First Report of the Presence of Tomato apical stunt viroid on Tomato in Sénégal

Abstract

Tomato apical stunt viroid (TASVd) was initially discovered in the Ivory Coast (2). It was later reported in Indonesia and more recently was found to be responsible for severe outbreaks in protected tomatoes in Israel (1) and Tunisia (3). Although not of quarantine status, TASVd is included in the EPPO alert list. In 2005, severe arrest of apical growth and leaf chlorosis were observed in tomato samples from northern Sénégal. Tomato yellow leaf curl virus was initially identified in some samples, but since the symptoms observed were reminiscent of those associated with viroid infection, samples were analyzed by return-polyacrylamide gel electrophoresis and molecular hybridization with a Potato spindle tuber viroid (PSTVd) probe. Positive results prompted a reanalysis by reverse transcription-PCR assays specific for PSTVd or TASVd. Positive amplification was only obtained with the TASVd-specific primers (Vir+ GGGGAAACCTGGAGGAA and Vir- GGGGATCCCTGAAGGAC), and the identity of the viroid confirmed by sequencing of the amplified fragment. The complete genome sequence obtained (GenBank Accession No. EF051631) shows 94 to 96% identity with other TASVd sequences in the databases, the highest homology being with the original Ivory Coast isolate (96%, 11 mutations, and 4 indels for the 362-nt genome). These results provide new information on the diversity of TASVd and of its detrimental potential for tomato crops and represent, to our knowledge, the first report of the presence of TASVd in Sénégal. References: (1) Y. Antignus et al. Phytoparasitica 30:502, 2002. (2) C. R. Walter. Acad. Sci. 292:537, 1981. (3) J. Th. J. Verhoeven et al. Plant Disease 90:528, 2006.

Viroid-infected Tomato and Capsicum Seed Shipments to Australia

“…Pospiviroid infections have been reported in capsicum and tomato crops internationally, and before Australia imposed mandatory testing there were several incursions of PSTVd in Australian crops, as well as one PCFVd incursion [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 12 , 13 , 14 , 15 , 16 , 17 , 26 ]. Given the numbers of infected seed lots detected in tests reported here, it is reasonable to infer that crop infections in Australia and elsewhere were caused by infected seed.…”

“…Others have argued that commercially produced vegetable seeds are unlikely to be responsible for most outbreaks of pospiviroids [ 10 , 52 ]. We believe that the evidence [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 42 , 43 ] indicates infected seed is responsible for long-distance transport of pospiviroids and for moving these pathogens to areas where previously they were not present, even though the rate of seed-transmission is probably low. Our study added another dimension to the weight of evidence by indicating a route of transport that is active, and indicating the potential for invasion is real.…”

“…Trade in plant materials, especially seeds, tissue cultures and nursery stock, can spread pathogens, changing their epidemiology and geographic distribution. Pospiviroids are emerging pathogens with several species discovered in solanaceous crop plants in the past 20 years, and more species are spreading to countries and continents where they have not been previously recorded [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. Pospiviroids have been detected in cultivated ornamental plants in nurseries, and it was proposed that ornamental plants are the source of the infections in crops [ 10 , 11 ].…”

Rasta Disease of Tomato in Ghana is Caused by the PospiviroidsPotato spindle tuber viroidandTomato apical stunt viroid

“…A viroid etiology for this disease is fully consistent with (i) failure to detect common tomato-infecting viruses in plants with rasta symptoms, (ii) the type of disease symptoms (i.e., severe stunting; epinasty, crumpling, and chlorosis of leaves; and necrosis of leaf veins, petioles, and stems), (iii) the infectious nature of RNA extracts from symptomatic leaf samples, and (iv) the development of rasta-like symptoms in tomato plants (Early Pak 7) mechanically inoculated with sap prepared from leaves of PSTVd-or TASVd-infected tomato plants. Although these viroids have been previously reported to infect tomato in other countries in Africa (Candresse et al 2007;OEPP/EPPO 2014;Walter 1981Walter , 1987, this is the first report from Ghana (note that an abstract of this work has been published by ). Taken together with our previous report that CLVd induces rasta-like symptoms in tomato in Mali and the subsequent detection of CLVd in a rasta sample from Ghana (data not shown) (Fig.…”

“…Over the past two decades, outbreaks of pospiviroids in tomato and pepper have been reported causing economic losses from many countries of the world, including Australia, China, the Dominican Republic, Israel, India, Japan, New Zealand, Thailand, and several countries in North and South America and Europe (Antignus et al 2002;Candresse et al 2010;Hailstones et al 2003;Lebas et al 2005;Ling and Bledsoe 2009;Ling and Sfetcu 2010;Ling and Zhang 2009;Ling et al , 2013Ling et al , 2014Matsushita et al 2008;Mishra et al 1991;Navarro et al 2009;Parrella and Numitone 2014;Pearson et al 2006;Reanwarakorn et al 2011;Singh et al 1993;Verhoeven et al 2004). In Africa, the first viroid reported to infect and cause yield loss in tomato was TASVd (Walter 1981(Walter , 1987, and it was recently reported infecting tomato plants in greenhouse production in Senegal (Candresse et al 2007). More recently, CLVd was reported causing severe symptoms in tomato plants in open fields in Mali .…”