Banana Rhizodeposition: Characterization of Root Border Cell Production and Effects on Chemotaxis and Motility of the Parasitic Nematode Radopholus  similis

Abstract

Rhizodeposition was collected from root tips of banana (Musa acuminata). Two varieties, Grande naine and Yangambi km5, susceptible and resistant towards the burrowing nematode Radopholus similis, respectively, were examined for root border cell production under in vitro and in soil growing conditions. Two types of cells were observed in rhizodeposition: spherical cells containing large amyloplasts, called statocytes (8% of total), and long ellipsoidal border cells (92%). Border cell production was high, related to root length and not different between the two cultivars. Rhizodeposition from plants grown in soil contained similar amounts of border cells, but viability was lower than in in vitro grown plants. Chemotaxis and motility assays were performed to test the effects of banana roots, roots without rhizodeposition, rhizodeposition, exudates and border cells on the behaviour of R. similis. Roots of both the susceptible and resistant variety attracted R. similis, but only in the presence of rhizodeposition. Isolated rhizodeposition of Yangambi km5 also attracted nematodes. Border cells and exudates did not affect nematode chemotaxis. Roots of both varieties induced quiescence in R. similis in the chemotaxis assay. Thirty to fifty percent of the nematodes became temporary quiescent in the motility assay with rhizodeposition and exudates. The effect lasted for 24 h for Grande naine and up to 3 days for Yangambi km5. Rhizodeposition collected from plants grown in soil affected neither R. similis chemotaxis nor motility. Overall, there were no indications that rhizodeposition is involved in preformed resistance against R. similis in Yangambi km5.

The dual effects of root-cap exudates on nematodes: from quiescence in plant-parasitic nematodes to frenzy in entomopathogenic nematodes

“…Quiescence is usually a reversible response in nematodes to toxic or unfavourable environmental conditions ( Evans and Perry, 1976 ). As plant-parasitic nematodes, as well as other pathogens, preferably choose the elongation zone right behind the root tip to penetrate root tissues ( Prot, 1980 ; Curl and Truelove, 1986 ; Gunawardena and Hawes, 2002 ), the induction of quiescence in root pathogens around this susceptible region has been interpreted as a defensive mechanism ( Hawes et al , 2000 ; Zhao et al , 2000 ; Wuyts et al , 2006 ). Recent findings showed that plant histone-linked extracellular DNA (exDNA) might be involved in this putative root tip defence ( Wen et al , 2009 ; Hawes et al , 2011 ; Hawes et al , 2012 ;).…”

Carbon flow in the rhizosphere: carbon trading at the soil–root interface

“…Recent work has also suggested that border cells can act as a decoy luring pathogenic nematodes and fungi away from the main root axis (Gunawardena and Hawes 2002;Rodger et al 2003). However, contradictory results have also been found highlighting the difficulties of manipulating border cell release and physiology for disease control (Wuyts et al 2006;Knox et al 2007). While border cells may provide a convenient mechanism for compound delivery to soil, further fundamental work is required to characterise the metabolomic and proteomic expression patterns in comparison to other root cells to understand and capitalize on their unique attributes (Jiang et al 2006).…”

Effective delivery of a nematode‐repellent peptide using a root‐cap‐specific promoter

“…Root border cells may play a role in plant defence by acting as decoys to prevent pathogens, including fungi and nematodes, attacking the root tip Zhao et al, 2000;Gunawardena and Hawes, 2002). However, the in vivo interaction between border cells, root cap exudates and plant parasitic nematodes is currently unclear (Rodger et al, 2003;Hubbard et al, 2005;Wuyts et al, 2006). The root cap cells are well suited for the transgenic production of a secreted peptide as they provide most of the root exudates released into the soil from uninjured roots (Hawes et al, 2003).…”