Detection and Identification of Sugarcane Pokkah Boeng Pathogens of Main Sugarcane Varieties in Yunnan Province

[Objectives]This study was conducted to identify the pathogen species and dominant species of sugarcane pokkah boeng in main varieties in Yunnan sugarcane areas,so as to promote the healthy and sustainable development of sugarcane industry.[Methods]Specific primers Fv-F3/Fv-R3 and Fp-F4/Fp-R4 were designed based on the ribosomal DNA non-internal transcribed spacer(rDNA-ITS)gene sequences of Fusarium verticillioides and Fusarium proliferarum,the main pathogens of sugarcane pokkah boeng,and 117 typical sugarcane pokkah boeng samples collected from main varieties in different sugarcane areas of Yunnan Province were detected and analyzed by PCR.[Results]Among the 117 sugarcane pokkah boeng samples,112 samples were detected with F.verticillioides with a positive detection rate of 95.7%;103 samples were detected with F.proliferarum with a positive detection rate of 88%;103 samples were infected by F.verticillioides+F.proliferarum,and the compound infection rate was 88%;and the two pathogens were not detected in 5 samples,which might be sugarcane pokkah boeng caused by other species.PCR amplification products of 23 F.verticillioides positive samples and 19 F.proliferarum positive samples from different sugarcane varieties in different sugarcane areas were sequenced.The BLAST alignment results showed that the sequences of the 23 amplification products of F.verticillioides shared 99.45%-100.00%homology with F.verticillioides(GenBank accession number:KU508286),and the sequences of the 19 amplification products of F.proliferarum shared 99.26%-100.00%homology with the sequence of F.proliferarum(GenBank accession number:MK252904).Part of the F.verticillioids and 11 F.proliferarum sequences were selected to construct a phylogenetic tree,and the phylogenetic analysis showed that they belonged to the F.verticillioids group and F.proliferarum group,respectively.The results showed that F.verticillioides and F.proliferarum were the main pathogens causing sugarcane pokkah boeng of the main sugarcane varieties in Yunnan,and there was a common phenomenon of compound infection.F.verticillioides was the dominant species in Pu er,Lincang,Honghe and Yuxi sugarcane areas,but the detection rate of F.proliferarum was also high,and there were other species.In the future,the discovery of resistant germplasm resources and breeding of resistant varieties should be carried out aiming at these two pathogens of sugarcane pokkah boeng.[Conclusions]The study provides technical support for rapid identification of sugarcane pokkah boeng pathogens,and scientific basis for breeding resistant varieties and scientific disease prevention and control.

AFLP Fingerprinting and Genetic Diversity of Main Sweetpotato Varieties in China

AFLP fingerprinting of the 98 main sweetpotato varieties planted in China has been constructed. Using 17 AFLP primer combinations which were selected from 1 208 primer combinations and generated the most amounts of polymorphic bands, AFLP analysis of the 98 main sweetpotato varieties gave a total of 410 clear polymorphic bands with an average of 24.12 polymorphic bands per primer combination. Each one of the 98 sweetpotato varieties could be clearly distinguished by EcoR I-cta/Mse I-ggc primer combination which generated the most polymorphic bands. AFLP-based genetic distance ranged from 0.0546 to 0.5709 with an average of 0.3799. The dendrogram based on AFLP markers indicated that sweetpotato varieties coming from the same regions or having same parents were clustered in the same groups. Analysis of molecular variance （AMOVA） revealed greater variations within regions （94.08%） than among regions （5.92%）. Thus, the genetic variations mainly existed within regions, while the variations among regions were very low in the tested sweetpotato varieties. Significant genetic variations existed between ＂Northern＂ and ＂Southern＂ sweetpotato varieties when Yangtze River was used as the dividing line.