Induced androgenesis in tomato (Lycopersicon esculentum Mill.). III. Characterization of the regenerants.

We present data on the morphological, cytological, biochemical and genetic characteristics of tomato regenerants obtained through anther culture. As a result of induced androgenesis, more than 6,000 rooted regenerants were developed that differed both from the donor plants and among each other with respect to habitus and leaf, flower and inflorescence morphology. Cytological analysis revealed a great variability in chromosome number in the cells of the regenerated plants. While most of the regenerants were mixoploid, the majority of the cells had a haploid chromosome number. R(1) and R(2) progenies were tested for their resistance to Clavibacter michiganense subsp. michiganense ( Cmm 7). Some of the regenerants were resistant to the pathogen. A biochemical analysis of fruit from R(3) and R(4) plants showed a higher content of dry matter, sugars and vitamin C in the regenerant plants obtained from the hybrids than in those from the cultivars and control plants. The values of the parameters of hybrid regenerants grown in the greenhouse were about 1.5-fold higher than those of the hybrid regenerants grown in the field, and this trend is clearly expressed in all of the hybrid regenerants. The results obtained suggest that induced androgenesis and gametoclonal variation may be used as an additional tool to create a large range of new forms. The application of the latter in breeding programs would accelerate the development of tomato lines and varieties that would be more productive, disease-resistant, highly nutritive and flavour-acceptable.

Identification of a novel mutation in the paired domain of PAX3 in an Iranian family with waardenburg syndrome type I.

Waardenburg syndrome Type I (WS1) is an autosomal dominant disorder that has previously been associated with mutations in the PAX3 gene on the 2q35 region. In this study, we used an Iranian WS1 family with seven affected individuals in three generations. The phenotypic characteristics of the family include sensorineural deafness, dystopia canthorum, hypopigmented skin patches of the upper limbs, congenital white forelock, confluent white eyebrows, nonpigmented iris, poliosis, and hypopigmentation of the retina. Herein, we report a previously unidentified single-base substitution in exon II (C-->T at position 218) that results in a change of serine to leucine (S73L) in this family. This change was not observed in 100 chromosomes of healthy unrelated individuals. This mutation is within the PAX3 paired domain region, a structure that is highly conserved and implicated in DNA binding. This is the first identification of a PAX3 mutation for this phenotype in the Iranian population. This also provides additional confirmation for the involvement of this gene in the etiology of WS1.

Mapping of primary congenital lymphedema to the 5q35.3 region.

Primary lymphedema is a chronic tissue swelling, most frequently of the lower limbs, resulting from deficient lymphatic drainage. The variability of the affected phenotype, incomplete penetrance, lack of large families, and possible genetic heterogeneity have hampered the identification of causative genes until now. We carried out a genomewide search, using a four-generation North American family with dominantly inherited primary congenital lymphedema (PCL), otherwise known as "Milroy disease," or "hereditary lymphedema type I" (MIM 153100). Linkage to markers from the 5q35.3 region in this and four additional, British families was established. A minimum of 79 directly scorable haplotypes (37 affected) in five families conspicuously segregated with the most telomeric region of 5q35.3, thus suggesting a major locus for PCL in this vicinity. No recombination was observed with D5S408 (Z = 10.03) and D5S2006 (Z = 8.46) with a combined multipoint score of 16.55. While D5S2073 and WIAF-2213 defined the upper centromeric boundary, no recombinants were obtained for the last telomeric marker of D5S2006. Four unaffected subjects were identified as gene carriers and provided an estimated penetrance ratio of.84 for this condition. A few of the positionally mapped genes in the 5q35 region that may potentially be involved in the etiology of this condition are CANX, FGFR4, HK3, and hnRPH1.

Study of the three-genome hybridLycopersicon esculentum Mill. -L. chilense Dun. -L. peruvianum var 'humifusum' Mill. and its use as a source for resistance.

L. peruvianum var 'humifusum' is reproductively the most isolated of the species of the genusLycopersicon. It can be crossed with the cultivated tomato usingL. chilense as an intermediary. After a series of backcrosses of the three-genome hybrid F1 (L. esculentum ×L. chilense) ×L. peruvianum var 'humifusum' withL. esculentum, accompanied by selection for resistance to some economically important diseases, several lines were established. One of these lines, Cm 180, which showed resistance toClavibacter michiganensis subsp.michiganensis, was subjected to genetic analysis. This resistance was found to be controlled by a single dominant gene (Cm) that was not allelic to the gene originating fromL. hirsutum f.glabratum. ThisCm gene was genetically mapped on chromosome 4. The germ plasm ofL. peruvianum var 'humifusum' in combination withL. chilense was transferred intoL. esculentum. Different breeding lines possessing resistance to various diseases and pests could be developed from this material.