Major and Emerging Fungal Diseases of Citrus in the Mediterranean Region

Abstract

This chapter deals with major endemic and emerging fungal diseases of citrus as well as with exotic fungal pathogens potentially harmful for citrus industry in the Mediterranean region, with particular emphasis on diseases reported in Italy and Maghreb countries. The aim is to provide an update of both the taxonomy of the causal agents and their ecology based on a molecular approach, as a preliminary step towards developing or upgrading integrated and sustainable disease management strategies. Potential or actual problems related to the intensification of new plantings, introduction of new citrus cultivars and substitution of sour orange with other rootstocks, globalization of commerce and climate changes are discussed. Fungal pathogens causing vascular, foliar, fruit, trunk and root diseases in commercial citrus orchards are reported, including Plenodomus tracheiphilus, Colletotrichum spp., Alternaria spp., Mycosphaerellaceae, Botryosphaeriaceae, Guignardia citricarpa and lignicolous basidiomycetes. Diseases caused by Phytophthora spp. (oomycetes) are also included as these pathogens have many biological, ecological and epidemiological features in common with the true fungi (eumycetes).

Lasiodiplodia mitidjana sp. nov. and other Botryosphaeriaceae species causing branch canker and dieback of Citrus sinensis in Algeria

“…Similar situations have been described in several citrus orchards, worldwide [8,17,22,23,41]. According to previous studies, abiotic factors, including drought, severe sunburn or freezing predispose the trees to xylem dysfunction, leading to these diseases [3,4,41].…”

“…Many types of citrus are grown in Algeria, including oranges (48 400 ha), clementines (10 817 ha), mandarins (2 347 ha), lemons (4 409 ha) and grapefruits (83 ha) [2]. Despite the high adaptation capacity of citrus trees to different climates [3], a number of unfavourable factors has led to a decrease of the total citrus yield in Algeria. Among these factors, ageing trees, droughts, inappropriate cultural practices and the effects of various pests and pathogens are the most important [3,4].…”

“…Despite the high adaptation capacity of citrus trees to different climates [3], a number of unfavourable factors has led to a decrease of the total citrus yield in Algeria. Among these factors, ageing trees, droughts, inappropriate cultural practices and the effects of various pests and pathogens are the most important [3,4]. Citrus diseases are numerous and diverse, and are caused by phytopathogenic agents belonging to viruses, viroids, phytoplasmas, bacteria, and fungi [3] Some pathogens cause very serious diseases, predisposing to, and inciting dieback, while others are less serious [3][4][5][6].…”

“…Recently, trunk diseases have become a growing threat in both, old and newly established orchards of citrus, worldwide. Symptoms include leaves that become yellow and fall early, shoots and twigs die, increasing the risk of citrus decay as the damage expands to the trunk [3,[7][8][9]. To date, among the fungi that impact citrus, Diaporthe species are well known for causing stem-end rot and melanose of fruits, young leaf and shoot gummosis and blight of perennial branches and trunks, in Greece, Italy, Malta, Portugal, Spain, China, Korea, New Zealand, and the USA [9][10][11][12][13].…”

An Overview on Citrus Mal Secco Disease: Approaches and Strategies to Select Tolerant Genotypes in C. limon

“…Crop Breeding, Genetics and Genomics 6 of 29 may also occur; they accelerate the progress of the disease since the inoculum spreads more efficiently through the vascular system. This form of the disease may kill the plant within a few weeks [21,56].…”