PCR-fingerprinting and RAPD approaches for tracing the source of yeast contamination in a carbonated orange juice production chain

Identification and characterization of epiphytic yeasts on apples in China

The first report regarding yeast diversity on apples from the two largest producing areas in China.

Two clonal lineages of Phytophthora citrophthora from citrus in South Africa represent a single phylogenetic species

Phytophthora citrophthora from citrus in eastern Corsica and Spain consists of distinct clonal lineages. In South Africa the extent of genetic variation among citrus-associated P. citrophthora isolates is unknown. This was investigated with isolates from South Africa (n =60), Spain (n =10) and six isolates representing three P. citrophthora groups CTR1, CTR2 and CTR3 previously identified with isozyme polymorphisms (Mchau and Coffey 1994). South African and Spanish isolates belonged to two lineages (G1, G2) based on an internal transcribed spacer (ITS) phylogeny, random amplified microsatellites (RAMS) and random amplified polymorphic DNA (RAPD) profiling. Although combined RAMS and RAPD data identified 14 genotypes, unweighted pair group method with arithmetic mean (UPGMA) analyses grouped the isolates into two clusters corresponding to lineages G1 and G2. Lineage G1 predominated among isolates from South Africa (92%) and Spain (100%). Phylogenetic analyses of the β-tubulin, cytochrome c oxidase subunit I (COX1) and ITS regions did not support the hypothesis that the two lineages represent distinct phylogenetic species but suggested that isozyme group CTR2 and possibly CTR3 are species distinct from P. citrophthora sensu stricto. Mating-type analyses, using tester strains from groups CTR2 and CTR3 revealed that most G1 lineage isolates (n =57) were sterile but that some were of the A1 mating type (n =8) whereas all G2 lineage isolates were A2 (n =5). The mating-type designation was confirmed with P. capsici tester strains. However, when A1 (G1 lineage) and A2 (G2 lineage including CTR1 reference isolates) mating-type isolates were paired in all possible combinations, no oogonia or antheridia were produced. This suggests that only tester strains P. capsici, CTR2 and CTR3 were able to produce sexual structures and that lineages G1 and G2 are sterile and reproductively isolated, which is supported by molecular data.

Outbreak of a New Phytophthora sp. Associated with Severe Decline of Almond Trees in Eastern Spain

Since 2007, a decline of young almond trees (Prunus dulcis) has been observed in different field-grown nurseries in Valencia (east-central Spain). Early symptoms in affected trees included chlorosis, wilting, cankers, and profuse stem gumming. A Phytophthora sp. was consistently isolated from cankers, roots, and soil of affected trees. It was a heterothallic species with amphigynous and/or paragynous antheridia, and its morphological features did not conform to any of the described Phytophthora species. Pathogenicity was proved by artificial inoculation, completing Koch's postulates. All isolates were sensitive to the phenylamide fungicides metalaxyl and mefenoxam. Amplification and sequencing of the internal transcribed spacer (ITS) region, translation elongation factor 1 alpha gene (EF-1α), the β-tubulin (β-tub) gene, and the region containing the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene fragment identified the species as Phytophthora taxon "niederhauserii", and phylogenetic analyses placed it in Phytophthora Clade 7b.

Analysis of genetic and virulence diversity of Cylindrocarpon liriodendri and C. macrodidymum associated with black foot disease of grapevine

Inter-simple sequence repeat (ISSR) analysis was used to investigate the genetic diversity of 87 Cylindrocarpon liriodendri and C. macrodidymum isolates, the causal agents of black foot disease of grapevine. The four ISSR primers (GT)7, (CCA)5, (CGA)5 and (TCG)5, were able to provide reproducible and polymorphic DNA fingerprint patterns and detected relevant genetic diversity in C. macrodidymum. The cluster analysis of ISSR data showed 21 different genotypes that were grouped in seven ISSR groups, from which two corresponded to C. liriodendri (G1 and G2) and five to C. macrodidymum (G3-G7). Nineteen isolates selected from the seven ISSR groups were inoculated in grapevine seedlings obtained from cv. 'Tempranillo'. The pathogenicity tests detected virulence diversity in C. macrodidymum. The isolates belonging to ISSR groups G6 and G7 were significantly more virulent than the other C. macrodidymum and C. liriodendri isolates.

Detection and identification of wild yeast contaminants of the industrial fuel ethanol fermentation process

Monitoring for wild yeast contaminants is an essential component of the management of the industrial fuel ethanol manufacturing process. Here we describe the isolation and molecular identification of 24 yeast species present in bioethanol distilleries in northeast Brazil that use sugar cane juice or cane molasses as feeding substrate. Most of the yeast species could be identified readily from their unique amplification-specific polymerase chain reaction (PCR) fingerprint. Yeast of the species Dekkera bruxellensis, Candida tropicalis, Pichia galeiformis, as well as a species of Candida that belongs to the C. intermedia clade, were found to be involved in acute contamination episodes; the remaining 20 species were classified as adventitious. Additional physiologic data confirmed that the presence of these major contaminants cause decreased bioethanol yield. We conclude that PCR fingerprinting can be used in an industrial setting to monitor yeast population dynamics to early identify the presence of the most important contaminant yeasts.