Defoliation and Infestation of Cucurbita pepo Genotypes by Diabroticite Beetles

Abstract

<jats:p>Seventy-six <jats:italic>Cucurbita pepo</jats:italic> L. cultivars and breeding lines were evaluated under field conditions for infestation levels and defoliation (leaf area consumed by beetles) by adult diabroticite beetles in 1992 and 1994. Striped and spotted cucumber beetles, <jats:italic>Acalymma vittatum</jats:italic> (F.) and <jats:italic>Diabrotica undecimpunctata howardi</jats:italic> Barber, respectively, were most common, but some western and northern corn rootworms, <jats:italic>D. virgifera virgifera</jats:italic> LeConte and <jats:italic>D. barberi</jats:italic> Smith and Lawrence, respectively, also were present. In general, pumpkin, delicata, acorn winter squash, scallop, and yellow straightneck summer squash types were the least infested and defoliated. Caserta/yellow, zucchini, caserta/zucchini, caserta, and precocious yellow straightneck types were the most infested and defoliated. The number of beetles per plant was correlated (<jats:italic>r</jats:italic> ≥ 0.72) with leaf defoliation and proportion of plants infested, indicating that beetle infestation is a good predictor of damage. The cultivars and breeding lines that were the least infested and defoliated can be used in breeding programs to develop desirable genotypes with reduced beetle preference. Conversely, those genotypes that were highly preferred have potential as trap crops for these beetle pests.</jats:p>

Divergence of defensive cucurbitacins in independent Cucurbita pepo domestication events leads to differences in specialist herbivore preference

“…pepo (CPP) over C. pepo ssp. ovifera (CPO) (Brzozowski et al, 2016; Ferguson et al, 1983; Hoffmann et al, 1996), despite neither domesticate having cucurbitacins in leaf tissue (Brzozowski et al, 2019; Metcalf et al, 1980, 1982). We sought to isolate the effect of cotyledon cucurbitacins on herbivore preference from other factors associated with subspecies, like defence inducibility (Brzozowski et al, 2019) and morphological traits (Paris, Lebeda, Křistkova, Andres, & Nee, 2012).…”

“…pepo (CPP) over C. pepo ssp. ovifera (CPO) (Brzozowski et al, 2016;Ferguson et al, 1983;Hoffmann et al, 1996), despite neither domesticate T A B L E 3 Differential expression of genes in the Bi-4 interval in cotyledons of C. p. ovifera ("CPO") and C. p. pepo ("CPP") at seedling radical emergence. A positive Log2FoldChange value indicates greater expression in CPP, and negative corresponds to greater expression in CPO.…”

“…While this pattern suggested pathway disruption in CPO, likely by a single gene (Sharma & Hall, 1971), the genetic mechanisms differentiating the subspecies are unknown. The specialized herbivore, Acalymma vittatum (Coleoptera: Chrysomelidae), feeds on all plant tissues (cotyledons, leaves, flowers, fruit and roots), but foliar preference is furthermore associated with subspecies: both the cotyledons (high cucurbitacins) and leaves (no cucurbitacins) of CPP are preferred over CPO (Brzozowski, Leckie, Gardner, Hoffmann, & Mazourek, 2016; Ferguson et al, 1983; Hoffmann, Robinson, Kyle, & Kirkwyland, 1996). Here we generated a new mapping population by crossing CPP and CPO to help disentangle the association between cucurbitacins and selection history, allowing us to identify genetic loci implicated in biosynthesis or accumulation, and to understand if plant‐wide herbivore preference is indeed predicated on cucurbitacins.…”

Inbreeding influences herbivory in Cucurbita pepo ssp. texana (Cucurbitaceae)

“…While the loss of leaf area as a result of beetle damage reduces photosynthetic capacity and results in loss of stored resources (Quesada et al 1995), beetles may also act as vectors for bacterial wilt and other pathogens (Agrios 1978;Hoffman et al 1996). Variation in susceptibility and tolerance to herbivory is often genetically based Rausher 1987, 1989;Kennedy and Barbour 1992), and evidence from inbred crop lines suggests that some mechanisms of herbivore resistance involve dominance relationships (Smith 1989;Kennedy and Barbour 1992).…”

Seeds and oil of the Styrian oil pumpkin: Components and biological activities

“…Rootworm feeding is associated with decreased water and nutrient uptake, and due to weakening of the root system, the plants become prone to mechanical damage by winds or heavy rain. Although Dvv is especially dangerous for corn, Dvv has been found to infest also various Cucurbita pepo cultivars [61]. Currently, there is no data available about the impact of Dvv on the Styrian oil pumpkin and its products.…”