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Tetraploid plants were produced by inducing chromosome doubling using colchicine in in vitro shoot tips of poplar and black locust clones. Many of the plants treated with colchicine showed modified morphological characteristics like stunted growth, thicker leaves and modified leaf morphology. The counting of chloroplast number in the epidermal guard cells of stomata was used for the rapid screening of tetraploids. The differences in mean chloroplast numbers between diploid and tetraploid plants were highly significant. For all plants tested, the tetraploid genotype had almost double the number of chloroplasts per guard cell compared to the diploid origin. Some plants were further analysed by flow cytometry to verify their ploidy status that was determined by chloroplast numbers. The results of this study demonstrated for the first time that chloroplast counting in poplar and black locust could be an effective and reliable method for prescreening large numbers of plants for their ploidy level. The protocol might be applicable in a wide scope of breeding programs.

Musa acuminata Colla (AA genomes) and Musa balbisiana Colla (BB genomes) are the wild progenitors of the cultivated banana, they are highly variable in Thailand. The genetic system is relatively unknown and complicated due to interspecific hybridization, heterozygosity and polyploidy, which are common in most clones. These factors make identification of closely related banana cultivars difficult, especially when sterile. The high annealing temperature-random amplified polymorphic DNA (RAPD) technique was used to estimate the genetic relationship between 22 selected banana cultivars, utilizing 14 random primers. Phylogenetic relationship was determined by unweighted pair group method with arithmetical averages cluster analysis. The dendrogram constructed from the similarity data showed that all the 22 cultivars analysed were closely related with a narrow genetic base. There were sufficient RAPD polymorphisms that were collectively useful in distinguishing the cultivars. The dendrogram grouped all the AA, BB, AAA, AAB and ABB genomes into a major cluster. Several subgroups are recognized within the major clade. As expected, Ensete glauca Roxb. (Musaceae) and Strelitzia reginae Banks (Strelitziaceae) were clearly differentiated from the analysed edible bananas. Our study showed that RAPD markers are sufficiently abundant to classify and readily dissect genetic differences between the closely related Musa germplasm and provide a basis for the selection of parents for improvement of this germplasm.Keywords Banana Á Molecular phylogeny Á Musa Á HAT-RAPD Á Thailand Abbreviations HAT-RAPD High annealing temperaturerandom amplified polymorphic DNA BpBase pair(s) UPGMA Unweighted pair group method with arithmetical averages

The aim of the present study was to identify genes involved in the hypersensitive response (HR) in 'Bo¨rner', a grapevine rootstock cultivar resistant to grape phylloxera. The HR was chemically induced in roots by an application of indol-3-acetic-acid (IAA). Comparisons between treated and untreated roots after different times of HR induction by IAA were realized by advanced custom DNA microarrays using 'Riesling', a phylloxerasensitive scion, as a control. IAA induction resulted in higher numbers of differentially expressed genes in 'Bo¨rner' than in 'Riesling'. In total, 27 putative HR-related genes were identified in 'Bo¨rner'. These genes are presumably involved in the production of phytoalexins, ethylene-associated gene products, cell wall proteins and transcription factors. Thus, the present study is contributing to a better understanding of the signal transduction pathways involved in the hypersensitive reaction underlying the necrosis formation after phylloxera attack in the rootstock cultivar 'Bo¨rner'.

We have studied the developmental effects of two dominant suppressor mutations of position-effect variegation mutations on female germ-line cells. Su-var(2)1(01), which has been shown to affect chromatin structure though altering histone deacetylation, and Su-var(3)3(03) are recessive female steriles and zygotic lethals in the presence of butyrate or an additional Y chromosome. We have analysed mosaic females with mutant germ-line and normal soma and concluded that intact functions of the Su-var(2)1 and the Su-var(3)3 genes are required for development of both the soma and the germ-line and that as indirect evidence suggest, their maternally provided products are needed for normal embryonic development. It is suggested that there is possibly a common control of chromatin structure and gene expression in the soma, female germ-line and embryonic cells of Drosophila.