Host plant resistance towards the cabbage whitefly in Brassica oleracea and its wild relatives

Abstract

The cabbage whitefly (Aleyrodes proletella) is a phloem-feeding insect that is a serious problem in Brassica oleracea crops like Brussels sprouts, kale and savoy cabbage. In order to develop whiteflyresistant varieties it is essential to identify effective sources of resistance. In this study, we screened a large collection of 432 accessions, including wild material and landraces of Brassica oleracea as well as crop wild relatives, to determine whitefly performance in a no-choice field experiment. Putatively resistant accessions were further tested under greenhouse conditions. Resistant accessions were identified among B. oleracea var. capitata (cabbage) landraces and in the species B. villosa, B. incana and B. montana. Whereas resistance in cabbage is only expressed in plants of at least 12 weeks old, some wild relatives were already starting to express resistance at 6 weeks. This could open up possibilities for breeding cabbages that are resistant at a young(er) plant age. Our research also shows again the importance of crop wild relatives for finding pest resistances.

Antibiosis resistance against larval cabbage root fly, Delia radicum, in wild Brassica-species

“…acephala Accession A was not tested in the field, but was included because a successful cross between B. fruticulosa and B. oleracea var. acephala Accession A had been made (Pelgrom et al 2015). Seed germination and plant growing conditions were the same as described in the experiment comparing larval and egg infestation.…”

“…In addition, differences in soil conditions might also influence herbivore-associated organisms, which subsequently affect insect physiology and the plant phenotype . Moreover, environmental conditions may have a large effect on tolerance, resulting in differences in plant performance (Painter 1951).…”

“…Resistance to flea beetles Phyllotreta cruciferae (Goeze 1777) was found in B. incana (Bodnaryk 1992). In addition, several authors (Bodnaryk 1992;Ramsey and Ellis 1996;Pelgrom et al 2015) have reported on accessions resistant to cabbage whitefly Aleyrodes proletella (Linnaeus 1758) (Hemiptera: Aphididae) among B. oleracea var. capitata landraces and in the wild species B. villosa, B. incana, B. montana, B. cretica, B. spinosa, B. insularis and B. macrocarpa.…”

“…Three resistance mechanisms have been described in the literature on Delia-Brassica interactions, antixenosis, antibiosis and tolerance (Painter 1951). Antixenosis, also called non-preference, is based on morphological and/or chemical characteristics that make a plant unattractive to insects for feeding or oviposition (Painter 1941;Kogan and Ortman 1978;Acquaah 2012).…”

“…This mechanism manifests itself after a host has been attacked and thus affects only the D. radicum larvae that feed on the root system. Tolerance refers to the ability of plants to grow and reproduce normally or to repair injury to a marked degree in spite of supporting a population approximately equal to that damaging a susceptible host (Painter 1951). Different from the other two mechanisms, tolerance is independent of the herbivore response, but is an adaptive mechanism for survival of a plant under herbivore pressure (Kogan and Ortman 1978).…”