摘要:

AbstractIdentification of resistance genes in individual plants requires the use of leaves that have homogeneous reactions to the pathogen. The reactions of the first two leaves of seedlings of 12 wheat differential varieties to 20Erysiphe graminisf.sp.triticiisolates were compared using in vitro tests on detached leaf segments. The expression of resistance and susceptibility did not differ significantly between the first two leaves with the 12 resistance genes tested. Consequently, the identification of specific powdery‐mildew‐resistance genes in individual plants is possible if approximately 10 segments of the primary and secondary leaves are used, each of them inoculated by one out of a set of 10 differential isolates. The reaction pattern of a plant to the tester isolates is interpreted according to a procedure in two steps, that are easily computerized. Identification of resistance genes in individual plants is particularly useful for resistance studies in heterogeneous plant populati

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01234.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAmong the wheatgrasses that are possible sources of genetic resistance for wheat to barley yellow‐dwarf‐virus disease (BYD) are those that have been commonly subsumed under the nameAgropyron elongatum(Host) P. Beauv. Two of these wheatgrass species are the diploidLophopymm elongatum(Host) Á. Löve (2n = 2x = 14) and the decaploidL. ponticum(Podp.) Á. Löve (2n = 10x = 70). These two species, the addition and substitution lines ofL. elongatumchromosomes in hexaploid wheat (Triticum aestivumL.), and derivatives of hybrids between hexaploid wheat andL. ponticum, were screened for resistance to BYD, as defined by visual symptoms in field‐grown plants. The two species, an amphiploid derived fromL. elongatumבChinese Spring’ wheat, and the derivatives involving L. ponticum chromosomes were all highly resistant. The substitution and addition lines ofL. elongatumchromosomes in ‘Chinese Spring’ revealed that the genetic control of resistance inL. elongatummust be complex, with more than one critical locus involved. Chromosomes 2E and 5E are involved and there are lesser contributions to resistance from the remaining wheatgrass chromosomes. One highly resistant derivative was determined to have only three pairs ofL. ponticumchromosomes. It has a wheat‐like morphology and shows promise for furt

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01235.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe objective of this study was to correlate root length of wheat (Triticum aestivumL.) genotypes grown in Al‐containing, acidic hydroponic solutions, with root weights from acid‐soil experiments and field scores from Brazilian acid‐field trials. A total of 43 wheat genotypes, primarily from Brazil, were evaluated by growing seedlings for 4 days in hydroponic solutions containing 0.0–4.0 mg/l Al. The root growth rate of all the genotypes was reduced with the addition of Al to the solution and the Al‐sensitive and Al‐tolerant wheat genotypes were clearly identified. Genotypes with intermediate Al‐tolerance levels showed variable root lengths in response to Al stress. Correlations between root length or a root tolerance index (RTI) in the Al solutions versus acid‐soil experiments and acid‐field trials were highly significant (r = 0.71–0.85, P<0.01). The most significant correlation was observed among seedlings grown in 1 mg/1 Al. This study presents evidence that this short duration and simple screening technique provides a highly significant correlation with previous acid‐soil Al‐tolerance evaluations. Furthermore, the data obtained suggest that hydroponic screening of wheat seedlings for Al tolerance may be used in breeding programmes or in screenin

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01236.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractPrevious studies in several Triticeae species have suggested that salt tolerance is a polygenic trait, but that genes on some chromosomes confer better tolerance to salt stress than others. This suggests an intriguing possibility that there may be a similar basis for salt tolerance in the species of the tribe Triticeae. In this study, chromosomal control of the tolerance to sudden salt stress, measured as the mean rate of leaf elongation in solution cultures with a single increment of 200 mM NaCl, was investigated in the genomes of cultivated barley (Hordeum vulgareL.), rye (Secale cerealeL.), andDasypyrum villosum(L.) Can‐dargy by using disomic addition lines of individual pairs of chromosomes or chromosome arms of each of the three species in the ‘Chinese Spring’ wheat genetic background. It was observed that the chromosomes of homoeologous groups 3, 4, and 5 in barley, 5 and 7 in rye, and 4 and 6 inD. villosumcarry loci with significant positive effects on salt tolerance. Increased doses of chromosomes of group 2, however, reduce or do not increase the tolerance to salt stress. These results are in agreement with a previous study of the tolerance of this salt stress regime in wheat and wheatgrass Lophopyrum elongatum. A ranking analysis of the chromosomal effects within each genome of the five Triticeae species investigated in this and previous studies revealed that the chromosomes of homoeologous groups 3 and 5 consistently confer large positive effects on the tolerance of sudden salt stress, while the chromosomes of homoeologous group 2 in increased dose have no or negative effects on the tolerance. This strongly suggests that species of the tribe Triticeae share some common genetic mechanisms of tolerance of sudden salt stress. The findings in this study give credence to the proposal that wild relatives can be exploited in the development of wheat cultivars with greater tolerance to salt s

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01237.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Japanese barley cultivar, ‘Chikurin Ibaraki 1’, is partially resistant to the PAV serotype of barley yellow‐dwarf virus (BYDV), but its induced mutant line, Ea52, is susceptible. The inheritance of resistance in cv. ‘Chikurin Ibaraki 1’ to BYDV‐PAV was investigated. The F, and F2 plants of crosses of cvs ‘Chikurin Ibaraki 1’, Ea52, ‘Vixen’, carrying theYd2gene of resistance, and ‘Plaisant’, a susceptible French cultivar, were tested in growth chamber and field conditions. Isolate RG, against which ‘Chikurin Ibaraki 1’ is partially resistant in growth chamber and field conditions, and isolate 2t, which overcomes the partial resistance of ‘Chikurin Ibaraki 1’ in field conditions (Chalhoub et al. 1994) were used. The segregation of F2 plants of crosses between ‘Chikurin Ibaraki 1’ and the susceptible cultivars to isolate RG (one resistant to three susceptible) suggests that the resistance of ‘Chikurin Ibaraki 1’ is controlled by a single recessive gene. All 537 F2 plants of ‘Chikurin Ibaraki 1’בVixen’ tested with isolate RG in growth chamber and field conditions were resistant. The F2 plants of this cross were all resistant to isolate 2t in growth chamber conditions but segregated with a ratio of one resistant to three susceptible in field conditions owing to the susceptibility of ‘Chikurin Ibaraki 1’ to this isolate. Results suggest that the resistance gene in ‘Chikurin Ibaraki 1’ is tightly linked or allelic with theYd2gene in ‘Vixen’. However, it differs from this gene in ‘Vixen

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01238.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractOne population of pearl millet (Pennisetum glaucum(L.) R. Br.) highly susceptible to downy mildew (Sclerospora graminicola(Sacc.) Schroet.) was subjected to two cycles of recurrent selection for downy mildew resistance using a modified greenhouse screening method. The response to selection was evaluated under greenhouse and field conditions using 50 random S1progenies and 50 random full‐sib progenies from each cycle bulk. Significant progress over cycles of selection was observed in all evaluation trials. These results demonstrated that, in a susceptible population, recurrent selection effectively increased the level of resistance to downy mildew. The modified greenhouse method for assessing resistance to downy mildew effectively differentiated genotypes and had the advantages of greater rapidity and suitability for use throughout the year, independent of season.A rapid decline of genotypic variance was observed in advanced cycles of selection, indicating that a small number of genes controls downy‐mildew resistance in this population. The comparison of genotypic and error variance components from S1progenies and full‐sib progenies suggested that full‐sib progenies can be used successfully in recurrent selection for increased downy‐mildew r

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01239.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractDecreasing the lipoxygenase content of soybean (Glycine max(L.) Merr.) seed is a prerequisite for its increased use in human foods. These investigations aim to analyse the variation of lipoxygenase contents in relation to the genotype or the nitrogen nutrition of the plant. Four genotypes from a divergent selection for N2fixation and the recurrent parent, Weber, were grown in pots, and twoBradyrhizobium japonicumstrains (G.49 and SMGS1) were used. Dinitrogen fixation was estimatedin situusing the acetylene–reduction assay. The lipoxygenase activity was determined polarographically on seeds taken from plants grown under controlled conditions in the presence or absence of symbiotic N2fixation. The large genotypic variation observed for the lipoxygenase contents was enhanced by high N2fixation. The variation range of lipoxygenase contents, which was obtained through the combination of the genotypic variation and the N2fixation activity, was relatively large with a ratio of 2 on a seed dry–weight basis and a ratio of 2.6 when the total proteins were considered. Decreased lipoxygenase content and increased total protein content can thus be considered in parallel in a genetic context, together with more efficient N2fixat

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01240.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effectiveness of 200‐ and 400‐m isolation distances were evaluated for small‐scale trials of oilseed rape (Brassica napusL.). These distances have been used for previous transgenic release experiments and are commonly adopted for production of basic and certified breeders seed. A 400‐m2donor plot contained plants with a dominant transgene conferring resistance to the herbicide glufosinate‐ammonium. This character was used as a selectable marker to measure the frequency of hybrid formation in 400‐m2target plots of non‐transgenic rape. Seeds produced by the non‐transgenic plants were permitted to fall onto the plots and allowed to germinate. At the first true‐leaf stage, the plants were sprayed with glufosinate‐ammonium. Surviving plants were resprayed, and a subsample assayed for the presence of the transgene using a colorimetric assay and Southern‐blot analysis. The average frequency of hybridization over two replicates was 0.0156% at 200 m and 0.0038% at 400 m. These estimates are within the limits established for the production of basic seed (0.1%). Results indicated that bees were the most likely agent for long‐di

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01241.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the course of a breeding programme for high‐linolenic‐acid linseed (oilflax,Linum usitatissimumL.) doubled‐haploid lines (DH‐lines) of three F1hybrids were generated using an anther‐culture technique. A total of 82 DH‐lines were generated and multiplied in 1993, of which 39 were suitable for testing in a repeated field trial in 1994. Yield, fat content and fatty‐acid composition were determined. The yield of the DH‐lines was not significantly different from that of respective mid‐parent values. Fatty‐acid composition and fat content showed remarkable variation, and DH‐lines exceeded cross parents in some cases for both fat content and linolenic‐acid proportion. Superior DH‐lines surpassed mid‐parent linolenic‐acid‐content values by 4.5% and fat content by 1.9%. The results indicate that anther culture is a

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01242.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe resistance toLeveillula tauricafrom an african pepper line H3Capsicum annuum) was evaluated and analysed, using the androgenetic haplodiploid progeny from an F1hybrid between H3 and a susceptible line. Tests were performed in natural infection conditions in two locations (France and Sicily). Stable behaviour of the parental and haplodiploid lines was observed in both locations, confirming the high level and stability of this resistance source in Mediterranean countries. Heritability of resistance was high and genetic analysis suggested that it is under oligogenic control. However, the number of genetic factors involved in resistance depended on infection conditions: two or three genetic factors with additive and partial dominance effects appear sufficient to confer resistance at the beginning of the epidemic or in weak infection conditions. However, additional genes are necessary to slow down further disease progress and secondary infections and at least five genetic factors are necessary to confer resistance in severe infection. In this case, both additive and epistatic effects are significant. The transfer of this resistance into cultivars will require the use of artificial inoculation procedures to control the severity of the test.

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1995.tb01243.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY