Genotype by environment interactions in barley (<Emphasis Type="Italic">Hordeum</Emphasis><Emphasis Type="Italic"> vulgare</Emphasis> L.): different responses of landraces,recombinant inbred lines and varieties to Mediterranean environment

Genotype-by-environment interactions (GEIs) can affect breeding progress because they often complicate the evaluation and selection of superior genotypes. This drawback can be reduced by gaining insights into GEI processes and genotype adaptation. Here, we have studied the GEIs over a set of 24 barley genotypes that were grown across six environments (location-by-year combinations) in Sardinia, Italy. Three groups of genotypes were analysed: barley landraces (LANs), recombinant inbred lines (RILs), and commercial varieties (VARs). The additive main effects and multiplicative interaction (AMMI) model was used for data analysis, and results evidenced no significant differences in grain yield averages for the 24 genotypes. However, there was a relevant GEI for yield mainly between two of the six environments (one characterised by warm pre-anthesis period and high spring rainfalls, and the other characterised by opposite features) and two groups of genotypes (VAR and LAN). Moreover, a negative trade-off between yield levels of genotypes was seen when the barley genotypes were grown in the contrasting environments. Overall, intermediate GEI levels were seen for RILs in comparison to LANs and VARs, and some of the RILs provided valuable yield levels (e.g. RILs 23 and 52). The results thus show the potential usefulness of LANs as a genetic resource for breeding, e.g. to obtain genotypes adapted to Mediterranean environments, such as the RILs analysed in this study. Most of the actual work was carried out when the first author was a PhD student in ‘Agro-meteorology and ecophysiology of agricultural and forest systems’ and she was affiliated to Dipartimento di Scienze Agronomiche e Genetica Vegetale Agraria, Università degli Studi di Sassari, Via E. de Nicola, Sassari 07100, Italy.     

A simple,rapid and reliable bioassay for evaluating seedling vigor under submergence in <Emphasis Type="Italic">indica</Emphasis> and <Emphasis Type="Italic">japonica</Emphasis> rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Submergence is a major stress causing yield losses particularly in the direct-seeded rice cultivation system and necessitates the development of a simple, rapid and reliable bioassay for a large scale screening of rice germplasms with tolerance against submergence stress. We developed two new bioassay methods that were based primarily on the seedling vigor evaluated by the ability of fast shoot elongation under submerged conditions, and compared their effectiveness with two other available methods. All four bioassay methods using cultivars of 7 indica and 6 japonica types revealed significant and consistent cultivar differences in seedling vigor under submergence and/or submergence tolerance. Japonica cultivars were more vigorous than indica cultivars, with Nipponbare being the most vigorous. The simplest test tube method showed the highest correlations to all other methods. Our results suggest that seedling vigor serves as a submergence avoidance mechanism and confers tolerance on rice seedlings to flooding during early crop establishment. A possible relationship is discussed between seedling vigor based on fast shoot elongation and submergence tolerance defined by recovery from submergence stress.     

Heritable improvement of frost tolerance in winter wheat by in vitro-selection of hydroxyproline-resistant proline overproducing mutants

In a previous study (Dörffling et al., J. Plant Physiol. 142, 222–225, 1993) in vitro-selection and regeneration of hydroxyproline (Hyp)-resistant lines of winter wheat (Triticum aestivum cv. Jo 3063) with increased frost tolerance and increased proline contents was reported. In this study the heritability of these traits was investigated. The F ₁progenies derived from the pollination of regenerated plants with pollen from wild type plants developed higher mean frost tolerance (lower LT ₅₀values) and higher proline levels compared with in vitro-controls and wild type plants. In the F ₂generation, which was obtained by self-pollination, segregation of the Hyp-lines in a 3:1 phenotypic ratio with regard to the traits frost tolerance and proline content was observed. Subsequent selection of extremes in the F ₂yielded homozygous plants in the F ₃generation. Lower LT ₅₀values and increased proline contents in those F ₃plants were significantly correlated. Furthermore, improved frost tolerance of one of the selected mutants was also observed in studies with whole plants in the F ₄generation. These results, which are similar to results of parallel studies on winter barley, provide strong evidence for the heritability of the traits 'increased frost tolerance' and 'increased proline content' obtained by this in vitro-selection procedure. The mutation seems to be due to a single incompletely dominant gene. A comparison of frost tolerance values from F ₃Hyp-progenies with those of seven standard varieties differing in frost tolerance indicates a considerable improvement of frost tolerance by the described in vitro-selection method.     

Evaluation of seedling and adult plant resistance to <Emphasis Type="Italic">Puccinia hordei</Emphasis> in barley

The responses of 92 barley genotypes to selected Puccinia hordei pathotypes were assessed in greenhouse tests at seedling growth stages and in the field at adult plant growth stages to identify known and/or unknown resistances. On the basis of multipathotype tests, 35 genotypes were postulated to carry Rph1, Rph2, Rph4, Rph5, Rph12, RphCantala, alone or in combination (Rph2 + Rph4 and Rph1 + Rph2), whereas 52 genotypes lacked seedling resistance to P. hordei to the pathotypes used. Five genotypes carried seedling resistance that was effective to all pathotypes, of which four were believed to carry uncharacterised resistance based on pedigree information. Field tests at adult plant growth stages indicated that while 28 genotypes were susceptible, 57 carried uncharacterised APR to P. hordei. Pedigree analysis indicated that APR in the test genotypes could have been derived from three different sources. The resistant responses of seven cultivars at adult plant growth stages were believed to be due to the presence of seedling resistance effective against the field pathotypes.     

<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of faba bean <Emphasis Type="Italic">(Vicia faba</Emphasis> L.) using embryo axes

A system for the production of transgenic faba bean by Agrobacterium-mediated transformation was developed. This system is based upon direct shoot organogenesis after transformation of meristematic cells derived from embryo axes. Explants were co-cultivated with A. tumefaciens strain EHA105/pGlsfa, which harbored a binary vector containing a gene encoding a sulphur rich sunflower albumin (SFA8) linked to the bar gene. Strain EHA 101/pAN109 carrying the binary plasmid containing the coding sequence of a mutant aspartate kinase gene (lysC) from E. coli in combination with neomycinphosphotransferase II gene (nptII) was used as well. The coding sequences of SFA8 and LysC genes were fused to seed specific promoters, either Vicia faba legumin B4 promoter (LeB4) or phaseolin promoter, respectively. Seven phosphinothricin (PPT) resistant clones from Mythos and Albatross cultivars were recovered. Integration, inheritance and expression of the transgenes were confirmed by Southern blot, PCR, enzyme activity assay and Western blot.     

Genetic analysis of resistance to flower bud thrips (<Emphasis Type="Italic">Megalurothrips sjostedti</Emphasis>) in cowpea (<Emphasis Type="Italic">Vigna unguiculata</Emphasis> [L.] Walp.)

Cowpea is an important legume in sub-Saharan Africa where its protein rich grains are consumed. Insect pests constitute a major constraint to cowpea production. Flower bud thrips (FTh) is the first major pest of cowpea at the reproductive stage and if not controlled with insecticides is capable of reducing grain yield significantly. Information on the inheritance of resistance to FTh is required to facilitate breeding of resistant cultivars. The genetics of resistance was studied in crosses of four cowpea lines. Maternal effect was implicated while frequency distributions of the F₂ and backcross generations suggest quantitative inheritance. Additive, dominance and epistatic gene effects made large contributions and since improved inbred lines are the desired product, selection should not be too severe in the early generations to allow for desirable gene recombination. This study suggested that some of the genes involved in the control of resistance to FTh are different in TVu1509 and Sanzi. Broad sense heritability ranged from 56% to 73%. Choice of maternal parent in a cross will be critical to the success of resistance breeding.     

Allotetraploid hybrids produced by protoplast fusion for seedless triploid <Emphasis Type="BoldItalic">Citrus</Emphasis> breeding

In connection with crop improvement strategies for marginal regions it has been proposed to increase the outcrossing rate in barley which would presuppose high and persistent pollen viability to ensure successful cross fertilisation. The present study was designed to investigate the viability of mature pollen from extruded and non-extruded anthers of cultivated and wild barley (Hordeum vulgare ssp vulgare and ssp spontaneum, respectively) in comparison with the closely related but obligatory outcrossing species H. bulbosum. Pollen viability (PV) was assessed employing the p-phenylenediamine-peroxidase-test on pollen derived from spikes or anthers immediately after collection and after treatment at 20, 30 and 40 ^∘C for 1, 2, 4, 8 and 16 h. The latter treatment was interposed after 8 h by a 10 h period of darkness at 12 ^∘C and thus called 26 h treatment, consecutively. Initial PV was high with 98% across all genotypes and even at 40 ^∘C did not fall below 80% after 8 h. After the 26 h treatment, PV of two H. vulgare genotypes originating from semi-arid regions and of H. bulbosum fell below 60% while the other genotypes retained a PV of > 80%. Viability of pollen of extruded anthers in H. vulgare ssp. spontaneum was on average slightly but significantly lower than PV of non-extruded anthers but still remained above 90%, even after the 26 h treatment at 40 ^∘C. Pollen viability of the outcrossing species H. bulbosum ranged on a very similar level as PV of H. vulgare. Results indicate that pollen of H. vulgare retains a sufficiently high level of viability to ensure successful cross-fertilisation over a period of at least 26 h even at high temperatures of up to 40 ^∘C.     

Nonparametric phenotypic stability analysis in advanced barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.) genotypes

The development of genotypes with adaptation to a wide range of environments is one of the most important goals of plant breeding programs. In order to compare nonparametric stability measures and to identify promising high-yield and stable barley (Hordeum vulgare L.), 20 barley genotypes selected from the Iran/ICARDA joint project and grown in nine environments during 2009-11 in Iran. Four nonparametric statistical tests of significance for genotype × environment (GE) interaction and 10 nonparametric measures of stability were used to identify stable genotypes in nine environments. Results of nonparametric tests of G×E interaction (Kubinger, Hildebrand, and Kroon/ Laan) and a combined ANOVA across environments, indicated the presence of both crossover and non-crossover interactions. Also, only TOP and rank-sum values were positively associated with high yield. Thus, in the simultaneous selection for high yield and stability, only the rank-sum and TOP methods were useful in terms of the principal component analysis results, and correlation analysis of nonparametric stability statistics and yield. According to these stability parameters (TOP and rank-sum), three genotypes (G13, G12, and G17) were the most stable for grain yield. The results also revealed that based on nonparametric test results, stability could be classified into three groups, according to agronomic and biological concepts of stability.     

Analysis of genetic architecture for some physiological characters in sesame (<Emphasis Type="Italic">Sesamum indicum</Emphasis> L.)

Combining ability for some important physiological parameters in sesame were examined to understand the nature of gene action and to identify parents for breeding programme. Seven diverse genotypes of sesame, their 21 F₁s and 21 F₂s were grown in summer, 2003, in a randomized complete block design with three replications. Data were collected on leaf area index (LAI) at 30, 45, 60 and 75 days after sowing (DAS), crop growth rate (CGR) estimated between 30–45 DAS, 45–60 DAS and 60–75 DAS, days to peak flowering (DPF), duration of flowering (DF), duration from peak flowering to maturity (DFM), oil content in percentage (OC) and oil yield (OY) plant⁻¹. Analysis of combining ability was done on the above physiological characters following Method-2, Model-I of Griffing (Aust J Biol Sci 9:463–493 1956). Variances due to general combining ability (GCA) and specific combining ability (SCA) for all the physiological traits were highly significant in both F₁ and F₂ generations indicating importance of both additive and non-additive gene actions for the inheritance of all the physiological characters in both F₁ and F₂ generations. Preponderance of non-additive gene action was recorded for CGRs, LAI 3, LAI 4, DPF, DF and OY in both the F₁ and the F₂ generations. For OC additive gene action was predominant in F₁ while non-additive gene action in F₂. The genotype OS-Sel-2 appeared as best overall general combiner in both the F₁ and the F₂ generations. For DPF, DF and DFM, the variety B 67 was best general combiner, followed by CST 2002, which could be utilized for developing early flowering and early maturing lines with determinate growth habit. Association between GCA-effects and mean performance of the parents suggested that the performance per se could be a good indicator of its ability to transmit the desirable attributes to its progenies. Crosses CST 2002 × TKG 22, CST 2002 × MT 34, MT 34 × AAUDT 9304-14-4, AAUDT 9304-14-4 × B 67, TKG 22 × Rama and TKG 22 × B 67 which showed high SCA-effect for OY, also exhibited positive and significant SCA-effects for other physiological component characters in F₁ generation. The overall results indicated that crosses CST 2002 × TKG 22 and MT 34 × AAUDT 9304-14-4 could be utilized for development of high oil yielding hybrids. The crosses OS-Sel-2 × AAUDT 9304-14-4, AAUDT 9304-14-4 × B 67 and MT 34 × OS-Sel-2 could be promising for isolation of superior recombinants for high oil yield coupled with early maturity and other growth characters in advanced generations of segregation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Molecular markers linked to <Emphasis Type="Italic">Bn</Emphasis>;<Emphasis Type="Italic">rf</Emphasis>: a recessive epistatic inhibitor gene of recessive genic male sterility in <Emphasis Type="Italic">Brassica napus </Emphasis>L.

7–7365AB is a recessive genic male sterile (RGMS) two-type line, which can be applied in a three-line system with the interim-maintainer, 7–7365C. Fertility of this system is controlled by two duplicate dominant epistatic genes (Bn;Ms3 and Bn;Ms4) and one recessive epistatic inhibitor gene (Bn;rf). Therefore an individual with the genotype of Bn;ms3ms3ms4ms4Rf_ exhibits male sterility, whereas, plant with Bn;ms3ms3ms4ms4rfrf shows fertility because homozygosity at the Bn;rf locus (Bn;rfrf) can inhibit the expression of two recessive male sterile genes in homozygous Bn;ms3ms3ms4ms4 plant. A cross of 7–7365A (Bn;ms3ms3ms4ms4RfRf) and 7–7365C (Bn;ms3ms3ms4ms4rfrf) can generate a complete male sterile population served as a mother line with restorer in alternative strips for the multiplication of hybrid seeds. In the present study, molecular mapping of the Bn;Rf gene was performed in a BC₁ population from the cross between 7–7365A and 7–7365C. Bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) technique was used to identify molecular markers linked to the gene of interest. From a survey of 768 primer combinations, seven AFLP markers were identified. The closest marker, XM5, was co-segregated with the Bn;Rf locus and successfully converted into a sequence characterized amplified region (SCAR) marker, designated as XSC5. Two flanking markers, XM3 and XM2, were 0.6 cM and 2.6 cM away from the target gene, respectively. XM1 was subsequently mapped on linkage group N7 using a doubled-haploid (DH) mapping population derived from the cross Tapidor × Ningyou7, available at IMSORB, UK. To further confirm the location of the Bn;Rf gene, additional simple sequence repeat (SSR) markers in linkage group N7 from the reference maps were screened in the BC₁ population. Two SSR markers, CB10594 and BRMS018, showed polymorphisms in our mapping population. The molecular markers found in the present study will facilitate the selection of interim-maintainer.     

Production and characterization of inter-sectional hybrids between <Emphasis Type="Italic">Kalanchoe spathulata</Emphasis> and <Emphasis Type="Italic">K. laxiflora</Emphasis> ( = <Emphasis Type="Italic">Bryophyllum crenatum</Emphasis>)

The genus Kalanchoe is currently divided into section Kalanchoe and section Bryophyllum, and there has been no successful report on the production of inter-sectional hybrids. Therefore, reciprocal crosses were made between Kalanchoe spathulata (sect. Kalanchoe) and K. laxiflora (sect. Bryophyllum) in order to obtain basic information on the reproductive barriers between these two sections. The seeds were aseptically germinated in vitro and the plants were grown in greenhouse till flowering. When K. spathulata was used as a maternal donor, 39 out of 80 plants showed intermediate characteristics between K. spathulata and K. laxiflora. In contrast, no plants were obtained in the reverse crosses. Hybridity of these plants was confirmed by flow cytometric analysis, chromosome numbers and RAPD analysis. Bulbil formation on the leaf margin as one of the conspicuous characteristics of K. laxiflora was not observed in the hybrids. Some of the hybrid lines showed some pollen fertility, but failed to yield viable seeds by self-pollination or backcross-pollination. Successful production of the inter-sectional hybrid between the two species suggests that they are not so distantly related as considered previously.     

Resynthesizing <Emphasis Type="Italic">Brassica napus</Emphasis> from interspecific hybridization between <Emphasis Type="Italic">Brassica rapa</Emphasis> and <Emphasis Type="Italic">B. oleracea</Emphasis> through ovary culture

Using three varieties of Brassica rapa, cv. Hauarad (accession 708), cv. Maoshan-3 (714) and cv. Youbai (715), as the maternal plants and one variety of B. oleracea cv. Jingfeng-1 (6012) as the paternal plant, crosses were made to produce interspecific hybrids through ovary culture techniques. A better response of seed formation was observed when ovaries were cultured in vitro at 9–12 days after pollination on the basal MS and B5 media supplemented with 6-benzylaminopurine (BA) and naphthylacetic acid (NAA). The best response was observed for cross 714×6012 with the rate of seeds per ovary reaching 43.0%. Seeds for cross 715×6012 showed the best germination response (66.7%) on the regeneration medium (MS+1.0 mg l^–1 BA+0.05 mg l^–1 NAA). In all three cross combinations, good response in terms of root number and length of plants was observed on the root induction medium (MS+1.0 mg l^–1 BA+0.1 mg l^–1 NAA). A better response was observed for the regenerated plants cultured for 14 days than for 7 days. The ovary-derived plants with well-developed root system were hardened for 8 days and their survival rate reached over 80%. Cytological studies showed that the chromosome number of all plants tested was 19 (the sum of both parents), indicating that these regenerated plants were all true hybrids of B. rapa (n = 10) × B. oleracea (n = 9). The regenerated plants were doubled with colchicine treatment, and the best response in the crosses 708×6012, 714×6012 and 715×6012 was observed when treated with 170 mg l^–1 colchicine for up to 30 h and their doubling frequency reached 52, 56 and 62%, respectively.     

Non-parametric measures of phenotypic stability in chickpea genotypes (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.)

Multi-environment trials (MET) play an important role in selecting the best cultivars and/or agronomic practices to be used in future years at different locations by assessing a cultivar's stability across environments before its commercial release. Objective of this study is to identify chickpea (Cicer arietinum L.) genotypes that have high yield and stable performance across different locations. The genotypes were developed by various breeders at different research institutes/stations of Iran and the International Center for Agricultural Research in Dray Areas (ICARDA), Syria. Several statistical methods were used to evaluate phenotypic stability of these test chickpea genotypes. The 17 genotypes were tested at six different research stations for two years in Iran. Three non-parametric statistical test of significance for genotype × environment (GE) interaction and ten nonparametric measures of stability analyses were used to identify stable genotypes across the 16 environments. The non-parametric measures (Kubinger, Hildebrand and Kroon/Van der) for G × E interaction were highly significant (P < 0.01), suggesting differential responses of the genotypes to the test environments. Based on high values of nonparametric superiority measure (Fox et al. 1990) and low values of Kang's (1988) rank-sum stability parameters, Flip 94-123C was identified as the most stable genotype. These non parametric parameters were observed to be associated with high mean yield. However, the other nonparametric methods were not positively correlated with mean yield and were therefore not used in classifying the genotypes. Simple correlation coefficients using Spearman’s rank correlation, calculated using ranks was used to measure the relationship between the stability parameters. To understand the nature of relationships among the nonparametric methods, a hierarchical cluster analysis based on non weighted values of genotypes, was performed. The 10 stability parameters fell into three groups.     

Genetic analysis of resistance to <Emphasis Type="Italic">soil-borne wheat mosaic virus</Emphasis> derived from <Emphasis Type="Italic">Aegilops tauschii</Emphasis>

Genetic Analysis of Resistance to Soil-Borne Wheat Mosaic Virus Derived from Aegilops tauschii. Euphytica. Soil-Borne Wheat Mosaic Virus (SBWMV), vectored by the soil inhabiting organism Polymyxa graminis, causes damage to wheat (Triticum aestivum) yields in most of the wheat growing regions of the world. In localized fields, the entire crop may be lost to the virus. Although many winter wheat cultivars contain resistance to SBWMV, the inheritance of resistance is poorly understood. A linkage analysis of a segregating recombinant inbred line population from the cross KS96WGRC40 × Wichita identified a gene of major effect conferring resistance to SBWMV in the germplasm KS96WGRC40. The SBWMV resistance gene within KS96WGRC40 was derived from accession TA2397 of Aegilops taushcii and is located on the long arm of chromosome 5D, flanked by microsatellite markers Xcfd10 and Xbarc144. The relationship of this locus with a previously identified QTL for SBWMV resistance and the Sbm1 gene conferring resistance to soil-borne cereal mosaic virus is not known, but suggests that a gene on 5DL conferring resistance to both viruses may be present in T. aestivum, as well as the D-genome donor Ae. tauschii.     

Ploidy level studies on the <Emphasis Type="Italic">Dioscorea cayenensis</Emphasis>/<Emphasis Type="Italic">Dioscorea rotundata</Emphasis> complex core set

The Guinea yams, Dioscorea cayenensis Lam. and D. rotundata Poir. (D. cayenensis–D. rotundata complex), represent a highly important crop, widely distributed in the humid and semi-humid tropics. The ploidy levels of 170 accessions of the core set of Guinea yams from West African countries was determined using flow cytometry with propidium iodide staining. One hundred and eight of the genotypes were found to be tetraploid, 47 were hexaploid and five were octoploid. One mixoploid individual containing tetraploid and hexaploid nuclei was also detected. A deeper analysis considering each separate taxon revealed that while for D. rotundata the majority of individuals were tetraploid, for D. cayenensis this ploidy level was not detected in any of the accessions. Also, no association between ploidy level and place of cultivation was found for the evaluated germplasm. The obtained data is highly valuable for breeding programs of Guinea yam, especially for the optimization of future hybridization experiments directed to the genetic improvement of this economically important crop.     

Genetics of resistance to <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> in <Emphasis Type="Italic">Cucumis sativus</Emphasis> var. <Emphasis Type="Italic">hardwickii</Emphasis> R. Alef

The genetics of resistance to Cucumber mosaic virus (CMV) in Cucumis sativus var. hardwickii R. Alef, the wild progenitor of cultivated cucumber was assessed by challenge inoculation and by natural infection of CMV. Among the 31 genotypes of C. sativus var. hardwickii collected from 21 locations in India the lowest mean percent disease intensity (PDI) was recorded in IC-277048 (6.33%) while the highest PDI was observed in IC-331631 (75.33%). All the four cultivated varieties (DC-1, DC-2, CHC-1 and CHC-2) showed very high PDI and susceptible disease reaction. Based on mean PDI, 8 genotypes were categorized as resistant, 13 as moderately resistant, 9 as moderately susceptible and one as susceptible. A chi-square test of frequency distribution based on mean PDI in F₂ progenies of six resistant × susceptible crosses revealed monogenic recessive Mendelian ratio 1(R):3(S) to be the best fit. This monogenic recessive model was further confirmed by 1(R):1(S) ratio as the best fit for back cross with resistant parent and no fit for either 3:1 or 1:1 in the back cross with the susceptible parent. The results revealed that CMV resistance in C. sativus var. hardwickii was controlled by a single recessive gene. Considering the cross compatibility between C. sativus var. hardwickii and cultivated cucumber, the resistance trait can be easily transferred to cultivated species through simple backcross breeding.     

Epistasis and heritability of resistance to <Emphasis Type="Italic">Phytophthora nicotianae</Emphasis> in pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.)

Gene effects of resistance to two isolates of Phytophthora nicotianae in two crosses of pepper were investigated using separate generation means analysis. Additive-dominance models were inadequate in all cases. Digenic parameter models were adequate in three cases and the probability of goodness of fit of models was negatively correlated with the aggressiveness of the pathogen. None of these models explained variation among generation means in the combined cross Beldi × CM334 with P. nicotianae isolate Pn_2. Additive × additive, dominance × dominance and dominance × additive effects were significant in most cases. Additive and dominance effects (of negative sign) contribute more to resistance than to susceptibility. Additive variance was greater than environmental and dominance variance and ranged from 0.038 to 0.224. Narrow-sense heritabilities were dependent upon the cross and inoculate and ranged from 86 to 92%. The results of this study indicate that selection with more aggressive isolates of the pathogen will be useful for enhancing resistance in pepper.     

Effect of hardening on frost tolerance and fatty acid composition of leaves and stems of a set of faba bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.) genotypes

Frost tolerance is a main component of winter-hardiness and improving it would promote faba bean (Vicia faba L.) cropping in cool-temperate regions. In many species, leaf fatty acid composition was found to be related to frost tolerance. The objective of this study was to determine, in a representative sample of genotypes, the effect of hardening on leaf and stem (1) frost tolerance and (2) fatty acid composition, and to seek correlations between them. First leaf, second leaf and stem of 31 faba bean genotypes were analyzed after hardening and without hardening. High frost tolerance of known winter genotypes and several experimental lines was shown. Hardening had a significant, positive effect on frost tolerance of all three organs. Stems were on average more frost tolerant than leaves. Hardening induced significant changes in the fatty acid composition: oleic acid decreased significantly in leaves by 3.24% and in stems by 1.77%, whereas linolenic acid increased in leaves by 6.28% and in stems by 9.06%. In stems, correlations between frost tolerance and fatty acid composition were not significant. Correlation coefficients strongly indicated that non-hardened oleic acid content, changes in oleic acid and in linoleic plus linolenic acid content in leaves partly explained their frost tolerance; 0.347 (P < 0.1) < |r| < 0.543 (P < 0.01). The results corroborate the importance of using genetic differences in the fatty acid metabolism in breeding grain legumes for frost tolerance.     

Development and characterisation of a <Emphasis Type="Italic">Brassica carinata</Emphasis> inbred line incorporating genes for low glucosinolate content from <Emphasis Type="Italic">B. juncea</Emphasis>

The presence of high levels of sinigrin in the seeds represents a serious constraint for the commercial utilisation of Ethiopian mustard (Brassica carinata A. Braun) meal. The objective of this research was the introgression of genes for low glucosinolate content from B. juncea into B. carinata. BC₁F₁ seed from crosses between double zero B. juncea line Heera and B. carinata line N2-142 was produced. Simultaneous selection for B. carinata phenotype and low glucosinolate content was conducted from BC₁F₂ to BC₁F₄ plant generations. Forty-three BC₁F₄ derived lines were selected and subject to a detailed phenotypic and molecular evaluation to identify lines with low glucosinolate content and genetic proximity to B. carinata. Sixteen phenotypic traits and 80 SSR markers were used. Eight BC₁F₄ derived lines were very close to N2-142 both at the phenotypic and molecular level. Three of them, with average glucosinolate contents from 52 to 61 micromoles g⁻¹, compared to 35 micromoles g⁻¹ for Heera and 86 micromoles g⁻¹ for N2-142, were selected and evaluated in two additional environments, resulting in average glucosinolate contents from 43 to 56 micromoles g⁻¹, compared to 29 micromoles g⁻¹ for Heera and 84 micromoles g⁻¹ for N2-142. The best line (BCH-1773), with a glucosinolate profile made up of sinigrin (>95%) and a chromosome number of 2n = 34, was further evaluated in two environments (field and pots in open-air conditions). Average glucosinolate contents over the four environments included in this research were 42, 31 and 74 micromoles g⁻¹ for BCH-1773, Heera and N2-142, respectively. These are the lowest stable levels of glucosinolates reported so far in B. carinata.     

Mapping the <Emphasis Type="Italic">compactum</Emphasis> locus in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) and its relationship to other spike morphology genes of the Triticeae

The spikes of club wheat are significantly more compact than spikes of common wheat due to the action of the dominant allele of the compactum (C) locus. Little is known about the location of C on chromosome 2D and the relationship between C and to other spike-compacting genes. Thus, a study was undertaken to place C on linkage maps and a chromosome deletion bin, and to assess its relatedness to the spike compacting genes zeocriton (Zeo) from barley and soft glume (Sog) from T. monococcum. Genetic mapping was based on recombinant inbred lines (RILs) from a cross between the cultivars Coda (club) and Brundage (common) and F₂ progeny from a cross between the club wheat Corrigin and a chromosome 2D substitution line [Chinese Spring (Ae. tauschii 2D)]. The C locus was flanked by Xwmc144 and Xwmc18 in the RIL population and it was completely linked to Xcfd116, Xgwm358 and Xcfd17 in the F₂ population. C could not be unambiguously placed to a chromosome bin because markers that were completely linked to C or flanked this locus were localized to chromosome bins on either side of the centromere (C-2DS1 and C-2DL3). Since C has been cytogenetically mapped to the long arm of chromosome 2D, we suspect C is located in bin C-2DL3. Comparative mapping suggested that C and Sog were present in homoeologous regions on chromosomes 2D and 2A^m, respectively. On the other hand, C and Zeo, on chromosome 2H, did not appear to be orthologous.