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Chickpea chlorotic dwarf virus (CpCDV) a polyphagous mastrevirus, family Geminiviridae, is reported to infect several economically important hosts, among which tomato, in numerous world areas. NGS studies have recently linked the "hard fruit syndrome" of watermelon to CpCDV infection. In this study, we surveyed for CpCDV infection tomato fields in several Tunisian areas and we report this virus for the first time in tomato in this Mediterranean country. We detected CpCDV by PCR with specific primers and obtained a full-length sequence of a tomato-derived isolate, resulting identical to the Tunisian watermelon-derived isolate, and classifiable as CpCDV strain A. Following tomato agro-inoculation of the CpCDV infectious clone under controlled conditions, we checked infection by stem squash, dot blotting and PCR, and demonstrated the ability of CpCDV to replicate in tomato tissues. The alterations observed in fruits of CpCDV-infected tomatoes were similar to those previously described for watermelon, providing hints about the perturbation of fruit development mediated by this virus.

Viruses, distributed worldwide on cucurbits, cause severe damage to crops. Virus surveys in 2003 and 2004 were made in all the major cucurbit-growing areas in Tunisia. Large populations of aphids (Aphis gossypii Glover) and severe yellowing symptoms of older leaves of cucurbits were observed in outdoor and under plastic-tunnel cultivation, suggesting the presence of Cucurbit aphid-borne yellows virus (CABYV, genus Polerovirus, family Luteoviridae). Leaf samples collected from symptomatic and asymptomatic plants of melon (Cucumis melo L.), cucumber (C. sativus L.), squash (Cucurbita pepo L.), watermelon (Citrullus lanatus L.), and ware cucurbit (Ecballium elaterium L. T. Richard) were screened for the presence of CABYV using enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR). Reference isolate, CABYV-N (GenBank Accession No. X76931) was provided by H. Lecoq (INRA-Monfavet Cedex, France). Sample extracts from fresh leaf tissues were tested using ELISA with an antiserum prepared against this isolate. In addition, total RNA was extracted from fresh leaf tissues according to the technique of Celix et al. (2) using the Titan RT-PCR kit from Roche Diagnostics (Penzberg, Germany). Forward primer (5′-GAGGCGAAGGCGAAGAAATC-3′) and reverse primer (5′-TCTGGACCTGGCACTTGATG-3′) were designed with the available sequence of the reference isolate. ELISA tests demonstrated that 91 plants were positive among 160 plants tested with severe yellowing symptoms. All asymptomatic plants were negative. RT-PCR results yielded an expected 550-bp product that was amplified from the reference isolate. Of the 160 plants tested using ELISA, 106 plants were screened with RT-PCR including the 91 plants that were positive in ELISA. These 91 plants also were positive after RT-PCR amplification as were 12 more plants. This demonstrated that the RT-PCR test is more sensitive. No amplicons were produced from extracts of asymptomatic plants, RNA preparations of Cucurbit yellow stunting disorder virus (CYSDV), or Beet pseudo yellows virus (BPYV) positive controls provided by B. Falk (University of California, Davis). CYSDV and BPYV can induce similar yellowing symptoms in cucurbits. The results of the ELISA and RT-PCR tests showed that CABYV is widely distributed on five cucurbit species in the major growing areas of Tunisia including the northern, Sahel, central, and southern regions where it was detected, respectively, in 10 of 25, 11 of 21, 24 of 37, and 58 of 77 samples tested. CABYV was detected at the rates of 63 of 72 on melon, 10 of 21 on cucumber, 17 of 24 on squash, 10 of 25 on watermelon, and 3 of 18 on ware cucurbit. CABYV also seems to be widespread throughout the Mediterranean Basin (1,3,4), but to our knowledge, this is the first report of the occurrence of CABYV in Tunisia on different species of cucurbit and ware cucurbit. References: (1) Y. Abou-Jawdah et al. Crop Prot. 19:217, 2000. (2) A. Celix et al. Phytopathology 86:1370, 1996. (3) M. Juarez et al. Plant Dis. 88:907, 2004. (4) H. Lecoq et al. Plant Pathol. 41:749, 1992.

In Tunisia, watermelon (Citrullus lanatus) is one of the most common and popular summer fruit crops. The crop is widely cultivated in the central and southern parts of the country with a yearly production of about 400,000 tons. Hard fruit syndrome of watermelon is a well-known syndrome, reported in Tunisia since 1994, when up to 70% incidence was reported in some areas; in recent years, the incidence ranged between 10 and 40%, leading growers to switch to alternative crops. The etiology of the hard fruit syndrome of watermelon is uncertain up to now, but two begomoviruses (Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus) have been recently found associated with this syndrome (Mnari-Hattab et al. 2014), suggesting a viral etiology for symptoms initially attributed to physiological and/or nutritional disorders. Between 2005 and 2015, watermelon fields were surveyed in different areas of Tunisia (Kairouan, Zaghouan, Gabes, Gafsa, and Beja). Samples were collected from unmarketable fruits exhibiting chlorotic mottling on rind and white hard portions inside the flesh. Total DNA from 11 samples were subjected to rolling circle amplification using ?29 DNA polymerase (TempliPhi kit, GE Healthcare, Little Chalfont, U.K.). A single DNA fragment of about 2,500 bp was obtained following SpeI digestion from three samples. The SpeI-cut DNA derived from a sample collected in Zaghouan Province in 2015 was cloned in pBluescript KS(+) and fully sequenced in both directions. The sequence was 2,571 nt long and exhibited the genomic organization typical of mastreviruses. Alignment analysis against 63 mastrevirus genome sequences using STD program (Muhire et al. 2013) showed high nucleotide sequence identity values with Chickpea chlorotic dwarf virus (CpCDV) genome isolates (about 86%), with the maximum identity score of 98% with an isolate from chickpea collected in Syria (FR687959); identity percentage toward other mastreviruses was less than 70%. The new CpCDV sequence was submitted to GenBank under accession number KX580024. A primer pair CpCDV-CP-F (5?-GCAGAATCAAGGGCGAAGAG-3?) and CpCDV-CP-R (5?-CGGACCGGGACCATAGTAAG-3?) was used to check for CpCDV infection in field watermelon samples; 10 of 11 samples were positive in PCR amplifying a 501-bp diagnostic fragment in the coat protein gene. PCR analyses were also conducted for 39 additional watermelon samples collected in Kairouan (21 samples), Gafsa (4 samples), and Zaghouan (14 samples), the main growing areas in Tunisia, during 2005, 2014, and 2015. Thirty-two of them tested positive for CpCDV. A 1.8-mer construct was engineered in the binary plasmid pBin19, used to transform Agrobacterium tumefaciens LBA4404, and then used to challenge Nicotiana benthamiana plants in infectivity assays. Symptoms of downward leaf curling were observed at 7 days post inoculation in upper uninoculated leaves that later became crumpled, with the plant exhibiting marked chlorosis and dwarfing. CpCDV infection was confirmed by tissue print hybridization using a digoxigenin-labeled probe. CpCDV infecting several species has been reported from many tropical and subtropical countries and was recently found in Tunisia on chickpea (Kumari et al. 2015). To our knowledge, this is the first report of CpCDV infecting watermelon. The finding of CpCDV in samples with the hard fruit syndrome adds an unexpected piece to the complex puzzle of its etiology issue.

In late summer 2017, a serious decline and dieback of plum trees was observed in many orchards in Tunisia. Black Star and Sun Gold were the varieties most affected, with an incidence of up to 20%. Symptoms include shoot blight with …

Surveys of yellowing viruses under nonheated and geothermal heated plastic tunnels and in open field crops of melon (Cucumis melo), cucumber (C. sativus), zucchini (Cucurbita pepo), squash (C. maxima), watermelon (Citrullus lanatus), and ware cucurbit (Ecballium elaterium) were carried out year-round during 2000–2001, 2003, and 2004 in the major cucurbit-growing areas in Tunisia. Severe yellowing symptoms on older leaves of cucurbits were observed in open fields and under plastic-tunnel production systems. These yellowing symptoms and large populations of aphids (Aphis gossypii) on a diversity of cucurbit crops in Tunisia support the hypothesis of a viral cause of the disease. Virus identification using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), followed by reverse transcription–polymerase chain reaction (RT-PCR) and immunocapture (IC)-RT-PCR showed that Cucurbit aphid-borne yellows virus (CABYV) was largely distributed in melon, cucumber, zucchini, squash, and watermelon crops. Ware cucurbit (E. elaterium) and lettuce (Lactuca sativa) crops were identified as potential CABYV reservoirs. The RT-PCR-amplified partial coat protein (CP) and P4 genes were cloned and sequenced from nine Tunisian CABYV isolates. CP and P4 gene nucleotide and amino acid sequence comparisons as well as phylogenetic reconstructions showed that the Tunisian isolates clustered into two major subgroups. Comparisons with CABYV sequences retrieved from GenBank showed high nucleotide and CP amino acid identities, and close relationships of the Tunisian isolates with Italian and French isolates.

Les cucurbitacees sont economiquement importantes en Tunisie, elles sont sujettes a plusieurs maladies virales qui ont des effets nefastes sur les rendements et la valeur marchande de la production. Des symptomes de mosaiques severes sur les feuilles ont ete observes dans toutes les cultures de cucurbitacees de plein champ et sous abris. Des prospections (2000–2001, 2002–2003) ont ete realisees afin de tenter d’identifier les virus responsables de ces symptomes. Les echantillons symptomatiques ont ete collectes dans les regions majeures de production des cucurbitacees et testes par DAS-ELISA pour la presence des virus suivants: ZYMV, WMV, MWMV, PRSV-W, ZYFV CMV, SqMV et MNSV. Cette etude a confirme la presence de six virus (WMV, CMV, PRSV-W, ZYMV, ZYFV et SqMV) deja decrits avec une evolution tres remarquable de la frequence du ZYMV dans toutes les regions prospectees et sur toutes les especes testees. Le pourcentage d’infection a atteint les 34% durant les prospections (2002–2003). Par contre le MWMV s’est revele absent au niveau de tous les echantillons testes. Par ailleurs, nous avons mis en evidence pour la premiere fois la presence du MNSV dans plus de 9% des echantillons testes et ce sur melon de plein champ et sous abris, sur courge et sur pasteque. En outre, nous rapportons pour la premiere fois l’infection d’une cucurbitacee sauvage, Ecballium elaterium, par le CMV, PRSV-W et WMV. Les resultats ont montre aussi qu’un pourcentage d’echantillons montrant des symptomes de mosaiques n’a pas ete explique par la presence de l’un ou l’autre des virus etudies. Ceci pourrait s’expliquer par l’existence d’autres virus ou de facteurs abiotiques qui restent a identifier.

Date palm (Phoenix dactylifera) is of significant economic importance and represents a key source of income to many farmers in southern Tunisia. Various biotic and abiotic factors such as pests, diseases and weather conditions affect date …

Strawberry is an annual crop along the coastal areas of northern Tunisia grown in plastic tunnels and in open fields. Charcoal rot in strawberry usually occurs after the plants are well established and begin to produce fruit: the roots …

Due to the favourable climate of the southern Mediterranean countries including Tunisia, cucurbits are grown year-round in open fields, and unheated and geothermally heated plastic tunnels. In January 2015, a serious disease affecting many…

In Tunisia, tomato ( Solanum lycopersicum ) is the most widely cultivated all year-round vegetable crop. Since 2011 abnormal yellowing symptoms have been observed on field grown tomato crops in Kairouan, a major growing area in Tunisia. …

In Tunisia, watermelon ( Citrullus lanatus ) is one of the most common and popular summer fruit crops, and is widely cultivated in the central and southern parts of the country. Since 1994, abnormal symptoms have been observed on fruits by …

The Tunisian citrus industry covers 18 000 ha localized mainly along the coast of the Mediterranean sea. The major phytosanitary problem is ‘mal secco’ of lemon trees, a dieback caused by Phoma tracheiphila . This fungal disease has been observed in Tunisia since 1953 (Crossa-Raynaud, 1960). Different symptoms occur on the tree depending upon whether P. tracheiphila attacks via the roots or shoots. The disease is named ‘mal nero’ when infection begins at the basal part of trees (trunk, roots) with a rapid progression of symptoms and browning of the hardwood may occur (Perrotta & Graniti, 1988; Solel & Salerno, 2000). During surveys in Cap Bon region of Tunisia in 2007, decline of mandarin (cv. Cassar) and orange (cv. New Hall) grafted on sour orange rootstock was observed in some orchards characterized by a heavy soil. Symptoms included a general collapse of the tree with leaves remaining attached. A transversal section of the dead tree trunk showed necrotic coloration of the hardwood. The same symptoms have been described in Italy by Perrota & Graniti (1988). Consistent fungal colonies, isolated from necrotic woody tissue producing pycnidia and pycnidiospores, were identified as P. tracheiphila . The identification of the pathogen was confirmed by PCR technique using the primer pair Pt-FOR2 + Pt-REV2 developed by Balmas et al . (2005) for detecting P. tracheiphila on infected lemon tissues. A pathogenicity test was conducted using susceptible 1-year-old sour orange plants grown in pasteurized potting medium. Mycelial plugs of two isolates each were inoculated separately into the basal stem of 10 sour orange plants. Ten non-inoculated plants were used as controls. Plants were grown in the greenhouse at 25 ° C, where they all developed typical disease symptoms after 45 days. Non-inoculated controls did not develop disease symptoms. Phoma tracheiphila was re-isolated from all diseased plants. This is the first report of ‘mal nero’ disease occurring naturally on mandarin and orange trees and the first time this disease has been reported in Tunisia. The Tunisian citrus industry is mostly grown on sour orange rootstocks, and therefore, ‘mal nero’ represents a serious threat.