Abstract
Meloidogyne spp. are the most damaging plant parasitic nematodes for horticultural crops worldwide. Pochonia chlamydosporia is a fungal egg parasite of root-knot and cyst nematodes able to colonize the roots of several plant species and shown to induce plant defense mechanisms in fungal-plant interaction studies, and local resistance in fungal-nematode-plant interactions. This work demonstrates the differential ability of two out of five P. chlamydosporia isolates, M10.43.21 and M10.55.6, to induce systemic resistance against M. incognita in tomato but not in cucumber in split-root experiments. The M10.43.21 isolate reduced infection (32–43%), reproduction (44–59%), and female fecundity (14.7–27.6%), while the isolate M10.55.6 only reduced consistently nematode reproduction (35–47.5%) in the two experiments carried out. The isolate M10.43.21 induced the expression of the salicylic acid pathway (PR-1 gene) in tomato roots 7 days after being inoculated with the fungal isolate and just after nematode inoculation, and at 7 and 42 days after nematode inoculation too. The jasmonate signaling pathway (Lox D gene) was also upregulated at 7 days after nematode inoculation. Thus, some isolates of P. chlamydosporia can induce systemic resistance against root-knot nematodes but this is plant species dependent.
Highlights
The root-knot nematodes (RKN), Meloidogyne spp., are obligate parasites of plants
The results of this study provide evidence for the ability of some P. chlamydosporia isolates to induce systemically resistance against M. incognita, and that this induction is dependent on the plant species
Martínez-Medina et al (2017) reported that Trichoderma harzianum T-78 induced the upregulation of genes related to salicylic acid at early stage of nematode infection, whereas those related to jasmonic acid were upregulated from 3 to 21 days after nematode inoculation
Summary
The root-knot nematodes (RKN), Meloidogyne spp., are obligate parasites of plants. The genus comprises more than 100 species, but only four of them are considered the most damaging plant parasitic nematodes due to its wide range of plant hosts, worldwide distribution, and high reproductive capacity (Jones et al, 2013). The RKN infective juveniles (J2) enter the root near the elongation zone and migrate intercellularly to establish a permanent feeding site into the vascular cylinder, inducing the formation of giant cells and root galls by affecting cell wall architecture, plant development, defenses, and metabolism (Shukla et al, 2018). J2 become sedentary, and molt three times to achieve the mature adult female stage. The most frequent and damaging tropical species, M. arenaria, M. incognita, and M. javanica, reproduce parthenogenetically.
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