| The crown gall disease is devastating disease of roses. But until now, the resistance resources in Rosa spp. and the corresponding resistance mechanism are unclear. In this study, the pathogenic bacteria of rose crown gall were identified and utilized for screening the resistance resources from garden rose cultivar and rose rootstocks. Furthermore, the hormonal, structural and gene expression responses for Rosa multiflora 'Inermis No4' to Agrobacterium tumefaciens were studied. The results obtained were as follows:Nine isolates were purified from crown galls in rose plants. 3 isolates were highly virulent A. tumefaciens, and 3 isolates were moderately virulent.Fifty materials of Rosa spp. were inoculated with the highly virulent strain J-5-1 as a test for resistance to crown gall disease. According to disease incidence, tumor size and weight and its impact on the hosts' growth, these materials were categorized as: highly resistant, moderately resistant, moderately susceptible and highly susceptible. R. rugosa, R. xanthina, R. hybrida 'Fire', R. hybrida 'Double Delight' , R. hybrida 'Blue Ribbon' were highly resistant to crown gall disease; R. multiflora 'Inermis No4' and other 16 samples were grouped as moderately resistant. R. multiflora f. carnea and other 16 samples were moderately susceptible. 11 samples were highly susceptible. Furthermore, in vitro testing method was introduced to escape the limitations of in vivo testing method. It showed that the tumor size formed on the plantlet stems which were cultured in vitro was significant different among the samples, and it could be used as an index for the hosts' susceptibility to A. tumefaciens. The result of in vitro testing method was basically consistent with that of in vivo testing method.There existed different physiological responses to A. tumefaciens between R. multiflora 'Inermis No4', which was moderately resistant, and R. multiflora f. carnea, moderately susceptible. It showed that the time-course of changes in free auxin (IAA) and zeatin riboside (ZR) and abscisic acid (ABA) concentrations showed different model within the 4 weeks of bacterial infection. The IAA and ZR and ABA concentrations reached their maximum at 3 dpi (days after inoculation) for R. multiflora 'Inermis No4', then began to decline or increased slowly at 21 dpi, whereas IAA and ZR and ABA concentrations increased successively for R. multiflora f. carnea.The A. tumefaciens-induced crown galls and their impacts on the host's vascular differentiation showed different pattern between R. multiflora 'Inermis No4' and R. multiflora f. carnea. Relatively slow cell division was observed at the inoculation sites of R. multiflora 'Inermis No4', and a few of globular bundles emerging in the fast-growing regions. The crown gall tissue on R. multiflora 'Inermis No4' was established on the base of extended host stem structure owning to the fast cell division along the inoculation sites, and its exterior was lignified. And special vascular bundles developed beneath the inoculation sites, which contained giant rays and abundant phloem elements, and absence of xylem, whereas the vascular differentiation above the inoculation sites was nearly uninterrupted.As for R. multiflora f. carnea, the host's vascular system developed rapidly at the inoculation sites, then, formed large gall outwardly, which contained tree-like branched bundles in fast-growing regions and globular bundles in slowly developing parts. Abundant vascular elements in the crown gall were interconnected with the host's vascular system. The stems of R. multiflora f. carnea showed pathologiccharacteristic. In the basipetal direction, the increased vascular bundles contained reduction vessel size. In the centripetal direction, the increased vascular bundles contained primary xylem with reduction vessel size and number and unaffected secondary xylem.Using suppression subtractive hybridization (SSH) and DNA macroarray, numerous genes of R. multiflora 'Inermis 4' were identified that were induced by A. tumefaciens infection. Forward and revers...
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