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The present investigation was carried out to decipher inheritance of resistance and to identify linked SSR markers for Phomopsis blight resistance in eggplant. An F2 population comprising 161 plants was developed from the cross of Pusa Kranti and BR‐40‐7. Genetic analysis was carried out using Chi square test. Artificial inoculation of fruits was carried out using pin prick method, and scoring was done as per the standard scoring scale. The F2 plants segregated into 92 susceptible (77—highly susceptible, 15—susceptible): 69 resistant (17—highly resistant, 27—resistant, 25—moderately resistant) suggesting complimentary epistasis with ratio of 9:7. To identify the putatively linked markers to resistance gene, parental polymorphic markers were subjected to bulk segregant analysis (BSA), and two markers (emk03O04 and emf11A03) could differentiate resistant and susceptible bulk and co‐segregated with resistance gene. The genetic distance between the identified markers was found to be 18.12 cM using QTL IciMapping V3.2 software depicting two new QTLs on chromosome number 6. The identified QTLs have great significant importance in marker assisted breeding programme. [ABSTRACT FROM AUTHOR]

The choice of parents is a vital first step in any variety development process. This is particularly imperative in tree crops that require minimally 15–20 years to complete a varietal development. The present study was conducted to determine genetic distances (GDs) between parental clones of Robusta coffee hybrids and assess the relationship between GD and hybrid performance. The experimental material consisted of 64 parental clones and 56 hybrids. The hybrids were evaluated over 11 years, planted in a randomized complete block design with six replications. GD among parental clones was determined based on 120 SNP markers. The results revealed a significant correlation (r = 0.351, p < 0.0082) between GD of parental clones and yield performance of their hybrids. Posterior selection of highest GD hybrids revealed an increase in yield gain over general mean with increasing GD between parental clones of hybrids. Furthermore, comparison of inter‐ and intra‐population hybrids classified using Bayesian clustering analysis revealed consistent outcome where inter‐group hybrids outperformed intra‐group hybrids for cumulative yield. These results supported the hypothesis that GD is related to the yield performance of Robusta coffee hybrids and is an efficient predicator of hybrid performance for yield. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the genotypic variation in maize doubled haploid (DH) lines response to brassinosteroid and gibberellin inhibitors. Plant responses to hormone inhibitors were determined in growth chamber experiments using germination paper for three different seedling treatments: application of propiconazole (Pcz), uniconazole (Ucz) or water (control). Mesocotyl length (ML) was more sensitive to hormone inhibitors, especially to the Ucz treatment, than other seedling traits. ML was significantly correlated with other traits in the Ucz treatment. All the seedling traits showed moderate‐to‐high broad sense heritability values, ranging from 0.39 to 0.82. The Euclidian genetic distances of inbred line pairs ranged from 1.27 to 19.94, indicating there was a high level of variability across the maize DH lines used in this study. DH lines with extreme MLs were identified, which can provide valuable breeding resources for improving abiotic stress tolerance, and for further genetic studies. [ABSTRACT FROM AUTHOR]

The present study aimed to assess the effect of contrasting levels of molecular and phenotypic diversity among polycross parents of orchardgrass on the performance of synthetic progeny with respect to physiological responses and drought tolerance. Four polycross groups each composed of six parental plants were evaluated under normal irrigation and drought stress conditions. A number of 923 inter simple sequence repeats and sequence related amplified polymorphism markers and several phenotypic traits were used to select contrasting levels of diversity (high and low) in parental genotypes. Highly significant correlation was observed between molecular distance and progeny performances at both normal irrigation and drought stress conditions. High molecular diversity among polycross parents led to a significant yield advantage of first generation progeny with averages of 34.40% for normal irrigation and 48.10% for drought stress conditions. Also crosses between genetically distant parents produced progeny with considerable drought tolerance and yield stability. Positive associations between phenotypic distance of parents and progeny performance were found for most physiological traits at both moisture regimes but phenotypic distances had weak association with forage yield, stress tolerance index and yield stability of progeny. Significant associations between drought tolerance index and some physiological traits confirmed the importance of these traits in conferring drought tolerance of orchardgrass. Our results underscore the effectiveness of marker‐assisted polycross breeding to improve drought tolerance and yield stability through physiological traits in orchardgrass. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the relationship between heterosis and genetic distance in upland cotton (Gossypium hirsutum L.). Heterosis in the different environments was evaluated and the relationship between heterosis and genetic distance (GD) was determined based on SSR markers for yield quantitative trait loci (QTL). Yields of seed cotton and lint showed a linear relationship with mid‐parent heterosis (MPH) and better‐parent heterosis (BPH). The variation in heterosis for other traits and their correlation with GD may be due to environmental factors or the effort of QTLs tested in the present study may vary in different environments. The present findings provide a foundation for heterotic grouping of parental lines and breeding of new cotton hybrids with improved seed cotton yield. This study calls for more research with stable QTLs as well as advance molecular marker techniques may be used in predicting yield heterosis in a more precise and reliable manner. [ABSTRACT FROM AUTHOR]

Firmness of skin is an important quality of processing cucumbers, which is a feature of the palisade epidermis in these types compared to flat epidermis in fresh cucumbers. This study was conducted to map the Pe (palisade epidermis) and analyse the candidate gene. Populations derived from the cross of two inbred lines, NCG122 with fruit flat epidermis and NCG121 with fruit palisade epidermis, were used to identify the inheritance of palisade epidermis and to map the gene involved in its development. The results showed that the palisade epidermis trait is controlled by a single gene, Pe, that is dominant over flat epidermis. Seven simple sequence repeat ( SSR) and five insertion deletion (Indel) markers were identified to be linked to the Pe gene. It was mapped to cucumber chromosome 5 (Chr.5) between SSR14611 and Indelpe12 with genetic distances of 0.3 cM and 0.2 cM, respectively. The physical distance of the genomic region harbouring the gene was 227.5 kb with 26 predicted candidate genes. The accuracy of marker-assisted selection using the molecular markers, Indelpe12 and SSR14611, was 68% and 88%, respectively. [ABSTRACT FROM AUTHOR]

A total of 85 Chinese Cymbidiums and one Zygopetalum were collected and analysed using 29 simple sequence repeats ( SSRs) and 12 intersimple sequence repeats ( ISSRs). These Chinese Cymbidiums are some of the most popular cultivars in market. The pairwise genetic distance between these accessions averaged 0.897, ranging from 0.259 to 1.000. A model-based clustering analysis revealed five genetic groups with serious admixture ancestry, as indicated by a fixation index of 0.156 and only 10.67% genetic variation among groups. By analysing the cross-compatibility and pollen morphology, Chinese Cymbidiums are revealed to have high compatibility for intra- and interspecific crosses. Notably, Zygopetalum mackayi had high compatibility with Chinese Cymbidiums and shared similar morphologies in terms of pollinia and pollen grain. This study is the first to report a successful cross between Zygopetalum and Chinese Cymbidiums. The high compatibility offers the potential for introducing Zygopetalum mackayi's superior traits into Chinese Cymbidiums. The similar pollen morphology as well as the low genetic differentiation might be related to the high cross-compatibility among these accessions. [ABSTRACT FROM AUTHOR]

Molecular marker technologies may provide a tool to overcome the forage yield plateau in timothy ( Phleum pratense L.). Therefore, a study was designed to investigate the relationship between marker-based genetic distance ( GD) estimates and yield. Genetic distances were estimated using Dice coefficients framed by 28 simple sequence repeat markers. In Experiment 1, parents with high general combining ability ( GCA) from two contrasting first-generation synthetic strains (exhibiting high and low yields) were compared. Average GDs of each strain were 0.74 (high) and 0.68 (low). These differences indicated that GD may be partially the basis for contrasting yields. In Experiment 2, GDs among 40 parents of a polycross were used for calculating general genetic distance ( GGD), which is indicative of their allelic complementation. Analyses revealed a significant (P < 0.01) moderate correlation ( r) between GGD and GCA for yield ( r = 0.45) and a significant (P < 0.01) residual mean square for the regression of yield on GGD, suggesting that considerable non-additive effects were associated with GCA. The results are indicative of the potential use of GD estimation for yield improvement in timothy. [ABSTRACT FROM AUTHOR]

The genus Amaranthus has gained much attention, particularly for its high economic and nutritional value. It is a genus of taxonomic complexity with many interspecific hybrids. For effective conservation and management of the germplasm collected, the development of a core set of accessions is especially important. A core set of 63 accessions was successfully developed from an entire collection of 634 accessions using the powercore 1.0. Among the tested methods for developing the core set - the advanced M strategy using the modified heuristic method ( HCC), randomly chosen collections and stratified random collections - HCC was found to be best, with 100% coverage of alleles and minimum redundancy. Allele frequency distribution of the core set developed with HCC was highly correlated with that of entire collections ( r = 0.91). Model-based structure analysis revealed the presence of three subpopulations and 11 admixtures in the selected core set, which is basically consistent with clustering based on the genetic distance. The results from this study will provide effective information for future germplasm conservation and improvement programmes in Amaranthus. [ABSTRACT FROM AUTHOR]

With 6 figures and 3 tables The present trial assesses the cytoplasmic effects of Brassica napus (AC) and Brassica carinata (BC) on certain characteristics of Brassica rapa (A), Brassica oleracea (C) and Brassica nigra (B). Alloplasmic lines were developed from AC × A, AC × C, BC × B and BC × C hybrids followed by recurrent backcrossing for seven generations. Twenty‐five populations from three generations were compared. The alloplasmic B. oleracea lines with AC‐cytoplasm exhibited the shortest filament length, weakly developed anthers, smaller petal size and more than two stigmas, whereas the alloplasmic B. rapa lines with AC‐cytoplasm were normal; the alloplasmic B. oleracea lines with BC‐cytoplasm formed three groups with short, middle or normal filament length, whereas the alloplasmic B. nigra lines with BC‐cytoplasm were normal. From these results, it was concluded that the cytoplasm effect of AC on C is greater than that on A; BC on C is greater than that on B, further suggesting that the cytoplasm effect of AC on C is greater than that of BC on C. [ABSTRACT FROM AUTHOR]

Chinese semi-winter rapeseed is genetically diverse from European winter rapeseed. Our objectives were (1) to evaluate the potential of semi-winter rapeseed for winter rapeseed hybrid breeding, (2) to assess the relative importance of general combining ability (GCA) vs. specific combining ability (SCA) among combinations between Chinese semi-winter and European winter rapeseed, and (3) to compare the strategies to predict heterosis based on parental genetic distance (GD) estimated from AFLP marker data and GCA for hybrid performance. Four winter male sterile lines from Germany as testers were crossed with 14 Chinese semi-winter rapeseed lines to develop 56 hybrids, which were evaluated together with their parents and commercial hybrids for seed yield, oil content and protein content under three environments in Germany. The Chinese parental lines were not adapted to local environmental conditions as demonstrated by lacking winter hardiness and poor seed yields per se. However, the hybrids between the Chinese parents and the adapted winter rapeseed lines exhibited high heterosis for seed yield. About 20% of the hybrids were significantly superior to the respective hybrid control under three environments. Additive gene effects mainly contributed to hybrid performance since the variance components of GCA were higher as compared with SCA. The correlation between parental GD and hybrid performance was found to be low whereas the correlation between GCA and hybrid performance was high and significant, with correlation coefficients of 0.95 for seed yield, 0.87 for oil content, and 0.91 for protein content, indicating that GCA can predict hybrid performance. These results demonstrate that Chinese semi-winter rapeseed germplasm has a great potential to increase seed yield in winter rapeseed hybrid breeding programmes in Europe. [ABSTRACT FROM AUTHOR]

Breeding for specific or wide adaptation would be more cost-efficient if preliminary indications on genotype adaptive responses could be provided by easily-detectable morphophysiological or molecular characteristics. We investigated the consistency among adaptation parameters, morphophysiological traits and SSR markers in estimating and structuring the genetic diversity among 24 durum wheat genotypes. Additive main effects and multiplicative interaction adaptation parameters were estimated across 14 Algerian locations belonging to a low- or a high-elevation subregion. Eight morphophysiological traits were assessed in two locations per subregion. Genotype Euclidean distances based on adaptation parameters were closely related to those based on morphophysiological traits ( r = 0.75, P = 0.01). Marker-based distances exhibited low correlation with those based on adaptation parameters ( r = 0.26, P = 0.01) or morphophysiological traits ( r = 0.32). The consistency between adaptation parameters and morphophysiological traits for genotype ordination and classification was greater than that between either information layer and SSR markers. Optima of phenology and plant height differed between subregions, whereas many kernels per spike and fertile tillers were associated with adaptation to both subregions. [ABSTRACT FROM AUTHOR]

Identifying the best inbred combinations for the development of commercial hybrid maize varieties remains the main challenge to maize breeders. The aim of this work was to study associations between the genetic distance (GD) of 21 inbreds and the corresponding F1 phenotypic data. Furthermore, the impact of grouping lines into genetically similar clusters was investigated. The 21 inbred lines were fingerprinted using amplified fragment length polymorphism markers. Parents and 210 F1 progeny were evaluated in the field. Joint data analysis mostly revealed a tighter association between GD and the F1 performance or mid parent heterosis in the intergroup than in the intragroup crosses. Despite these correlations, intergoup crosses should always be field-tested before their release. Crosses showing low GD values should be discarded to avoid field-testing costs. Better F1 hybrid performance predictions can be achieved by integrating molecular and F1 phenotypic data. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the relationship between parental molecular marker diversity and hybrid performance in both intra- and interspecific hybrids of cotton to evaluate the feasibility of predicting hybrid performance using molecular markers. Three cytoplasmic male sterile (CMS) lines were crossed with 10 restorer lines to produce 22 F1 hybrids during 2003. Of 22 F1s, 14 hybrids were intraspecific ( Gossypium hirsutum × G. hirsutum) and eight interspecific ( G. hirsutum × G. barbadense). These 22 F1 hybrids and their parents were evaluated for yield and fibre quality traits at Zhejiang University, Hangzhou, China during 2004 and 2005. Genetic distances (GD) among the parents were calculated from 56 random-amplified polymorphic DNAs (RAPD) and 66 simple sequence repeat (SSR) marker data, and their correlation with hybrid performance and heterosis were analysed. The parents could be discriminated into G. hirsutum and G. barbadense clusters by cluster analysis based on both RAPD and SSR markers data. The correlation ( r = 0.503, P ≤ 0.05) was calculated between GDrapd (GD based on RAPD markers) and GDssr (GD based on SSR markers). Correlation of GD with hybrid performance and heterosis differed considerably between intra- and interspecific hybrids. The correlation between GD and hybrid performance was non-significant for most of traits within the hybrids of G. hirsutum species. However, it was significantly and positively correlated for fibre length, fibre strength and elongation in interspecific hybrids. The relationship between GD and heterosis was observed to be positively significant for boll weight within hybrids of G. hirsutum with significant and negative correlations for fibre length and elongation. In conclusion, the power of predicting hybrid performance using molecular markers in cotton is low. But, the relationship between SSR marker heterozygosity and hybrid performance can be used to predict fibre length during interspecific hybrid cotton breeding. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the relationship between genetic and phenotypic distances of parents and the genetic potential of crosses as measured by the frequency of transgressive segregants in homozygous populations. Material for the study involved 17 barley cross-combinations. In each cross, the parental genotypes, F2 hybrids and doubled haploid (DH) lines were analysed. Yield and yield-related traits were observed in the experiments. Phenotypic (univariate and multivariate) and genetic distances (GD) were investigated between pairs of parental genotypes. Genetic distance was evaluated by using random amplified polymorphic DNA markers. In F2 generations, the genetic coefficient of variability (GCV) was evaluated. Within all the cross-combinations studied, each DH line was compared with both parents to distinguish the positive and negative transgressive lines. In addition, the coefficient of gene distribution ( r) along parental genomes was evaluated. Relationships between frequency of transgression and both phenotypic and GDs, GCV and r, were assessed by regression analysis. It was found that for all the traits studied the frequency of transgressive lines depended mainly on gene distribution ( r). Genetic distance between parents appeared to be significant for the occurrence of transgression effects in plant height, ear length, grain weight per ear and grain yield per plot. Regression analysis has shown that phenotypic differences between parental genotypes were also important for the frequency of transgressive lines. A weak relationship was found between the variation of F2 hybrids and the occurrence of transgressive lines. The results indicate that occurrence of transgressive segregants in a homozygous population should be considered as a phenomenon dependent simultaneously on several factors characterizing parental genotypes. Among them, the most important are: gene distribution, phenotypic diversity and GD. [ABSTRACT FROM AUTHOR]

A cDNA-AFLP transcript profiling was employed to examine three representative tissues (seedling, ovary and leaf) of nine Korean cucumber ( Cucumis sativus L.) F1 hybrids. Differential accumulation of transcript-derived fragments (TDFs) was detected in 92 profiles. Genetic distance-based cluster analysis partitioned these hybrids into four main groupings, consistent with their phenotypic relationships. Although several polymorphic profiles were confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) analysis, many were not reproducible, indicating that a large portion of the observed polymorphisms were based on sequence variation of transcripts rather than expression of variation. Thus, it is proposed that cDNA-AFLP profiling be based on a dual descriptor system (sequence and expression). Data indicate that such a system would provide an efficient genetic marker system for identifying polymorphisms in narrow genetic pools. [ABSTRACT FROM AUTHOR]

Significant relative midparent heterosis (MPH%) for grain yield in triticale (× Triticosecale Wittm.) has generated interest in the development of hybrid cultivars. The objectives of this study were to (i) examine the association between parental genetic distance (GD) and specific combining ability (SCA), (ii) investigate the existence of genetically distant heterotic groups in elite germplasm, and (iii) draw conclusions for future hybrid breeding in winter triticale. Genetic distance between 61 lines was estimated, based on 93 polymorphic simple sequence repeat (SSR) marker loci and 10 AFLP (amplified fragment length polymorphism) primer-enzyme combinations (PEC). Agronomic data of 206 F1 crosses and their 61 parental lines grown in six German environments were published recently in a companion study. Correlations were made between SCA for grain yield, number of spikes/m2, 1000-kernel weight and number of kernels per spike with GD estimates of the 56 female and five male parents (testers). Principal co-ordinate analyses (PCoA) based on SSR data revealed no distinct subgroups in the germplasm. Correlations between GD and SCA were low for all traits (|r| ≤ 0.31), which hampers the prediction of SCA from molecular data. A multi-stage procedure is recommended for future hybrid breeding in triticale by applying a pragmatic approach for the grouping of germplasm following the early history of hybrid breeding of maize. [ABSTRACT FROM AUTHOR]

Camelina is an alternative oilseed crop species with limited information about the origin and diversity of available germplasm. Therefore, a set of 130 camelina accessions from a world collection was evaluated for oil content, protein content and 1000-seed weight in field experiments grown in three macro-environments in Austria. Based on phenotypic data, accessions were categorized into four groups with different seed characteristics using k-means cluster analysis or principal component extraction. Subsequently, a representative set of 41 accessions was subjected to random amplified polymorphic DNA (RAPD) analysis. Of 24 primers, 15 were polymorphic producing a total of 30 marker loci. Genetic distance estimates between the 41 accessions were calculated, based both on RAPD polymorphism and on seed quality characteristics, and dendrograms were generated for comparison. Similarities were found between the two different clustering approaches, and grouping was partly in agreement with pedigree information or geographic origin. However, as the two estimates of diversity sampled different segments of the genome, i.e. regions coding for seed characteristics or phenotypically neutral genomic regions highlighted by discrete markers, the correlation between the two distance matrices was low. [ABSTRACT FROM AUTHOR]

Perennial ryegrass {Lolium perenne L.) is the most important grass species for temperate grassland agriculture. The level and distribution of genetic variation in gene bank ecotype collections is still largely unknown but of great interest for the planning of breeding programmes. The objectives of this study were to (i) assess the molecular variance and population structure of German ecotypes at the regional and population level, (ii) assign ecotypes to germplasm pools and (iii) compare the relationship between German ecotypes and previouslyinvestigated European cultivars of perennial ryegrass, A total of 22 ecotypes originating from three geographic areas in Germany, each with a sample size of 20 individual plants, were investigated with 156 polymorphic RAPD markers. Genetic distance among ecotypes ranged from 0.27 to 0.48. An analysis of molecular variance (AMOVA) revealed a much larger variation within populations (71%) than among them (29%). Ecotypes from North Germany were significantly different from those of South and Middle Germany. Thus, two distinct germplasm pools could be identified. The 22 ecotypes and 22 previously investigated cultivars shared 98% of the molecular variance. [ABSTRACT FROM AUTHOR]

A set of 155 SSR (107) and SCAR (48) markers were used to evaluate 53 cucumber (Cucumis sativusL.) accessions of diverse origin to characterize genetic relationships and to define a standard marker array that was most effective in detecting genetic differences in this germplasm array. A multivariate marker-based analysis of diverse germplasm using this standard marker array (17 SSR and 5 SCAR markers) was compared with results from a set of 70 previously reported RAPD markers, and then used to explore the potential value of these genetic markers for plant variety protection (PVP) and the establishment of essential derivation (ED) threshold values in this species using elite lines and hybrids and backcross progeny. Diversity analysis allowed identification of distinctly different lines that were used for the construction of three sets of backcross families (BC1-BC3). While general genetic relationships among accessions were similar in SSR/SCAR analyses (rs = 0.65) using two genetic distance (GD) estimators, differences in accession relationships were detected between RAPD and SSR/SCAR marker evaluations regardless of the estimator used. The GDs among elite germplasm with known pedigrees were relatively small (0.06–0.23 for any pairwise comparison). GD values decreased and degree of fixation (at three to seven loci depending on the mating) increased with increased backcrossing such that recurrent parent allelic fixation occurred in least one family of each of the BC3 families. In many instances the degree of fixation of loci was not uniformly achieved in the BC3. Although the level of genetic polymorphisms will likely restrict the use of molecular markers for PVP and the establishment of ED values, the use of single nucleotide differences will likely provide opportunities to define specific functional distances that have potential for PVP in cucumber. Nevertheless, without an expanded, genetically robust standard marker array (e.g. 50 codominant markers), ED threshold values will be difficult to define in this species, and perhaps will require the appraisal of single nucleotide polymorphisms as discriminators of difference in this species. [ABSTRACT FROM AUTHOR]

Abstract The growing number of candidate varieties presented every year at each national Plant Variety Protection Office and their decreasing genetic variability forces strategies to be adopted that will reduce costs without losing rigour when deciding about the acceptance or rejection of a candidate variety. Molecular markers have been envisaged as a reliable tool to establish differences, but can molecular markers be used for assessing distinctness? A comparison between a molecular and a morphological characterization of 41 seed samples belonging to 36 cucumber varieties and including several external controls has been carried out to investigate the applicability of molecular markers in the context of distinctness, uniformity and stability (DUS) tests and the protection of new varieties. Both types of character indicate the same relationships among main groups, Dutch and Beth-Alpha types, and Gerking and Slice types, the correlation between distance matrices being only 0.6489. Varieties considered uniform for morphological traits proved not to be so for molecular markers. Therefore, molecular characterization is not offering the same estimates of uniformity and relatedness between varieties as does morphological characterization. External controls were used to establish distinction limits with morphological and molecular dendrograms to focus on those varieties, which were suspiciously similar. The results with cucumber show that molecular identity could be used to assess any lack of distinctness and so corroborate the morphological assessment of candidate varieties. The morphological trait ‘type’ provides distinct characterization of varieties and the molecular characterization of candidate varieties could be used to design better field experiments to assess distinction within each group of morphological cucumber type. [ABSTRACT FROM AUTHOR]

Abstract Improving grain yield and quality of ‘Tongil’-type rice (indica /japonica ) continues to be a major breeding objective in Korea. In this study, genetic divergence among 13 ‘Tongil’-type rice cultivars was evaluated and the relationship between genetic distance and hybrid performance in all possible nonreciprocal crosses between them assessed. The 78 F1 hybrids together with the 13 parents were evaluated for eight traits of agronomic importance, including yield, in a replicated field trial. The 13 parents were examined for DNA polymorphism using 71 microsatellite or simple sequence repeats and 46 random decamer oligonucleotide primers. A total of 319 polymorphic variants were generated and, based on the polymorphism data, genetic distances (GDs) ranged from 0.021 to 0.437. Cluster analysis based on GDs revealed associations among cultivars which was in agreement with the pedigree data. Heterosis was observed in hybrids for most of the traits, and yield exhibited the highest heterosis among the eight traits examined. The correlation values of GDs with F1 performance were mostly non-significant, except for yield, culm length and spikelets per panicle. The correlations of GDs with midparent and better-parent heterosis were not significant enough to be of predictive value. These results indicate that GDs based on the microsatellite and random amplified polymorphic DNA (RAPD) markers may not be useful for predicting heterotic combinations in ‘Tongil’-type rice and support the idea that the level of correlation between hybrid performance and genetic divergence is dependent on the germplasm used. [ABSTRACT FROM AUTHOR]

Abstract The Indica–Japonica differentiation of three photoperiod-sensitive and/or thermosensitive genetic male-sterile rice (PGMS or TGMS, respectively) lines and 47 male parental lines from seven ecotypes were studied for their restriction fragment length polymorphism marker data to determine which ecotype crosses with the three PGMS and/or TGMS lines could lead to higher yield potential, and to estimate the relationship between the Indica–Japonica differentiation of parents and heterosis in grain yield and its components. The results indicated that hybrids derived from ‘N422s’ and the early-middle ripening Indica varieties from southern China, and hybrids between ‘Pei’ai64s' and three Japonica ecotypes, including North-eastern Japonica varieties, restoring lines of Japonica hybrid rice and north China Japonica varieties, showed the highest grain yields. There was less variation of yield among the F1 s between ‘108s’ and the seven ecotypes than among the other F1 s. Highly significant positive correlations between heterosis of the F1 yield and genetic distance of the parents were detected, although the correlation between F1 yield performance and genetic distance did not reach a significant level. Considerable variation of correlation between heterosis and genetic distance was also detected in the Indica × Indica crosses and Indica × Japonica crosses. There was much higher correlation (r = 0.63) between the F1 yield performance and the genetic distance of parents in the Indica × Indica crosses than in the others. It is proposed that a genetic distance of 0.4–0.8 between the two parents of hybrid rice might be appropriate not only for F1 performance, but also for heterosis. [ABSTRACT FROM AUTHOR]

Significant heterosis for seed yield in oilseed rape has created interest in the development of hybrid cultivars. The DNA-based marker protocol, sequence-related amplified polymorphism (SRAP) was used to determine genetic diversity among oilseed rape maintainer and restorer lines. This measure was used in an attempt to establish an association between genetic distance and heterosis in hybrids for various agronomic traits. A total of 118 polymorphic loci were generated by 18 SRAP primer combinations. Based on the polymorphism generated by the markers, calculated similarity index values ranged from 0.46 to 0.97. Cluster analysis grouped 10 maintainer and 12 restorer lines into three groups, with the exception of two maintainer lines, PM5 and PM9, which fell outside these groups. The grouping of the lines was largely in agreement with the available pedigree data on their origin and agronomic performance. Analysis of variance among inbred lines and their resulting F1 hybrids over two locations revealed significant differences for plant height, days to maturity and seed yield, but not for oil content. Substantial mid-parent heterosis was observed only for seed yield, and ranged from 26% to 169%. All hybrids surpassed their respective inbred lines for this trait, except for a single cross combination of related lines. In general, crosses of lines located in different clusters yielded more than those from the same clusters. Regression analysis revealed a statistically significant relationship between the genetic distance of the parents and seed yield in their hybrid, and their derived mid-parent and high-parent heterosis. The correlation coefficient between genetic distance and yield (0.64) indicated a moderately strong relationship, so it is possible that some of the SRAP markers might be linked to quantitative trait loci for seed yield. [ABSTRACT FROM AUTHOR]

Abstract Tropical maize inbred lines, eight derived from a Thai synthetic population (BR-105) and 10 from a Brazilian composite population (BR-106), were assayed for restriction fragment length polymorphisms with 185 clone–enzyme combinations. The aim of this study was to investigate genetic distances among tropical maize material and their relationship to heterotic group allocation and hybrid performance. Genetic distances (GDs) were on average greater for BR-105 × BR-106 lines (0.77) than for BR-106 × BR-106 (0.71) and for BR-105 × BR-105 (0.69) lines. Cluster analysis resulted in a clear separation of BR-105 and BR-106 populations and was according to pedigree information. Correlations of parental GDs with single crosses and their heterosis for grain yield were high for line crosses from the same heterotic group and low for line combinations from different heterotic groups. Our results suggest that RFLP-based GDs are efficient and reliable to assess and allocate genotypes from tropical maize populations into heterotic groups. However, RFLP-based GDs are not suitable for predicting the performance of line crosses from genetically different heterotic groups. [ABSTRACT FROM AUTHOR]

The applicability of random amplified polymorphic DNA (RAPD) markers in the cultivated rubber tree, Hevea, was evaluated using 43 decamer oligonucleotide primers in a set of 24 clones selected in different South-East Asian countries. A total of 220 0.35-3.5 kb DNA fragments were amplified, of which 111 were polymorphic. Of these, 80 fragments (RAPD markers) which were repeatable and clearly scorable across all genotypes were used to estimate genetic distances among the clones tested. The estimated genetic distances ranged from 0.05 (RRII 308 and PB 5/51) to 0.75 (RRIC 100 and SCATC 88-13). A mean genetic distance of 0.5 indicates a rather high genetic variability among the tested clones. As expected, because of the breeding history of Hevea, UPGMA cluster analysis and Principal Coordinate Analysis (PCoA) indicated the absence of a distinct geographical grouping. The possible application of RAPD markers for clone identification and also for analysis of genetic relationships among Hevea clones is discussed. [ABSTRACT FROM AUTHOR]

Eleven winter rapeseed inbred lines (I4) were characterized according to isozyme banding patterns from seven polymorphic enzyme systems. All lines could be qualitatively and quantitatively distinguished using two enzyme systems, shikimate dehydrogenase (SDH) and diaphorase (DIA). Genetic distances were calculated among lines and 15 selected two-line hybrids were planted as experimental synthetics in field-trials. Syn-0 populations produced seed yields between 0.4% lower and 12.9% higher than the mean yields of the respective parental lines. Syn-1 seed yields were 11-24.1 % higher than the respective parental lines and the yield improvement was positively correlated with the genetic distance between the parental lines. This tendency suggests that genetic distances between cross components, calculated from isozyme polymorphism, can be used in prognosis of yield performance of synthetic rapeseed cultivars. Isozyme analysis was also applied to study fertilization behaviour in line mixtures, and differences among parental lines were observed with regard to the tendency for self-pollination or out-crossing. The partially very high outcrossing rate suggests the possible existence of a self-incompatibility system. [ABSTRACT FROM AUTHOR]

The genetic distances between two cultivated wheat (Triticum aestivum L.) varieties (Martonvásári 9, Martonvásári 15), a Martonvásári 9 line possessing the crossability gene kr1, and 21 accessions of T. timopheevi Zhuk and T. araraticum Jakubz, were estimated, based on agromorphological, physiological and biochemical analysis of data. Cluster analysis based on Mahalanobis' D² values was applied. All 21 accessions of T. timopheevi and T. araraticum could be classified into eight clusters. Clusters I and II consisted of all the T. timopheevi, while T. araraticum was located in six clusters. Discriminant analysis was applied to test significant differences between cluster pairs. The genetic distance (GD) based on the electrophoretic data of gliadins indicated two types of electrophoregrams in T. timopheevvi, distinguished as groups A and B. T. araraticum accessions were variable as regards the spectra. Mean, minimum and maximum GD were estimated within and between different wheat groups based on acid polyacrylamide gel electrophoresis. [ABSTRACT FROM AUTHOR]

Four inbred lines of carrot (cytoplasmic male-steriles and corresponding maintainers) and eight of their F1 hybrids were studied with the amplified fragment length polymorphism (AFLP) technique to examine their genetic relationship and produce markers useful for testing hybrid seed purity. Eighty-six polymorphic amplicons were identified in bulked DNA samples using eight primer pair combinations. Genetic distance was estimated on the basis of the presence or absence of polymorphic bands. The dendrogram plotted on the basis of the AFLP data closely represented the pedigree relationships of the lines and their hybrids. From one to six amplicons specific for a breeding line were identified. Most of them were also present in the DNA bulks of respective F1 hybrids. However, screening performed on individual plants of two parental lines and the corresponding hybrid indicated insufficient uniformity of parental lines, limiting the applicability of AFLP markers for testing hybrid seed purity. [ABSTRACT FROM AUTHOR]