Citrus leprosis (CL) is a serious threat to the citrus industry, especially for sweet oranges. For a long time, Citrus spp. were considered the only susceptible hosts. However, other plant species were also found either experimentally or naturally to be susceptible to Citrus leprosis virus C (CiLV-C). To assess the experimental host range of CiLV-C, a large number of plant species were inoculated with Brevipalpus phoenicis, viruliferous to CiLV-C, under experimental conditions. Out of the 140 tested species (43 families), 59 species (24 families) developed localized chlorotic and/or necrotic lesions upon inoculation of leaves with viruliferous mites, and 40 species (18 families) of them yielded positive results for CiLV-C detection in at least one of the following assays: ELISA, RT-PCR, transmission electron microscopy and immunfluorescence. For those that developed lesions and yielded negative results in CiLV-C detection assays, the results may be attributed to the small number of lesions and their necrotic state with very little viral material. The fact that a considerable number of plant species are susceptible to the virus after mite inoculation brings up implications for the epidemiology, quarantine and evolution of the citrus leprosis pathosystem.

Coffee plants exhibiting a range of symptoms including mild to severe curling of leaf margins, chlorosis and deformation of leaves, stunting of plants, shortening of internodes, and dieback of branches have been reported since 1995 in several regions of Costa Rica's Central Valley. The symptoms are referred to by coffee producers in Costa Rica as "crespera" disease and have been associated with the presence of the bacterium Xylella fastidiosa. Coffee plants determined to be infected by the bacterium by enzyme linked immunosorbent assay (ELISA), were used for both transmission electron microscopy (TEM) and for isolation of the bacterium in PW broth or agar. Petioles examined by TEM contained rod-shaped bacteria inside the xylem vessels. The bacteria measured 0.3 to 0.5 microm in width and 1.5 to 3.0 microm in length, and had rippled cell walls 10 to 40 nm in thickness, typical of X. fastidiosa. Small, circular, dome-shaped colonies were observed 7 to 26 days after plating of plant extracts on PW agar. The colonies were comprised of Gram-negative rods of variable length and a characteristic slight longitudinal bending. TEM of the isolated bacteria showed characteristic rippled cell walls, similar to those observed in plant tissue. ELISA and PCR with specific primer pairs 272-l-int/272-2-int and RST31/RST33 confirmed the identity of the isolated bacteria as X. fastidiosa. RFLP analysis of the amplification products revealed diversity within X. fastidiosa strains from Costa Rica and suggest closer genetic proximity to strains from the United States of America than to other coffee or citrus strains from Brazil.

Garita, L. C, Tassi, A. D., Calegario, R. F., Kitajima, E. W., Carbonell, S. A. M., and Freitas-Astúa, J. 2013. Common bean: Experimental indicator plant for Citrus leprosis virus C and some other cytoplasmic-type Srev;/>a//JMi-transmitted viruses. Plant Dis. 97:1346-1351.Citrus leprosis (CL) caused by Citrus leprosis virus C (CiLV-C) is present in Latin America from Mexico to Argentina, where citrus plants are grown. CiLV-C is transmitted by the tenuipalpid mite, Brevipalpus phoenicis, causing localized lesions on citrus leaves, fruit, and stems. One limitation to study of the virus-vector-host relationship in this pathosystem is the lack of a suitable assay plant. On Citrus spp. used as susceptible hosts, symptoms may take weeks or months to appear after experimental inoculation by viruliferous mites. Common bean (Phaseolus vulgaris) was found to respond with localized necrotic lesions after inoculation with viruliferous B. phoenicis in 5 days. Thus far, 113 tested common bean varieties and lines and some recent accessions of varied genetic background behaved in a similar way.

Dry common bean plants (Phaseolus vulgaris) from the main production regions of Costa Rica have been affected by a disease, locally called 'amachamiento'. Main symptoms are a severe loss of bean pods due to flowering reduction or abortion, interveinal chlorosis, deformed leaves with corrugated midrib; with diseased plants remaining green at harvest. Morales et al. (1999) associated 'amachamiento' to Cowpea chlorotic mottle virus (CCMV), but CCMV was shown not to induce such symptoms in bean (Gá mez, 1976). A total of 104 plants with symptoms were collected and analyzed by DAS-ELISA for CCMV, and also three comoviruses and five potyviruses commonly infecting P. vulgaris. Negative DAS-ELISA results were shown by 57% of plants for all viruses studied. Nested PCR with universal 16S rRNA phytoplasma primers (P1 ⁄ P7 and R16R2-R16F2n) was used to search for phytoplasma in those symptom-bearing plants negative for DAS-ELISA, and three symptomless plants. R16R2-R16F2n PCR products of 1AE2-kb were amplified from more than 60 plants with symptoms, but not from the symptomless plants. RFLP patterns with RsaI, HhaI, KpnI, BfaI, HaeIII, HpaII, AluI, and MseI characterized the

Since the late 1990s, chlorotic mottling, marginal scorch, deformation of leaves, defoliation, shortening of internodes, and branch dieback have been observed in avocado trees (Persea americana Mill.) in Costa Rica. The symptoms are not uniformly distributed in the tree, so some branches are symptomatic while others are not. These symptoms are similar to several leaf scorch diseases caused by the bacterium Xylella fastidiosa Wells (2,4). This bacterium has been detected in coffee and citrus plants in Costa Rica. Of 227 avocado trees tested by double-antibody sandwich (DAS)-ELISA with X. fastidiosa specific antiserum (Agdia Inc., Elkhart, IN) from 2000–2004, 188 were positive. Results of ELISA tests of individual trees varied with the season and branches tested. Fifteen greenhouse-grown, ELISA-negative avocado seedlings were grafted with budwood from an ELISA-positive tree. Eight of these developed scorch symptoms and one also showed chlorotic mottling and deformation, showing that the disease is graft transmitted. All of these features are characteristic of diseases caused by X. fastidiosa (2,4). Transmission electron microscopy of leaf petioles from three field trees positive by ELISA, revealed rod-shaped bacilli approximately 1.6 to 2.0 μm long and 0.3 μm in diameter with a rippled cell wall inside xylem vessels and embedded in a matrix; morphology and measurements that are consistent with those reported for X. fastidiosa (2). DNA extraction and PCR attempts have been limited by mucilaginous sap from avocado. Positive PCR results (approximately 472-bp band) were obtained from two of the grafted seedlings and seven field trees from two distinct geographical locations (Alajuela and San José provinces) with DNA extractions from the plant sap using DNeasy Plant Mini Kit (Qiagen GmbH, Hilden, Germany) following a modified protocol (1) and nested PCR (3). Four of the PCR products, including one from the grafted seedlings, were cloned and sequenced in duplicate. GenBank sequences EU021997 to EU022000 present 99 to 100% sequence identity to a Pierce's disease strain from California (Temecula1) and 94 to 95% to a citrus variegated chlorosis strain from Brazil (Found-5). Several attempts have been made to isolate the bacterium in ‘periwinkle wilt’ and buffered cysteine-yeast extract media with negative results, probably because of the rapid production of mucilaginous sap when the avocado tissues were sampled. To our knowledge, this is the first report of X. fastidiosa in avocado trees. References: (1) M. J. Green et al. Plant Dis. 83:482, 1999. (2) S. S. Hearon et al. Can. J. Bot. 58:1986, 1980. (3) M. R. Pooler and J. S. Hartung. Curr. Microbiol. 31:377, 1995. (4) A. H. Purcell et al. Phytopathology 89:53, 1999.