Identification of NBS-LRR Class Ctv Resistance-Gene in Egyptian Sour Orange and Lime Rootstocks

摘要

Sour orange (Citrus aurantium L., 2n=2x=18) is used as a rootstock of citrus. The aim of the study is to address two questions. How is sour orange rootstock resistant of Citrus tristeza virus (CTV) containing on Ctv resistance gene? How are different sour orange accessions with the same gene? Using degenerate primer designed from conserved NBS-LRR (Nucleotide binding site-leucine rich repeat) motifs to detect of Ctv resistance gene in seedlings of different citrus rootstocks from Egypt, it was observed that Egyptian lime and some accessions from sour orange 'Balady' contained the NBS-LRR class Ctv resistance gene and others did not. The genetic variability between sour orange accessions was assessed using ISSR-PCR. Four out of five ISSR primers, there were 41 scorable amplified DNA fragments ranging in size from 1130 to 65 bp, whereas 21 fragments were polymorphic with percentage of 51.22. Primer-2 recorded the highest percentage (57.14), while primer-1 displayed the lowest percentage (42.86). The primers 3 and 5 showed the polymorphic percentage of 55.56 and 50, respectively. Among the 21 polymorphic bands 12 bands were specific markers with total average of 29.27%. Sour orange 'Balady' had the highest number with seven markers. Standard sour orange scored four markers and 'Roistacher' showed one unique marker. On the other hand, sour orange (Spanish) did not induce any marker.