Introgression of alleles of the isozymic locus glucosephosphate isomerase-2 (GPI-2) from the CC genome of Brassica carinata to the CC genome of Brassica alboglabra and their independent segregation from seed colour

A yellowish brown‐seeded Brassica alboglabra was resynthesized from a (B. alboglabra×Brassica carinata) ×B. alboglabra cross, followed by self‐pollination. The resynthesized B. alboglabra lost the allele of the isozymic locus glucosephosphate isomerase‐2 (GPI‐2) from natural B. alboglabra, which was replaced by an allele from the corresponding genome in B. carinata. A simple Mendelian segregation of these two alleles was observed in the F₂ population of a natural × resynthesized B. alboglabra cross. Furthermore, these two alleles segregated independently from the seed colour.     

Cell lines and plants obtained after protoplast fusions of Rosa+Rosa,Rosa+Prunus and Rosa+Rubus

Summary Protoplasts of three Rosa cultivars were fused with each other, with protoplasts of Prunus `Colt' and with protoplasts of Rubus laciniatus, using polyethylene glycol 4000 as a fusogen. Protoplasts of Prunus were incapable of cell division and those of Rosa and Rubus were disabled by treatments with metabolic inhibitors, either iodoacetate (IOA) or rhodamine 6-G (R6G). Parental protoplasts were then fused in combinations that required complementation for their survival. RAPD analysis of 41 fusion-derived cell lines showed that two lines resulting from fusions of Rosa + Rosa and one from a fusion of Rosa + Prunus, contained some DNA markers from both fusion partners. The others contained markers of only one fusion parent. This showed that after protoplast fusion, the heterokaryons did not develop into cell lines with stable hybrid nuclei. Plants regenerated from cell lines derived from Rosa + Prunus and Rosa + Rubus fusions contained DNA markers of only Rosa and their DNA amounts were no greater than that of the Rosa parent. However, they differed morphologically from the Rosa parent to a remarkable degree, possibly because they inherited undetected genes of Prunus or Rubus, or because they were somaclonal variants of the Rosa parent. Alternative strategies for the production of somatic hybrids are discussed.     

SSR and STS markers for wheat stripe rust resistance gene <Emphasis Type="Italic">Yr26</Emphasis>

Stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating wheat diseases worldwide. Triticum aestivum-Haynaldia villosa 6VS/6AL translocation lines carrying the Yr26 gene on chromosome 1B, are resistant to most races of Pst used in virulence tests. In order to better utilize Yr26 for wheat improvement, we attempted to screen SSR and EST-based STS markers closely linked with Yr26. A total of 500 F₂ plants and the F_2:3 progenies derived from a cross between 92R137 and susceptible cultivar Yangmai 5 were inoculated with race CYR32. The analysis confirmed that stripe rust resistance was controlled by a single dominant gene, Yr26. Among 35 pairs of genomic SSR markers and 81 pairs of STS markers derived from EST sequences located on chromosome 1B, Yr26 was flanked by 5 SSR and 7 STS markers. The markers were mapped in deletion bins using CS aneuploid and deletion lines. The closest flanking marker loci, Xwe173 and Xbarc181, mapped in 1BL and the genetic distances from Yr26 were 1.4 cM and 6.7 cM, respectively. Some of these markers were previously reported on 1BS. Eight common wheat cultivars and lines developed from the T. aestivum-H. villosa 6VS/6AL translocation lines by different research groups were tested for presence of the markers. Five lines with Yr26 carried the flanking markers whereas three lines without Yr26 did not. The results indicated that the flanking markers should be useful in marker-assisted selection for incorporating Yr26 into wheat cultivars.     

Classification of Azolla spp., section Azolla

Summary Azolla accessions (section Azolla) from the germplasm collections of the International Rice Research Institute and Washington State University were fingerprinted and classified by enzyme electrophoresis and leaf trichome morphology. A. filiculoides was enzymatically distinctive and also reliably identified by its prominent one-celled trichomes. Neotropical accessions labelled as A. filiculoides proved to be members of other species. Two groups of isolates were designated A. rubra, but those from Japan were identified as A. filiculoides. The A. rubra of Australia-New Zealand was biochemically unique and possessed less protuberant trichomes than A. filiculoides. A. microphylla, A. mexicana, and A. caroliniana were phenetically similar, but a. microphylla was identifiable from the others in the banding patterns of certain enzymes. A. mexicana and A. caroliniana were closely related enzymatically. The two-celled leaf trichomes of these three species were similar in size and shape.     

Use of a synthetic hexaploid Triticum miguschovae for transfer of leaf rust resistance to common wheat

Summary Triticum miguschovae, a genome addition synthetic, was used as a source for transfer of leaf rust (Puccinia recondita tritici) resistance to common wheat. This synthetic, developed from two wild species Triticum militinae and Aegilops squarrosa, proves a valuable donor of the genes for leaf rust resistance. Leaf rust resistance was transferred from T. miguschovae by both dominant and recessive genes. Stable lines phenotypically similar to their recurrent parents Kavkaz and Bezostaya 1 but differing from them in a high level of leaf rust resistance were obtained. The genes for resistance in 3 selected lines differed from each other and from the known effective genes Lr9, Lr19, and Lr24. The resistance of one of them (line 1229) is controlled by two complementary interacting genes located on chromosome 7B and 1D was revealed by monosomic analysis.     

A new gene conferring resistance to anthracnose in Andean common bean (Phaseolus vulgaris L.) cultivar ‘Jalo Vermelho’

‘Jalo Vermelho’ is a large seeded Andean landrace of common bean (Phaseolus vulgaris L.) that constitutes an important source of anthracnose resistance, disease caused by Colletotrichum lindemuthianum. This landrace has different resistance spectrum, when compared with cultivars of Andean origin, indicating the presence of an anthracnose‐resistant gene different from Co‐1 locus. This anthracnose resistance was characterized by inheritance and allelism tests were carried out on the following genes: Co‐1, Co‐1², Co‐1³, Co‐1⁵, Co‐2, Co‐3, Co‐4, Co‐5, Co‐6, Co‐7, Co‐9, Co‐10, Co‐11 and Co‐13. Resistance to races 23, 55, 89 and 453 in ‘Jalo Vermelho’ was conditioned by a single dominant gene. Allelism tests in F₂ populations demonstrated that ‘Jalo Vermelho’ carries a dominant gene located at a distinct locus, differing from previously characterized genes. Based on its independence from previously described loci, the authors propose that the ‘Jalo Vermelho’s gene should be named Co‐12. This new gene is a valuable source of resistance to anthracnose which can be transferred to commercial cultivars to enhance the effectiveness of resistance gene pyramiding in bean breeding programmes.     

Comparative Analysis of High-Molecular-Weight Glutenin Subunit Composition in Various Triticum Species

Variation in high-molecular-weight glutenin subunit composition amongst Triticum durum cvs. of different origins was investigated by SDS-PAGE and compared with that reported for T. dicoccum and T. aestivum. Tetraploid wheat collections (408 cvs.) were found to carry nearly twice as many Glu-A1 and Glu-B1 alleles as a hexaploid wheat sample of comparable size. In each of the taxa considered, allelic variation at the Glu-B1 locus was markedly greater than that observed for Glu-A1. However, because all the Glu-B1 subunits so far discovered exhibit a restricted and distinctive mobility range during. SDS-PAGE, it is suggested that they are derived from a single source, possibly from Aegilops searsii. Most durum cvs. carried a ‘null’Glu-A1 allele and therefore fewer subunits than dicoccums and common wheats. It is argued that differences in the frequency of occurrence of ‘null’Glu-1 alleles between taxa probably resulted from random samplings made by early agriculturalists and breeders, rather than from an inherent tendency of polyploid wheats to suppress the activity of “redundant” genes.     

Characterisation and origin of rust and powdery mildew resistance genes in VPM1 wheat

Summary The expression of rust resistances conferred by closely linked genes derived from VPM1 varied with environmental conditions and with genetic backgrounds. Under low light and low temperature conditions seedlings carrying Yr17 showed susceptible responses. Stem rust and leaf rust resistance genes Sr38 and Lr37 tended to confer more resistance at 17±2° C than at normal temperatures above > 20° C. These studies supported the hypothesis that Yr17, Lr37 and Sr38 were derived from Aegilops ventricosa, whereas Pm4b was probably derived from T. persicum. Studies on certain addition lines and parental stocks indicated that wheat cytoplasm may enhance the expression of Sr38.     

Studies on the use of Solanum acaule as a bridge between Solanum tuberosum and species in the series Bulbocastana,Cardiophylla and Pinnatisecta

Preliminary results have indicated that Solanum acaule can serve as an intermediate for gene transfer from Solanum species in the Mexican series Bulbocastana, Cardiophylla and Pinnatisecta to Solanum tuberosum. Clones of S. acaule vary in their effectiveness as female parents in crosses with the Mexican species. The F1 hybrids obtained were sterile triploids. Fertile hexaploids were produced from the triploids by colchicine treatment. The hexaploid from the cross S. acaule x S. pinnatisectum was successfully crossed with diploid and tetraploid forms of series Tuberosa. Some of the resultant triple hybrids were self-fertile.     

Cytological and Microsatellite Mapping of the Gene for Brittle Rachis in a Triticum Aestivum-Aegilops Tauschii Introgression Line

Summary Aegilops tauschii (Coss.) Schmal. (2n = 2x = 14, DD), a wild relative of wheat has been considered to be a valuable source of variation for improvement of cultivated wheats. However, undesirable genes can be incorporated into the cultivated varieties from wild relatives. The spontaneous spike shattering caused by the brittle rachis character is of adaptive value in wild grass species, but not in cultivated varieties. The rachis of R-61, which was derived from the cross of T. aestivum cv. Bet Hashita with an accession of Ae. tauschii, was brittle. Using telosomic stocks, the brittle rachis gene Br ⁶¹ (tentatively designated) of B-61 was located on the short arm of chromosome 3D and the distance of Br ⁶¹ to the centromere was 31.9 cM. The distance of Br ⁶¹ from the centromeric marker Xgdm72 was 25.3 cM on the short arm of chromosome 3D. The location of Br ⁶¹ was similar to Br ₁ whose location was determined by telosomic mapping and microsatellite mapping. Discrepancy of disarticulation type was found between R-61 and Aegilops tauschii suggesting that the recombination around the regions of Br ₁ locus and Br ^t locus created the wedge type disarticulation of R-61.     

Genetical assessment of diploid progenitors of <Emphasis Type="Italic">S. scabra</Emphasis> by isozyme,RAPD and STS markers: a possible strategy for improvement of drought tolerant allo-tetraploid <Emphasis Type="Italic">S. scabra</Emphasis> species

Assessment of genetic variations of two progenitors of S. scabra was investigated employing isozyme, RAPD and STS markers. Earlier reports have conclusively indicated S. seabrana and S. viscosa as two diploid progenitors of allo-tetraploid S. scabra. A total of 476 RAPD bands generated from 32 primers, 104 STS fragments from 17 primer pairs and 73 isoforms from 14 enzyme systems indicated significant sharing of these bands to S. scabra with that of S. seabrana in comparison to its other progenitor i.e., S. viscosa. High frequencies of isozyme band sharing between S. seabrana and S. scabra (0.125–0.30) as well as high genetic similarities (59%) of it with S. seabrana as reveled from dendrogram analysis indicated impact of close proximity of the occurrence of S. seabrana in the development of S. scabra. The proportion of bands shared by RAPD (40%) and STS (40%) markers were also observed high between S. seabrana and S. scabra. However, the numbers of unique bands were less in all these species. More correspondence and sharing of bands by S. seabrana towards S. scabra suggested using selected lines of S. seabrana the genetic base of allo-tetraploid, drought tolerant S. scabra lines can be broaden.     

Response of tolerant breeding lines of tomato, Lycopersicon esculentum, originating from three different sources (L. peruvianum, L. pimpinellifolium and L. chilense) to early controlled inoculation by tomato yellow leaf curl virus (TYLCV)

Selection of tomato plants supposedly tolerant to tomato yellow leaf curl virus (TYLCV), based solely on the absence of symptoms in an infested field can be misleading. An inoculation routine was therefore established to avoid escapes and to overcome difficulties associated with the age of the plant at the time of infection. The inoculation routine was applied to a selection of resistant/tolerant individuals generated through a diallel F¹ cross and to F² segregating populations originating from three wild tomato species described as tolerant to TYLCV: Lycopersicon peruvianum EC 104395, Lycopersicon pimpinellifolium Hirsute and Lycopersicon chilense LA 1969. Clear differences were observed between susceptible symptomatic and tolerant symptomless tomato genotypes, indicating that the uncertainty resulting from escapes, from different levels of inoculum, and from the time of inoculation, can be eliminated. The genes involved in tolerance provided different levels of protection; combinations of various tolerant sources and levels in a single genotype gave a higher level of tolerance. Differences in level of protection were found between genes from the same source and between sources; none of the sources tested had complete dominance. The results obtained with the F² segregating population showed that tolerance from L. pimpinellifolium is controlled by one major gene, that from L. chilense by two genes, and that from L. peruvianum by three genes with no dominant effect. The combination of sources for resistance can thus have positive or negative synergistic effects, or no effect. We suggest that a maximal level of tolerance can be obtained by the additive effect of the partly dominant genes from L. pimpinellifolium and L. chilense.     

Alien introgression of spring habit dominant genes into bread wheat

Summary Alien dominant genes of spring habit were introgressed into bread wheat. The introgression was undertaken by simple crossing of winter bread wheat to related spring species or genera, followed by backcrossing to winter bread wheat, and did not involve the use of the ph mutants or embryo culture. The introgressed genes were located mostly on chromosomes of homoeologous group 5, and were allelic to the known Vrn genes in bread wheat. Nevertheless three groups of lines were discovered with the genes possibly located on other chromosomes. These genes were non-allelic to each other and to known Vrn genes and were designated Vrn6 ^Sc , Vrn7 ^Sc (introgressed from Secale cereale) and Vrn8 ^Ts (from Triticum sphaerococcum).     

Inheritance of Fusarium resistance in a jointless tomato as affected by the X gametophytic factor

Summary Hybridization between tomato with xx and XX gametophytic genotypes exhibited in segregating generations, deviations from the expected monogenic inheritance of Fusarium wilt resistance conditioned by gene I. These deviations resul ted from gametophytic preference, linkage and the presence of modifying loci associated with the gene I. Although information on the inheritance of Fusarium wilt resistance is based on backcross data, information obtained from the pedigree procedure and testcrosses made with BC₁S₂ plants all supports the presence of modifiers.Michigan Agricultural Experiment Station Journal Number 5457.     

Genetic mapping of the genes for non-glaucous phenotypes in tetraploid wheat

Glaucousness is a visual trait related to the colour of the photosynthetic surface and hence it can be easily selected. It is associated both with the deposition and orientation of wax platelets on the cuticle of the photosynthetic surface. It is known that the glaucous leaf character is determined by the W1 gene, and Iw1 and Iw1 ^DIC genes from Triticum dicoccoides, which act as an epistatic inhibitor to a glaucousness. The aim of the present study was to map W1, Iw1 and Iw1 ^DIC from T. dicoccoides in the short arm of chromosome 2B of tetraploid wheat. Segregation of F₂ populations of three hybrids indicated that the marker Xgwm455 is linked with and distal to Iw1 (16.7 cM), two markers are tightly linked with W1, and Iw1 ^DIC is linked with Xgwm614 and Xwmc661 distally located on chromosome 2BS. From three derived maps, it is suggested that Iw1 ^DIC locus is different from W1. We discuss the difference between Vir and Iw1 ^DIC from T. dicoccoides.     

Introgression of leaf blight resistance from Allium roylei Stearn into onion (A. cepa L.)

Summary Segregation analysis in BC₁ and F₂ progenies from interspecific hybrids between Allium roylei and A. cepa demonstrated that leaf blight resistance is conditioned by one single dominant gene from A. roylei. This gene, designated Bs ₁ , was unlinked to the genes Pd ₁ and Pd ₂ determining downy mildew resistance. The prospects of exploiting A. roylei as a source for disease resistances in onion breeding are very promising.     

A 192bp allele at the <Emphasis Type="Italic">Xgwm261</Emphasis> locus is not always associated with the <Emphasis Type="Italic">Rht8</Emphasis> dwarfing gene in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

The height-reducing gene Rht8 was introduced into Italian wheats by breeder Nazareno Strampelli from the Japanese landrace Akakomugi, and has been widely used in wheats adapted to southern and eastern European conditions. Following identification of a close linkage to Rht8, microsatellite marker Gwm261 has been used extensively to screen large numbers of diverse international germplasm. A 192bp allele at this locus has been taken as “diagnostic” for Rht8 and used to infer the international distribution of Rht8. In this paper, we report several instances of cultivars and mapping populations that vary for the presence of the 192bp allele at the Xgwm261 locus (Xgwm261 ₁₉₂ ), but with no associated reduction in height, suggesting a lack of association with Rht8. For instance, in the population derived from a cross between Sunco (Rht-B1b, Xgwm261 ₁₆₅ ) and Tasman (Rht-D1b, Xgwm261 ₁₉₂ ), there were significant height differences associated with the segregation of Rht-B1b and Rht-D1b, but no height differences between Xgwm261 genotypes. Similar results were obtained in a population derived from the cross between Molineux (Rht-B1b, Xgwm261 ₁₉₂ ) and Trident (Rht-D1b Xgwm261 ₂₀₈ ). In contrast, the cross between Trident and Chuanmai 18 (Xgwm261 ₁₉₂ ) gave significant height effects at both the Rht-D1 and Xgwm261 loci, with no epistatic interaction between loci. Chuanmai 18 is closely related to the Strampelli wheat Mara (ancestrally derived from Akakomugi) and is therefore likely to carry Rht8. The old Japanese cultivar Norin 10, used by Norman Borlaug to introduce Rht-B1b and Rht-D1b into Mexican wheats, also has a 192bp allele at the Xgwm261 locus, and the sequence of the amplified product is identical to that of Akakomugi. We suggest that the widespread use of Norin 10-derived germplasm during and after the Green Revolution introduced a second haplotype into international germplasm, in which Xgwm261 ₁₉₂ has no association with Rht8. Therefore, the presence of Xgwm261 ₁₉₂ is only indicative of Rht8 in wheat cultivars that have inherited this allele from Akakomugi or a Strampelli wheat ancestor.     

Somatic Embryogenesis and Plant Regeneration from Tritordeum

Regeneration of plants by somatic embryogenesis from immature embryos of hexaploid tritordeum (AABBH^chH^ch, amphiploid Hordeum chilense×Triticum turgidum conv. durum) and durum wheat (Triticum tergidum) was induced on MS medium supplemented with different 2.4-D concentrations. Well-defined embryoids were formed with a high frequency on the scutellar callus from 1 or 2 weeks onwards and plantlets were developed from them. In the best cases from one single explant more than 100 plants could be obtained. Plants were also regenerated by somatic embryogenesis from inflorescences of Hordeum chilense×Triticum turgiditm conv. durum hybrid and its respective hexa-amphiploid. With regard to callus induction and regenerative ability, evident differences between hexa- and octoploid (H. chilense×T. aestivum) tritordeum were found, the latter showing a very low response.