Self-incompatibility in pears (Pyrus communis L., Pyrus serotina Rehd. and Pyrus ussuriensis) Review

Self-incompatibility system and allele pool of three different pear species, European pear (Pyrus communis), Japanese pear (P. serotina) and Chinese pear (P ussuriensis) are displayed. Several inconsistencies and the absence of the harmonization of three different allele series are revealed in the European pears. By collecting data from several reports eight incompatibility groups of Japanese pear cultivars could be established. A self-compatible genotype is analysed in details and shown to be a stylar-part mutant. As Japanese pear was the first fruit tree species from which S-ribonucleases were identified, the history of S-genotyping from the beginning to the latest achievements and technical developments can be also monitored from the experiments enumerated. In Chinese pears, seven S-alleles and one incompatibility group could be identified.

Molecular Markers Associated with Morphological Traits in Watermelon

Morphological traits were examined in an F3 generation derived from a cross between C. lanatus var. lanatus [(Thunb.) Matsum. & Nakai] and C. lanatus var. citroides. At least three genes, C (yellow) vs. c (red), i (inhibitory to C) vs. I (non-inhibitory to C), and y (yellow) vs. yw (white), with epistatic and inhibitory actions were found to govern the inheritance of fruit flesh color. The high frequency of yellow-fleshed fruit and low frequencies of white and red fruits can be explained by the presence of a new allele (yw recessive to y) in the multiple allele series at the Y locus. The low frequency of tan colored seeds in segregating populations could be explained by at least three genes governing inheritance of seed-coat color. Single factor analysis of variance was conducted for each pairwise combination of random amplified polymorphic DNA (RAPD) locus and fruit or seed characteristics. Several RAPD loci were identified to be loosely linked to morphological characteristics.

Microsatellite markers useful throughout the genus Dianthus

Using repeats found in sequences from Dianthus species present in the EMBL database, primers for STMS (sequence-tagged microsatellite site) analysis were developed and tested. Five loci were polymorphic and amplified products of sufficient quality in nearly all of the 26 Dianthus species tested, except MS-DINGSTA, which amplified in only one-third of the species. Loci MS-DINMADSBOX and MS-DCDIA30 produced allele series that were mostly two nucleotides (the repeat unit) apart. MS-DCAMCRBSY and MS-DINCARACC also amplified regular series of alleles, but more than two fragments per individual were detected in a number of species. Both loci code for a member of the ACC synthase gene family. The observation that the loci amplified across a wide range of Dianthus species may imply that the different species within the genus are relatively closely related. Alternatively, it may indicate that the regions selected for primer design (some of which are in coding regions) are well conserved. These microsatellites will be useful for the measurement of genetic diversity in natural populations of Dianthus species and the identification of carnation varieties. Key words: SSR, simple sequence repeat, identification, STMS, sequence-tagged microsatellite site.

Transmission Genetics of Allorecognition in Hydractinia symbiolmgicarpus (Cnidaria: Hydrozoa)

Allorecognition is ubiquitous, or nearly so, amongst colonial invertebrates. Despite the prominent role that such phenomena have played both in evolutionary theory and in speculations on the origin of the vertebrate immune system, unambiguous data on the transmission genetics of fusibility (i.e., the ability of two individuals to fuse upon tissue contact) is lacking for any metazoan outside of the phylum Chordata. We have developed lines of the hydroid Hydractinia symbiolongzcarpus (Phylum Cnidaria) inbred for fusibility and here report results of breeding experiments establishing that fusibility segregates as expected for a single locus with codominantly expressed alleles, with one shared allele producing a fusible phenotype. Surveys of fusibility in field populations and additional breeding experiments indicate the presence of an extensive allele series.