Plant-parasitic nematodes (PPNs) cause big crop losses globally. Safe and reliable methods for their durable management strategies can astutely harness various beneficial relationships among plant immune system and related microbiomes. The molecular mechanisms basic to these relations reveal wide arrays of significant roles for plant-healthy growth. This review focuses on such relations to prime and immunize plants against PPNs. It highlights molecular issues facing PPN-resistant varieties with possible genetic breeding as solutions. Few resistant plant varieties, emergence of resistant pathotypes, fitness costs, and specific settings that may hinder the resistance are exemplified issues. These issues call for optimal uses of the microbiome to bridge the gap for boosting plant immunity. In contrast, widely spread microbiomes of plant growth-promoting rhizobacteria, biological control fungi, and arbuscular mycorrhizal fungi can immunize plants against PPNs. Related plant signaling hormones and transcription factors that regulate gene expression and modulate nematode-responsive genes to ease positive/negative adaptation are presented. Relevant genome editing and other molecular techniques are discussed to attract further attention for improved microbiome’s usage. They are promising, but only under specific biotic/abiotic settings. Hence, proper abiotic/biotic factors related to systemic acquired resistance (SAR) that impact plant–microbe interactions to immunize plants against PPNs are emphasized. For PPN control, the microbiomes can be added as inoculants and/or steering the indigenous rhizosphere ones. Consequently, SAR is mediated by the accumulation of the salicylic acid and subsequent expression of pathogenesis-related genes. To activate SAR, adequate priming and induction of plant defense against PPNs would rely on closely linked and crucial factors. They include the engaged microbiome species/strains, plant genotypes, existing fauna/flora, and compatibility with other involved biologicals as well as methods and rates/concentrations of the inoculants. Thus, it is suggested herein to test the related microbiomes on a case-by-case basis to avoid erratic results. A few reports focused on root-knot nematodes, but this review offered attractive examples for the related gains in immunizing plants to other key PPN species. The end in view is to optimize the related molecular plant defence and expand the use of the microbiomes against PPN species. Achieving such goals needs to raise growers’ awareness to harness advanced strategies tackled herein to boost the roles of SAR-inducing microbes. These microbes enjoy wide spectrum efficacy, low-fitness cost, and inheritance to next generations in sustainable agriculture.
Mahfouz M. M. Abd-Elgawad (Tue,) studied this question.