Temporal distribution and pathogenicity of the predominant tomato-infecting begomoviruses in Taiwan

Between 1998 and 2009, the four tomato-infecting begomovirus species detected in Taiwan were Ageratum yellow vein Hualien virus (AYVHuV), Tomato leaf curl Taiwan virus (ToLCTWV), Tomato yellow leaf curl Thailand virus (TYLCTHV) and a newly defined species Tomato leaf curl Hsinchu virus (ToLCHsV). AYVHuV was detected occasionally in 2003 and ToLCHsV only in 2000-2001, whilst ToLCTWV was detected throughout the period. TYLCTHV was first detected in 2005. Between 1998 and 2005, >99% of the begomovirus-positive samples were infected with ToLCTWV. In 2007 in western Taiwan, 16% of the positive samples were infected with ToLCTWV, 35% with TYLCTHV and 49% with mixed infection (ToLCTWV/TYLCTHV). In contrast, in eastern Taiwan the proportions were 84% ToLCTWV, 2% TYLCTHV and 14% mixed infection. However, throughout Taiwan in 2008-2009, most positive samples were either identified as TYLCTHV (51%) or mixed infection (ToLCTWV/TYLCTHV; 41%), and only 8% were ToLCTWV. This shows a clear trend of shifting from ToLCTWV to TYLCTHV and mixed infection over a short time period in Taiwan. Sequence analyses indicated that tomato-infecting AYVHuV, an apparent recombinant between ToLCTWV and AYVHuV from Ageratum, represents a new strain Hsinchu. TYLCTHV Taiwan isolates were highly similar to each other, whereas ToLCTWV isolates had greater diversity and were classified into three strains which had one country-wide and two local distributions. ToLCTWV and TYLCTHV were confirmed as monopartite and bipartite begomoviruses, respectively, by agroinfection followed by transmission with Bemisia tabaci biotype B. In addition, TYLCTHV was found to be mechanically transmissible together with viral DNA-B

Distribution and genetic diversity of begomoviruses infecting tomato and pepper plants in the Philippines

Begomoviruses were found to be the major viruses infecting tomato plants in the Philippines based on the surveys conducted from 2005 to 2006. Pepper-infecting begomoviruses were also detected. Isolates of four distinct begomovirus species, Ageratum yellow vein virus (AYVV), Tomato leaf curl Cebu virus (ToLCCeV), Tomato leaf curl Mindanao virus (ToLCMiV) and Tomato leaf curl Philippines virus (ToLCPV), were characterised at the DNA sequence level by comparing 20 DNA-As from tomato samples comprising 13 from Luzon, 2 from Cebu and 5 from Mindanao Islands, along with 3 DNA-As from pepper samples, 1 each from Luzon, Cebu and Mindanao Islands. Two of these species (ToLCCeV and ToLCMiV) were distinct novel begomoviruses, while AYVV was detected for the first time in the Philippines. By geographic distribution, two tomato begomoviruses (ToLCPV and ToLCCeV) were detected in Luzon and Cebu Islands. The ToLCMiV was also detected in Luzon Island. The three tomato begomoviruses, AYVV, ToLCCeV and ToLCMiV, were detected in Mindanao Island. A ToLCPV isolate infecting pepper was also detected in Luzon Island, while ToLCCeV was detected in pepper samples from Cebu and Mindanao Islands. The diversity of viruses and their distinct geographic distribution need to be taken into consideration in the development and deployment of resistance against begomoviruses in the Philippines. Strategies for the use of post-transcriptional gene silencing for the control of tomato-infecting begomoviruses in the Philippines are discussed