Intergeneric Hybrids between Aegilops squarrosa and Secale cereale and their Meiotic Chromosome Behaviour

Three hybrid plants with different combinations of D and R genomes were produced from crosses between Aegilops squarrosa (2×: and 4×) and Secale cereale (2× and 4×) using embryo culture. Production frequencies of mature hybrids, having the genomes DR, DDR and DDRR, were 2.0%, 5.2% and 2.2 %, respectively, of florets pollinated. Amphidiploids were obtained directly from the cross between tetraploid parents. The majority of their morphological features were intermediate between those of the parents but, as with rye, the rachis was tough. Diploid and triploid hybrids were completely seed-sterile, whereas the amphidiploid had an average self-fertility of 4.5 % with a range of 0 to 45 %. The somatic chromosome numbers of diploids, triploids and amphidiploids were 2n = 14, 21 and 28, respectively. At meiotic metaphase I, the mean chromosome associations were 0.01 III + 0.26 II + 13.4 I in diploids, 6.96 II + 7.1 I in triploids, and 10.5 II + 7.9 I in amphidiploids. In diploids, pairing between D and R chromosomes was observed in the form of end-to-end types without chiasmata. Homologous pairing between D chromosomes was predominant in plants having two sets of D genomes. Amphidiploids showed a diploid-like chromosome behaviour. Homoeologous pairing was not observed in either triploids or amphidiploids.     

Evaluation of a collection of wild wheat relative Aegilops geniculata Roth and identification of potential sources for useful traits

A collection comprising 157 Aegilops geniculata accessionsoriginating from different ecogeographical regions was established atENSA-INRA, Montpellier. The accessions were studied for physiologicaltraits related to drought and heat stress and screened for resistance tobarley yellow dwarf virus (BYDV) and rusts. Some accessions were alsotested for resistance to Hessian fly and cereal cyst nematodes (CCN). The study allowed to distinguish different adaptive strategies to theclimatic constraints encountered by Aegilops populations in theirregion of origin. They led to significant differences in biomass and grainproduction and should be taken into account in the utilisation of Ae.geniculata germplasm in wheat breeding programs. Two accessions withresistance to BYDV were found. Both originated from South of France. Theinterest of Ae. geniculata as a source of rust resistance was confirmedand accessions with resistance to the three rusts were identified. Highresistance against populations of Heterodera avenae and H.latipons was found in accessions from Spain, Bulgaria, Jordan and Tunisia.Sources of resistance to Hessian fly were also identified.     

Screening relatives of wheat for snow mold resistance and freeing tolerance

Four hundred and eighty one accessions of species and subspecies of genera Triticum and Aegilops were evaluated for resistance to speckled snow mold caused by Typhula ishikariensis and for freezing tolerance. All Triticum and seven of Aegilops species were severely affected by snow mold. Among surviving Aegilops spp., only the Ae. cylindrica accessions exhibited resistance similar to that of the most resistant winter wheat cultivar, PI 173438. After repeated screening of accessions of Ae. cylindrica, 12 accessions were identified as having resistance similar to that of PI 173438; eleven of those were considered more freezing tolerant than PI 173438, but less than wheat cv. Valjevskaya, the freezing tolerant check. Accessions of Ae. cylindrica with snow mold resistance exceeding that of PI 173438, and with freezing tolerance, are currently being screened. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genome-specific markers of tetraploid wheats and their putative diploid progenitor species

The objective of this study was to isolate genome‐specific markers from the genomes of tetraploid wheats and the putative donor diploid species on the basis of random amplified polymorphic DNA analysis followed by cross‐hybridization. Twenty different Triticum and Aegilops species and accessions were analysed by polymerase chain reaction (PCR) using 30 random primers. The polymorphic PCR fragments were then isolated, labelled and used in cross‐hybridization screenings. The hybridization results established that one marker was specific to the Ae. speltoides S genome, two to the A genome, one to the B genome and five to the G genomes of polyploid species (and to the genomes of the corresponding progenitor species). Four markers were identified that were specific to both the B and G genomes. Analysis of the Triticum and Aegilops species and accessions supported the notion that Ae. speltoides is more closely related to the B and G genomes of polyploid wheat species than were other members of the Sitopsis section. The data also indicated that the B and G genomes had originated from different accessions of Ae. speltoides.     

Endopeptidase EP-1 as a Marker for the Eyespot Resistance Gene Pch-1 from Aegilops ventricosa in Wheat Line 'H-93-70'

Biochemical marker endopeptidase EP-1 was used to determine that an eyespot resistance gene, transferred from Aegilops ventricosa to the hexaploid wheat line ‘H-93-70’ is located on the long arm of the chromosome 7D.     

Ph I-induced transfer of leaf and stripe rust-resistance genes from Aegilops triuncialis and Ae. geniculata to bread wheat

Leaf and stripe rusts are severe foliar diseases of bread wheat. Recently, chromosomes 5M^g from the related species Aegilops geniculata that confers resistance to both leaf and stripe rust and 5U^t from Ae. triuncialis conferring resistance to leaf rust have been transferred to bread wheat in the form of disomic DS5M^g(5D) and DS5U^t(5A) chromosome substitution lines. The objective of this study was to shorten the alien segments in these lines using Ph ^I-mediated, induced homoeologous recombination. Putativerecombinants were evaluated for their rust resistance, and by genomic in situ hybridization and microsatellite analyses. One agronomically useful wheat-Ae. geniculata recombinant resistant to leaf and stripe rust was identified that had only a small terminal segment of the 5M^gL arm transferred to the long arm of an unidentified wheat chromosome. This germplasm can be used directly in breeding programs. Only one leaf rust-resistant wheat-Ae. triuncialis recombinant, which consists of most of the complete 5U^t chromosome with a small terminal segment derived from 5AS, was identified. This germplasm will need further chromosome engineering before it can be used in wheat improvement. This revised version was published online in August 2006 with corrections to the Cover Date.     

Eyespot resistance in wheat ×Aegilops kotschyi backcross lines

In wheat, eyespot caused by PseudoCercosporella herpotrichoides, is one of the main foot‐rot diseases. Yield losses up to 40% occur in some years. Plant protection by fungicide application is possible, but a better way is through resistance breeding. Two resistance sources are currently used: Aegilops ventricosa and the old French variety ‘Cappelle Desprez’. A new source of resistance has been found in the accession AE120 of Ae. kotschyi from the Gatersleben gene bank with the genome constitution UUSvSv. This accession has been crossed and backcrossed twice to susceptible wheat varieties, and in each generation, plants with a relatively high level of resistance have been selected. From this material, lines have been developed and tested in F₆ to F₈. Finally, several lines could be classified as moderately resistant, such as the French variety ‘Cappelle Desprez’ after resistance determination during milk ripeness (DC75). No line reached the high resistance level achieved with Pch‐1 from Ae. ventricosa. The yield of these lines under infection conditions was higher compared with ‘Cappelle Desprez’. The line 6018‐96‐3 showed a high yield of 64.3 dt/ha compared with 59.6 dt/ha, on the average, in combination with the best expression of eyespot resistance in the adult growth stage over 3 years.     

Gametocidal effects and resistance to wheat leaf rust and stem rust in derivatives of a Triticum turgidum ssp. durum/Aegilops speltoides hybrid

Summary Genes for leaf rust and stem rust resistance and segregation distortion (Gc), that seemed to derive from an Aegilops spetroides ssp. ligustica accession, were transferred to common wheat. While the advanced backcrosses had normal meioses and 42 chromosomes, high levels of male and female sterility, abnormal endosperm development and chromosome aberrations were evident. These effects were more pronounced in Gc-heterozygotes than in homozygotes. Gametes without Gc genes did not survive, and the Gc-associated defects were always inherited with the resistance. Since the resistance genes were effective against local pathotypes of the leaf rust and stem rust pathogens, an attempt was made to disrupt the Gc-system through irradiation, treatment with the mutagen N-nitroso-N-methyl-urea or growing the material at elevated temperatures. A very low frequency of the treated material showed slightly better fertility and seed development. However, these effects did not persist in subsequent generations and were apparently not strong enough to allow the recovery of segregates which had lost the Gc gene(s).     

Aneuploids as a key for new molecular cloning strategies: development of DNA markers by microdissection using Triticum aestivum-Aegilops markgrafii chromosome addition line B

Summary We established a chromosome specific DNA library of the Aegilops markgrafii chromosome B. Eight microdissected chromosomes B obtained from a monosomic T. aestivum-Aegilops markgrafii addition line were PCR-amplified and the DNA was cloned in Escherichia coli DH5. Clones were characterized by dot blot hybridization with total Ae. markgrafii DNA. 62% of clones represented repetitive sequences and 38% low or single copy sequences. The estimated length of excised inserts varied between less than 200 bp and more than 500 bp. The average size of inserts was 310 bp.Abbreviations bp base pairs - DOP-PCR degenerated oligonucleotide primed polymerase chain reaction     

D2类山羊草细胞质普通小麦核代换系育性在不同光温条件下的差异

将D2类山羊草[粗厚山羊草（Ae.crassa)、牡山羊草（Ae.juvenalis)和瓦维洛夫山羊草（Ae.vavilovii)]细胞质普通小麦核代换系于1997－1998年分别种植在不同纬度的5个地点，并进行分期播种。从不同地点核代换系和核亲本的育性表现，分析D2类山羊草细胞质核代换系对日长、温度的敏感性及其差异。结果表明：（1）D2类山羊草细胞质小麦核代换系的3种类型存在差异，粗厚山羊草对日长、温度反应最为敏感，其次是瓦维洛夫山羊草，牡山羊草对光周期较钝感。（2）日长和温度两种生态因子对D2类山羊草细胞质核的育性变异的作用程度不同，日长是主控因子，温度在日长因子相近时方显示其作用。（3）核质互作是D2类山羊草细胞质小麦核代换系育性对光温反应的遗传方式。