Prepenetration stages in infection of clematis by Phoma clematidina

A detailed study of conidial germination, germ-tube growth and the formation of infection structures in Phoma clematidina , the causal agent of clematis wilt, is described for two clematis varieties differing in disease resistance. On both the resistant and susceptible varieties, the fungus entered leaves and stems by direct penetration of the cuticle, often, but not always, following the formation of infection structures. More germ tubes per conidium were formed on the susceptible host, but these germ tubes were on average shorter than on the resistant host. Although germ tubes regularly entered the plant via trichomes, stomata were not found to be sites of entry. Following penetration of the cuticle of resistant plants, germ-tube growth was sometimes restricted to the subcuticular region, and halo formation occurred at the sites where penetration was attempted. Subcuticular growth and halo formation were not observed on susceptible plants. These observations may partly explain the resistance of small-flowered clematis varieties to P. clematidina .     

Construction of a cDNA library of Bemisia tabaci for use in the ''yeast two-hybrid screen'' method

Bemisia tabaci was reported for the first time in the Mediterranean part of Croatia in 2000. It was found in glasshouses in the agricultural area between the towns of Trogir and Omis, on the following crops: Euphorbia pulcherrima , Thunbergia grandiflora , Cucumis sativus (cucumber), Solanum melongena (aubergine), Phaseolus spp. (beans), Ficus carica (fig), Rubus spp. and several weeds of the families Asteraceae and Solanaceae . In 2001, monitoring for the pest was organized all over the country, in each of the 21 counties. In each county, there were several monitoring points so that all the major vegetable and flower producers were included. A special effort was made to record the spread of B. tabaci in the region where it was first found, bearing in mind that optimal conditions for outdoor spread exist along the Adriatic coast. Yellow sticky traps and visual inspection are used to monitor for B. tabaci . Eradication measures are being applied, and regulatory measures have been taken to prevent further spread of B. tabaci to continental parts of Croatia.     

Genetic analyses of resistance of the wheat differential cultivars Carstens V and Spaldings Prolific to two races of Puccinia striiformis

Genetic analysis of resistance of wheat seedlings to two races of Puccinia striiformis was conducted on F₁, F₂ and F₃ generations from crosses Carstens V (CV) × Lee, Spaldings Prolific (SPA) × Lee and CV × SPA. F₂ generations from crosses of CV and SPA with Strubes Dickkopf (SD) were also studied. The plants were classified into six resistance classes and analysed by factorial correspondence analysis and nonhierarchical classification. The two P. striiformis isolates tested were a French isolate of race 43E138 and a Lebanese isolate of race 2E16, selected for the differences in their virulence spectra for the common differential cultivars Strubes Dickkopf and Nord Desprez. Resistance of CV and SPA was recessive and dominant to races 43E138 and 2E16, respectively. CV possessed three or four resistance genes, one of them being expressed with both races. Two genes of CV had a cumulative effect for resistance to 43E138 and two or three gave dominant resistance to 2E16. SPA had three resistance genes, all of which gave resistance to 2E16 and two of which also gave resistance to 43E138. SPA had one gene in common with CV for resistance to both races. Furthermore, the gene for resistance to race 2E16 in CV and SPA was allelic with a gene in SD, and was probably Yr25 .