Etiology, Epidemiology and Management of Citrus Black Rot Caused by Alternaria Citri- An Outlook

Abstract

Citrus is an important fruit crop of the world. It is the most important commercial fruit crop having higher moisture contents and nutrient composition. Citrus losses are mainly due to diseases that highly affect their quality and quantity. Black rot of fruit caused by Alternaria citri, is a significant fungal disease of citrus that causes severe losses in citrus orchards of the world. It affects most of the members of the citrus family and often causes severe losses. The disease primarily affects the aboveground parts of plants, leaves explicitly, and fruits. The first symptoms, however, usually appear on the leaves as black necrotic lesions. Later black necrotic lesions are also formed on fruits, and with the age of plants, the fruits become soft and black rot. The disease has been controlled by cultural practices and by growing resistant cultivars that do not allow the entry of the pathogen. Preharvest fungicides are also applied to prevent the disease but are not highly effective. Postharvest sprays with fungicides have also controlled the disease. However, fungicides are not eco-friendly, and demands for alternatives are arising. Other options are the application of biological control agents; however, biological agents are not effective under field conditions. The present review summarizes the current status of black rot of citrus and its management strategies.

Bacterial and Fungal Biocontrol Agents for Plant Disease Protection: Journey from Lab to Field, Current Status, Challenges, and Global Perspectives

“…Microbial root colonization is significantly influenced by traits of the host plants and surrounding microorganisms [ 24 ]. Plants have been proposed to actively attract soil microorganisms by releasing chemicals into the rhizosphere to encourage bacteria that are beneficial to plant growth and health [ 64 , 85 ]. Arabidopsis thaliana roots secrete malic acid, which helps B. subtilis colonize the roots, providing improved plant defense against P. syringae [ 86 ].…”

“…BCA field efficacy may be equal to or better than that of synthetic pesticides; however, this could change over time and across regions. In other words, a BCA that inhibits or controls disease in the lab is unlikely to be efficient in open-field trials [ 85 , 88 ]. This is a result of all of the complex interactions that take place between the host, pathogen, antagonist, and environment.…”

“…Several studies have been conducted that show the effect of plants on BCAs’ biocontrol activities. The degree of rhizosphere colonization, the production of antibiotics by BCA, and the stimulation of induced systematic resistance vary among different plant species [ 85 ]. In the rhizosphere region, the interaction between BCAs and pathogens is mostly influenced by root exudate excretion, water and mineral absorption, and other surrounding microbes [ 8 , 85 ].…”

“…The degree of rhizosphere colonization, the production of antibiotics by BCA, and the stimulation of induced systematic resistance vary among different plant species [ 85 ]. In the rhizosphere region, the interaction between BCAs and pathogens is mostly influenced by root exudate excretion, water and mineral absorption, and other surrounding microbes [ 8 , 85 ]. The expression of plant genes is reported to be involved in the rhizosphere enrichment process that provides fitness to the plants by recruiting microbes from the surroundings [ 92 ].…”

Antifungal Activity of Green and Chemically Synthesized ZnO Nanoparticles against Alternaria citri, the Causal Agent Citrus Black Rot

“…The first symptoms, however, usually appear on the leaves as black necrotic lesions. Later, black necrotic lesions form on the fruits, and as the plants’ age, the fruits become soft and black-rotted ( Umer et al, 2021 ). In a 10-year survey of citrus-associated diseases from several countries in the Mediterranean region, high disease pressure has been detected in all areas, forcing citrus growers to adapt fungicidal spray programs.…”