Fluorescence and genomic in situ hybridization (FISH and GISH) were used to establish the cytogenetic constitution of two wheat × Thinopyrum intermedium partial amphiploids H95 and 55(1-57). Both partial amphiploids are high-protein lines having resistance to leaf rust, yellow rust and powdery mildew and have in total 56 chromosomes per cell. Repetitive DNA probes (pTa71, Afa family and pSc119.2) were used to identify the individual wheat chromosomes and to reveal the distribution of these probes within the alien chromosomes. FISH detected 6B tetrasomy in H95 and a null (1D)-tetrasomy (1B) in 55(1-57). GISH was carried out using biotin labeled Th. intermedium DNA and digoxigenin labeled Pseudoroegneria spicata DNA as probes, subsequently. GISH results revealed 44 wheat chromosomes and four Thinopyrum chromosome pairs, including three S and one J chromosome pairs in line H95. Line 55(1-57), contained 42 wheat chromosomes and six Th. intermedium pairs, including two S and one J(S) pairs. Additionally, two identical translocated chromosome pairs with diminished affinity to the alien chromatin were detected in both amphiploids. Another two translocations were found in 55(1-57), with satellite sections from the Thinopyrum J genome.

Common and dwarf bunt (Tilletia caries (DC.) Tul & C. Tul, T. foetida (Wallr.) Liro and T. controversa (Kühn) are potentially important wheat diseases in Romania, especially in organic farming and on small farms, unable in most cases to properly treat the seed. Growing bunt resistant cultivars can be an efficient way to reduce expenses and protect the environment, by reducing use of pesticides. For these reasons, a small breeding program was started in 1972, by crossing the old Turkish wheat PI 178383 (a Bt9 and Bt10 carrier) with adapted cultivars. Later, in an attempt to diversify the resistance genes used in the program, several gene sources (including Bt5, Bt8, Bt11, Bt12 etc.), received from Dr. Bob Metzger (Oregon State University, U.S.) were used as parents. Since, our research effort has focused on: (1) continuously checking the efficiency of known bunt resistance genes against local populations (isolates) of bunt; (2) improving the competitiveness of bunt resistant germplasm by repeated cycles of crossing with adapted cultivars and selection for both bunt resistance and agronomic type and (3) searching for new bunt resistance genes. (1) About ten years of artificial testing with 6-10 isolates/year of bunt collected from Romanian locations representative for natural occurrence of Tilletia species, has constantly shown that Bt5, Bt10, Bt11, Bt12 expressed a high level of resistance. Along with original sources provided primarily by Dr. Bob Metzger and more recently, also by Prof. Blair Goates (National Small Grains Germplasm Research Facility, West Aberdeen, U.S.), advanced lines carrying the most efficient genes were tested and confirmed the transfer of this trait. (2) All bunt resistance gene sources available to us were very tall, susceptible to powdery mildew and leaf rust, were low yielding and had poor baking quality. Progress in improving the competitiveness of bunt resistant lines in the absence of bunt has been slow, but every new cycle has shown definite improvements over the previous ones. Presently available bunt resistant lines are semidwarf and powdery mildew resistant, are better adapted to local conditions and give yields of 90-100% as compared with current check cultivars. They are still deficient in leaf rust resistance and bread making quality. New lines with improved leaf rust resistance and quality are in preliminary yield tests. Accelerated progress is expected by using molecular markers for some of the bunt resistance genes. Markers will also be used to pyramid resistance genes. (3) Search for new bunt resistance sources has identified two potential sources with resistance, presumably coming from the Brazilian cultivar Colonias and from the rye genome. Further testing with a wider range of bunt isolates is under way. Positive experience in accelerated selection of higher resistance to other wheat pathogens, accumulated from larger forms of trans-national cooperation (ring tests), emphasized the need of such approach with regard to common bunt, too. The XV th Biennial Work...

The present state of genetic control of in vitro responses of wheat and of the prospects of its improvement and practical use are presented. The genetic factors affecting different stages of callus induction and of organogenesis in immature embryos are discussed. The dominant genotypic role in the in vitro processes and the cytoplasmic influence on the latter are shown. GenotypeÂenvironment and nucleusÂcytoplasm interactions were observed. Some unsolved problems needing further investigations of cereals at the tissue culture level are pointed out.

Genomic in situ hybridization and fluorescence in situ hybridization were used to define the cytogenetic constitution of the intergeneric introgression line 29(1-57) obtained from the wheat × Thinopyrum intermedium (wheatgrass) cross. This line is a highprotein line resistant to leaf rust, yellow rust, and powdery mildew under field conditions and has 42 chromosomes. GISH analysis using a total genomic DNA probe from Thinopyrum intermedium resulted in the identification of 14 chromosomes of wheatgrass origin. The sequential GISH patterns obtained using St-genomic and J-genomic DNA as probes and ABD-genomic DNA from wheat as a blocker led to a better determination of the genomic type of wheatgrass chromosomes. Rearrangements involving Thinopyrum chromosomes and the A, B, and D genomes of wheat were not observed. FISH using the repetitive DNA probes pSc119.2, Afa-family, and pTa71 allowed for identification of all the wheat chromosomes present.