The Diversity Of Apple Ring Rot In Apple Production Areas Around Bohai Bay

Bohai Bay region is one of the apple main producing areas in China, apple ring rot isthe serious diseases of apple branches and fruit of the region, the disease incidence rateincreased year by year. Deeply study on the apple ring rot symptoms and pathogen diversityare very urgent, this paper mainly observation and description disease symptoms of the BohaiBay in3provinces,23cities in different years and different periods, and widely collection,separation and purification of the pathogens, a total of216isolates were studied on the culture,morphological characteristics, phylogenetic relationships and pathogenicity. The main resultsare as follows:1. Apple ring rot symptoms mainly showed the six types in the Bohai Bay, such as ringswelled, ring sunken, dry rot, shoot blight blister and fruit ring types. Ring swelled and ringsunken types are mainly symptoms in branches, ring type mainly occurred on the fruits.2. According to the color of the colonies, size, mycelial dense, edges and back of thecharacteristics of pathogens culture, they were divided into five types. Based on the structureof the fruiting body chamber, color, conidiogenous cell, spores （conidia and ascospores） shape,color, size, structure, the septa, the size of the spores of morphological characteristics, thestrains fruiting bodies are mostly black or gray, hypergenesis, half-defixed or defixed, solitaryor acervate, mostly spherical or flat spherical, minority are the cylindrical or irregular shape,the fruiting body can produce three types of spores: conidia, ascospores and smallspores,some strains are three types of spores mixed. The strains were identificated Botryosphaeriadothidea, and other strains are different in morphological characteristics and needed to clarifyits taxonomic status.3. Applying DnaSP4.0haplotype software and analysis176ITS sequences. The strainsof the pathogen are divided into the10haplotypes, and the Hap₁and Hap₂are dominantspecies in the Bohai Bay, and the other small numbers strains belonged to other haploid types.According to ITS, beta-tubulin and EF-1alpha multi-gene phylogenetic single and and jointlyanalysis. The ITS sequence results showed that the tested strains are divided into two groups,Hap₁and Hap₂were a same group including total of114strains, and had high homologywith B. dothidea; another group had low homology with B. dothidea three conserved regionsof ITS1,5.8S, ITS2had different levels of variation. Beta-tubulin sequence also showed thetwo groups, the result was same as ITS sequences. EF-1alpha sequence analysis also showedthat the two groups, it was different system relationship to ITS sequences and partlyconsistent with beta-tubulin sequence. Combing with multi-gene phylogenetic analysis showed that B.dothidea had significant intraspecific interspecific variation around Bohai Bayregion.4. Applying to indoor artifical wound and natural lenticels inoculation on the apple fruit.the results showed that the pathogen had virulence differentiation, a few strains virulencewere strong, some of medium and a few weak around the Bohai Bay region. Thepathogenicity differentiation was not directly related to their geographic distribution.Based on the above findings, the symptoms of apple ring rot were diversity, thepathogens population structure were very single, the dominant group was B. dothidea aroundBohai Bay region.