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1.
Herbage yield trials are necessary to test if candidate varieties are well suited for organic conditions. In order to elucidate a particular suitability for organic conditions, we run such trials in parallel under both organic and conventional conditions. Here, we report on second and third year results of the sowings 2004 and 2005. These trials are part of a targeted breeding programme for organic conditions. Irregular colonisation of pure grass plots with adventitious plants, in particular white clover, was recognized as a major constraint to the quality of the results obtained under organic conditions. The coefficients of variance in dry matter yield almost doubled when compared to conventional trials, and significant differences in annual yield among varieties were rare. However, when herbage yield was corrected for the estimated fraction of adventitious plant colonization at each cut, the number of instances with statistically significant differences for annual yield among varieties increased more than fourfold. Dry matter yields under organic and conventional conditions were significantly and positively correlated. However, analysis of variance showed a significant culture type by variety interaction for annual dry matter yield in 12 out of 24 trials. When diploid and tetraploid varieties of the same Lolium species were tested in one common trial, only tetraploid varieties were identified as being particularly well suited for organic conditions, while in these trials, the great majority of apparently poorly suited varieties were diploid. This suggests that breeding tetraploid Lolium varieties is promising when aiming at a favourable response to organic agriculture.  相似文献   

2.
Evaluating faba beans for rust resistance using detached leaves   总被引：2，自引：0，他引：2  
A method was developed for testing detached leavesof faba beans for their response to rust disease.Leaves 5 to 8, counting from the shoot tip, wereexcised and maintained on a water-retaining medium,with 5 ppm gibberellic acid, in an enclosed box in atemperature-controlled glasshouse. Leaves treated inthis way remained in good health for up to 30 days.Rust spores were dispersed in a slurry of talc andwater and applied to the abaxial leaf surface. Diseasedevelopment of seven rust populations, collected fromseveral locations in eastern Australia, was monitoredfor 15 days on eight faba bean accessions. Fouraccessions were BPL lines which ICARDA claimed to havesome resistance, two were ILB lines from ICARDA whichhad been found to have stronger field resistance innorthern New South Wales, Australia, and the remainingtwo were known susceptibles. The detached-leaf testshowed that the two cultivars were susceptible, thefour BPL lines were intermediate and ILB 3107 and ILB3025 were slow-rusting. One rust population, which hadbeen stored under liquid nitrogen for several years,was less effective at inducing disease symptoms thanthe other six, which were all freshly collected. Theinteractions between host accessions and rustpopulations were statistically significant but minor,as the cultivars remained in their categories ofresistance or susceptibility. The detached-leaftechnique is thus suitable for use in screeningindividual plants for reaction to several differentpathogen species or genotypes without danger ofcross-contamination or induced resistance.  相似文献   

3.
M. I. E. Arabi 《Euphytica》2005,145(1-2):161-170
Barley breeders in Syria attempting to develop barley (Hordeum vulgare L.) cultivars resistant to barley leaf stripe (BLS) disease caused by Pyrenophora graminea Ito & Kuribayashi [anamorph Drechslera graminea (Rabenh. Ex. Schlech. Shoem.)]. Information on the combining ability for BLS resistance in Syria is not available. This study was conducted to evaluate, in 10 genetically diverse barley parents, general combining ability (GCA) and specific combining ability (SCA) effects towards the determination of the genetic basis of disease resistance and to estimate genetic variability for yield components and its modification by BLS. Ten parental genotypes varying in their reactions to BLS were crossed in a half-diallel mating design to generate 45 full-sib families. The families and the parents were inoculated with P. graminea and evaluated for resistance in replicated field tests (three inoculated and three non-inoculated plots). The parents chosen showed wide variations for resistance to BLS. Genetic component analysis showed significant effects for both GCA and SCA for resistance to BLS, suggesting that additive as well as non-additive genetic mechanisms were involved in the expression of resistance in these parents. GCA effects were more important than SCA effects. Resistant parents exhibited high negative GCA indicating that additive gene effects were more predominant, and suggesting their prime suitability for use in barley breeding programs to improve resistance to BLS. Narrow-sense heritability was 58% and broad-sense heritability was 99% indicating that selection for BLS resistance should be effective in these crosses. A high genetic variability for the agronomic traits studied was observed. Yield components decreased significantly in inoculated plants and more pronounced in diseased plants. Significant GCA was observed for all traits. Values for GCA were, in some cases, significantly modified by BLS. This indicates that attention must be paid to the danger of drawing conclusion in quantitative genetics studies dealing with both diseased and healthy plants. Two genotypes, Banteng and Igri, had high negative GCA effects and are promising parents for enhancement of BLS resistance.  相似文献   

4.
Protoplast fusion can be used to produce somatic hybrids of species that cannot be obtained by sexual hybridization. The possibility to introgress genes from Solanum species into the cultivated tomato species Lycopersicon esculentum, and to obtain novel cytoplasm-nucleus combinations (cybrids) was considered as an important strategy to extend the genetic variation available for tomato breeding. Somatic hybrids between L. esculentum and other Lycopersicon species, as well as between L. esculentum and Solanum or Nicotiana species, have been produced. Specific mutants, genotypes with antibiotic resistances, and metabolic inhibition by iodoacetate or iodoacetamide and irradiation were used for the selection of hybrids. In addition, the improvement of protoplast culture techniques and the use of the favourable tissue culture traits derived from species such as L. peruvianum, which have been introduced into tomato by classical breeding, allowed the efficient recovery of somatic hybrids. However, the occurrence of somatic incongruity in fusion combinations of L. esculentum and Solanum and even more in L. esculentum and Nicotiana, did not allow the production of true cybrids and/or fertile hybrids, indicating the importance of both cytoplasm-nucleus and nucleus-nucleus interactions in somatic incongruity. Another problem with fusions between distantly related species is the strongly reduced fertility of the hybrids and the very limited homoeologous recombination between chromosomes of the parental species. Partial genome transfer from donor to recipient through microprotoplast (+) protoplast fusion, and the production of monosomic or disomic chromosome addition lines, light overcome some of these problems. In symmetric somatic hybrids between L. esculentum and S. tuberosum the occurrence of limited somatic and meiotic recombination was demonstrated. Fertile progeny plants could be obtained, though at a low frequency, when embryo rescue was performed on a large scale after backcrossing hexaploid somatic tomato (+) potato hybrids with a tetraploid potato genotype. The potential value of genomic in situ hybridization (GISH) and RFLPs for the analysis of the genome/chromosome composition of the hybrids has been demonstrated for intergeneric somatic hybrids between Lycopersicon and Solanum.Abbreviations cpDNA chloroplast DNA - mtDNA mitochondrial DNA  相似文献   

5.
Summary Calluses of spring and winter wheats (Triticum aestivum L.) were selected for Fusarium resistance in vitro, using the double-layer culture technique. Potato-dextrose agar medium in vials was inoculated with mycelia of Fusarium graminearum and F. culmorum. After one week, fungal cells were killed by autoclaving and the agar medium containing the thermostable toxic metabolites was overlayered with MS callus-growing medium. Later, wheat calluses were placed on the upper medium for 4–5 weeks, and from the surviving calluses plants were regenerated. R2 seedling populations from self-fertilized R1 plants of 4 varieties were tested for Fusarium resistance by artificial infections in the greenhouse, and 3% of the regenerated R2 plants have been found to be more resistant than the original cultivars.  相似文献   

6.
Summary The efficacy of some organic solvents for storing pollen grains of five leguminous taxa has been assessed and compared with pollen stored under controlled temperature and humidity conditions. The success obtained in the former was invariably less than that in the latter in all the taxa. The results suggest that the use of organic solvents holds some promise only for short-term and not for long-term sotrage.  相似文献   

7.
Summary Calli of resistant, intermediary and susceptible wheat (Triticum aestivum L.) varieties were selected using culture filtrates of Fusarium graminearum and F. culmorum and the regenerants were evaluated for resistance up to R3. Czapek-Dox broth medium was inoculated with mycelia of Fusarium isolates and incubated for 2–6 weeks. Filtrates were added to MS callus growing medium, then 5 weeks-old calli were transferred onto this medium (MST) for 4–5 weeks. MST containing 30% filtrate was found to be suitable for selection. Resistant calli were transferred again to fresh MST for further two selection cycles. The surviving calli produced less fertile regenerated lines (R0) than the non-selected ones. Among 18 R1 lines tested for Fusarium-resistance in the seedling stage by artificial inoculation in the greenhouse, two (11.1%) were significantly more resistant, one (5.6%) was more susceptible than the original cultivar and the rest (83.3%) behaved similarly to the donor plants. Among unselected R3 lines of three varieties, practically the same number of resistant plants were found as among the related selected ones. When the R3 selfed generations obtained through double-layer and culture filtrate selection techniques were tested for Fusarium-resistance, 35.7% of the lines were found to be more resistant than the original cultivars, none was more susceptible and 64.3% had a reaction similar to that of the source materials. Thus, inheritance of the disease reaction was not stable in all cases. Success of in vitro selection for Fusarium-resistance depended also on the genotype, and toxin analysis showed that although being effective, the selective media contained deoxynivalenol only exceptionally. In selecting wheat for Fusarium-resistance in vitro, the culture filtrate technique proved better than the double-layer procedure.  相似文献   

8.
Sweetpotato virus disease (SPVD) is due to the dual infection and synergistic interaction of Sweetpotato feathery mottle potyvirus (SPFMV) and Sweetpotato chlorotic stunt crinivirus(SPCSV), and causes up to 98% yield loss in sweetpotato in East Africa. This study was conducted to determine the inheritance of resistance to SPVD in sweetpotato and to estimate the nature of genetic variance. Ten parental clones varying in reaction to SPVD were crossed in a half diallel mating design to generate 45 full-sib families. The families were graft-inoculated with SPCSV and SPFMV to induce SPVD and evaluated for resistance in a randomized complete block design at two sites in Namulonge, Uganda during 1998–2000. In serological assays for SPFMV and SPCSV,resistance to symptom development and recovery from initial systemic SPVD symptoms, characterised resistant genotypes. Genetic component analysis showed significant effects for both general combining ability (GCA) and specific combining ability (SCA) for resistance to SPVD. GCA to SCA variance component ratios were large (0.51–0.87), hence GCA effects were more important than SCA effects. Resistant parents exhibited high GCA indicating that additive gene effects were predominant in the inheritance of resistance to SPVD and recovery. Narrow-sense heritability (31–41%) and broad-sense heritability (73–98%) were moderate to high, indicating that rapid genetic gains for SPVD resistance could be accomplished by mass selection breeding techniques. Two genotypes, New Kawogo and Sowola, had high negative GCA effects and had several families in specific crosses,which exhibited rapid recovery from SPVD,and are promising parents for enhancement of SPVD resistance and recovery. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

9.
Summary The current powdery mildew (Sphaerotheca fuligninea) resistant cucumber varieties suffer from leaf chlorosis during autumn, winter and early spring cultivation in the Netherlands. Therefore screening was carried out for novel powdery mildew resistance genes. From 177 accessions, derived from different sources, 108 accessions proved to be partially resistant to S. fuliginea. Crosses were made with 53 resistant accessions to distinguish the presence of novel genes. It is likely that the accessions C. sativus 2145, C. sativus LV 41, PI 188807, Vladivostokij, White and Yellow 1 have one or more recessive powdery mildew resistance genes, different from powdery mildew resistance genes of the line NPI, which was used for variety breeding. Powdery mildew resistance tests with S. fuliginea give similar results in different regions of the world.Abbreviations pmr powdery mildew resistance  相似文献   

10.
Although quality of potato tubers is an important topic with regard to food and industrial processing, the consequences of future atmospheric carbon dioxide (CO2) enrichment on related attributes are still unclear. Effects of elevated CO2 concentrations on yield quality of potato (Solanum tuberosum L. cv. Bintje) were thus investigated in two full growing seasons under 380, 550 or 680 μmol mol?1 CO2 in open-top chambers (OTCs). When averaged over both years, tuber malformation was increased by 62.8% as CO2 levels raised from 380 to 550 μmol mol?1, resulting in a negative impact on tuber quality. In contrast, elevated CO2 caused lower tuber greening and therefore enhanced tuber market value. Physical potato quality remained largely unchanged, except for the positive relationships between CO2 and dry matter content, resulting in higher tuber quality for industrial processing. Significant relationships were also observed between CO2 concentrations and several chemical quality parameters. The concentrations of glucose, fructose and total reducing carbohydrates were positively related to CO2 levels, which decrease tuber quality due to the higher risk for browning and generation of acrylamide of fried products. The concentrations of protein, potassium, and as a trend of calcium, were negatively related to CO2 enrichment, suggesting adverse impacts on tuber quality for human nutrition and aesthetic and sensory quality during processing. Significant negative relationships between CO2 treatments and concentrations of leucine, phenylalanine and methionine, and as a trend for di-tyrosine, histidine and aspartic acid, were also indicated, which may decrease nutrition quality of potatoes because of the reduction in physiologically valuable amino acids. With regard to organic acids, CO2-related alterations were restricted to lower concentrations of citric acid. This may reduce the processing quality of potato tuber, as there is a higher risk of discoloration, and at the same time improve quality aspects related to taste. In addition, the experiments indicated negative relationships between CO2 concentrations and total glycoalkaloids and α-chaconine, which may have negative effects on the taste of potato at low concentration of glycoalkaloids of the present study. Concomitantly, the CO2-induced decrease in glykoalkaloids may be regarded as an improvement of quality in terms of lower toxicological potential. CO2 enrichment may thus cause substantial impacts, both positive and negative, on tuber quality of potato with regard to commercial value, industrial processing and consumer nutrition and health in the future. Currently, no clear evidence exists whether CO2-induced beneficial changes will outweigh adverse effects on tuber quality.  相似文献   

11.
A set of test crosses of diploid potatoes was used to identify QTLs for foliage resistance against Phytophthora infestans and QTLs for foliage maturity type, and to assess their genetic relationship. The most important locus for both traits was found on chromosome 5 near marker GP21: the allele of marker GP21 that is associated with resistance to late blight is also associated with late foliage maturity. An additional QTL with a small effect on foliage maturity type was identified on chromosome 3, and additional QTLs for late blight resistance were found on chromosomes 3 and 10. Another QTL was detected on chromosome 7 when resistance was adjusted for the effect of foliage maturity type. The additional QTLs for resistance against P. infestans on chromosomes 3 and 10 seem to be independent of foliage maturity type and are not affected by epistatic effects of the locus on chromosome 5. The effects of the additional QTLs for resistance are small, but early maturing genotypes that necessarily have the allele for susceptibility for late blight on chromosome 5 may benefit from the resistance that is provided by these QTLs on chromosomes 3 and 10.  相似文献   

12.
Summary Interspecific hybrids of Phaseolus vulgaris and Phaseolus acutifolius or Phaseolus filiformis have been evaluated for evidence of heterosis for symbiotic nitrogen fixation activity. Hybrids showing composite leghemoglobin profiles were selected for comparison. Rooted cuttings from hybrids and their respective parents were used to estimate nitrogen fixation (acetylene reduction) rates and to determine nitrogen accumulation during the growth period. Some hybrids of Phasolus vulgaris × Phaseolus acutifolius and Phaseolus vulgaris × Phaseolus filiformis had significantly (P<0.01) higher nitrogen fixation rates and in the latter case, accumulated more total nitrogen, than either parent. The interspecific hybrids also showed more complex leghemoglobin profiles than either parent.  相似文献   

13.
Eight genotypes of Saccharum officinarum were crossed with Saccharum spontaneum and 14 genotypes of S. officinarum were crossed with Erianthus arundinaceus. A total of 39 hybrids were evolved. These 39 hybrids were raised in the field and used as donor clones for in vitro culture studies. Plantlets were regenerated from 1-month-old callus. The grown up plants were transplanted to well prepared field, to study the variations generated for the biometric as well as for biochemical characters. There were significant differences between the donor clones and their sub clones for all the character of interest. The somatic segregation was gradual and wider, showing a range of divergence from the mean towards the end of the scale. Fifty-one sub clones were selected with commercial potential which have 13% fibre, 200 cm stalk length, 10 cm internode length and pure obtainable cane sugar per cent of 10.  相似文献   

14.
M.W. Farnham  M. Wang  C.E. Thomas 《Euphytica》2002,128(3):405-407
Downy mildew, incited by Peronospora parasitica (Pers.: Fr.) Fr., is a destructive disease of broccoli (Brassica oleraceaL., Italica Group). Resistant cultivars represent a desirable control method to provide a practical, environmentally benign, and long-term means of limiting damage from this disease. Doubled-haploid (DH) lines developed by us exhibit a high level of downy mildew resistance at the cotyledon stage. To determine the mode of inheritance for this resistance, a resistant DH line was crossed to a susceptible DH line to make an F1, from which F2 and backcross (BC) populations were developed. All populations were evaluated for response to artificial inoculation with P. parasitica at the cotyledon stage. All F1 plants (including reciprocals) were as resistant as the resistant parent, indicating no maternal effect for this trait. F2 populations segregated approximately 3resistant to 1 susceptible, BC populations using the resistant parent as the recurrent parent contained all resistant plants, and the BC to the susceptible parent segregated 1 resistant to 1 susceptible. These results indicate that resistance is controlled by a single dominant gene. This gene should be easily incorporated into F1 hybrids and used commercially to prevent downy mildew at the cotyledon stage. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

15.
Cassava bacterial blight (CBB), caused by Xanthomonas axonopodis pv. manihotis (Xam), is a particularly destructive disease in South America and Africa. The movement of infected asymptomatic stems is a major means of pathogen dispersal as well as infected seeds. The success of a cassava-seed certification program depends on the availability of reliable tests to detect the pathogen in vegetative planting materials and true seeds. We report here the different methods that permitted to detect the pathogen in cassava tissues. A polymerase chain reaction (PCR) test was developed for this pathogen. The PCR assay worked well for pathogen detection in extracts from leaf and stem lesions and the minimum number of cells that could be detected ranged from 3 × 102 to 104 CFU per ml. Nested-PCR worked well for Xam detection from naturally infected seeds. This technique was specific, sensitive, and rapid for detecting Xam in cassava true seeds. The highest detection level found was 1–2 viable cells per reaction. A dot-blot assay was developed by evaluating a 898 bp DNA fragment unique to Xam strains as a diagnostic DNA probe. The probe detected Xam strains in crude extracts of leaf and stem lesions, cassava fruits and sexual seeds that were naturally infected. Overall sensitivity of the dot-blot method was about103CFU per reaction. The dot-blot hybridization technique can be easily used for culture indexing. A monoclonal antibody (MAb) was also used for an enzyme-linked immunosorbent assay (ELISA) and tested with various infected tissues. Overall sensitivity of the method was about103CFU per reaction. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

16.
Summary About 1000 Brassica oleracea accessions were evaluated in glasshouse tests for response to Plasmodiophora brassicae (clubroot). Resistance was confirmed in some north and west European kales and cabbage. A new source of resistance in cabbage, from Eire, is reported. Most other accessions were highly susceptible but lower levels of susceptibility were observed in open pollinated Brussels sprouts and forms of south European cabbage, cauliflower and broccoli. Modern breeding (as in the production of hybrid cultivars) appears to have resulted in increased susceptibility in several crop types. The implications of these results for the exploitation of germplasm are discussed.  相似文献   

17.
Summary Fusarium oxysporum causes the most serious fungus disease in tulip. Breeding for resistant cultivars may considerably contribute to a solution of the problem.Bulbs of various cultivars planted in contaminated soil showed important and significant differences in resistance. Inoculation trials in the field and in the glasshouse have led to recommendations for the screening of juvenile and adult bulbs.  相似文献   

18.
The pedigree method is often used for developing inbred lines in maize (Zea mays L.). This study was conducted to assess the effectiveness of pedigree selection for improving resistance to Gibberella ear rot in four maize populations. Selection was based on the severity of ear rot symptoms after inoculation with macroconidial suspensions of Fusarium graminearum (Schwabe) into the silk channel (for two populations) and into the developing kernels (for two other populations). Samples of the selfed families (S1 to S5), recovered from remnant seed from the selection programs, were evaluated for disease resistance during three years, using inoculation and evaluation protocols similar to those used during selection. Among-family selection was effective in both of the populations selected after silk inoculation and in one of the populations selected after kernel inoculation. Responses to selection were more evident in later than in earlier generations for both types of inoculation. Changes in the estimated genetic gain over generations were consistent with changes in the variances among families, which tended to increase in early generations and to decrease in later generations. Selection after kernel inoculation seemed to have been more effective than selection after silk inoculation in developing families with more stable resistance. Based on the results obtained here, it seems that responses to family selection could be accelerated without increasing operational costs by increasing selection intensity in later generations and inoculating fewer plants per family.  相似文献   

19.
Summary The progress of a backcross breeding programme to introduce resistance against the cereal cyst nematode into wheat is described. Methods of resistance screening and criteria for selection are detailed and the results discussed with reference to alternative procedures for the introduction of new resistance genes into major breeding programmes.  相似文献   

20.
Seventeen tea accessions belonging to Chinese (Camellia sinensis), Assamic (C. sinensis var. assamica), and Shan tea (C. sinensis var. pubilimba) groups, which are either commercially planted or new promising tea germplasm, were morphologically described at Phu Tho province (Viet Nam) and assessed for their diversity. Fourteen phyllometric parameters were qualitatively and quantitatively investigated using digital image analysis. The accessions were then discriminated by a dedicated artificial neural network for univocal plant identification and a hierarchical cluster analysis was performed in order to build a dendrogram reporting the relationships among them. Results proved the diversity of investigated tea morphotypes from Phu Tho province based on a morphological screening. More, the artificial neural network was able to perform a correct identification for almost all the accessions using simple dedicated instruments.  相似文献   

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