ABSTRACT
Isolates of Rhizoctonia spp. were obtained during the spring of 2007 from diseased cotton and tobacco seedlings showing damping-off symptoms. The sampled fields were located in the main cotton- and tobacco-cultivating regions of central and northern Greece. Among the 79 isolates obtained from cotton plants, 17 were binucleate and 62 were multinucleate whereas, among the 89 isolates obtained from tobacco plants, 87 were multinucleate and only 2 were binucleate. Characterization of anastomosis groups (AGs) was performed with hyphal anastomosis reactions using tester isolates of known AG groups. Anastomosis reactions in cotton mutlinucleate isolates showed that 54 of them belonged in Rhizoctonia solani AG-4, 6 in AG-7, 1 in AG-2, and 1 in AG-3. In the 87 tobacco multinucleate isolates, anastomosis reactions showed that 70 of them belonged in R. solani AG-2, 16 in AG-4, and 1 in AG-5. In addition, molecular characterization was carried out using the specific ribosomal DNA internal transcribed spacer region, in a randomly selected number of isolates. In cotton, the most prevalent AG was AG-4, with 18 isolates to the subgroup HG-I, 1 isolate to the subgroup HG-II, and 7 isolates to the subgroup HG-III, followed by AG-7 (7 isolates), AG-2-1 (1 isolate), and AG-3 (1 isolate). In tobacco, the most prevalent group was AG-2-1 (70 isolates), followed by AG-4 (6 isolates to the subgroup HG-I and 5 isolates to the subgroup HG-III) and a single isolate belonging to AG-5. Phylogenetic analysis showed that the isolates were distinctly separated based on their AG types. Pathogenicity and aggressiveness of the isolates to several hosts was determined. AG-4 isolates from either cotton or tobacco were the most aggressive on the hosts tested, while AG-2-1 isolates were of moderate aggressiveness and were not pathogenic on barley.
ABSTRACT
Thirty-five Colletotrichum lindemuthianum isolates were obtained from bean (Phaseolus vulgaris) fields in 23 prefectures of Greece during a survey conducted in 2003 and 2004. Race characterization based on the standardized set of 12 differential cultivars demonstrated the presence of races 2, 6, and 22, which are reported for first time in Greece, while race 22 is reported for the first time in the world. In addition, pathotype diversity showed significant correlation with the geographical origin of these isolates. All three races caused disease symptoms only on cultivars of Andean origin, suggesting that Greek isolates originated from South American countries. Virulence spectrum of the same isolates was also examined on a set of 30 Greek bean cultivars showing seven types of virulence. Based on their reactions to the pathogen isolates, Greek cultivars were divided into nine groups. Among these cultivars, two (Ithomi FS60 and Larisa) were resistant to all tested isolates, including the reference isolates. Molecular diversity was detected using random amplified polymorphic DNA (RAPD) primers and the restriction fragment length polymorphism (RFLP) analysis of the ribosomal DNA internal transcribed spacers, which revealed two main clusters of isolates. Thirty-two out of 35 isolates belonged to the same main cluster in both methods, indicating that Greek isolates have genotypic similarities. This study provides the information on population diversity of C. lindemuthianum, which can be useful in agricultural practices and in plant breeding programs.
ABSTRACT
Contrary to other genetic disorders, the genetic study of sex determination anomalies in humans stumbles over the difficulty in observing large pedigrees. In goats, abnormalities in sex determination are intimately linked to a dominant Mendelian gene coding for the "polled" (hornless) character, which could render this species an interesting animal model for the rare human cases of SRY-negative XX males. In this report, we describe genetic linkage between the polled/intersex synchome (PIS) and four microsatellite markers of the distal region of goat Chromosome 1 (CHI1), quite distinct from the bovine "polled" region. According to comparative mapping data, no sex-determining gene has been described so far in homologous regions in the human. This genetic localization constitutes a first step towards identifying a new autosomal sex-determining gene in mammals.
