Root infection by the nematode Meloidogyne incognita modulates leaf antiherbivore defenses and plant resistance to Spodoptera exigua

Abstract

Studies on plant-mediated interactions between root parasitic nematodes and aboveground herbivores are rapidly increasing. However, the outcomes for the interacting organisms vary, and the mechanisms involved remain ambiguous. We hypothesized that the impact of root infection by the root-knot nematode Meloidogyne incognita on the performance of the aboveground caterpillar Spodoptera exigua is modulated by the nematode’s infection cycle. We challenged root-knot nematode infected tomato plants with caterpillars when the nematode’s infection cycle was either at the invasion, galling, or reproduction stage. We found that M. incognita root infection enhanced S. exigua performance during the galling stage, while it did not affect the caterpilar’s performance at the invasion and reproduction stages. Molecular and chemical analyses performed at the different stages of the nematode infection cycle revealed that M. incognita root infection systemically affected the jasmonic acid-, salicylic acid- and abscisic acid-related responses, as well as changes in the leaf metabolome during S. exigua feeding. The M. incognita induced leaf responses significantly varied over the nematode’s root infection cycle. These findings suggest that specific leaf responses triggered systemically by the nematode at its different life-cycle stages underlie the differential impact of M. incognita on plant resistance against the caterpillar S. exigua.

Steroidal glycoside profile differences among primary roots system and adventitious roots in Solanum dulcamara

“…This MS spectrum was obtained on the same platform under the same experimental conditions and reported in earlier studies (e.g. Mbaluto et al 2021 ; Martínez-Medina et al 2021 ). We found that in the same region of the chromatogram where the m / z values 414.3372 and 416.3528 occurred, other peaks following a comparable deglycosylation fragmentation pattern were present.…”

Brown planthopper infestation on rice reduces plant susceptibility to Meloidogyne graminicola by reducing root sugar allocation

“…Pests' successful colonization relies on them overcoming plant defence and obtaining nutrients like sugars and amino acids (Yamada & Osakabe, 2018; Zhang et al ., 2020; Gupta et al ., 2021). Plant systemic acquired resistance and induced systemic resistance are crucial in plant‐mediated interactions between organisms (Louis et al ., 2015; Lee et al ., 2017; Martinez‐Medina et al ., 2017, 2021; Karssemeijer et al ., 2020; Mbaluto et al ., 2021a,b). The role of sugar allocation in plant‐mediated interactions between pests and beneficial microbes has been evidenced.…”

“…Moreover, the outcomes of these interactions vary from case to case. For instance, infection by the rice root‐knot nematode Meloidogyne graminicola Golden and Birchfield can promote aboveground blast disease in rice (Kyndt et al ., 2017), whereas the impact of Meloidogyne incognita infection on the aboveground caterpillar Spodoptera exigua on tomato depends on the nematode's parasitic stage (Mbaluto et al ., 2021b). Despite the relevance of these studies on plant‐mediated interactions, our understanding of the underlying mechanisms remains rudimentary.…”