Search Results - (Author, Cooperation:R. Chetelat)

2012-06-30

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Chloroplasts/*genetics/physiology ; Chromosome Mapping ; Chromosomes, Plant ; Fruit/genetics/growth & development ; Lycopersicon esculentum/*genetics/*growth & development ; Phenotype ; Plant Proteins/*genetics/physiology ; Transcription Factors/*genetics/physiology

0014-5793

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource

1432-2242

Key words Comparative mapping ; Homoeologous recombination ; Segregation distortion ; Solanaceae ; Tomato

Springer Online Journal Archives 1860-2000

Biology

Abstract  The wild nightshade Solanum lycopersicoides (accessionLA2951) was backcrossed to the cultivated tomato (Lycopersicon esculentum cv ’VF36’), then inbred through single-seed descent for several generations. Over 300 backcross-inbred families thereby derived were genotyped at 139 marker loci, consisting of RFLPs, allozymes, and monogenic morphological markers, to identify introgressed S. lycopersicoides chromosomes and segments thereof. The pattern of genotypes observed in the lines indicated a high degree of overall synteny between the S. lycopersicoides genome and that of tomato. Two putative single-copy RFLP probes revealed secondary loci in this wide cross. Recovery of the L. esculentum genome was more rapid than expected, with an average value in the BC2 generation of 97.8%, versus the expected value of 87.5%. This was due to widespread segregation distortion that favored L. esculentum alleles as well as a tendency for plants homozygous for in- trogressed segments to be partially or completely male-sterile, thereby preventing the fixation of S. lycopersicoides markers in many lines. Despite these difficulties, nearly every S. lycopersicoides marker (or approximately 98% of the genome, measured in centi Morgans) was represented in at least 1 backcross-inbred line, with only a region on chromosome 4L missing from the population as a whole. Although the extent of transmission and fixation of introgressed segments varied according to chromosome, overall approximately 66% of the S. lycopersicoides genome was represented by homozygous in- trogressions with sufficient fertility to reproduce by self-pollination. An excess of terminal (vs. interstitial) segments was noted, and putative heterozygous substitutions for chromosomes 6, 7, 8, and 10 were found. Recombination within certain introgressed regions was reduced over 100-fold. These backcross-inbred lines are expected to facilitate the genetic analysis of traits identified in S. lycopersicoides and their transfer into horticultural tomatoes.

Electronic Resource

1432-2242

Tomato ; Solanum lycopersicoides ; Self-incompatibility ; Incongruity ; RFLPs ; Isozymes

Springer Online Journal Archives 1860-2000

Biology

Summary We have previously described gene introgression from the wild nightshade Solanum lycopersicoides into tomato (Lycopersicon esculentum) through the use of either diploid or sesquidiploid hybrids (the latter consisting of two genomes of L. esculentum and one genome of S. lycopersicoides). Both types of intergeneric hybrids display pollen sterility, but workable ovule fertility. Unilateral incompatibility prevents their direct hybridization with staminate L. esculentum. Pollen of a self-compattible form of the related wild species L. pennellii is compatible with pistils of L. esculentum x S. lycopersicoides hybrids. This trait was backcrossed from L. pennellii to L. esculentum in order to develop bridging lines that could be used to obtain progeny from the intergeneric hybrids and to study the inheritance of bridging ability. In progeny of L. esculentum x S. lycopersicoides hybrids pollinated with L. pennellii-derived bridging lines, preferential transmission of L. pennellii alleles was observed for certain isozyme and RFLP markers on chromosomes 1, 6 and 10. The skewed segregations suggest linkage to three major pollen-expressed compatibility loci. This was confirmed by observations of pollen tube growth, which indicated that compatibility with pistils of the diploid intergeneric hybrid occurred only in bridging lines at least heterozygous for the L. pennellii markers on chromosomes 1, 6 and 10. Compatibility with the sesquidiploid hybrid required only the chromosome 1 and 6 loci, indicating an apparent effect of gene dosage on expression of incompatibility in the pistil. In an F2 L. esculentum x L. pennellii population, preferential transmission of L. pennellii alleles was observed for the same markers on chromosomes 1 and 10, as well as other markers on chromosomes 3, 11, and 12, but not 6. The chromosome 1 pollen compatibility locus maps to or near the S-locus, which determines S-allele specificity. The results are discussed in relation to existing genetic models for unilateral incompatibility, including the possible involvement of the S-locus.

Electronic Resource

1432-2242

Tomato ; Lycopersicon esculentum ; Solanum lycopersicoides ; Intergeneric hybridization ; Recombination

Springer Online Journal Archives 1860-2000

Biology

Summary Sesquidiploid hybrids of L. esculentum (L) x S. lycopersicoides (S) were backcrossed to L via L. pennellii (P) as a bridging species in order to detect and measure recombination. Although use of P injected its traits into the populations, the investigated traits were proven to originate from S. The appearance of S traits in diploids in the immediate progeny of sesquidiploids but mainly of derived alien addition types proved the occurrence of recombination at rates varying from 1.6% to 16%. In subsequent BC's, these traits were inherited in dominant Mendelian fashion, except for deviations favoring recurrent parent alleles, sometimes with highly significant deviations from 1∶1. Inheritance was investigated in BC and F2 ex BC for 13 traits with strong phenotypic modifications of morphological, physiological, and isozymic nature. Monogenic determination was confirmed in most instances by tight linkages. For most of the traits, small progenies allowed only rough estimates of linkage intensities, but for Wa (gene for White anthers, universal in S), a test cross with four markers on chromosome 8 established its locus 2 cM distal to dl, proximally on 8L. Also noteworthy is the linkage of Dls, a gene determining sensitivity of flowering to long days, close to sp, situated subterminally on 6L. For the majority of traits, these manifestations of linkage proved that the appearance of S traits resulted from recombination, not alien chromosome substitution — a conclusion also reinforced by observations of chromosome pairing in alien addition types and diploid derivatives. Recombined S alleles have loci in various chromosome positions. Although they were discovered on the shorter chromosomes (nos. 6–12), hybridization barriers precluded tests with the longer chromosomes. Thus, no evidence was found for restriction of recombination to certain chromosomes or chromosomal regions. The prospects therefore appear favorable for deriving valuable traits from the S parent.

Electronic Resource

1432-2242

Key words CMV ; Lycopersicon esculentum ; Disease resistance ; Breeding ; Cmr

Springer Online Journal Archives 1860-2000

Biology

Abstract  Cucumber mosaic virus (CMV) infects a wide variety of crop plants and in tomato (Lycopersicon esculentum Mill.) causes significant economic losses in many growing regions, particularly the Mediterranean. The objective of the present study was to identify the number and map locations of genes controlling resistance to CMV in breeding lines (BC1–inbreds) derived from the related wild species L. chilense. These lines also carried the gene Tm-2 a for resistance to ToMV, which facilitated the interpretation of disease symptoms. The segregation for CMV resistance in the BC2F1 and BC2F2 generations, following mechanical inoculation with subgroup-I isolates, was consistent with expectations for a single dominant gene, for which the symbol Cmr (cucumber mosaic resistance) was given. Resistant and susceptible BC1-inbreds were analyzed with RFLP and isozyme markers to identify genomic regions introgressed from L. chilense. The only L. chilense-specific markers found were on chromosome 12; some resistant lines contained a single introgression comprising the entire short arm and part of the long arm of this chromosome, while others contained a recombinant derivative of this introgression. The chromosome 12 markers were significantly associated with CMV resistance in both qualitative and quantitative models of inheritance. The qualitative analysis, however, demonstrated that CMV resistance was not expressed as a reliable monogenic character, suggesting a lack of penetrance, significant environmental effects, or the existence of additional (undetected) resistance factors. In the quantitative analysis, the marker interval TG68 – CT79 showed the most significant association with CMV resistance. No association between CMV resistance and the Tm-2 a gene was observed. These breeding lines are potentially useful sources of CMV resistance for tomato improvement, in which context knowledge of the map location of Cmr should accelerate introgression by marker-assisted selection.

Electronic Resource

1432-2242

Marker-assisted selection ; RFLPs ; Breeding ; PCR ; Invertase

Springer Online Journal Archives 1860-2000

Biology

Abstract High sucrose concentration in fruit of Lycopersicon chmielewskii is governed by the recessive sucrose accumulator gene (sucr) that is situated in the pericentromeric region of chromosome 3. The sucr gene was introgressed into the genetic background of the hexose-accumulating cultivated tomato (L. esculentum cv ‘Hunt 100’) by marker-assisted selection using tightly linked RFLP markers and a tomato acid invertase cDNA as probes for sucr. RFLP mapping indicated that the segment containing sucr comprised over 43.2 cM in the BC1F2 generation, representing over one-third of the total length of chromosome 3. By selecting for crossovers between sucr and the flanking visual marker r (yellow fruit flesh) and RFLP marker TG288, we were able to reduce the size of the sucr introgression fragment to 0.8–7.1 cM by the BC5 generation. Smaller recombinant fragments were not obtained despite screening a large BC6F2 population. The smallest sucr introgression reduced recombination between the flanking visual markers sy (sunny) and bls (baby lea syndrome) by 38%. To facilitate future introgression and recombination experiments, a PCR-based test for the sucr gene was developed using primers specific to the tomato invertase gene. This assay takes advantage of a small deletion that maps to the second intron of the L. chmielewskii nvertase gene. The assay detected significant allelic variation both within and between hexose- and sucrose-accumulating Lycopersicon spp.

Electronic Resource

1432-2242

Soluble solids ; RFLPs ; reeding ; Invertase ; Marker-assisted selection

Springer Online Journal Archives 1860-2000

Biology

Abstract A gene controlling fruit sucrose accumulation, sucr, was introgressed from the wild tomato species Lycopersicon chmielewskii into the genetic background of a hexose-accumulating cultivated tomato, L. esculentum. During introgression, the size of the L. chmielewskii chromosomal segment containing sucr was reduced by selection for recombination between RFLP markers for the sucr gene and flanking loci. The effects of sucr on soluble solids content, fruit size, yield and other fruit parameters were studied in the genetic background of the processing tomato cultivar ‘Huntl00’. In a segregating BC5F2 generation, the smallest introgression containing sucr-associated markers was necessary and sufficient to confer high-level sucrose accumulation, the effects of which were completely recessive. Fruit of sucr/sucr genotypes were smaller than those of +/sucr or +/+ genotypes at all stages of development. The timing of sugar accumulation and total sugar concentration were unaffected by sugar composition. No differences in total fruit biomass (fresh weight of red and green fruit) at harvest were observed between the genotypes, and sucrose accumulators produced greater numbers of fruit than hexose accumulators in one family. However, the proportion of ripe fruit at harvest, and hence yield of ripe fruit, as well as average ripe fruit weight and seed set were reduced in sucr/sucr genotypes. Sucrose accumulation was also associated with increased soluble solids content, consistency, serum viscosity, predicted paste yield and acidity, and decreased color rating. In the first backcross to L. chmielewskii, hexose accumulators (+/sucr) had larger fruit than sucrose accumulators (sucr/sucr), while no difference in soluble solids was detected.

Electronic Resource