Objective Sweetpotato leaf curl disease is an important disease affecting the production of sweetpotato. This study aims to monitor the occurrence and distribution of sweetpotato leaf curl disease in major sweetpotato production areas of Guangdong Province, and to clarify the genetic characteristics of the Guangdong population of sweetpotato leaf curl virus (SPLCV), providing a theoretical basis for the prevention and control of such disease.

Method From 2019 to 2023, systematic surveys were conducted in 4 major sweetpotato production areas of Guangdong Province, including Guangzhou, Maoming, Zhanjiang, and Shanwei. Suspected samples were collected, and the full-length genome sequences of SPLCV isolates were obtained by RCA amplification, molecular cloning, and sequence analysis methods. Further, biological software tools such as SDT, MEGA, RDP and DnaSP were utilized to analyze the genomic structural characteristics, full-length sequence similarity, phylogenetic analysis, recombination and population polymorphism between SPLCV Guangdong isolates.

Result The full-length genome sequences of three new SPLCV isolates were obtained from Guangzhou (GS01), Zhanjiang (GS02), and Maoming (MM01). Sequence analysis revealed that the genomic structure of the Guangdong population of SPLCV was generally consistent, all encoding six ORFs, but there were differences in the full-length genome sequences. The sequence similarity among the SPLCV Guangdong isolates ranged from 87.00% to 99.90%, with the GS01 isolate exhibiting significant sequence differences and low similarity (87.00% to 87.90%) to other isolates. Phylogenetic tree analysis also indicated that the GS01 isolate was genetically distant from the other six Guangdong isolates, clustering in different branches, suggesting that the source of the GS01 isolate was different from that of the other Guangdong isolates. Recombination analysis showed that no recombination occurred between SPLCV Guangdong isolates. Population polymorphism analysis revealed that the nucleotide diversity of SPLCV Guangdong isolates was 0.06544, with a relatively low degree of variation. Further selection pressure analysis of AV1, AV2, AC1, AC2, AC3, and AC4 genes of SPLCV Guangdong isolates revealed that AC4 gene experienced high selection pressure, within a state of diversity selection.

Conclusion The study found that sweetpotato leaf curl disease occurred in Guangzhou, Maoming, and Zhanjiang sweetpotato production areas in Guangdong Province, and there were certain differences in the SPLCV Guangdong population. AC4 gene mutation was the main cause of the variation in the SPLCV Guangdong population. At the same time, SPLCV was first detected in Maoming sweetpotato production area, indicating that the distribution of SPLCV in Guangdong Province is expanding and posing a threat to the safety of sweetpotato production. Therefore, it is necessary to strengthen the monitoring of SPLCV and the regulation of sweetpotato seedling transportation, timely control Bemisia tabaci in the field, to effectively control the occurrence and damage of sweetpotato leaf curl disease.