Herbivory and jasmonate treatment affect reproductive traits in wild Lima bean, but without transgenerational effects

Abstract

Premise: Plant responses to herbivores and their elicitors include changes in traits associated with phenology, defense, and reproduction. Induced responses by chewing herbivores are known to be hormonally mediated by the jasmonate pathway and can cascade and affect late-season seed predators and pollinators. Moreover, herbivoreinduced plant responses can be transmitted to the next generation. Whether herbivore-induced transgenerational effects also apply to phenological traits is less well understood. Methods: Here, we explored responses of wild lima bean plants (Phaseolus lunatus) to herbivory and jasmonate treatment and possible transgenerational effects of herbivore-induced early flowering. In a controlled field experiment, we exposed lima bean plants to herbivory by leaf beetles or methyl jasmonate sprays (MJ). We then compared plant development, phenology, reproductive fitness and seed traits among these treatments and undamaged, untreated control plants. Results: We found that MJ and leaf herbivory induced similar responses, with treated plants growing less, flowering earlier, and producing fewer seeds than undamaged plants. However, seed size, phenolics and cyanogenic glycosides concentrations did not differ among treatments. Seed germination rates and flowering time of the offspring were similar among maternal treatments. Conclusions: Overall, the results confirm that responses of lima bean to herbivory by leaf beetles are mediated by jasmonate; however, effects on phenological traits are not transmitted to the next generation. We discuss why transgenerational effects of herbivory might be restricted to traits that directly target herbivores.

Airborne cues accelerate flowering and promote photosynthesis in Brassica rapa

“…To our knowledge, effects of herbivory on flowering time and flower production have been documented but are still scarce (Brys et al, 2011; Paige & Whitham, 1987; Strauss et al, 2001). Earlier studies have reported variable effects across species with some showing acceleration of flowering upon feeding (Bustos‐Segura et al, 2021), while others have shown a delay to flowering (Agrawal et al, 1999; Lemoine et al, 2017) or a reduction in the number of flowers produced (Strauss et al, 2001). This variation could depend on the amount of leaf damage caused by herbivory as plants may compensate for low leaf herbivory by producing a greater number of flowers and seeds (Poveda et al, 2013; Poveda et al, 2018).…”

MYC transcription factors coordinate tryptophan‐dependent defence responses and compromise seed yield in Arabidopsis

“…Similarly, Hu et al (2021) demonstrated that MYCs repress cell proliferation in the seed integument. Studies showing that elicitation of leaf defence via exogenous JA compromises reproductive performance (Baldwin, 1998;Agrawal et al, 1999;Redman et al, 2001;Bustos-Segura et al, 2021) have suggested that the redirection of nutrients to the biosynthesis of defence compounds may contribute to declines in reproductive fitness. For example, JA-elicited defence reduced the availability of N for use in seed production (Baldwin et al, 1998).…”

“…The ability of exogenous JA to compromise reproductive output supports the notion that induction of plant defence carries fitness costs (Baldwin, 1998; Baldwin et al ., 1998; Agrawal et al ., 1999; Redman et al ., 2001; Bustos‐Segura et al ., 2021). These observations are consistent with genetic evidence showing that the mutation of 10 JAZ s in Arabidopsis, or loss of the single JAZ gene in the liverwort Marchantia polymorpha , compromises reproductive success (Guo et al ., 2018b; Howe & Yoshida, 2019; Monte et al ., 2019).…”