Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

First report of powdery mildew caused by Erysiphe cruciferarum on Brassica campestris var. pekinensis, B. carinata, Eruca sativa, E. vesicaria in Australia and on B. rapa and B. oleracea var. capitata in Western Australia.

Abstract

Inspection of field plantings of diverse cruciferous species, mainly oilseed varieties sown for agronomic assessment at Crawley, Western Australia, in September 2012, indicated the occurrence of extensive leaf and stem colonization by powdery mildew at the late flowering stage. Whitish patches that were 3-4 cm in length were observed on stems of B. campestris var. pekinensis, B. carinata, B. oleracea var. capitata, B. rapa [B. campestris], Eruca sativa [E. vesicaria] and E. vesicaria. These patches coalesced to form a dense, white, powdery layer. Infected leaves showed signs of early senescence. On all inoculated species, abundant conidia typical of those produced by Erysiphe cruciferarum were observed. Mycelia were amphigenous, in patches, often spreading to become effused. Conidiophores were 3- to 4-celled and unbranched, with cylindrical foot cells. Across all host species, conidia were mostly produced singly with an overall mean measured length of 19.7-35.4 µm (mean 26.9 µm), and a measured width of 7.1-12.9 µm (mean 9.7 µm). BLAST analyses showed a >99% nucleotide identity for E. cruciferarum. This is thought to be the first record of Erysiphe cruciferarum on B. campestris var. pekinensis, B. carinata, E. sativa and E. vesicaria in Australia, and on B. rapa and B. oleracea var. capitata in Western Australia.