Phenotypic diversity and relationships of fruit quality traits in apricot (Prunus armeniaca L.) germplasm

Fruit quality attributes were studied for two consecutive years in forty-three apricot cultivars and selections grown in a Mediterranean climate. Physical parameters (weight, size, flesh and skin colour, percentage of blush, firmness and percentage of dry matter), chemical parameters (total soluble solids content and acidity) and sensory parameters (attractiveness, taste, aroma and texture) were evaluated. A high variability was found in the set of the evaluated apricot genotypes and significant differences were found among them in all studied quality attributes. Year-by-year variations were observed for some pomological traits such as harvest date, flesh colour, fruit weight, firmness and soluble solids content. A high correlation was found among some apricot quality attributes. In addition, principal component analysis (PCA) made it possible to establish similar groups of genotypes depending on their quality characteristics as well as to study relationships among pomological traits in the set of apricot genotypes evaluated.     

Amplified fragment length polymorphism as a tool for molecular characterization of almond germplasm: genetic diversity among cultivated genotypes and related wild species of almond,and its relationships with agronomic traits

Amplified fragment length polymorphism (AFLP) analysis is a rapid and efficient method for producing DNA fingerprints and molecular characterization. Our objectives were to: estimate genetic similarities (GS), marker indices, and polymorphic information contents (PICs) for AFLP markers in almond cultivars; assess the genetic diversity of almond cultivars and wild species, using GS estimated from AFLP fingerprints and molecular characterization; and facilitate the use of markers in inter-specific introgression and cultivar improvement. The genetic diversity of 45 almond cultivars from Iran, Europe, and America, were studied assaying 19 primer combinations. In addition, several agronomic traits were evaluated, including flowering and maturity times, self-incompatibility, and kernel and fruit properties. Out of the 813 polymerase chain reaction fragments that were scored, 781 (96.23%) were polymorphic. GS ranged from 0.5 to 0.96, marker indices ranged from 51.37 to 78.79, and PICs ranged from 0.56 to 0.86. Results allowed the unique molecular identification of all assayed genotypes. However, the correlation between genetic similarity clustering as based on AFLP and clustering for agronomic traits was low. Cluster analysis based on AFLP data clearly differentiated the genotypes and wild species according to their origin and pedigree, whereas, cluster analysis based on agronomic data differentiated according the pomological characterization. Our results showed the great genetic diversity of the almond cultivars and their interest for almond breeding.     

Genetic diversity evaluation of a loquat (<Emphasis Type="Italic">Eriobotrya japonica</Emphasis> (Thunb) Lindl) germplasm collection by SSRs and <Emphasis Type="Italic">S</Emphasis>-allele fragments

Loquat (Eriobotrya japonica (Thunb.) Lindl.) is a minor Rosaceae fruit of growing interest as an alternative to the main fruit crops. In this context, the selection of new cultivars to satisfy the market demand will request the suitable characterization of the available germplasm. In this work, genetic relationships among 83 loquat accessions from different countries belonging to the European loquat germplasm collection, held at the Instituto Valenciano de Investigaciones Agrarias (IVIA) in Moncada (Spain) were evaluated using microsatellites and S-allele fragments. A total of nine single sequence repeats (SSRs) from Malus and Eriobotrya genera revealed 53 informative alleles and the S-RNases consensus primers detected 11 self-incompatibility putative alleles. The combined data allow to distinguish unambiguously 80 out of the 83 accessions studied. Unweighted pair-group method (UPGMA) cluster and principal coordinates analysis (PCoA), based on Dice’s genetic distance, generally grouped genotypes according to their geographic origins and pedigrees. Discrepancies and similarities of the results obtained with other variability analysis, based on pomological traits or molecular markers, on the same loquat collection are discussed.     

Analysis of glutamate oxaloacetate transaminase (GOT) isozyme variants in diploid tuberous Solanum; inheritance and linkage relationships to ds1 (desynapsis), y (tuber flesh colour), cr (crumpled) and yc (yellow cotyledon)

Summary Employing polyacrylamide gradient-gel electrophoresis, the genetic control of leaf glutamate oxaloacetate transaminase (GOT) isozyme variants and their linkage to ds1 (desynapsis), y (tuber flesh colour), cr (crumpled) and yc (yellow cotyledon) were studied in diploid tuberous Solanum species hybrids.Leaf GOT isozymes proved to be dimeric and under the control of two independently segregating loci (Got-1 and Got-2) with two (1 ^s , 1 ^f ) and three (2 ^s , 2 ^f , 2 ⁿ )alleles respectively. The 2 ⁿ allele was concluded to encode a 2 ^fallozyme subunit capable of forming heterodimeric but no homodimeric active molecules. As expected with Got-1 and Got-2 isozymes being localized in different cellular compartments, no intergenic heterodimer formation was observed.In contrast to earlier studies, a gradual rather than discrete transition between the tuber flesh colour classes white and yellow was observed in segregating progenies. Adopting a standardized classification method, however, monogenic recessive inheritance of white tuber flesh was confirmed. Got-1, ds1 and cr were found to represent a single linkage group. Among the presently studied marker loci no further linkages were detected. As to linkage analysis, the difficulties imposed by gametophytic incompatibility in nearly all diploid potato species and by the frequent occurrence of recessive (sub)lethal genes are discussed.     

Traditional management of cassava morphological and genetic diversity by the Makushi Amerindians (Guyana, South America): Perspectives for on-farm conservation of crop genetic resources

In this paper we present original data on morphological and genetic diversity of cassava managed by the Makushi Amerindians from Guyana. Although they propagate cassava exclusively vegetatively by means of stem cuttings, many Amerindian farmers also use and multiply volunteer plants grown from seeds produced by sexual reproduction. Morphological characters were recorded for 29 varieties cultivated by the Makushi and two populations of plants originating from volunteer cassava seedlings. Genetic characterisation with AFLP markers was available for 21 of the examined varieties. The morphological and agronomic characters were highly variable among varieties. Every variety could be differentiated from any other one, except for one pair of varieties. However, high intra-varietal variability existed, which might lead to confusions between phenotypically similar varieties by the Makushi. Seedlings were on average different from the pool of the varieties studied, but 67% were found to resemble closely enough one of the varieties to be liable to be assigned to it. Confusion between very similar varieties, as well as assignment of seedlings to a variety, should generate genetic variability within varieties, which was detected with AFLP markers. As in other sites in Amazonia, there was only a weak correlation between inter-varietal distances assessed with molecular and with morphological markers, suggesting that diversification of morphological characters has taken place repeatedly and independently across the Amazonian range of the crop. Diversifying selection, exchanges of varieties between farmers, and incorporation of sexually produced volunteer plants are key mechanisms responsible for the high diversity observed. Strategies of conservation of genetic resources should take these dynamic processes into account. This revised version was published online in July 2006 with corrections to the Cover Date.     

一份新的水稻斑点叶突变体spl32的鉴定和基因定位

从F2(粤晶丝苗2号/H4)群体中,鉴定出一份显性斑点叶突变体spl32(spotted leaf 32)。其叶片褐色斑点受自然光诱导,在幼穗分化期从叶尖逐渐扩散至叶鞘,台盼蓝染色表明斑点并非由细胞死亡引起。以从F5杂合个体分离出的正常叶色植株为对照,斑点叶植株的穗粒数、结实率显著降低。斑点出现后,spl32的POD活性和MDA含量均显著高于对照;同时,spl32叶片光合色素含量降低,但荧光动力学参数并无显著变化。抽穗期人工接菌表明,spl32对水稻白叶枯病菌抗性较对照显著提高。遗传分析表明spl32斑点性状由一个显性基因Spl32(t)控制,利用F2(02428/spl32)群体将其定位在第11染色体Ind-c和RM206之间,推测该基因为一个新的水稻斑点叶基因。     

Characterization of resistance genes against scald (Rhynchosporium secalis (Oudem.) J.J. Davis) in barley (Hordeum vulgare L.) lines from central Norway, by means of genetic markers and pathotype tests

Rhynchosporium secalis is a serious pathogen of barley (Hordeum vulgare L.) in central Norway. A breeding effort was initiated in 1977 to introduce resistance from different sources into adapted genotypes, and the first cultivar from the program was recently released. However, little is known about the resistance genes introgressed in this cultivar or in advanced breeding lines. An effort was made to address this issue through a set of isolates and available molecular markers. Fourteen breeding lines and their resistance donors were investigated by evaluating their reactions to 11 R. secalis isolates. Bulked segregant analysis was used to identify molecular markers linked to resistance genes in 12 of the breeding lines. The isolates were found to be of less discriminating value than the markers. Useful information has been obtained as to the nature of several of the resistance genes introgressed. Eight of the 12 breeding lines contained introgressed genes that were located at the `complex Rh' locus on chromosome 3H and hence may not easily be pyramided into the same genotype. Previous information about the nature of the resistance in `Jet' is questioned. Neither of the resistance genes Rh or Rh2 seems to have been incorporated into Norwegian breeding material.     

The myrobalan (<Emphasis Type="Italic">Prunus cerasifera</Emphasis> L.): a useful diploid model for studying the molecular genetics of self-incompatibility in plums

A series of PCR methods were used to detect S-RNase alleles and SFB alleles and to determine S-genotypes in 25 accessions of myrobalan (Prunus cerasifera L.). Firstly, primers flanking the polymorphic second intron were used to identify S-RNases in agarose gels. These primers amplified one or two bands per accession in 25 accessions. Then consensus primers were designed for amplifying the polymorphic first intron, unique to Prunus S-RNases, for automated fluorescent detection. Each accession produced one or two peaks. New primers were then developed to amplify the intron in the SFB gene, for detection by fluorescence. Cross-referencing PCR bands and peaks indicated 15 S-alleles were present in the 25 accessions. Cloning, sequencing and comparison with published data indicated that the amplified products were S-RNase alleles. Sequence information was used to design primers specific for each S-RNase. Full and consistent S-genotypes were obtained by cross-comparing PCR data for 23 of the 25 accessions, and two accessions appeared to have a single allele. Pollen-tube microscopy indicated function of some but not all of the S-alleles sequenced.     

Inter simple sequence repeat (ISSR) markers as a tool for the assessment of both genetic diversity and gene pool origin in common bean (Phaseolus vulgaris L.)

In this study, we report the use of ISSR to assess genetic diversity and to determine the relationships among ten cultivars of common bean developed in Argentina and three materials from France. ISSR markers resolved two major groups corresponding to the Andean and Mesoamerican gene pools of common bean. We compared the results of previous analysis, performed with RAPD markers (Galván et al., 2001), with the results generated by means of ISSR. It appears that ISSR are better tools than RAPDs to identify beans by gene pool of origin though they did not revealed as many differences between individuals as RAPDs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Indicators of resistance of sunflower plant to basal stalk rot (Sclerotinia sclerotiorum): Symptomatological,biochemical, anatomical,and morphological characters of the host

Summary The object of this work was a study of the relationship between the field reactions of different sunflower genotypes to basal stalk rot (in terms of severe (dead plants) and incipient wilting, and lesion length) and some biochemical (phenol concentration), morphological (plant height, and stem and flower-bud diameters) and anatomical (xylem and cortical indexes) characters of the host. Plants from 8 inbred lines at closed flower-bud stage were artificially inoculated with mycelium at the base of the stem. The percentage of dead plants for each inbred line and the lesion length and wilting range for individual plants after 7 days were recorded.A positive and highly significant correlation coefficient between the percentage of dead plants and lesion length was found for the three years of the study (r=0.83; P<0.01). A highly significant association between lesion length and wilting range for individual plants was always found (P=0.00). Postinfectional phenol content exhibited a strong negative correlation with lesion length and the percentage of dead plants in all the experiments (P=0.05). Association between postinfectional phenol content and wilting range for individual plants was significant for all the years studied (P<0.05). No correlation between phenol levels in healthy plants of the different sunflower genotypes and their susceptibility was found. Morphological characters positively correlated with lesion length but only plant height exhibited significant values for the three years. Associations between wilting range and morphological characters for individual plants were significant for one of the two years analyzed (P<0.05). Xylem index showed a negative correlation with lesion length which was significant one of the two years studied.The lesion length measure seems to be a simple and direct method for resistance screening before the flowering period. Although strong relations with postinfectional phenol levels were found, their determinations would be too much time consuming and not completely reliable. The relationships between other characters measured and disease resistance would indicate that physiological mechanisms could be related to resistance.     

Possibilities of family selection in a cultivar of lucerne,Medicago sativa L., for resistance to the stem nematode,Ditylenchus dipsaci (Kühn) Filipjev

Summary Half-sib families representing the lucerne cultivar Resis were tested for resistance to a stem nematode population, recovered from lucerne. The percentage resistance of the HS-families varied from 13 to 88%. The mean resistance for the cultivar was approximately 50%. Half-sib family selection would be more efficient than recurrent mass selection. The observed data suggest the action of a few genes with relatively large effects.     

Manova and discriminant analyses of phenotypic data as a guide for parent selection in kiwifruit (Actinidia deliciosa) breeding

Evaluation of seedling populations assists in identifying those plants most desirable as parents for a breeding programme. A multivariate analysis of variance (Manova) showed that the seedling populations from 6 kiwifruit (Actinidia deliciosa) crosses differed in their overall merit. Discriminant functions were then used to identify the characters most powerful in distinguishing between populations. The populations were placed in order of their function scores which represent overall merit, and the superior populations were determined. The results showed that `Bruno' was a superior female parent for the production of seedlings with high discriminant function scores for floriferousness (male offspring)and productivity and high vitamin C content (female offspring). One male parent D-1-20 was consistently superior to D-1-6 the other male parent. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic and molecular analysis of the restoration of fertility ( Rf ) genes for Ogura male-sterility from a Japanese wild radish ( Raphanus sativus var. hortensis f. raphanistroides Makino)

Ogura male-sterile cytoplasm is one of the most extensively studied cytoplasms in Brassicaceae. In this study, in order to gain better understanding of the variation and evolution of the restoration of the fertility (Rf) gene for Ogura male-sterile cytoplasm, the nucleotide sequence of the orf687 homologue in the Japanese wild radish (Raphanus sativus var. hortensis f. raphanistroides Makino) was analyzed using an F₂ population made with a cross between a Japanese wild radish plant containing the Rf gene and ‘Uchiki-Gensuke’ (a maintainer of Ogura-male sterility). Segregation of male-fertile/-sterile plants in the F₂ generation suggested that another unidentified Rf gene unlinked to orf687 exists in the Japanese wild radish. The genotype of orf687 was determined for each F₂ plant by Southern hybridization with an orf687 gene probe, mismatch-specific endonuclease digestion of PCR products, and direct sequencing of a PCR product. Genotyping revealed that some fertility-restored plants are homozygotic for the ‘Uchiki-Gensuke’ type orf687 allele, supporting the idea that another gene different from orf687 also functions as an Rf gene for Ogura male-sterility. Protein analysis using an antibody raised against the Ogura-specific ORF138 protein suggests a mechanism of fertility restoration by the unidentified Rf similar to that by orf687. Sequence analysis of orf687 from a Japanese wild radish plant and ‘Uchiki-Gensuke’ revealed that both orf687 regions encode a mitochondrially-targeted protein consisting of 687 amino acids with 16 PPR motifs. Comparison of the deduced amino acid sequences with those of the known orf687 sequences from ‘Yuan hong’ and ‘Kosena’ containing Rf and recessive one (rf), respectively, showed that three unique amino acid replacements are present in ORF687 of the Japanese wild radish. Two of the three replacements, that from lysine to isoleucine at position 232 and from asparagine to asparate at position 240, confer negative charges to the protein. Since the Rf of ‘Yuan hong’ was reported to have a unique replacement that confers a negative charge to ORF687 (from asparagine to aspartate at position 170), it is proposed that the amino acid replacements conferring a negative charge to ORF687 are important for determining the status of the Rf/rf gene.     

Evaluation of a collection of faba bean (Vicia faba L.) genotypes originating from the Maghreb for resistance to chocolate spot (Botrytis fabae) by assessment in the field and laboratory

Screening of 136 faba bean lines forresistance to chocolate spot caused by thefungus Botrytis fabae was conductedin field conditions with artificialinoculation. Detached leaves of thesegenotypes were also assessed for diseaseseverity after inoculation under controlledconditions with a B. fabaesuspension. The BPL710 and Aguadulcegenotypes were inserted as resistant andsusceptible checks, respectively. Diseasesymptoms were scored visually in bothexperiments. Diameter of lesions andproduction of spores were measured in thedetached leaf assay. The disease scoreindex and diameter of lesions were used tocalculate the area under the diseaseprogress curve (AUDPC) to measure thedisease progress. Significant differenceswere detected among genotypes for reactionto the disease in the field. However, nocomplete resistance was observed. Forhighly susceptible and highly resistantgenotypes, the laboratory assay generallyled to the same result as the field test,nevertheless, for more intermediate levelsthe agreement was weak. On detached leaves,diameter of lesions was significantlycorrelated to the AUDPC of disease scores(r = 0.89) and moderately correlated tosporulation (r = 0.52). The correlationbetween field AUDPC and detached leaf AUDPCof disease scores was low (r = 0.26). A lowcorrelation was also observed between fieldAUDPC and lesion size (r = 0.30) andbetween field AUDPC and sporulation (r =0.32). Among the 136 genotypes evaluated inthis study, nine were convincingly andhighly resistant in both tests. FRYM167 andFRYA58 genotypes were the most resistantwith low AUDPC of disease scores, low AUDPCof lesion diameter and low sporeproduction. These genotypes obviously havepartial resistance.     

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

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

A stability analysis of time to flowering as a screen for responsiveness to temperature and photoperiod in cowpea (Vigna unguiculata)

Summary Twenty-one genotypes of cowpea (Vigna unguiculata), comprising landraces and varieties, were grown in 22 photothermal environments in Nigeria and Niger, West Africa, and a stability analysis of days from sowing to flowering (f) was carried out. Cowpeas are rarely insensitive to photoperiod; they are typically quantitative shortday plants wherein f is delayed when photoperiod (P) is longer than the critical photoperiod (P _c ). Therefore, in order to quantify genotypic variation in temperature sensitivity, genotype f was regressed against the mean trial f in circumstances where P c (i.e. approximately 13 hd^-1) and mean temperature (T) was between 19° and 28° C. Correspondingly, in order to assess genotypic variation in photoperiod sensitivity, trials where T was near optimal (25°–28° C) but where P ranged from 10–14.5 hd^-1 were used. These stability analyses detected no significant differences (P>0.05) between genotypes 9n temperature sensitivity but revealed significant differences (P<0.001) in photoperiod sensitivity. Regression coefficients from the stability analysis were strongly correlated (r=0.94, 19df) with a photoperiod sensitivity constant, c, determined from a photothermal flowering model. A stability analysis of f from field trials can therefore identify and quantify genotypic variation in response to temperature and photoperiod in cowpea.Abbreviations f days from sowing to flowering - P mean photoperiod - P _c critical photoperiod - P _ce ceiling photoperiod - T mean temperature - T _b base temperature - T _o optimum temperature - SDP short-day plant     

Mapping of a gene (Vir) for a non-glaucous, viridescent phenotype in bread wheat derived from Triticum dicoccoides, and its association with yield variation

The introgression of desirable genes or alleles from the wild relatives of hexaploid wheat can be a valuable source of genetic variation for wheat breeders to enhance modern varieties. The UK Group 1 bread making variety Shamrock is an example where the introgression of genetic material from wild emmer (Triticum dicoccoides) has been used to develop a modern cultivar. A striking character of Shamrock is its unique viridescent colour compared to other UK wheats, a trait that coincides with a non-glaucous phenotype. A doubled haploid population segregating for the trait (Shamrock × Shango) was examined to map the location of Vir, and analyse any associated pleiotropic effects. The viridescence gene located to the distal end of the short arm of chromosome 2B. QTL analysis of productivity traits shows an association between Vir and a significant delay in senescence, resulting in an extension of the grain filling period. A stable yield QTL, accounting for up to a quarter of the variation in one case, was also identified at or near Vir, indicating significant yield benefits either by linkage or pleiotropy.     

Regeneration and characterization of somatic hybrid plants of Citrus sinensis (sweet orange) and Citrus micrantha, a progenitor species of lime

Most commercial citrus fruit species and cultivars are inter- and intra-specific hybrids. Conventional hybridization in citrus is largely handicapped by apomixis and long juvenility. As an alternative, somatic hybridization via protoplast fusion has been employed to create novel citrus germplasm. Witches' broom disease of lime (WBDL) emerged in Oman during the 1970s, which has been spreading to the neighboring countries. The disease is extremely destructive. A possible solution to the WBDL problem is to develop resistant hybrids. Resistance is available among the citrus relatives of lime i.e., sweet orange. Somatic hybrids combining sweet orange with lime have been produced but the fruit characteristics are different from lime. Herein, we report the development of somatic hybrids between a progenitor of lime (Citrus micrantha) and sweet orange (Citrus sinensis) in efforts to recreate a lime-like fruit using sweet orange as a donor of disease resistance gene(s). Successful somatic hybridization was verified by ploidy analyses using flow cytometry and RAPD analyses. This is the first report of using a progenitor species in somatic hybridization experiments in efforts to resynthesize an improved lime.