Gerbera Main Disease Pathogens And Resistance Gene Analogs Cloning From Gerbera Jamesonii

Gerbera jamesonii Bolus is one of the most famous cut flowers in the world, which belongs to family Asteraceae. However, gerbera leaf spot, powdery mildew and root rot speading in Beijing and surrouding areas cause great economics loss to the growers. Clarify disease pathogens and find disease resistance genes mean a lot to prevent and cure gerbera disease. This study mainly identified pathogens of three gerbera diseases using Koch'postulates, cloned Resistance Gene Analogs (RGAs) of gerbera, and analized the relationship between RGAs and resistance genes. The main research conclusions were shown as follows:1. The pathogens of gerbera leaf spot disease, identified on the basis of pathogenic test as well as morphological character and molecular identification, were taxonomically described as Alternaria alternata (Fr.) Keissl and Alternaria tenuissima (Fr.) Wiltshire, GenBank accession numbers are GQ169728 and GQ169727.2. The pathogen of gerbera root rot disease, identified on the basis of pathogenic test as well as morphological character and molecular identification, was taxonomically described as Fusarium equiseti (Corda) Sacc, GenBank accession numbers is HM008677.3. The pathogen of gerbera powdery mildew disease, identified on the basis of pathogenic test as well as morphological character and molecular identification, was taxonomically described as Podosphaera fusca (Fr.) U. Braun & Shishkoff (also called P. xanthii,P. balsaminae,Sphaerotheca fusca and S. fuliginea), GenBank accession numbers is HM002584. Trials determined the teliospores germinating biology of P. fusca to provide basis for control teliospores germinate in order to avoid the disease, by the way of adjusting ecology environment. The optimum teliospores germinating temperature range was 22℃to 25℃, especially 25℃. Germinating rate was extraordinarily high when pH was 6, and water may be necessary for the teliospores germination. The effectiveness of Verticillium lecanii preparation as curatively applications in the control of gerbera powdery mildew was tested, the result showed that conidiophores concentration 2.6g/L-3.3g/L of V. lecanii could control gerbera powdery mildew disease more effectively.4. Specific fragments of 250bp,2000bp,700bp and 2500bp were cloned from genomic DNA of Hongselianren and Shuifen by PCR with three-pair primers out of nine designed according to the conserved domains of reported Resistance Genes. Before transformed into E.coli DH5a these specific fragments were recyled and inserted into pEASY-T3 vector. Thirty positive recombinants were obtained and confirmed through colony PCR identification.5. Fifteen out of these 30 sequenced clones had high homology contrast with reported R gene through blasting in GenBank, among which 9 RGAs had complete open reading frames (ORFs). Further cluster analysis showed that these 9 RGAs in gerbera may belong to TIR-NBS-LRR and non-TIR-NBS-LRR, which confirmed the previous study that two types NBS-LRR genes exist in dicotyledon. Eight LRR repeat units can be found in 3'and 5'ends of derived amino acid of LR1.