الفهرس 
Introduction
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Abstract
The present work was carried out to investigate certain ecological, biological and genetic aspects of Whitefly and associated Squash leaf curl virus during 2004 and 2005. The obtained results are summarized as follows: 1-Ecological studies: The first appearance of the whitefly occurred during the late of April 2004 with low adult number and then gradually increased to reach the highest level of infestation during the mid of July of the same season and during early of August for nymphal stages. The same trend was recorded in 2005 summer season but with different numbers recording the peak of abundance during the last week of August for adult stage and during the early of the same month for nymphs population. In Nili plantation, the early infestation was during the late of April 2004 and increased till reaching to their maximum population level during mid of both July and August for adult stages. During 2005 cultivation, the adult and nymphal infestation was obviously denoted that the population was in a gradually increased reaching to their highest level during late of August. The virus infection ratio in this study in Nili plantation was high during early and mid of August 2004 and late of August 2005. The plants sowing in summer 2005 was the best for growing the adults of this insect in comparison with other planting times. Also, it was noticed that there were very highly significant difference between those sowing in different planting dates and virus ratio infection on squash. The inoculation access period on the transmission of virus was significantly affected with time proceeding, where the complete transmission observed after spending 72 hours, but the exposure time 15 minutes was not affected. The total sugar and carbohydrates in the diseased leaves of squash were considerably lower than in healthy leaves. 2-Biological study : The incubation period of insect did not significantly affected. Also, there were not clearly observed differences between the different insect life cycle of the two insect sexes in the different three generations, but The longevity period of the adult female was highly significant 3- Nucleotide sequence of Egyptian isolate of Squash leaf curl virus:This strain was obtained from Qaluobia Governorate. The virus transmitted by the whitefly causing harmful symptoms to them on leaves and fruits. The PCR technique for detection the DNA where the length of DNA was 1.35 kb.The virus components DNA was isolated from primer which already obtained from Gene Bank and cloned within TOPO-TA plasmid and inoculated into E.coli bacteria and nucleotide sequence was occurred for determination the nitrogenous bases sequences and compared with the strains of Jordan and Arizona (USA) , where the similarity was 97-99% and 84-89 for Oman and Israel strains