Antixenotic Resistance of Cabbage to Onion Thrips (Thysanoptera: Thripidae). I. Light Reflectance

Abstract

Onion thrips (Thrips tabaci Lindeman) has become a signiÞcant pest of cabbage (Brasssica oleracea L.) in regions with a dry continental climate. Thrips-resistant cabbage varieties have been developed in breeding programs, but the mechanisms of resistance remain largely unknown. Antixenosis, one of the three resistance mechanisms, may play a role but no plant trait has been identiÞed as a source of antixenosis. A series of studies were conducted to identify resistance mechanisms in this insectÐ crop interaction and to seek plant traits that were correlated to resistance. In this Þrst article of the series, the result of studying antixenosis and overall resistance of cabbage and the correlation between antixenosis and light reßectance characteristics are reported. There were distinct differences in the overall resistance to thrips between the six cabbage varieties studied. There were more pronounced differences between varieties based on the number of damaged head leaves compared with the use of damage ratings as a measure of overall resistance. Varieties also differed in their level of antixenosis; proportional abundance of thrips adults on head-forming leaves was more closely correlated to overall resistance of cabbage than actual thrips numbers. Some of the variables computed from the recorded reßectance spectra of cabbage were correlated to thrips abundance on head-forming leaves only in the Þrst but not in the second year of this study, suggesting that either spectral characteristics do not affect antixenosis or other variables may affect thripsÕ responses to spectral cues. Furthermore, multiple spray applications of a kaolin particle-based product signiÞcantly changed the light reßectance characteristics of cabbage, but it did not reduce the actual thrips abundance on head-forming leaves.

Field assessment of the susceptibility of onion cultivars to thrips attack – preliminary results

“…While finding the same differences in resistance between the tested cultivars is relatively easy, determining the causes of this phenomenon can be very difficult. Various studies on the resistance of onions to Thrips tabaci have also been conducted, and resistance has been linked to leaf structure and colour (FAIL et al 2013, HUDAK & PÉNZES 2004, DIAZ-MONTANO et al 2010, TRDAN et al 2004. Resistance can be affected by factors such as the sugar and nitrogen levels in the leaves (ANANTHAKRISHNAN & GOPICHANDRAN 1993, PANDA & KUSH 1995.…”

Onion thrips (Thrips tabaci (Thysanoptera: Thripidae)) in cabbage on Prince Edward Island: observations on planting date and variety choice

“…The color of the outer head-forming leaves did correlate with the number of thrips adults found in the cabbage heads. A follow up study by Fail et al ( 2013 ) demonstrated that light reflectance can correlate with thrips presence in some years but not others, suggesting that other variables may influence thrips’ response to spectral cues. Bálint et al ( 2013a ) evaluated epidermal thickness between resistant and susceptible cabbage varieties.…”

Anatomical and Biochemical Traits Associated with Field Resistance of Onion Cultivars to Onion Thrips and the Effect of Mechanical Injury on the Level of Biochemical Compounds in Onion Leaves

“…Plant antixenosis negatively affects insect colonization processes, resulting in a reduced initial infestation level, due to a feature (or set of features) that deters insects from settling and feeding [24]. The expression of antixenosis in genotypes may be a consequence of morphological, physical, and chemical features in plants and mainly affects the visual [26,27] and olfactory stimuli [28] involved in the host-finding behavior of thrips. In contrast, antibiosis negatively affects insect pest biology and their progeny (survival, development, and reproduction and are strongly influenced by the poor plant's nutritional quality (inadequate composition and concentration of soluble proteins and carbohydrates) [29,30], primary metabolites (e.g., lectins, proteinase, and amylase inhibitors), and secondary plant compounds (e.g., chlorogenic acid, glycoalkaloids, flavonoids, jasmonic acid) [31,32].…”