Vol. 15 Issue 1
Halwani, E., El-Ssum, R. and Olama, Z.A.
The nutritional requirements of Agrobacterium tumefaciens in production of extracellular polysaccharides (EPS) were studied in a chemical defined medium containing 10% centrifuged date molasses as a sole carbon source. The maximum EPS yield was obtained at pH 7, in presence of 7 g/L KNO3, with 5% of 12 hour old inocula and incubated statically in Kole flaks at 30°C. As in secondary metabolite production, EPS production started late in the exponential phase and the maximum yield was obtained at the stationary phase. Among the inducers tested, succinic acid proved to be the best for the yield of EPS. The rheological properties of polymer solutions were also studied. Viscosity was not affected by pH and temperature. The pure polysaccharide was not toxic and the polymer solution showed a good emulsifying activity.
E.M. Amin
Sex differentiation and gonadal development in the freshwater European eel, Anguilla anguilla L. was histologically studied for elvers, young and adults. The sex groups were divided into undifferentiated elver and adult and definite female or male. The successive examinations of the eel's gonads revealed that the primordial germ cells first appear in 6.4-10.0 cm elvers and the oogonia in 15.0 cm ones. Elvers destined to become females differentiate sexually at a length beyond 19.0 cm and those destined to become males beyond 27.0 cm, but some adult fish 38.0 cm in length still have undifferentiated gonads. Hermaphrodite gonads occur at a length of 32.0-35.0 cm. The ovary is the main gonad that directly develops, while the testis plays the role of secondary sex development. The oocytes proliferate rapidly, but the testis enters a period of quiescence. Both sexes posses gonads in immature conditions, the oocytes at the previtellogenic stage and spermatogonia in late multiplication stage. The presence of a vas deferens during gonadal development signals testicular differentiation, and its absence leads to ovarian development.
Khaled A. S. Al-Rasheid
Benthos samples were collected from the submerged topmost 1-3 cm of sediments in freshwater ponds in Al-Hassa Oasis, Eastern Region, Saudi Arabia for the identification and recording of free-living benthic ciliates of the Oasis. A total of 37 species belonging to 25 genera in 21 families was identified, 21 of which are know to be typical marine species. All represent new records to the fauna of Saudi Arabia. The distribution of each species within the Oasis was recorded.
Mohammad H. Al-Qunaibet, Essam A. Aboalwafa and Khalid M. Al-Fuhaid
This paper analyzes production costs' structure and the relative importance of each cost item in broiler projects using a sample of 38 projects that make up 88% of the total number of broiler projects in the Central Region, Saudi Arabia in 1992. These projects were classified in three categories according to the final product:
1) live broiler projects: with 24 projects,
2) live and processed broiler projects: with 7 projects, and
3) processed broiler projects: with 7 projects.
Results showed that the average total cost (ATC) for a live broiler is 5.75 Saudi Riyals (SR) broiler compared to SR 4.036/kg of live broiler. In live and processed broiler projects the ATC is SR 6.82/broiler and 5.907SR/kg, respectively. In processed broiler projects the ATC is 6.614 SR/broiler and 7.53 SR/kg. Results showed that the ATC decreases as production capacity increases confirming the concept of increasing returns of scale.
Mohammed A. Al-Saleh and Ibrahim M. Al-Shahwan
During 1992 and 1993 growing seasons, 385 cucurbit plant samples showing virus like symptoms have been collected for the purpose of identifying nine viruses that might cause cucurbit diseases in Riyadh, Gassim and Hail regions. The direct or indirect ELISA and agar double diffusion tests have been used for the identification. All the nine plant viruses to which the tests were performed have been identified in the central area of Saudi Arabia (Riyadh, Gassim and Hail regions). The zucchini yellow mosaic virus (ZYMV) was identified from all cultivated cucurbit species: cucumber (Cucumis sativus L.), melon (Cucumis melo L.), watermelon (Citrullus lanatus Thunb.), pumpkin (Cucurbita maxima Duch.), squash (Cucurbita pepo L.), bottle gourd (Lagenaria siceraria L.) and snake cucumber (Cucumis melo var flecuoses). The squash mosaic (CMV), watermelon mosaic virus-1(WMV-1) which is known as papaya ringspot virus (PRSV) were identified from all previously mentioned cucurbit species except from bottle gourd, pumpkin and snake cucumber respectively. The watermelon mosaic virus-2 (WMV-2) was identified from all species except pumpkin and snake cucumber. The Prune dwarf virus (PDV) has been identified from cucumber, melon, squash, and pumpkin. The cucumber green mottle mosaic virus (CGMMV) was identified from watermelon, melon, and bottle gourd. The cucumber leaf spot virus (CLSV) was identified from the plants of squash, pumpkin and bottle gourd, while the beet western yellows virus (BtWYV) was identified from the bottle gourd plants only.
The results of this study confirmed that the ZYMV was the most detected virus affecting all the cucurbit species in the different locations of the central area of Saudi Arabia, with 60.5% of detection. The lowest detection percentage (0.5%) was observed with BtWYV. The immunological tests revealed that most of the tested samples had mixed infections, also it revealed that about 25.7% of these samples gave negative reactions to all of the tested viruses.
This is the first complete and comprehensive study on viruses that infect cucurbits in Riyadh, Gassim and Hail regions which together form the central area of Saudi Arabia. In this study, the WMV-1 was identified in the central area for the first time, while four cucurbit viruses which include BtWYV, CLSV, PDV and WMV-2 were identified for the first time not only in the central area alone, but in Saudi Arabia as a whole.