الملخص الإنجليزي
tomato yellow leaf curl virus is a member in begomovirus genus which transmitted by whitefly (Bemisia tabaci). It has a main role in causing great economic losses for the tomato crops all over the world. The disease incidence was recorded as high as 100% in non protected fields while it was less than 10% in Agryl protected fields. Typical symptoms of this disease represented in the yellowing, upward curling of the leaves and severe stunting of the whole plant. Total nucleic acid isolated from whitefly genders was used as template to amplify the core coat protein (CP) and satellite DNA (DNA-B) by using polymerase chain reaction (PCR). Two Primer pairs used FD-CP382/RD-CP1038 and SATO1/SATO2 for CP and DNA-B, respectively. The PCR amplification yielded, 12 positive samples for the CP out of 18 and 3 positive samples out of 18 for the DNA-B of the sizes 650pb and 1350pb, respectively. The female whitefly has more efficiency in transmitting the TYLCV than male whitefly and the DNA-B can be transmitted from one plant to another by whitefly. The minimum viral acquisition and transmission rates by whitefly were evaluated by using PCR and recording symptoms visually, which were 30 min and 15 min, respectively. The Agryl cover was used in the field experiment to evaluate the optimum period for covering the tomato plants against whitefly. The period of 8 weeks covering with Agryl cover approved to be the best period for getting the best yield and protection. TYLCV transmitting whiteflies were used to screen 17 inbred-lines to see their susceptibility toward TYLCV. Nine out of seventeen inbred-lines were found resistant whereas eight of them showed moderate to a high susceptibility to TYLCV. Amplification fragment length polymorphism (AFLP) was done by using six primer combinations which as follow: (E- AAC/ MCAG), (E- AAC/ M-CAC), (E- ACA/ M-CT), (E- AGG/ M-CTT), (E- AGG/MCAA) and (E- AGG/ M-CAG). It revealed a high polymorphism among inbredlines, AFLP analysis showed a clustering among some of the resistant inbred-lines and also for high susceptible inbred-lines by using dendrogram. The clustering indicates to the genetic relationship among these inbred-lines. This can contribute to make some decisions by breeders in relation to the choice of the appropriate parents and linkage for the resistance genes.
