3%, 16.05-50.30% and 24-78.0% respectively. Present study deals with estimation of interrelationship between some quality factors through correlation and regression analysis are important for the assessment of seed quality. There were negative correlations between seedling mortality and purity percentage and between germination rate and fungus frequency. On the other hand, positive correlations were found between germination rate and purity percentage, between seedling mortality and fungus frequency, between purity percentage and fungus frequency, between germination rate and seed moisture and between fungus frequency and seed moisture. CB 8 was superior from the other cotton variety as it showed higher physical purity of seed (98.41%), higher seed germination (92%), lower fungal incidence (24%) and lower mortality of seedling (23.91%). Bioresearch Commu. 8(1): 1061-1067, 2022 (January)

In Vitro Evaluation of Herbicides on Beneficial and Pathogenic Microorganisms

An experiment was conducted in the laboratory to evaluate the effect of herbicides on beneficial and pathogenic microorganisms. Eighteen treatments included six herbicides at three different doses viz., cyhalofop-butyl (80, 160 and 240 ppm), cyhalofop-butyl + penoxsulam (150, 300 and 450 ppm), bispyribac-sodium (25, 50 and 75 ppm), fenoxaprop-p-ethyl (60, 12 and 180 ppm), carfentrazone-ethyl (20, 40 and 60 ppm) and chlorimuron-ethyl + metsulfuron-methyl (4, 8 and 12 ppm) evaluated on beneficial microbial bioagents (Trichoderma viride and Pseudomonas fluorescens) and pathogenic microorganisms (Rhizoctonia solani, Pyricularia oryzae and Xanthomonas oryzae pv. oryzae). Results revealed that bispyribac-sodium and cyhalofop-butyl + penoxsulam had greatest inhibitory effect on pathogenic microorganisms Rhizoctonia solani (47.76 and 54.40%) and Pyricularia oryzae (49.07 and 61.12%), but showed no effect on Xanthomonasoryzaepv. oryzae, and were less harmful to biocontrol agents Trichoderma viride and Pseudomonas fluorescens at recommended doses, which were effective in control of broad spectrum of weed flora in rice ecosystem.

Halo Tolerance of Biocontrol Agents against Root Rot of Mung Bean (Vigna radiata (L.) Wilczek var. radiata) Caused by Macrophomina phaseolina (Tassi) Goid in Salt Affected Soils

Root rot of mung bean [Vigna radiata (L.) Wilczek var. radiata] is major disease and claims huge yield loss if they occur in the field. The pathogen is basically soil borne and survivability may vary depends on soil condition. The fungicide chemicals are available to manage the disease; however, the biocontrol agents are nowadays available for the disease management and the microbial activity of the biocontrol agents is influenced by existing soil condition including soil pH. Hence, a study was conducted to find out the halo tolerance capacity of the biocontrol agents against root rot disease in salt affected soils under in vitro, in vivo and field condition. The root rot pathogen Macrophomina phaseolina was isolated from infected root. Efficacy of biocontrol agents against growth of M. phaseolina was assessed in vitro. The results revealed that TNAU strain of Bacillus subtilis reduced the mycelial growth of the M. phaseolina significantly when media supplemented with NaCl at 5% (1.4 cm), 7.5% (1.5 cm), 10% (1.6cm) and 12.5% (1.6 cm) and without NaCl (1.2 cm) and similar trend of reduction also expressed by BCA1 strain of B. subtilis, Pseudomonas fluorescens and Trichoderma viride under in vitro. The performance of the biocontrol agents against the pathogen is slightly reduced when media supplemented with NaCl. The reduction of mycelia weight of M.phaeolina was more in media added with TNAU strain of B.subtilis and the performance of TNAU strain of B.subtilis on reduction of mycelial weight of M.phaseolina is reduced when the broth added with NaCl at 5% (3.15g), 7.5% (3.25g), 10% (3.32g) and 12.5%(3.65g) level and which is followed by P. fluorescens, BCA 1 strain of B. subtilis and Trichoderma viride. Under pot culture conditions, the effect of talc formulated biocontrol agents and challenge inoculation with pathogen was assessed against root rot incidence. It was found that the soil application of TNAU strain of B.subtilis performed better in reducing the root rot incidence at pH of 7.0 (2.37%), 7.5 (4.50%), 8.0 (5.53%) and 8.7 (6.57%) and followed by BCA 1 of B.subtilis in all pH level. Among the biocontrol agents, TNAU strain of B.subtilis applied as seed as well as soil application expressed more population in the rhizosphere in all pH level. The biocontrol agents applied as soil application had more populations of the agents in the soil when compared to seed treatment. The halo tolerance performance of the biocontrol agents was also assessed under field condition in pH of 7.5 and 8.7 during 2019-20 and 2020-21. It was found that the minimum root rot incidence and maximum yield was observed from soil application of TNAU strain of B subtilis at 2.5 kg/ha but the effect is on par with soil application of BCA1 strain of B.subtilis at 2.5 kg/ha.