The Deletion Stocks of Common Wheat

Purpose:To describe and characterize the association of hereditary cutaneous lichen amyloidosis with multiple endocrine neoplasia type 2a (MEN 2a) Design:Survey of a family for two diseas

Multiple endocrine neoplasia type 2a associated with cutaneous lichen amyloidosis

Certain alien chromosomes have been found to be preferentially transmitted in wheat. They are derived from differnt species of Aegilops, a genus related to wheat (Triticum). Such chromosomes ensure their own selective retention in wheat by causing sterility in gametes not carrying them, hence they are termed gametocidal chromosomes. There are at least three types of the gametocidal chromosomes that have different mode of gametocidal action and homoeology. The gametocidal chromosomes in the same homoeologous group (group 2, 3, or 4) have the same gametocidal action. Some of the gametocidal chromosomes induce chromosome mutations in either gametophytes or zygotes of common wheat with specific genotypes. The chromosome mutations preferentially occur in gametophytes without the gametocidal chromosome or in the zygotes when the gametocidal chromosome is delivered by the pollen. Chromosome mapping using induced deletions is under way.

Gametocidal chromosomes and their induction of chromosome mutations in wheat

Diploid A genome species of wheat harbour immense variability for biotic stresses and productivity traits, and these could be transferred efficiently to hexaploid wheat through marker assisted selection, provided the target genes are tagged at diploid level first. Here we report an integrated molecular linkage map of A genome diploid wheat based on 93 recombinant inbred lines (RILs) derived from Triticum boeoticum × Triticum monococcum inter sub-specific cross. The parental lines were analysed with 306 simple sequence repeat (SSR) and 194 RFLP markers, including 66 bin mapped ESTs. Out of 306 SSRs tested for polymorphism, 74 (24.2%) did not show amplification (null) in both the parents. Overall, 171 (73.7%) of the 232 remaining SSR and 98 (50.5%) of the 194 RFLP markers were polymorphic. Both A and D genome specific SSR markers showed similar transferability to A genome of diploid wheat species. The 176 polymorphic markers, that were assayed on a set of 93 RILs, yielded 188 polymorphic loci and 177 of these as well as two additional morphological traits mapped on seven linkage groups with a total map length of 1,262 cM, which is longer than most of the available A genome linkage maps in diploid and hexaploid wheat. About 58 loci showed distorted segregation with majority of these mapping on chromosome 2Am. With a few exceptions, the position and order of the markers was similar to the ones in other maps of the wheat A genome. Chromosome 1Am of T. monococcum and T. boeoticum showed a small paracentric inversion relative to the A genome of hexaploid wheat. The described linkage map could be useful for gene tagging, marker assisted gene introgression from diploid into hexaploid wheat as well as for map based cloning of genes from diploid A genome species and orthologous genes from hexaploid wheat.

An integrated molecular linkage map of diploid wheat based on a Triticum boeoticum x T. monococcum RIL population.

Accessions from Cicer echinospermum, a wild relative of chickpea (Cicer arietinum L.), contain resistance to the fungal disease ascochyta blight, a devastating disease of chickpea. A linkage map was constructed based on an interspecific F2 population, derived from a cross between a susceptible chickpea cultivar (Lasseter) and a resistant C. echinospermum accession (PI 527930). The linkage map incorporated 83 molecular markers, that included RAPD, ISSR, STMS and RGA markers; eight markers remained unlinked. The map comprised eight linkage groups and covered a map distance of 570 cM. Six out of the eight linkage groups were correlated to linkage groups from the integrated Cicer map using STMS markers. Quantitative trait loci (QTLs) associated with ascochyta blight resistance were detected using interval mapping and single-point analysis. The F2 population was evaluated for seedling and stem resistance in glasshouse trials. At least two QTLs were identified for seedling resistance, both of which were located within linkage group 4. Five markers were associated with stem resistance, four of which were also associated with seedling resistance. QTLs from previous studies also mapped to LG 4, suggesting that this linkage group is an important region of the Cicer genome for resistance to ascochyta blight.

Preliminary investigation of QTLs associated with seedling resistance to ascochyta blight from Cicer echinospermum, a wild relative of chickpea.

A new gametocidal gene was found in a common wheat cultivar Chinese Spring carrying the cytoplasm of Aegilops speltoides strain KU 5725 (Plant Germplasm Institute, Kyoto University). Monosomic anal...

Gametocidal genes in wheat and its relatives. III. Chromosome location and effects of two Aegilops speltoides-derived gametocidal genes in common wheat

K. Tsunewaki

Papers

Gametocidal genes in wheat and its relatives. III. Chromosome location and effects of two Aegilops speltoides-derived gametocidal genes in common wheat