Encountering epidemic effects of leaf spot disease (Alternaria brassicae) on Aloe vera by fungal biocontrol agents in agrifields—An ecofriendly approach

Abstract

Aloe vera (L.) Burm.f. is a highly important and extensively cultivated medicinal plant and that is also extensively used in the cosmetic industry. It has been frequently reported to suffer from Alternaria leaf spot disease in various parts of the world. Various fungicides used to combat this disease, have deleterious effects on the environment and on pharmacologically important constituents of Aloe vera. To avoid the harmful effects of fungicides an ecofriendly approach has been adopted here. A weekly survey was conducted during 2013–2015 in and around North 24 Parganas (West Bengal) to obtain the percentage of disease index (PDI). For biological control of the disease, screening of the antagonistic efficacy of biocontrol agents was carried out through the in vitro dual-culture-plate method and scanning electron microscopy (SEM) was used to study the mechanism. The in vitro effects of fungicides on the radial growth of the pathogen were evaluated through the poison food method and were compared with potent antagonistic fungi. Field application of potent antagonistic fungi was conducted through the dip-and-spray method. The results showed that, the PDI peaked during the hot and humid conditions of May to September (76.57%–98.57%) but decreased during the winter, December-January (35.71–46.66%). Trichoderma asperellum exerted the greatest inhibition of the radial growth of A. brassicae acting through non volatile (70.39%) and volatile metabolites (72.17%). A SEM study confirmed the hyperparasitic nature of T. asperellum through hyphal coiling-T. asperellum was similar to 2% blitox-50 (73.92%) and better than 2% bavistin (59.77%) (in vitro). In agricultural field trials (2013–15), Trichoderma application restricted the disease to the smallest area (PDI 24.00–29.33%) in comparison to untreated plots (73.33%). In conclusion, saplings treated with the dip method (108 spores / mL) and sprayed 4 times with a spore suspension of biocontrol agents such as T. asperellum, T. viride and T. harzianum, standardized at a rate of 2.5 L / plot (36 sq ft) (108 spores/ mL) are suggested for the ecofriendly management of this epidemic leaf spot disease of Aloe vera in agricultural fields.

Epidemiological studies on base rot disease of Aloe vera caused by Fusarium oxysporum

“…(2018) [6] studied epidemiology of leaf spot disease of Aloe vera and found that, the FBI peaked during the hot and humid conditions of May to September (76.57%-98.57%) but decreased during the winter, December-January (35.7 1-46.66%). Saini et al (2018) [10] reported that the highest disease severity (86.89%) for leaf rot disease was recorded in the month of July at an average temperature of 28.7 0 C and 80.3% relative humidity.…”

A Novel Bacillus safensis-Based Formulation along with Mycorrhiza Inoculation for Controlling Alternaria alternata and Simultaneously Improving Growth, Nutrient Uptake, and Steviol Glycosides in Stevia rebaudiana under Field Conditions

“…The Bacillus sp. strain CL12 enhanced the growth parameters, including flavonoid and antioxidant activity and metabolite (curcumin) content, in Curcuma longa due to the solubilization of nutrients and the production of hormones, siderophore, and lytic enzymes [ 38 ]. Bacillus spp.…”

An in-sight analysis of molecular evolution of Trichoderma as emerging human pathogen

“…In support of this proposed line of evolution it has been noted that maximum members of Trichoderma are ubiquous and grow in soil or rhizospheric soil as saprophyte (141,33,34,30) and appear in other environments. They frequently come in contact with members of other fungi (same kingdom), involve in host parasitic interaction and gradually become mycopararasite (8)(9)(10)(11)(12)(13).…”

“…It plays a major role in ecology as decomposer of plant and animal residues in the soil. Several species of this genus have excellent antagonistic properties against plant pathogenic fungi and plant growth promoting agents (8)(9)(10)(11)(12)(13)(14)(15). Therefore, they are frequently being applied in agri elds for the biological control of several plant diseases (16,12).…”

“…Several species of this genus have excellent antagonistic properties against plant pathogenic fungi and plant growth promoting agents (8)(9)(10)(11)(12)(13)(14)(15). Therefore, they are frequently being applied in agri elds for the biological control of several plant diseases (16,12). Most environmental opportunistic species of Trichoderma are generally abundant in agricultural habitat (17).…”