بابک عدولی
یحیی تاجور
محمدباقر بالابندی
مسعود معصومی
کاظم نجفی
حمیدرضا قلی پور
یونس ابراهیمی
بابک / نگارندهعدولی

It is difficult to observe the chromosomes of citrus in detail due to their small size. Therefore, many cytologists have attempted to improve the techniques for chromosome counts in citrus. In present study Squash technique is used for citrus chromosome counting and distincting the ploidy level of natural hybrids of citrus which established in Kotra citrus collection. In this method, the open-pollinated seeds of 25 natural hybrid ripen fruits are washed and sterilized by 1% solution of Natrium Hypochloride. The seed coats are removed ( for faster and better germination ) and planted in clean petridishes at 25 c. After germination, one centimeter of root tips detached and following steps were carried : 1. Pretreat the root tips by 20% solution of Colchicine and one drop of Dimethylsulfoxide (DMSO). 2. Wash and fix in ethanol acetic acid (3:1) at room temperature. 3. Wash in ice water. 4. Treat with ethanol acetic acid (3:1). 5. Wash in ice water. 6. Cut root tips into 1-2 mm length and discard the rest. 7. Transfer of root tips to 2% solution of cellulase and pectinase. 8. Stain in 2% solution of aceto orcein and wash with acetic acid. 9. Place a root tip on the slide glass and add a drop of acetic acid (45%) and putting a cover slip on the sample. 10. Squash gently. 11. Observation the chromosomes and make the michrophotograph. The plant material used were the 25 natural hybrids of citrus contain : Adeeb, Atabakee, Bakraee, Syavaraz (no. 1,2,3 and 4), She-mahalle, Moallem-kooh, Mino, Hybrids no.1,2,3,4,5,6,7,8,9,10,11,12&13, Limou-golabee-amole (Mina) and Limou-astaraee. Eighteen chromosomes (diploid) were observed in all the natural hybrids used.

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