Locating the alien chromatin segment in common wheat-Aegilops longissima mildew resistant transfers

By use of the Chinese Spring ph 1b mutant, recombination was induced between the 3S1 short arm telosome of Ae. longissima and its group-3 wheat homoeologues. Transfer was thus obtained of chromosomal segments bearing the alien Pm 13 mildew resistance gene into several common wheat lines. To identify the wheat chromosome involved in each transfer, these were subjected to monosomic and C-banding analyses. Probably due to preferential 3B-3S1 pairing, irrespective of the group-3 wheat chromosome present as monosome in the critical steps of the transfer work, in 2/3 of the cases 3B turned out to be the recipient chromosome, whereas 3D was the one involved in the remaining ones. Assessment of the residual pairing ability of the recombinant chromosomes in F1's between four 3B and three 3D transfer lines and their corresponding wheat ditelosomic as well as 3S1 substitution lines, indicated about coincident values (about 40 % pairing with DT3BS) in three of the 3B recombinants, a significantly different pattern in the fourth one (10 %) and a more continuous variation among the 3D ones. An overall prevailing terminal location of the wheat-alien chromatin exchange points is tentatively hypothesized

Dissecting a wheat QTL for yield present in a range of environments: from the QTL to candidate genes

Previous studies with 95 bread wheat doubled haploid lines (DHLs) from the cross Chinese Spring (CS)xSQ1 trialled over 24 yearxtreatmentxlocations identified major yield quantitative trait loci (QTLs) in homoeologous locations on 7AL and 7BL, expressed mainly under stressed and non-stressed conditions, respectively. SQ1 and CS contributed alleles increasing yield on 7AL and 7BL, respectively. The yield component most strongly associated with these QTLs was grains per ear. Additional results which focus on the 7AL yield QTL are presented here. Trials monitoring agronomic, morphological, physiological, and anatomical traits revealed that the 7AL yield QTL was not associated with differences in flowering time or plant height, but with significant differences in biomass at maturity and anthesis, biomass per tiller, and biomass during tillering. In some trials, flag leaf chlorophyll content and leaf width at tillering were also associated with the QTL. Thus, it is likely that the yield gene(s) on 7AL affects plant productivity. Near-isogenic lines (NILs) for the 7AL yield QTL with CS or SQ1 alleles in an SQ1 BACKGROUND: showed the SQ1 allele to be associated with > 20% higher yield per ear, significantly higher flag leaf chlorophyll content, and wider flag leaves. Epidermal cell width and distance between leaf vascular bundles did not differ significantly between NILs, so the yield-associated gene may influence the number of cell files across the leaf through effects on cell division. Interestingly, comparative mapping with rice identified AINTEGUMENTA and G-protein subunit genes affecting lateral cell division at locations homologous to the wheat 7AL yield QTL

Isolation of a chromosomally engineered durum wheat line carrying the common wheat Glu-D1d allele

A 1DL chromosomal segment, containing the Glu-D1d allele coding for the '5+10' HMW glutenin subunits, has been transferred into the 1AL arm of a tetraploid derivative by means of ph1c induced homoeologous recombination in backcross progeny derived from an initial common wheat x durum wheat cross. The involvement of 1 AL in the exchange, which could not be directly proved by the protein assay because of the null condition at the Glu-Al locus in all durum wheat parents used, was unequivocally demonstrated using the D genome specific, highly repeated DNA sequence pAs1 as probe in fluorescence in situ hybridization (FISH) experiments. The Glu-D1d tetraploid carrier in fact exhibits a normal 1AS and a recombined 1AL, with a distal segment of clear 1DL origin. The difference between the FISH patterns of recombined and normal 1AL was used to discriminate homozygous from heterozygous Glu-D1d carriers already in F2 populations, in which the recombined chromosome appeared to be transmitted normally through both germlines. Preliminary tests also show no reduction in fertility due to either one or two doses of the engineered chromosome, whose impact on various pasta and bread making quality parameters will be assessed. (© Inra/Elsevier)Isolement par manipulation chromosomique d'une lignée de blé dur contenant l'allèle Glu-D1d du blé tendre. Au moyen de la recombinaison homéologue induite par la mutation ph1c dans la descendance issue du rétrocroisement d'un blé tendre par un blé dur, un segment du chromosome 1DL a été transféré dans le bras 1AL d'un dérivé tétraploïde. Le segment contient l'allèle Glu-D1 codant pour les sous-unités des gluténines de poids moléculaire élevé (HMW) « 5 + 10 ». L'implication dans l'échange du chromosome 1AL, qu'il n'a pas été possible de démontrer par l'essai protéique à cause de la condition nulle de l'allèle au locus Glu-A1 de tous les blés durs employés, a été démontrée par l'hybridation in situ en fluorescence (FISH) avec la séquence répétée pAs1 spécifique du génome D. En effet, la lignée tétraploïde contenant l'allèle Glu-D1d montre un 1AS normal et un 1AL recombiné, avec un segment distal qui provient clairement du chromosome 1DL. Les différents profils d'hybridation des chromosomes 1AL normal et recombiné ont été utilisés pour distinguer les homozygotes Glu-D1d des hétérozygotes dans les populations F2, dans lesquelles nous avons observé une transmission normale du chromosome recombiné par les voies mâle et femelle. Des essais préliminaires n'ont indiqué aucune réduction de la fertilité tant des homozygotes que des hétérozygotes pour le chromosome recombiné. (© Inra/Elsevier