and Central Siberian Botanical Garden, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia (A.A.K.) Bread wheat (Triticum aestivum) inflorescences, or spikes, are characteristically unbranched and normally bear one spikelet per rachis node. Wheat mutants on which supernumerary spikelets (SSs) develop are particularly useful resources for work towards understanding the genetic mechanisms underlying wheat inflorescence architecture and, ultimately, yield components. Here, we report the characterization of genetically unrelated mutants leading to the identification of the wheat FRIZZY PANICLE (FZP) gene, encoding a member of the APETALA2/Ethylene Response Factor transcription factor family, which drives the SS trait in bread wheat. Structural and functional characterization of the three wheat FZP homoeologous genes (WFZP) revealed that coding mutations of WFZP-D cause the SS phenotype, with the most severe effect when WFZP-D lesions are combined with a frameshift mutation in WFZP-A. We provide WFZPbased resources that may be useful for genetic manipulations with the aim of improving bread wheat yield by increasing grain number.

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Advanced backcross QTL analysis was used to identify QTLs for seedling and adult plant resistance to leaf rust in introgression lines derived from a cross between the spring wheat cultivar 'Saratovskaya 29' and a synthetic allopolyploid wheat (T. timopheevii/T. tauschii). F 2 mapping populations involving two backcross selections ('BC5' and 'BC9' lines) were genotyped with microsatellite markers. Two significant QTL for adult plant resistance were identified in line 'BC5': one on chromosome 2B, but originating from chromosome 2G, explained 31% of the trait variance. The other, derived from T. tauschii and mapped to the short arm of chromosome 2D explained 19% of the trait variance. In the second line, one major seedling and adult plant resistance QTL was identified on chromosome 2B. Both QTL co-located to the same marker interval. Such introgression lines, resulting from the reconstruction of common wheat genome, are of interest both as initial material for breeding and improvement of current cultivars, and as a resource for the study of the interaction and transformation of genomes.

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The results of genetic studies of common wheat that have been conducted in Novosibirsk, Russia, over the past 20 years by a research team are summarized. The research strategy was to develop a collection of aneuploids and substitution lines to be further used for chromosomal localization of genes and in the study of the genetic variability of wheat. On the basis of two cultivars, namely Saratovskaya 29 and Diamant, we have developed 6 sets of aneuploids with a complete set of monosomic lines for each, plus sets of lines ditelosomic and monotelosomic for "standard" arms. Exploiting the monotelosomics, 108 single chromosome intervarietal substitutions, 13 lines with alien substitutions (mono-and disomics) and 11 addition lines have been developed. A collection of lines isogenic for dominant marker genes of morphological characters has also been developed. The genetic collection was used in chromosomal localization of 15 genes, for many of which chromosome arms have been determined. Positively or negatively, the question of allelism within some loci has been answered.