Sugarcane bacilliform viruses (SCBV; genus Badnavirus; family Caulimoviridae) are a threat to the global exchange of sugarcane germplasm. To investigate the prevalence and genetic diversity of SCBV across major Chinese sugarcane-growing areas, a total of 280 sugarcane leaf tissue samples collected from six provinces in China, 25 from three states in the USA and five from Queensland, Australia, were tested for the presence of SCBV by polymerase chain reaction (PCR) using newly designed degenerate primers targeting a 720-base pair (bp) fragment of the reverse transcriptase/ribonuclease H (RT/RNase H) genomic region. PCR-amplified fragments from 94 SCBV-positive samples were then cloned, sequenced and analysed for their genetic diversity. The results revealed a considerable haplotype diversity within individual SCBV isolates. Recombination analyses showed weak signatures of recombination among some of the SCBV sequences. Phylogenetic analysis revealed the segregation of global SCBV isolates into three major monophyletic clades encompassing 18 subgroups, including five previously undescribed subgroups named as SCBV-N to -R. Population genetic analysis data indicated that relatively low levels of genetic exchange have occurred between SCBV populations from different sugarcane production regions of the world. Together with the new set of degenerate SCBV-specific primers designed in this study, our results will advance the understanding of SCBV population structure in a semi-perennial host plant and aid the screening of global sugarcane germplasm to minimize the spread of genetic variants of the virus via contaminated plant materials.

Sugarcane yellow leaf virus (SCYLV; genus Polerovirus, family Luteoviridae) is a recombinant virus associated with yellow leaf disease, a serious threat to sugarcane in China and worldwide. Among the nine known SCYLV genotypes existing worldwide, COL, HAW, REU, IND, CHN1, CHN2, BRA, CUB and PER, the last five have been reported in China. In this study, the complete genome sequences (5,880 nt) of GZ-GZ18 and HN-CP502 isolates from the Chinese provinces of Guizhou and Hainan, respectively, were cloned, sequenced and characterized. Phylogenetic analysis showed that, among 29 SCYLV isolates described worldwide, the two Chinese isolates clustered together into an independent clade based on the near-complete genome nucleotide (ORF0-ORF5) or amino acid sequences of individual genes, except for the MP protein (ORF4). We propose that the two isolates represent a novel genotype, CHN3, diverging from other genotypes by 1.7-13.6 % nucleotide differences in ORF0-ORF5, and 2.7-28.1 %, 1.8-20.4 %, 0.5-5.1 % and 2.7-15.9 % amino acid differences in P0 (ORF0), RdRp (RNA-dependent RNA polymerase) (ORF1+2), CP (coat protein) (ORF3) and RT (readthrough protein) (ORF3+5), respectively. CHN3 was closely related to the BRA, HAW and PER genotypes, differing by 1.7-3.8 % in the near-complete genome nucleotide sequence. Recombination analysis further identified CHN3 as a new recombinant strain, arising from the major parent CHN-HN1 and the minor parent CHN-GD-WY19. Recombination breakpoints were distributed mostly within the RdRp region in CHN3 and the four significant recombinant genotypes, IND, REU, CUB and BRA. Recombination is considered to contribute significantly to the evolution and emergence of such new SCYLV variants.

vNOTES is a feasible approach for sacrocolpopexy, with promising short-term efficacy and safety data. Larger studies across multiple sites and surgeons should evaluate the long-term efficacy and safety profile of vNOTES sacrocolpopexy.

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