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Project description

Probiotics and bacteriotherapy to improve mass rearing of Mediterranean fruit flies and performance of SIT male medflies. (02XA006)
Program Exotic Pests and Diseases Research Program
Principal
investigator
C.R. Lauzon, Biological Sciences, CSU Hayward
Host/habitat Citrus; Tree Crops
Pest Mediterranean Fruit Fly Ceratitis capitata
Discipline Entomology
Review
panel
Agricultural Systems
Start year (duration)  2002 (Two Years)
Objectives Determine if a probiotic larval diet improves the production of male and female Mediterranean fruit flies.

Assess the contribution of a probiotic larval diet to improvements in larval and adult intestinal health.

Determine if probiotics ingested by larvae survive the irradiation process, and/or protect the intestinal environment of SIT males.

Compare under field conditions the mating performance of SIT male MFF from larvae that fed on probiotic larval diet versus those that fed on standard larval diet.

Project
Summary
The key midgut- and salivary-specific proteins of the glassy-winged sharpshooter will be identified, cloned and characterized using a genomics approach. This will be accomplished through the construction of a normalized cDNA microarray and subsequent screening of the array using tissue specific cDNAs as probes. This approach will allow use to identify proteins whose function is essential for the normal absorption of nutrients and the maintenance of osmotic balance across the gut epithelial membrane. It also will allow us to characterize the proteins produced in the salivary glands that are essential for the establishment of effective feeding sites. The characterization of these proteins will lay the foundation for a antibody based approach to GWSS and Pierce's disease control.
Final report California and Florida are at considerable risk for the establishment of the Mediterranean fruit fly (MFF) due to its favorable climate and host availability. Colonization of MFF in either of these states would result in devastating losses of crops, personal, state, and national income, jobs, and global trade. To avert this type of economic and personal disaster, programs, such as "The Preventative Release Program," and strategies such as the Sterile Insect Technique, need to be optimized. Crashes in production may occur with little or no warning and are often due to pathogens that contaminate diet and infect insect life stages. Also, reports of poor survival rates of SIT males in the field coincide with the findings of Lauzon and Potter (in press) that the gut tissue of SIT males is damaged by radiation used in the sterilization process. Our goal is to find an effective, feasible way to improve production of MFF, and the health and performance of SIT males through the use of probiotics. Probiotics are beneficial gut bacteria known to prevent the establishment of pathogens and exert restorative and healthy effects on a host gut. Artificial rearing of MFF precludes the exposure and/or establishment of beneficial gut bacteria.

We found that adding probiotics to larval diet did not show measurable differences in gross characteristics associated with quality production. Such gross metrics do not reveal physiological benefits derived from consumption of probiotics, therefore, studies on adult fitness were conducted. We found that a probiotic diet improved SIT mating performance and prevented the growth of unwanted microbes in standard diet. The probiotics survived radiation used for sterilization and were passed to offspring. This finding suggests that bacteria are important to MFF survival. In sum, probiotics show promise for improving fruit fly management.

Second-year
progress
Our goal is to improve the performance of mass reared and sterile medflies (MFF) through diet. In nature, MFF consume bacteria in their food, such as fruit nectars and bird feces. Some of these bacterial species have been shown to be beneficial inhabitants of their gut. In past work, we have found that if these beneficial bacteria, called probiotics, are added to MFF adult diet, the radiation-damaged gut of sterile adult flies improves. This improvement may result in a fly that lives longer and performs better in a preventative release program (PRP). The purpose of the PRP is to avert the establishment of MFF by continuously releasing sterile MFF into areas where female MFF may occur. Mass rearing facilities must meet the demands of a PRP and provide flies that will perform well in the field. Our aim is to create a mass reared fly that behaves the same as a wild fly.

This year, we have found that certain adult probiotic diet formulations improve mating performance, calling activity, or life expectancy of sterile male MFF while the same is not true for these males when fed on larval probiotic formulations. We have found that probiotic larval or adult diets contain fewer bacterial contaminants than standard diets. We determined that probiotics survive the irradiation process and are passed through successive generations of flies. We are currently assessing MFF production in relation to larval diet. Our findings suggest that a probiotic diet protocol in a rearing facility is feasible.

First-year
progress
We aim to formulate a medfly (MFF) larval diet that contains beneficial gut bacteria and determine if this type of diet is better than the current larval diet used for mass-rearing of medflies. We have found that by adding beneficial gut bacteria to medfly adult diet, the radiation-damaged gut of sterile adult flies improves. This improvement may result in a healthier fly, one that lives longer and performs better in a preventative release program (PRP). The purpose of a PRP is to avert the establishment of MFF, a pest of fruits and nuts, by continuously releasing sterile male medflies into areas where wild female medflies may occur. Mass-rearing facilities must meet the continual demands of a PRP and provide flies that will be fit enough, post-irradiation, to perform well in the field. We are taking a dietary approach to improve production and performance of sterile MFF.

Thus far, we have examined the growth and survival of the beneficial gut bacteria (probiotics), in larval diet. We have found that the probiotics grow in the diet despite the presence of preservatives and the acid nature of the larval diet. We also found that bacteria that contaminate the diet are inhibited and/or killed by the probiotics. This finding may lead to decreases in the use of preservatives that may be unhealthy for larval consumption and costs to make the diet. We have optimized processing of larval gut tissue for microscopic analyses. In July, we will travel to Hawaii to test the diet.

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