Red‐foliaged apples affect the establishment, growth, and development of the light brown apple moth, Epiphyas postvittana

Abstract

Anthocyanins have diverse roles in plant reproduction and in response to both abiotic and biotic stress. By over‐expressing the apple MYB transcription factor, MYB10, we have generated apple trees, Malus × domestica Borkh. (Rosaceae), with highly pigmented red foliage due to the presence of high concentrations of cyanidin‐based anthocyanins. In this study, we investigated the impact of the high anthocyanic apple leaves on the behaviour, feeding, and life cycle parameters of the light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), a widespread herbivorous pest of apples. Behaviour of 1‐ to 3‐day‐old larvae towards red anthocyanin‐rich and green apple leaves was studied in choice and no‐choice trials, and survival, growth, and development of larvae feeding on red and green apple leaves from the neonate to pupation were compared. First‐instar E. postvittana showed a statistically significant preference for green over red leaves from three transgenic red apple lines and a preference for the less red old leaves over the bright red new leaves. This was significantly different from their behaviour towards wild type green leaves, where new leaves were selected over old. In complete darkness, first‐instar E. postvittana showed no significant preference for the green leaves, indicating that visual cues were important. Although larval survival was not greatly affected by feeding on the red foliage, larval growth and development were significantly affected by feeding on leaves from some of the transgenic red apple lines. Liquid chromatography‐mass spectrometry analysis of leaf phenolics showed that both anthocyanins and quercetin glycosides were significantly raised in the red transgenic lines compared with wild types.

Flowers for bees, autumn colours for whom? An experimental test with autumn colouration in mountain birches (Betula pubescens ssp. czerepanovii) as a signal against the moth Epirrita autumnata

“…The combined results of the present two studies with the mountain birch and E. autumnata are conflicting, which inevitably lead the new inference in the direction of dismissing timing of senescence as an honest signal of parasite defence (in this system). Yet, given the handicap signal's most recent supportive evidence (Zheng et al, 2010;Cooney et al, 2012;Gerchman et al, 2012;Markwick et al, 2013), and given the vast number of parasite species, along with ever-apparent extravagant autumn displays, more than a handful manipulative experiments are required before the proposed link between handicap signals and autumn colours can be considered charted territory. 'Autumn tree colours as a handicap signal' (Hamilton & Brown, 2001) may thus still give the compass direction for the next experiments that provide waypoints for a future meta-analysis.…”

Red/purple leaf margin coloration: Potential ecological and physiological functions

“…Some studies have further suggested that anthocyanins themselves may impair herbivore growth and vigor. A recent study on geneticallymodified Malus  domestica engineered to express high levels of anthocyanin pigments in leaves demonstrated that the light brown apple moth, Epiphyas postvittana, not only prefers to feed on greener leaves, but exhibits significant reductions in development and growth when fed red leaves compared to green (Markwick et al, 2013). Similar results were found for Pieris brassica larvae reared on either red or green cabbage leaves (Maskato et al, 2014), and slugs reared on either Anthocyanin + or -phenotypes of wild radish (Irwin et al, 2003).…”

“…Whether this deters insects by giving the appearance of dead/ necrotic leaf tissues as proposed by Stone (1979), or is perceived as its own, distinct signal, is yet unclear. Döring et al (2009) showed that aphid species find red and brown similarly unattractive compared to green and yellow surfaces, and several studies have demonstrated that insects prefer landing (Kostal and Finch, 1996;Ramírez et al, 2008;Archetti, 2009b;Döring et al, 2009;Maskato et al, 2014), feeding (Numata et al, 2004;Karageorgou and Manetas, 2006;Markwick et al, 2013), and ovipositing (Maskato et al, 2014) on green over red leaves. However, results are not always consistent across insect taxa (Irwin et al, 2003).…”

Leaf colour polymorphisms: a balance between plant defence and photosynthesis

“…Our data are consistent with previous studies, which documented a herbivore preference for individual plants with green over red foliage (Hagen, Folstad & Jakobsen ; Archetti & Leather ; Markwick et al . ; Maskato et al . ).…”

“…; Markwick et al . ). No study has yet supported all three predictions; hence, the hypothesis remains controversial.…”