Potencial de resistencia a virus en especies silvestres de Solanum

Se evaluó la reacción de plántulas de 67 entradas de especies silvestres de Solanum a los virus: enrollamiento de la hoja (PLRV), virus Y de la Papa (PVY), virus X de la Papa (PVX), virus S de la Papa (PVS), virus Latente de los Andes (APLV), virus Moteado Andino (APMV) y al viroide del Tubérculo Ahusado (PSTVd). Se probaron: 33 entradas de Solanum acaule, 9 de S. bukasovii, 5 de S. colombianum, 2 de S. chomatofilum, 1 de S. coelestispetalum, 2 de S. marinasense, 2 de S. raphanifolium, 1 de S. tundalomense y 12 entradas no identificadas. Los estudios se realizaron entre 1980-1984 en las instalaciones del Centro Internacional de la Papa (CIP), La Molina, Lima-Perú. Por las reacciones observadas se establecieron tres categorías o tipos de reacción: susceptibilidad, tolerancia y alta resistencia. S. acaule resultó ser altamente resistente para PLRV, PVY (inoculación mecánica de jugo infeccioso), PVX y PVS. Para APLV, la entrada OCH-13389 (espécimen no identificado) se mostró con alta resistencia.

Molecular bases of the postzygotic barriers in interspecific crosses between the wild potato species Solanum acaule and Solanum commersonii

To investigate the molecular bases of postzygotic hybridization barriers in tuber-bearing Solanums, the wild species Solanum commersonii Dunal ex Poir. (cmm, 2n = 2x = 24, 1EBN) and Solanum acaule Bitter (acl, 2n = 4x = 48, 2EBN) were crossed in intra- and interspecific genotypic combinations, and the transcriptome of immature seeds was analyzed by using the cDNA-AFLP technique. From a total of 423 analyzed cDNA fragments, 107 (25.3%) were differentially regulated in the compatible (acl × acl and cmm × cmm) versus incompatible (acl × cmm) crosses. DNA sequence data were obtained from 21 fragments and RT–PCR analyses were carried out with five fragments to validate the cDNA-AFLP differential pattern. Sequence analysis suggested a possible role for the differentially expressed sequences in cytokinesis, cell cycle, secondary and hormonal metabolism, biodegradation, and transport. In situ hybridization experiments with fragments encoding an ubiquitin-fold modifier 1 precursor and a possible vesicle transport protein revealed expression of these genes in the embryo and endosperm. The results suggest that the collapse of the embryo and endosperm in incompatible crosses may be related to alterations in cell cycle and cytokinesis.

First Report of Seedborne Cherry leaf roll virus in Wild Potato, Solanum acaule, from South America

A virus, designated JCM-79, was isolated from wild potato (Solanum acaule Bitt.) plants grown from true seed received at USDA-APHIS Potato Quarantine Program from Peru. JCM-79 was mechanically transmissible to Nicotiana clevelandii and N. tabacum cv. Samsun NN. Symptoms in the original S. acaule were general chlorosis and spreading necrotic lesions. Symptoms in N. tabacum and N. clevelandii included necrotic ringspots on inoculated leaves and oak-leaf patterns or necrotic spots, respectively, on upper leaves. Cultivated potatoes (S. tuberosum) infected with JCM-79 by grafting from N. clevelandii were symptomless but virus was detected by back-inoculation to N. clevelandii. Viral nucleoproteins were purified by differential centrifugation and sucrose density gradient fractionation from N. clevelandii and N. tabacum. Transmission electron microscopy of nucleoproteins revealed isometric particles approximately 25 nm in diameter. Two RNA species of approximately 8,000 and 6,500 nucleotides were obtained from nucleoproteins digested with sodium dodecyl sulfate and Proteinase K. The above characteristics suggested JCM-79 was a nepovirus or nepovirus-like in nature. Reverse transcription (RT)-PCR tests for Cherry rasp leaf virus, genus Cheravirus, which was reported from potato (3), were negative. An approximately 1,600-bp cDNA clone was obtained from RNA of JCM-79 by oligo dT primed reverse transcription and second strand cDNA synthesis. Sequence analysis (GenBank No. GU321989) revealed the closest homology (82%) to nucleotides 327 to 1801 of Accession No. S84125 Cherry leaf roll virus (CLRV), genus Nepovirus. Subsequent RT-PCR tests with CLRV-specific primers (4) resulted in amplification of a 417-bp product from nucleic acid extracts of infected N. clevelandii and N. tabacum. The amplified product from N. clevelandii was cloned and three clones were sequenced in both directions. The consensus sequence (GenBank No. GU321988) showed approximately 90% homology to the 3′ untranslated region of isolates of CLRV including those from birch, walnut, and sweet cherry (GenBank Nos. S84124, Z34265, and AJ877128, respectively). JCM-79 was also detected in extracts of infected plants by ELISA using CLRV-cherry reagents (Bioreba AG, Reinach, Switzerland). These results indicate JCM-79 represents a new variant of CLRV. To our knowledge, this is the first report of CLRV naturally infecting S. acaule. S. acaule is common in the Andean regions of South America and has been used for crosses with S. tuberosum because of its pathogen resistance (1). The fact that JCM-79 is seed transmitted in S. acaule suggests that this virus could be a threat to potato-breeding programs. Another nepo-like virus with properties similar to JCM-79, designated Potato virus U (PVU), was reported from South America, but PVU was not serologically related to CLRV (2). References: (1) K. Hosaka and D. M. Spooner. Theor. Appl. Genet. 84:851, 1992. (2) R. A. C. Jones et al. Phytopathology 73:195, 1983. (3) J. R. Thompson et al. Arch. Virol. 149:2141, 2004. (4) B. Werner et al. Eur. J. For. Pathol. 27:309, 1997.