Genetic variation in phytochemicals in leaves of pepper (Capsicum) in relation to thrips resistance

Abstract

Phytochemicals not only determine the taste and smell of plants and their products, they also play a crucial role in resistance against pests and pathogens. In previous work, we identified a form of resistance to thrips (Frankliniella occidentalis) expressed in leaves of pepper (Capsicum annuum). In the current study, we characterized leaves of an interspecific C. annuum × C. chinense F 2 population for variation in their global phytochemical composition by an untargeted metabolomics approach. Quantitative trait locus (QTL) mapping resulted in metabolite QTLs (mQTLs) for 304 of the 674 metabolites detected. We compared the QTL mapping results to those obtained earlier on fruits in the same population. Very different QTL hotspots were found, suggesting that the metabolite composition of leaves and fruits is regulated independently. Six leaf mQTLs co-located with the major QTL for resistance to thrips, which we previously identified in the same F 2 population. Four of them were significantly correlated to thrips resistance, including two diterpene glycosides and a flavonoid compound which may indicate a possible role of these metabolites in thrips resistance. If a causal role of some of these metabolites in resistance can be proven this will help in the identification of the causal gene(s) and it may provide leads for the identification of other sources of thrips resistance in Capsicum and in other species.

Metabolomics of Thrips Resistance in Pepper (Capsicum spp.) Reveals Monomer and Dimer Acyclic Diterpene Glycosides as Potential Chemical Defenses

“…To our knowledge, this is the first study that links the dimer DTG to thrips resistance. Our results are in line with other recent studies on DTG and highlight the emerging role of DTG as defenses against insects in Solanaceae (Heiling et al 2010 ; Poreddy et al 2015 ; Maharijaya et al 2018 ).…”

“…High levels of tocopherols and low levels of aromatic amino acids in leaves of Capsicum have been related to thrips resistance (Maharijaya et al 2012 ; Mollema and Cole 1996 ). In addition, a recent study on metabolite QTLs and thrips resistance using a C. annuum x C. chinense F2 mapping population showed that high levels some acyclic diterpene glycosides were weakly but significantly correlated to thrips mortality (Maharijaya et al 2018 ).…”

QTL mapping of insect resistance components of Solanum galapagense

“…In a Solanum pennellii introgression population, hot spots and cold spots were detected for mQTLs related to secondary metabolism in tomato fruit pericarp (Alseekh et al 2015), while in pepper fruits two closely linked mQTL hot spots were detected that regulated the relative levels of 35 and 103 secondary metabolites, respectively (Wahyuni et al 2014). In leaves of the same pepper population, three mQTL hot spots were detected, of which one overlapped with the fruit mQTL hot spots (Maharijaya et al 2018). Clustering of mQTLs may point at a common regulator and/or involvement in the same biochemical process (Fu et al 2009).…”

“…2), the strongest one with more than 200 mQTLs at the end of Chromosome 2. Identifying hot spots and cold spots for mQTLs in plant genomes is not uncommon (Carreno-Quintero et al 2012; Keurentjes et al 2006; Maharijaya et al 2018; Rowe et al 2008; Wahyuni et al 2014). In a Solanum pennellii introgression population, hot spots and cold spots were detected for mQTLs related to secondary metabolism in tomato fruit pericarp (Alseekh et al 2015), while in pepper fruits two closely linked mQTL hot spots were detected that regulated the relative levels of 35 and 103 secondary metabolites, respectively (Wahyuni et al 2014).…”

Resistance to three thrips species in Capsicum spp. depends on site conditions and geographic regions

“…In Capsicum, the few QTL mapping studies on thrips resistance focused only on F. occidentalis (Maharijaya et al, 2018(Maharijaya et al, , 2015. It is unclear whether the one currently identified QTL for F. occidentalis resistance applies to resistance to other thrips species, but our results suggest this is unlikely.…”