Comparative assessment of red and white cabbage resistance against diamondback moth (Plutella xylostella L.)

Abstract Cabbage defense against diamondback moth (DBM, Plutella xylostella L.) is primarily influenced by various factors, particularly the leaf anatomical traits and phytochemical composition. Four cabbage varieties were assessed for resistance to DBM during the 2020 and 2021 growing seasons at the Agricultural Research Station, University of Basrah (Basra, Iraq). The results indicated that the red cabbage ( Brassica oleracea var. capiata f. rubra ) varieties Hanar and Kirmizi exhibited low infestation by DBM (1.06 and 1.24 larvae/plant, respectively). However, white cabbage ( Brassica oleracea var. capitata f. alba ) varieties Dalal and Ortus showed the highest infestation levels (11.18 and 9.74 larvae/plant, respectively). The cuticles, epidermal layers, and parenchymal cells of red cabbage were thicker than those of the white cabbage. The tested varieties varied in their contents of pigments, proteins, carbohydrates, phenols, and glucosinolates. These variations were associated with different levels of DBM infestation. The red cabbage Kirmizi and Hanar showed low infestation, which was likely related to their higher contents of anthocyanins, carotene, phenols, and the glucosinolates progoitrin, goitrin, sinigrin, glucoraphanin, and total glucosinolates. In contrast, the white cabbage varieties, particularly the susceptible cultivar Dalal, had the lowest values of these compounds and consequently showed higher infestation. This study demonstrates that anatomical traits and phytochemical composition are key determinants of cabbage resistance to DBM. Therefore, cultivation of resistant red cabbage varieties offers a promising approach for integrated pest management programs.