Primarily identification of pear variants and analysis of their genetic relationship by SRAP markers
To identify wether there exit genetic variation happened in Japanese pear(Pyrus pyrifolia Nakai),27 accessions including the two variants '02-1' and '02-2' and other twenty-five cultivars were studied by method of sequence-related amplified polymorphism(SRAP) markers.Firstly,the SRAP-PCR reaction system was opti-mized with orthogonal design.22 pairs of suitable primers screened out from 88 ones were used to detect the dif-ferential fragment among the pear cultivars.The genetic relationships between accessions were analyzed by hier-archical clustering.The result showed that the optimal SRAP-PCR system was composed of 2.4 mmol·L-1 Mg2+,0.1 mmol·L-1 dNTPs,1.5U DNA polymerase,80 ng DNA template,and 0.18 μmol·L-1 primer in 25 μL total reac-tion volume.Compared with pear cultivar 'Qingxiang',seven and thirteen differential fragments were detected in '02-1' and '02-2',respectively,which indicated that there was genetic variation at the DNA level.Variant '02-1' was closely related to 'Qingxiang';and variant '02-2','Shinseiki' and 'Huanghua' fell into a cluster firstly,and then clustered with 'Qingxiang'.It was postulated that '02-1' was a sport,and '02-2' might be a strain origmated from 'Qingxiang'.