Molecular cytogenetic characterization of Thinopyrum genomes conferring perennial growth habit in wheat- Thinopyrum amphiploids

Seven wheat‐Thinopyrum amphiploids, AT 3425, AgCs, PI 550710, PI 550711, PI 550712, PI 550713 and PI 550714, were evaluated for perennial growth habit in the field. Three of them, AgCs, AT 3425, and PI 550713, were identified as perennials. Fluorescent genomic in situ hybridization (FGISH) patterns of mitotic chromosomes indicated that AgCs had seven pairs of Thinopyrum chromosomes and 21 pairs of wheat chromosomes. PI 550713 and AT 3425 showed similar FGISH patterns of mitotic chromosomes with three pairs of wheat‐Thinopyrum translocated chromosomes, seven pairs of Thinopyrum chromosomes, and 18 pairs of wheat chromosomes. Thinopyrum chromosome pairing in the Fi hybrid of AT 3425 with AgCs demonstrated differences between Thinopyrum genomes in these two amphiploids. Based on chromosome constitutions, pairing and reported pedigrees, AgCs and AT 3425 were identified as a wheat‐Thinopyrum elongatum amphiploid and partial wheat‐Thinopyrum ponticum amphiploid, respectively. Chromosome pairing in the F₁ hybrid between AT 3425 and PI 550713 revealed that these two amphiploids contained the same Thinopyrum genome. Two different Thinopyrum genomes conferring perennial growth habit were identified from the perennial amphiploids and characterized cytogenetically.     

Identification of wheat–Thinopyrum intermedium 2Ai-2 ditelosomic addition and substitution lines with resistance to barley yellow dwarf virus

Among the regenerated plants derived from immature hybrid embryos of wheat–Thinopyrum intermedium disomic addition line Z6 × common wheat variety ‘Zhong8601’, a plant with a telocentric chromosome and barley yellow dwarf virus (BYDV) resistance was obtained. The telocentric chromosome paired with an entire Thinopyrum chromosome to form a heteromorphic bivalent at meiotic metaphase I. Genomic in situ hybridization showed that the telosome originated from Th. intermedium. Two ditelosomic additions and one disomic substitution were identified among the offspring of the plant. Two random amplified polymorphic DNA molecular markers were identified among 150 random primers used to detect the different arms of the alien chromosome. These might be useful for developing translocation lines with BYDV resistance.     

Characterization of a partial amphiploid between Triticum aestivum cv. Chinese Spring and Thinopyrum intermedium ssp. trichophorum

A partial amphiploid, TE-3, between Triticum aestivum cv. Chinese Spring (CS) and Thinopyrum intermedium ssp. trichophorum was characterized by cytological observation, genomic in situ hybridization (GISH), seed storage protein electrophoresis and disease resistance screening. The TE-3 plants were deeply covered with pubescence, which is characteristic of the Th. intermedium ssp. trichophorum parent. Feulgen staining of the somatic metaphases revealed that the chromosome number varied from 52 to 56. TE-3 pollen mother cells (PMCs) regularly showed two to four univalents and 25 to 27 bivalents, indicating a degree of cytological instability. Giemsa-C banding showed that the Thinopyrum chromosomes in TE-3 produced strong heterochromatin bands. GISH analysis suggested that the alien chromosomes in TE-3 consisted of eight St chromosomes, four J^s chromosomes, and two J genome chromosomes, as well as two St-J translocation chromosomes. Seeds storage proteins separated by acid polyacrylamide gel electrophoresis (APAGE) and sodium dodecyl sulphate – polyacrylamide gel electrophoresis (SDS-PAGE) showed that TE-3 expressed some of Th. intermedium ssp. trichophorum specific gliadin and glutenin bands. When inoculated with stripe rust and powdery mildew isolates, TE-3 expressed resistance derived from its Thinopyrum parent. It appears that TE-3 can be used as a donor source in wheat breeding programs to introduce novel variation for quality and disease resistance.     

Hybrids between durum wheat and Thinopyrum junceiforme: Prospects for breeding for scab resistance

Tetraploid wheatgrass, Thinopyrum junceiforme(2n = 4x = 28; J₁J₁J₂J₂), a wild relative of wheat, is an excellent source of resistance to Fusarium head blight. Intergeneric F₁ hybrids (2n = 4x = 28; ABJ₁J₂) between durum wheat (Triticum turgidum; 2n = 4x = 28; AABB) cultivars Lloyd or Langdon and Th. junceiforme were synthesized. Most of the pairing in F₁ hybrids was between the J₁- and J₂-genome chromosomes. Some pairing occurred between wheat chromosomes and alien chromosomes, resulting in segmental exchange that was confirmed by fluorescent in situ hybridization (FISH). The F₁hybrids were largely male-sterile and were backcrossed, as the female parent, to the respective durum cultivar. Backcrosses from Lloyd × Th. junceiforme hybrids yielded fertile partial amphiploids (2n = 6x = 42; AABBJ₁J₂) as a result of functioning of unreduced female gametes of the hybrid. Lloyd proved to be a more useful durum parent than Langdon in crosses with Th. junceiforme designed to transfer scab resistance genes. Pairing in the amphiploids was characterized by preferential pairing,which resulted in bivalent formation. However, some intergeneric pairing also occurred. Several fertile hybrid derivatives were produced by further backcrossing and selfing. The introduction of alien chromatin into the durum complement was confirmed by FISH. Hybrid derivative lines had significantly lower mean infection scores (p = 0.01), the best showing 10.93% infection, whereas the parental durum cultivars had 70.34% to 89.46% infection. Hybridization with wild relatives may offer an excellent means of introducing scab resistance into durum wheat. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular cytogenetic characterization of two partial wheat Elytrigia elongata amphiploids resistant to powdery mildew

Two new partial amphiploids SN20 and SN122, derived from crosses between Elytrigia elongata and common wheat Yannong15 and Shannongfu63, were found resistant to powdery mildew, a serious fungal wheat disease. Cytogenetic observations showed that each SN20 and SN122 plant had 56 chromosomes. The chromosomes in most pollen mother cells formed approximately 28 bivalents, thereby showing a high degree of cytogenetic stability. Genomic in situ hybridization using St‐genomic DNA from Pseudoroegneria strigosa as a probe and ABD‐genomic DNA from Chinese Spring wheat as a blocker demonstrated that the genomic formulas for the alien chromosomes in SN20 and SN122 were 2 St + 10 J^S + 2 J and 2 St + 8 J^S + 4 J, respectively. These wheat E. elongata partial amphiploids represent a potential novel source of resistance to powdery mildew for wheat breeding.     

Genomic constitution of a partial amphiploid OK7211542 used as a source of immunity to barley yellow dwarf virus for bread wheat

A combination of genomic in situ hybridization (GISH) and meiotic pairing analysis of crosses between a series of 2n= 56 partial amphiploids confirmed that the alien genome of the BYDV-immune Agro-tricum line OK7211542 is derived from Thinopyrum ponticum and not from Thinopyrum intermedium. The evidence from meiotic pairing analysis indicated that the chromosome constitution of OK7211542 is similar to another Agrotricum line, ORRPX, which was derived from a cross of wheat and Th. ponticum, but different from other Agrotricum lines, Zhong 5 and TAF 46 which were derived from the crosses between wheat and Th. intermedium. The GISH analysis confirmed that OK7211542 contained one complete set of 14 Th. ponticum chromosomes, in which no S chromosome was present in the alien genome. GISH also detected a small alien translocation attached to one of the wheat chromosomes, a result that was consistent with the pairing data.     

携带抗黄矮病基因染色体的分离

抗黄矮病小麦一中间堰麦草异附加系Z2 (2n=44)携带一对完整的中间僵麦草染色体,用Z2作母本与普通小麦品种中8601杂交,获得杂种F1(2n=43=21Ⅱ+1I)。利用激光显微切割技术将F1花粉母细胞减数分裂中期I及后期I的呈单价体的中间僵麦草染色体分离出来,经去蛋白、Sau3AI酶切后,进行PCR体外扩增。结果表明利用激光显微切割可分离     

Genotypic control of chromosome pairing in amphiploids involving the cultivated oat Avena sativa L.

Summary A genotype of the diploid species Avena longiglumis (Cw 57) has been shown to modify the genetic control of diploid-like chromosome pairing in the cultivated oat, A. sativa (2n=6x=42) leading to increased homoeologous chromosome pairing in 4x hybrids between the two species (Rajhathy & Thomas, 1974). The Cw 57 genotype has a similar effect in increasing homoeologous chromosome pairing in amphiploids combining diploid and hexaploid genomes including associations between alien chromosomes and their corresponding pairs in hexaploid species. The effect of the Cw 57 genotype is probably in altering the specificity of chromosome pairing in the early stages of meiosis. The use of the Cw 57 genotype to induce homoeologous chromosome pairing as a technique for the transfer of desirable alien variation into the cultivated oat is discussed.     

抗黄矮病小麦种质的分子标记

应用基因组原位杂交技术分析了抗小麦黄矮病种质的遗传组成,研究表明小麦一中间但麦草部分双二倍体无芒中4(2n=56)具有40条小麦染色体、5对中间僵麦草染色体、3对小麦/中间僵麦草易位染色体,其中1对是罗伯逊氏易位染色体。结果表明无芒中4与远中5的遗传组成有明显差异,是两种不同类型的材料。抗黄矮病小麦种质F940418, T10     

Development and characterization of common wheat-Thinopyrum intermedium translocation lines with resistance to barley yellow dwarf virus

We developed some wheat-Th. intermedium translocation lines,Yw642, Yw443 and Yw243, etc., showing good BYDV resistance from L1by induced homoeologous pairing using CS ph mutant. Characterization ofthese wheat lines was carried out by GISH and RFLP analysis. The resultsof GISH showed that the lines, YWw42, Yw443 and Yw243, etc., arehomozygous wheat-Th. intermedium translocation lines, in which thechromosome segments of Th. intermedium were transferred to thedistal end of a pair of wheat chromosomes. RFLP analysis indicated that thetranslocation chromosome of the wheat lines is T7DS · 7DL-7XL. Thebreakpoint of the translocation is located on the distal end of 7DL, betweenXpsr965 and Xpsr680 about 90–99 cm from the centromere. The BYDVgene is located on the distal end of 7XL around Xpsr680, Xpsr687 andXwg380. The RFLP markers of psr680, psr687 and wg380 werecosegregated with the BYDV resistance respectively and could be used formolecular assisted selection (MAS) in wheat breeding program for BYDVresistance.     

The contribution of Hordeum chilense to partial resistance of tritordeum to wheat brown rust

Summary Hexaploid and octoploid tritordeum and their Triticum spp. parents were studied in the seedling stage to compare their components of partial resistance to Puccinia recondita f.sp. tritici. The components studied were infection frequency, latency period and size of uredia. The non-host Hordeum chilense parent does not confer any increase of partial resistance to wheat brown rust to its amphiploids with wheat.     

The inheritance of resistance to powdery mildew in interspecific hybrids and induced amphiploids of Zinnia elegans Jacq. and Z. angustifolia HBK

Summary Sterile interspecific hybrids and colchicine-induced amphiploids of Zinnia elegans Jacq. and Z. angustifolia HBK were examined to determine the mode of inheritance of resistance to Erysiphe cichoracearum DC ex Merat. Fertility was restored through colchicine treatment of two sterile hybrids of species reciprocal parentage which differed in ray petal response to the pathogen. Derived amphiploids were subsequently intercrossed to overcome the lack of segregation for this trait due to genetic control of pairing upon chromosome doubling. Resistance to E. cichoracearum appears to be complexly inherited in both leaves and ray florets of sterile hybrids and induced amphiploids. Two major dominant genes have been implicated in conferring resistance in ray petal tissue of derived amphiploids. Data obtained from the F₁ hybrid progeny of the intercrossed amphiploids indicate that this trait is not cytoplasmically inherited. It is speculated that the genes conferring resistance in the ray florets are acting independently from those controlling leaf resistance and that most, if not all, of the resistance genes are inherited from Z. angustifolia.Scientific Article No. A-3825, Contribution No. 6804 of the Maryland Agricultural Experiment Station.     

Expression of barley yellow dwarf virus and Russian wheat aphid resistance genes in and fertility of spring wheat × triticale hybrids and backcross lines

Summary The Barley Yellow Dwarf Virus disease (BYDV) and the Russian wheat aphid (RWA) Diuraphis noxia (Mordvilko) have caused significant losses to wheat and barley in several areas of the world. Important sources of resistance to both BYDV and RWA have been found in Triticale. Different generations of interspecific wheat x Triticale crosses were produced and the progenies were screened for BYDV and RWA tolerance. Plants with equal chromosome numbers showed different levels of fertility. A significant correlation was observed between pollen fertility and seed set in primary florets (r=0.57). In generaL, pollen fertility, seed set and the number of euploid plants (2n=42) increased from one generation to the next. The expression of BYDV tolerance varied from population to population. Additive effects were predominant in F₁ and some backcross populations. A dominant effect of rye tolerance genes was also observed in few populations. A monogenic trait or a quantitative (polygenic) character would not agree with the observed segregation patterns. The heritability of this oligogenic tolerance was quite different between populations and in many populations the tolerance genes were only partially expressed. Some transgressive segregation for tolerance and sensitivity was demonstrated. The genes controlling tolerance to RWA in Triticale lines, Muskox 658 and Nord Kivu were not expressed in advanced lines resistant to BYDV. This indicates that tolerance genes for BYDV and RWA in these lines are located on different chromosomes.     

Comparison of TAF46 and Zhong 5 resistances to barley yellow dwarf virus from Thinopyrum intermedium in wheat

Barley yellow dwarf virus (BYDV) is one of the most important plant viruses in the world. Two sources of resistance to BYDV derived from Thinopyrum intermedium were compared in wheat backgrounds. A source of resistance was confirmed in the partial amphiploid TAF46, the group 7 addition line L1, and translocation TC14. The other source of resistance derives from the partial amphiploid Zhong 5 and is present in the group 2 addition line Z6. Six ditelosomic addition lines have been derived from Z6. The resistance of genotypes derived from Zhong 5 is more effective at reducing virus multiplication throughout plant growth than that of genotypes derived from TAF46. The translocation line TC14, derived from TAF46 showed 30% plants escaping virus infection whereas all plants derived from Zhong 5 were infected. This suggests that the two sources of resistance are associated with differing mechanisms of resistance. Methods to better understand the genetic control and the mechanisms of these two resistances are suggested. The pyramiding of different sources of resistance to construct durable resistance is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic variation for tolerance or resistance to barley yellow dwarf virus in durum wheat

Summary One durum wheat line (Triticum durum), cv. 82PCD476, with useful BYDV tolerance or resistance, was singled out of 5 152 lines evaluated between 1979 and 1986. A few other lines such as cv. Boohai and cv. 12th IDSN 227, slightly inferior to cv. 82PCD476, also showed some value. With an hybrid of cv. 12th IDSN227 with the susceptible cv. 84PCY-S531, broad-sense heritability values of 0.37–0.41 were obtained for symptoms and a heritability value of 0.55 was obtained for the total weight of spikes. The weight of spikes was considered as a good indicator of wheat tolerance to BYDV. Although BYDV resistance or tolerance genes are not very common in durum wheat, sources of heritable resistance could be found. However, the resistance ofT. aestivum to BYDV was superior to the one found inT. durum.Cintribution no. 323     

Identifying the alien chromosomes in wheat – Leymus multicaulis derivatives using GISH and RFLP techniques

Genomic in situ hybridization (GISH) and restriction fragment length polymorphism (RFLP) were used to identify the Leymus multicaulis (XXNN, 2n = 28) chromosomes in wheat-L. muliticaulis derivatives. Fifteen lines containing L. multicaulis alien chromosomes or chromosomal fragments were identified. All alien chromosomes or fragments in these 15 lines were from the X genome and none were from the N genome. Eleven L. multicaulis disomic addition lines and four translocation-addition lines were identified with chromosome rearrangements among homoeologous groups 2, 3, 6 and 7. Only homoeologous group 1 lacked rearrangements in addition or translocation chromosomes. The results revealed that translocation in non-homoeologous chromosomes widely exists in the Triticeae and therefore it is necessary to identify the alien chromosomes (segments) in a wheat background using these combined techniques. During the course of the work, probe PSR112, was found to detect X genome addition lines involving L. multicaulischromosomes. This may prove to be a valuable probe for the identification of alien chromosomes in a wheat background. This revised version was published online in August 2006 with corrections to the Cover Date.     

Molecular cytogenetic analysis of a durum wheat ×Thinopyrum distichum hybrid used as a new source of resistance to Fusarium head blight in the greenhouse

Fusarium head blight (FHB, scab), caused by Fusarium graminearum Schwabe, is a serious and damaging disease of wheat. Although some hexaploid wheat lines express a good level of resistance to FHB, the resistance available in hexaploid wheat has not yet been transferred to durum wheat. A germplasm collection of Triticum durum× alien hybrid lines was tested as a potential source of resistance to FHB under controlled conditions. Their FHB reaction was evaluated in three tests against conidial suspensions of three strains of F. graminearum at the flowering stage. Two T. durum×Thinopyrum distichum hybrid lines, ‘AFR4’ and ‘AFR5′, expressed a significantly higher level of resistance to the spread of FHB than other durum‐alien hybrid lines and a resistant common wheat line ‘Nyu‐Bay’. Genomic in situ hybridization using total genomic DNA from alien grass species demonstrated that ‘AFR5’ had 13 or 14 alien genome chromosomes plus 27 or 28 wheat chromosomes, while ‘AFR4’ had 22 alien genome and 28 wheat chromosomes. All of the alien chromosomes present in these two lines belonged to the J genome. ‘AFR5’ is likely to be more useful as a source of FHB resistance than ‘AFR4’ because of its relatively normal meiotic behaviour, high fertility and fewer number of alien chromosomes. ‘AFR5’ shows good potential as a source for transferring FHB resistance gene into wheat. The development of T. durum addition lines carrying resistance genes from ‘AFR5’ is underway.     

Molecular and agronomic characterization of wheat-Agropyron intermedium recombinant chromosomes

Thirty‐six wheat‐Agropyron intermedium (host) Beauv. [Syn. Trichopyrum intermedium (host) A. Love, Elytrigia intermedia (host) Nevski, Thinopyrum intermedium (host) Barkworth and Dewey] 7A/7Ai‐1 recombinant chromosomes were characterized using DNA markers. Analysis of recombinant chromosomes using 15 restriction fragment length polymorphism probes identified the homoeologous crossover products that had varying length of A. intermedium chromatin introgressed onto chromosome 7A of common wheat. The linear order of the probe loci was established along the lengths of the chromosomes. The short arm recombinants that had A. intermedium chromatin distal to the locus Xpsr108 and proximal to the locus Xpsr119 were resistant to wheat stem rust, indicating that the rust resistance gene (Sr44) was located on the distal part of chromosome arm 4Ai‐1s. The barley yellow dwarf virus (BYDV) resistance gene reported to be present on the long arm of chromosome 7Ai‐1 was found to be ineffective against the BYDV serotype used in the present study.     

Reaction of tritordeum to Fusarium culmorum and Septoria nodorum

Summary Hordeum chilense is a wild barley extensively used in wide crosses in the Triticeae. It could be a valuable source of resistance to Fusarium culmorum and Septoria nodorum. Some H. chilense x Triticum spp. amphiploids, named tritordeums, were more resistant than the parental wheat line to these diseases, others were not. Average contents of ergosterol and deoxynivalenol (DON) suggested that resistance to colonization by Fusarium was the highest for Hordeum chilense, followed by tritordeum and wheat in decreasing order. In particular, the H. chilense genotypes H7 and H17 enhanced the wheat resistance to F. culmorum in its tritordeum offsprings. Resistance to S. nodorum in tritordeum was not associated with tall plant height. There is sufficient genetic variation for resistance to F. culmorum and S. nodorum among tritordeum to allow the breeding of lines combining short straw and resistance to both diseases.     

Potential new genes for resistance to <Emphasis Type="Italic">Mycosphaerella graminicola</Emphasis> identified in <Emphasis Type="Italic">Triticum aestivum</Emphasis> × <Emphasis Type="Italic">Lophopyrum elongatum</Emphasis> disomic substitution lines

Lophopyrum species carry many desirable agronomic traits, including disease resistance, which can be transferred to wheat by interspecific hybridization. To identify potentially new genes for disease and insect resistance carried by individual Lophopyrum chromosomes, 19 of 21 possible wheat cultivar Chinese Spring × Lophopyrum elongatum disomic substitution lines were tested for resistance to barley yellow dwarf virus (BYDV), cereal yellow dwarf virus (CYDV), the Hessian fly Mayetiola destructor, and the fungal pathogens Blumeria graminis and Mycosphaerella graminicola (asexual stage: Septoria tritici). Low resistance to BYDV occurred in some of the disomic substitution lines, but viral titers were significantly higher than those of two Lophopyrum species tested. This suggested that genes on more than one Lophopyrum chromosome are required for complete resistance to this virus. A potentially new gene for resistance to CYDV was detected on wheatgrass chromosome 3E. All of the substitution lines were susceptible to Mayetiola destructor and one strain of B. graminis. Disomic substitution lines containing wheatgrass chromosomes 1E and 6E were significantly more resistant to M. graminicola compared to Chinese Spring. Although neither chromosome by itself conferred resistance as high as that in the wheatgrass parent, they do appear to contain potentially new genes for resistance against this pathogen that could be useful for future plant-improvement programs.