OVIPOSITION PREFERENCE AND OFFSPRING PERFORMANCE OF THE ORIENTAL FRUIT FLY BACTROCERA DORSALIS (DIPTERA, TEPHRITIDAE) ON EIGHT HOST PLANTS

1. Université Cheikh Anta DIOP de Dakar, Département de Biologie Animale, BP 5005, Dakar, Sénégal. 2. Direction de la Protection des Végétaux-Sénégal, Km 15, Route de Rufisque. BP: 20054 Thiaroye, Dakar,Sénégal. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 30 November 2019 Final Accepted: 31 December 2019 Published: January 2020


ISSN: 2320-5407
Int. J. Adv. Res. 8(01), 931-937 932 The best knowledge of the B. dorsalis behavior on its host plants is an essential element to develop an effective and sustainable control strategy against this pest. It has been shown that the physico-chemical characteristics of host fruits play an important role in the fecundity and development of B. dorsalis (Papachristos et al., 2008;Rattanapun et al., 2009). In Senegal, (Diatta et al., 2013) were studied the B. dorsalis preference on five (5) fruit species without evaluated the larval performance of this pest neither the fruit physicochemical parameters that were tested. Thus, this study was therefore undertaken to assess the effect of eight (8) fruit species on the fecundity and the development of the immature stages of B. dorsalis (Diptera, Tephritidae) in relation with the pH and Total soluble solids of those fruits.

Materials and Methods:-
The study was conducted in the agricultural zoology laboratory of the Direction de la protection des végétaux in Senegal. The temperature of this laboratory was 27 ° C ± 2 and the photoperiod (light / dark) 12 hours / 12 hours.

Bactrocera dorsalis rearing:
The adults of B. dorsalis used in this study were reared in cages at the agricultural zoology laboratory of the Direction de la protection des végétaux. Flies were fed on a mixture of sugar, peptone and yeast hydrolysate.Water was also provided regularly with cotton whose base was immersed in a small plastic bottle. Egg-laying devices made with perforated plastic containersand coatedwith fruit jus were regularly introduced inside the cages for 24 hours. Eggs were collected and placed on an artificial diet for the immature stages development. The composition of the diet was wheat bran, yeast hydrolysate, sugar, distilled water, benzoate Sodium and HCL.

Measurement ofthe total soluble solids and pH of fruits:
Six fruits from each species were selected to measure the total soluble solid and pH. Total soluble solid of fruits was determined by using a digital refractometer (HI 96801). The pH was measured with a pHmeter.

Oviposition preference: Choice test:
The experiments were conducted inside1 by 0.6 by 0.6 m cages at the laboratory. In total, 50 couples of B. dorsalis, sexually mature (12 to 15 days old) and virgin, were introduced into each cage one day before the experiment. For each fruit, a nail attached to a wire was pointed at its base to facilitate its suspension in the cage. Indeed, the fruits were suspended simultaneously in each cage as oviposition substrate to females and distant 25 cm. After 24 h, the fruits were removed from the cages and incubated individually in plastic containers with sand until the development of larvae into pupae. These pupae were extracted from the sand for each fruit and counted to determine the egglaying preference of B. dorsalis for all the fruits. Three replicated cages were maintained and the experiment was repeated thrice.

No-choice test:
A fruit from each species was placed individually in a 30 by 30 by 30 cm plexiglass cagethat containing 10 couples of B. dorsalis at 12 to 15 days old. There were 9 replicates of each species. After 24 hours, fruits were removed from cages and incubated individually in plastic containers containing sterilized sand until all larvae had pupated. The recovered pupae from each fruit were counted to determine the egg-laying preference of B. dorsalis for all the fruits.

Offspring performance:
To obtain newly laid eggs, an artificial egging device made with perforated plastic container swabbed with fruit juice were introduced inside the rearing cages of B. dorsalis for 2 hours.

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Bactrocera dorsalis eggs were collected by washing the artificial egging device and placed in a container containing water to select viable eggs. Viable eggs sank to the bottom of the container, while non-viable ones floated on the surface (Balagawi et al., 2005).
Each fruit species was weighed, washed and slited before insert B. dorsalis eggs using a fine paintbrush at rate of 10 per 100g of fruit.The fruits were subsequently individually incubated over plastic container containing sterilized sand as pupation substrate. From the fifth day, the sand is sieved daily to collect newly formed pupae.The pupae recovered each day from each fruit were counted and placed in Petri dishes until adult emergence. Emerged flies were also sexed and counted daily.The biological parameters studied were the duration of the immature stages, rate of eggs that survived to pupae and sex ratio. There were six replicates of each fruit species.

Statistical analysis:
The data were processed using Microsoft Excel spreadsheet and Xlstat. Analysis of variance (one-way ANOVA) was generated for treatments and means were compared (LSD) by Fisher test at 0.05 probability.

Results:-
Total soluble solids and pH of fruits:  Table Ishows the total soluble solids and pH of the eight fruit species. There were significant differences (P < 0.05) in the total soluble solids and pH between the fruit species. Total soluble solids values were varied between 4.18 ± 0.99 (Tomato) and 14.11 ± 0.99 (mango) °Brix depending on the fruit species (Table I). Papaya had the highest mean pH (5.61±0.08), while lemon had the lowest (2.47±0.08).

Oviposition preference:
There was a significant difference in the number of puparia recovered from the eight fruit species exposed to Bactrocera dorsalis in choice (F= 4.774; P= 0.000) and no-choicetests (F= 12.003; P< 0.0001). In the no-choice test, highest number of puparia was recovered from papaya (101.56 puparia per fruit) and mango (69.89 puparia per fruit), whereas the lowest recovery was observed in tomato and lemon (0.22 puparia per fruit).
In the no-choice test, among the eight fruit species tested, papaya (172.67 puparia per fruit) and mango (85.55 puparia per fruit) recorded the highest number of puparia, whereas the lowest were occurred on the lemon (0.22 puparia per fruit) and sweet orange (0.57 puparia per fruit). Statistical analysis showed that there were significant differences in development period from egg to adult and the rates of eggs that survived to pupae in overall the test fruits. The shortest development times were recorded in papaya and mango with respectively 17.68 ± 0.61 and 18.68 ± 0.61 days (Table III). Mango and pomelo were recorded highest rates of eggs that survived to pupae with respectively 67.83 ± 8.11% and 51.28 ± 11.48% (Table  III). However, lemon was the unfavorable fruit for offspring survival of B. dorsalis, with a longer development time (22.16 ± 0.61 days) and a lower percentage of eggs survival to puparia (19.09 ± 11%) as compared to other fruits.
Consistent with the results of sex ratio, Mandarin, lemon, guava, orange and tomato favors females than males. Whereas in the papaya, pomelo and mango the males were higher than the females.  Our results were also showed that oviposition preference of B. dorsalis varied significantly with fruit species in choice and no-choice conditions. In the two experiment conditions, the highest number of puparia was recovered from papaya and mango. These agree with results obtained by Rwomushana et al., (2008) in Kenya and 935 Koswanudin et al., (2018) in Indonesia who showed that B. dorsalis which showed prefers papaya and mango over other fruits tested under laboratory conditions. However, our results are not totally agree with those of (Diatta et al., 2013) who showed that in laboratory conditions B. dorsalis prefers more papaya and citrus followed mango. The higher numbers of pupae that recorded in papaya and mango can be explained by the pericarp (soft) and the volatile compounds of these fruits which play an important role in the B. dorsalis egg-laying. In fact, fruit flies favour favour laying their eggs on fruits with soft pericarp than those with harder pericarp ( Statistical analysis showed that there were significant differences in development period from egg to adult and the rates of eggs that survived to pupae in overall the test fruits. Oviposition preference results showed that B. dorsalis prefers papaya and mango more than the other fruits tested in choice and no-choice conditions. These oviposition preference results agree with those obteined from larval performance study on mango with a shorter development time after the papaya and a higher egg-pupae survival rate compared to other fruits. Although papaya recorded the shortest immature development time, a very low rate of eggs that survived to pupae was observed on this fruit. This low survival rate is due to microbiological contamination that influenced by the high pH (5.61 ± 0.08) recorded in this fruit. This hypothesis was supported by Dias et al., (2019) who showed that on diet with pH 6.0, no larval hatching occurred for Anastrepha fraterculus and Ceratitis capitata, possibly due to the rapid microbiological contamination of the diet. However, lemon was the unfavorable fruit for offspring survival of B. dorsalis, with a longer development time (

Conclusion:-
This study showed that B. dorsalis prefers lay eggs on papaya and mango, whereas lemon was the least preferred fruit for this pest at laboratory conditions.
The study showed also that the physico-chemical parameters of fruits and the development of immature stages of B. dorsalis vary significantly depending the fruit species.On overall fruits tested, mango was recorded the highest total 936 soluble solid and seems to be the most favorable fruit for the development of B. dorsalis with a shorter development time after the papaya and a higher percentage of eggs survival to puparia as compared to other fruits. However, the lemon with the most acidic pH proved to be the unfavorable fruit for offspring survival of B. dorsalis, with a longer development time and a lower percentage of eggs survival to puparia as compared to other fruits.