Diversity Of Morphology, Pathogenicity, And Genetics Of Marssonina Rosae In China

Sixty-one collections of Rosae leaves showing black spot from Rosa chinensis, Rosa multiflora, Rosa rugosa, Rosa xanthina were collected during from 2007 to 2008, as much as possible cover the east, north and south of China.22 Marssonina rosae isolations were obtained from these samples.We found that the conidial size had obvious difference by determining 61 collections of pathogens. There was a relationship between colony color, conidial size and average growth rate of colony. The longer conidia(L>18.0μm)could form yellow colonies ,smaller conidia (L<16.5μm)form black colonies, when the conidial size was from 16.5μm to 18.0μm, the colony color was dark brown, while the average growth rate of black colonies was significantly higher than the yellow colonies and dark brown. There were host populations and varietal populations, and R. xanthina, R. rugosa, R. multiflora and R. chinensis was 4 hosts populations differentiation. There were also varietal populations in the same hosts. So host origins could form Morphological diversity of M. Rosae. The results testified geographic origins could form morphological diversity of M. Rosae. There were geographic populations and population differentiation of M. Rosae in china. We divided into 5 geographic populations of M. Rosae: north of east china; north china, northwest china and north of central china; south of east china; south china and southwest china; south of central china.We found that different modern rose varieties showed obvious different resistance by stating and analysing the pathogenicity index of different roses after inoculating different isolations of M.rosae. Floribunda Rose'Hong maozi'and Hybrid Tea Roses'Samantha'are high susceptibe varieties. Floribunda Rose'Betty prior'and Grandiflora Roses'Queen Elizabeth'are medium resistant varieties. Hybrid Tea Roses'silva'and Hybrid Tea Roses'Pink Panther'are high resistant varieties.we also found that different isolations of M. rosae had different pathogenicities, and the pathogenicity index of Mr2 was 46.67±18.25, but Mr3 was only 8.17±5.08, the difference was extremely significant (P<0.01). 20 isolations of M. rosae were divided into three types: high pathogenicity, medium pathogenicity and low pathogenicity. Mr2,Mr13,Mr47 and Mr1 were high pathogenicity, Mr10,Mr12,Mr15,Mr46,Mr49,Mr55,Mr45 and Mr14 were middle pathogenicity, Mr3,Mr9,Mr11,Mr16,Mr48,Mr53,Mr54 and Mr56 were low pathogenicity. There is no difference between the northern, represented by Beijing and Shandong province, and the southern represented by Fujian, Zhejiang and Guangdong province.By identification of anastomosis, the results showed that the majority of 20 strains can occur completely or partially intergrated, but there was great difference between different strains. The strain Mr48 from Hubei could occur completely intergrated with all the strains, but the strain Mr11 from Shandong could hardly occur completely intergrated with any strain, and there was also difference between strains from the same place, the strain Mr49 could only occur completely intergrated with strain Mr54,Mr55 and Mr48. The results indicated that hyphal fusion is related to host but not the geographic origins.By blast analysis of ITS1 sequence between 4 tested strains and other strians of Marssonina, the similarity of ITS1 sequence from strains Mr2, Mr46 and Mr47 with AY904059 has reached 100% , and they had nearly genetic relationships. The similarity of ITS1 sequence from strains Mr22 with AY904059 was 97%, they had further genetic relationships. The above related strains were all from M. rosae, and the host of FJ493247,FJ493248 and FJ493249 was R. chinensis, but the host of FJ493242 was R. multiflora. their ITS1 sequences was different, there were 6 obvious different sites which were site 3,15,33,43,87 and 148. These six sites are respectively A,C,C,A,C,G from isolations of R. chinensis, but they are G,T,G,G,T,A from isolations of R. multiflora. We also found that ITS1 sequence was hypervariable region in M. Rosae and there was genetic diversity of M. Rosae.