The Effect of Erwinia amylovora Infection in Apple Saplings and Fruit on the Behavior of Delia platura (Diptera: Anthomyiidae)

The Vector Manipulation Hypothesis (VMH) posits that phytopathogens develop strategies to enhance dissemination by mediating behavior change in insect vectors. The VMH is poorly studied in phytopathogenic bacteria, especially in systems with numerous, occasional vectors. Erwinia amylovora is a bacterial pathogen of pome fruit that produces a bacterial ooze and is mechanically vectored by insects after they feed on ooze. The blossom blight phase of the disease exhibits manipulation of honeybees, leading to enhanced transmission, but whether the same occurs during the shoot blight phase of the disease is unknown. The goal of this study was to evaluate the effect of E. amylovora on the behavior of Delia platura, a fly with a worldwide endemic presence that may transmit E. amylovora. We show that D. platura prefer infected, oozing fruit to uninfected fruit in choice tests and that preference subsides when bacterial ooze is removed from the infected fruit. Flies did not exhibit a preference between infected saplings and uninfected saplings. The volatiles of infected fruit did not attract D. platura, indicating that diseased fruit odor is not responsible for the observed preference for infected fruit. Flies did not differentiate between sapling odors until infected trees had died, at which point they preferred uninfected tree odors. This study supports previous hypotheses suggesting that E. amylovora takes advantage of existing plant–insect interactions, though it is not fully understood how significantly behavioral changes affect transmission. Additional pathosystems with occasional, nonspecific vectors should be studied to further understanding of the VMH.

Response of Male Queensland Fruit Fly (Diptera: Tephritidae) to Host Fruit Odors

The surveillance and management of Dacini fruit fly pests are commonly split by fly gender: male trapping focuses on the dacine ‘male-lures’, whereas female trapping focuses on lures based on host-fruit volatiles. Although the males of several Dacini species have been reported to be attracted to host fruit volatiles, the option of using host-fruit traps for males has, to date, been ignored. Males of the cue-lure responsive fruit fly Bactrocera tryoni (Froggatt) have been recorded as responding to host-fruit volatile blends, but it is not known how frequently this happens, if it is age-dependent, or the strength of the response relative to cue-lure throughout the year. Here, we conducted an olfactometer experiment to test the lifetime (weeks 1–15) response of B. tryoni males to the odor of tomato, a known host of this fly, and compare catches of wild males to tomato-based traps and cue-lure traps in the field. Bactrocera tryoni males started to respond to tomato odor as they sexually matured (2 to 3 wk olds) and thereafter showed consistent olfactory response until advanced age (15 wk). In the field, wild males were captured by tomato-based traps throughout the year at a level not significantly different from cue-lure traps. The reason for the consistent B. tryoni male response to host fruit odor at this stage is not known, but it certainly occurs at a level greater than can be continued to be ignored for both basic and applied research.

Sensory and Composition Analyses of the Aqueous Phases from the Concentration of Guava (Psidium Guava L.) and Mango (Mangifera Indica L.) Juices and the Process-Induced Losses of Vitamin C

Introduction:One of the major problems in the juice industry is the loss of the fruit aroma during the thermal concentration techniques. During this process, the water evaporation, which carries the volatiles, compromises the juice’s flavor. In the fruit juice concentration by vacuum evaporation, the aqueous fraction with the volatiles is composed of only one phase.Methods:This study analyses the volatiles of the aqueous fractions from the concentration of mango and guava juices in a vacuum evaporator under different temperatures. The volatiles from the aqueous fractions were analyzed using mass spectrometry and the sensorial analysis evaluated the fruit aroma intensity.Results:Eighteen volatiles were identified in mango juice, among them, monoterpenes, sesquiterpenes and ketones were the major ones. The major compounds found in both mango juice and its aqueous fractions were 3-carene, β-pinene, β-terpinene and limonene. In the volatile profile of the aqueous fraction from the guava juice, the predominant compounds were aldehydes, such asn-hexanal and, the alcohol eucalyptol. 24 compounds were identified, including alcohols, sesquiterpenes, esters and ketones, and all characteristic volatiles were present in the guava fruit. Under the different temperature and vacuum conditions, the loss of vitamin C ranged from 35 to 77% for mango and from 15 to 55% for guava juices.Conclusion:Aqueous fractions collected early in the concentration under different temperatures were richer in the distinctive fruit odor when compared with the fractions collected at the end of the process. The loss of vitamin C was higher at higher temperatures and vacuum applied.

Sequential divergence and the multiplicative origin of community diversity

Phenotypic and genetic variation in one species can influence the composition of interacting organisms within communities and across ecosystems. As a result, the divergence of one species may not be an isolated process, as the origin of one taxon could create new niche opportunities for other species to exploit, leading to the genesis of many new taxa in a process termed “sequential divergence.” Here, we test for such a multiplicative effect of sequential divergence in a community of host-specific parasitoid wasps, Diachasma alloeum, Utetes canaliculatus, and Diachasmimorpha mellea (Hymenoptera: Braconidae), that attack Rhagoletis pomonella fruit flies (Diptera: Tephritidae). Flies in the R. pomonella species complex radiated by sympatrically shifting and ecologically adapting to new host plants, the most recent example being the apple-infesting host race of R. pomonella formed via a host plant shift from hawthorn-infesting flies within the last 160 y. Using population genetics, field-based behavioral observations, host fruit odor discrimination assays, and analyses of life history timing, we show that the same host-related ecological selection pressures that differentially adapt and reproductively isolate Rhagoletis to their respective host plants (host-associated differences in the timing of adult eclosion, host fruit odor preference and avoidance behaviors, and mating site fidelity) cascade through the ecosystem and induce host-associated genetic divergence for each of the three members of the parasitoid community. Thus, divergent selection at lower trophic levels can potentially multiplicatively and rapidly amplify biodiversity at higher levels on an ecological time scale, which may sequentially contribute to the rich diversity of life.