Phytophthora spp. associated with citrus: diversity, diagnostics and integrated management with a focus on India

Abstract

Phytophthora species, as aggressive and cosmopolitan oomycete pathogens, continue to cause substantial damage to citrus crops worldwide, resulting in considerable yield losses and economic impacts. This review provides a comprehensive update on the current understanding of the diversity, diagnostics, genomics, epidemiology, and sustainable management strategies for Phytophthora spp. affecting citrus with a particular focus on Indian citrus scenario. We discuss the taxonomic diversity within the genus Phytophthora, focusing on those species most commonly associated with citrus, such as P. nicotianae, P. citrophthora and P. palmivora and others that induce root rot, collar rot, gummosis and other devastating citrus diseases. The review also highlights advancements in diagnostic technologies, particularly molecular techniques such as PCR, next-generation sequencing, loop-mediated isothermal amplification and DNA metabarcoding, which have revolutionized early detection and pathogen surveillance. The global distribution patterns of Phytophthora species are outlined, with Indian data and management practices used as a regional case study. In addressing sustainable management, this review emphasizes integrated disease management (IDM) approaches, including biological control, chemical treatment, resistant rootstocks, cultural practices, and soil health strategies. The potential for environmentally sustainable practices, such as the use of disease-suppressive biocontrol agents, and the manipulation of soil microbiomes, is critically examined in the context of reducing reliance on chemical inputs with particular relevance to India and other Asian countries, where extensive research works have been conducted. This review concludes by identifying research gaps and suggesting future directions for improving diagnostics, genetic resistance, and environmentally conscious disease management practices aiming to enhance crop sustainability and productivity.