Abstract
Diamondback moth (DBM), Plutella xylostella L., is a devastating pest of cabbage worldwide whose feeding attributes are influenced by glucosinolate profiles of the plant. Identifying the specific glucosinolates associated with plants’ resistance mechanism can provide cues to novel points of intervention in developing resistant cultivars. We studied the DBM larval feeding preference and extent of damage on cabbage leaves via controlled glass-house and in vitro multiple- and two-choice feeding tests. These feeding attributes were associated with the individual glucosinolate profiles, analyzed by HPLC, of each of the eight cabbage genotypes using multivariate analytical approach to identify the glucosinolates that may have roles in resistance. Both the glass-house and in vitro multiple-choice feeding tests identified the genotype BN4303, BN4059, and BN4072 as the least preferred (resistant) and Rubra, YR Gold and BN3383 as most preferred (susceptible) genotypes by DBM larvae. The principal component analysis separated the genotypes based on lower feeding scores in association with higher contents of glucobrassicin, glucoiberin, glucoiberverin in one direction and 4-hydroxyglucobrassicin, glucoerucin, glucoraphanin, and progoitrin in opposite direction in a way to explain the major variation in resistant versus susceptible genotypes based on their extent of preference and leaf area damage. The simultaneous presence (or higher contents) of glucobrassicin, glucoiberin, and glucoiberverin and the absence (or lower contents) of 4-hydroxyglucobrassicin, glucoerucin, glucoraphanin, and progoitrin in the least preferred genotypes and vice-versa in most preferred genotypes indicated their apparent role as putative repellents and attractants of DBM larvae in cabbage genotypes, respectively. These novel findings add to the current knowledgebase on the roles of glucosinolates in plant–herbivore interactions and will be helpful in setting breeding priorities for improving the resistance against DBM in cabbage using conventional and biotechnological approaches.
Highlights
Brassica oleracea is one of the most important human food crop species commonly consumed as vegetables, with a range of commercially valuable subspecies that includes cabbage, cone cabbage, cauliflower, broccoli, gai lan, kale, kohlrabi, collard greens, savoy, and Brussels sprouts etc
Glucoiberverin, and glucobrassicin, all of the rest of the 11 glucosinolates were detected in the genotypes, Rubra and YR Gold
The genotypes, YR Gold contained the highest (157.6 μmol g−1 DW) total glucosinolate followed by BN4059 (49.4 μmol g−1 DW) and Rubra (46.8 μmol g−1 DW) which was characterized largely by the higher concentration of 4-hydroxyglucobrassicin (87.6 μmol g−1 DW) and progoitrin (24.8 μmol g−1 DW) in YR Gold, sinigrin in BN4059 (30.0 μmol g−1 DW) and 4-hydroxyglucobrassicin in Rubra (26.1 μmol g−1 DW)
Summary
Brassica oleracea is one of the most important human food crop species commonly consumed as vegetables, with a range of commercially valuable subspecies that includes cabbage, cone cabbage, cauliflower, broccoli, gai lan, kale, kohlrabi, collard greens, savoy, and Brussels sprouts etc. Cabbage are naturally rich in potassium, fiber, folic acid, beta-carotene, vitamins C, and K while containing less fat, cholesterol, and sodium. This make it important in terms of health, medical, and clinical benefits as evident by their protective role against cancer, heart disease, diabetes, and hypertension (van Poppel et al, 1999; Finley, 2003; King and Barker, 2008; Verkerk et al, 2009; Kapusta-Duch et al, 2012). Chemical control of the pest were proven cost ineffective and environmentally hazardous along with the chances of rapid development of resistance toward insecticides and potential negative effects on their natural enemies (Grzywacz et al, 2010). Development of resistant varieties can be the most sustainable approach which requires wider understanding of the plants overall defense mechanisms with regards to the natural variation in plants’ performances against DBM
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