A 105-kilobase bacterial artificial chromosome (BAC) clone from the ovate-containing region of tomato chromosome 2 was sequenced and annotated. The tomato BAC sequence was then compared, gene by gene, with the sequenced portions of the Arabidopsis thaliana genome. Rather than matching a single portion of the Arabidopsis genome, the tomato clone shows conservation of gene content and order with four different segments of Arabidopsis chromosomes 2-5. The gene order and content of these individual Arabidopsis segments indicate that they derived from a common ancestral segment through two or more rounds of large-scale genome duplication eventspossibly polyploidy. One of these duplication events is ancient and may predate the divergence of the Arabidopsis and tomato lineages. The other is more recent and is estimated to have occurred after the divergence of tomato and Arabidopsis Ϸ112 million years ago. Together, these data suggest that, on the scale of BAC-sized segments of DNA, chromosomal rearrangements (e.g., inversions and translocations) have been only a minor factor in the divergence of genome organization among plants. Rather, the dominating factors have been repeated rounds of large-scale genome duplication followed by selective gene loss. We hypothesize that these processes have led to the network of synteny revealed between tomato and Arabidopsis and predict that such networks of synteny will be common when making comparisons among higher plant taxa (e.g., families). genome evolution ͉ polyploidy

No abstract

Although tomato has been the subject of extensive quantitative trait loci (QTLs) mapping experiments, most of this work has been conducted on transient populations (e.g., F 2 or backcross) and few homozygous, permanent mapping populations are available. To help remedy this situation, we have developed a set of inbred backcross lines (IBLs) from the interspecific cross between Lycopersicon esculentum cv. E6203 and L. pimpinellifolium (LA1589). A total of 170 BC 2 F 1 plants were selfed for five generations to create a set of homozygous BC 2 F 6 lines by single-seed descent. These lines were then genotyped for 127 marker loci covering the entire tomato genome. These IBLs were evaluated for 22 quantitative traits. In all, 71 significant QTLs were identified, 15% (11/71) of which mapped to the same chromosomal positions as QTLs identified in earlier studies using the same cross. For 48% (34/71) of the detected QTLs, the wild allele was associated with improved agronomic performance. A number of new QTLs were identified including several of significant agronomic importance for tomato production: fruit shape, firmness, fruit color, scar size, seed and flower number, leaf curliness, plant growth, fertility, and flowering time. To improve the utility of the IBL population, a subset of 100 lines giving the most uniform genome coverage and map resolution was selected using a randomized greedy algorithm as implemented in the software package MapPop (http://www.bio.unc.edu/faculty/vision/lab/ mappop/). The map, phenotypic data, and seeds for the IBL population are publicly available (http://soldb.cit.cornell.edu) and will provide tomato geneticists and breeders with a genetic resource for mapping, gene discovery, and breeding.Key words: tomato, Lycopersicon esculentum, IBLs, QTL, mapping.Résumé : Bien que la tomate ait été l'objet de nombreuses études de cartographie des loci de caratère quantitatif (QTL), la plupart de ces travaux ont été réalisés sur des populations non-fixées (F 2 ou rétrocroisement) et peu de populations homozygotes, permanentes sont disponibles. Afin de remédier à cette situation, les auteurs ont développé une collection de lignées rétrocroisées fixées (« inbred backcross lines », IBL) à partir d'un croisement interspécifique entre le Lycopersicon esculentum cv. E6203 et le L. pimpinellifolium (LA1589). Cent soixante-dix plants BC 2 F 1 ont été reproduits par descendance monosporale pendant cinq générations pour produire des lignées BC 2 F 6 homozygotes. Ces lignées ont ensuite été génotypées à l'aide de 127 locus marqueurs couvrant l'ensemble du génome de la tomate. Ces IBL ont été évaluées pour 22 caractères quantitatifs. Au total, 71 QTL significatifs ont été identifiés, dont 15 % (11/71) étaient situés à la même position chromosomique que lors d'études antérieures faisant appel à ce même croisement. Pour 48 % (34/71) des locus détectés, l'allèle sauvage était associé à une performance agronomique améliorée. Plusieurs nouveaux QTL ont été identifiés dont plusieurs de grande importance agro...

Bruchid, Callosobruchus spp. (Coleoptera: Bruchidae), is a serious pest during storage of seeds of mungbean (Vigna radiata (L.) Wilczek) and other Vigna species. A source of resistance to this pest has been identified in Vigna sublobata (Roxb.) Bairig. accession TC1966. Two hundred recombinant inbred lines at the F(12) generation have been developed for molecular mapping of bruchid resistance (Br) gene in TC1966. Through bulked segregant analysis (BSA), ten randomly amplified polymorphic DNA (RAPD) markers associated with the bruchid resistance gene were successfully identified. A total of four closely linked RAPDs were cloned and transformed into sequence characterized amplified region (SCAR) and cleaved amplified polymorphism (CAP) markers. Seven CAPs developed from the identified RAPD markers showed tighter linkage with the Br gene than the original RAPD. Through transformation of RAPDs into CAPs, codominant markers for bruchid resistance were successfully obtained. Homozygous genotypes of these PCR-based markers were estimated to contribute 85% of the variance for seed damage when the insect assay was performed under favorable growth conditions for bruchid

No abstract