Maritza Institute for Vegetable Crops, 32 Brezovsko shosse str., Plovdive-4003, BULGARIA
The gene Del, responsible for Delta-carotene synthesis in tomato fruits, was reported by Tomes (1963). Its source was L. hirsutum f. typicum. The gene is found in the genome of all green fruited species (Soost 1956; Rick 1973; Chalukova, Stoeva 1988). Del^hirs^, Del^chm^ and Del^pen^ proved to be allelic (Chalukova, Stoeva 1988; Chalukova et al. 1990). The aim of the present investigation was to locate the gene Del, since no references on the subject have been available to us. In that purpose we used line DelDel, kindly presented by Dr. Darby, Glasshouse Crop Research Institute, UK and the marker lines for all chromosomes, excepting 7 and 9, presented by the Tomato Genetics Stock Center, Davis, California.
Results of the segregation in BC1P2 (line DelDel x LA 1171 - fd aud) and in BC1P2 (line DelDel x LA 1177 - alb mua) showed that Del was located on chromosome 12 (Table 1). Data from F2 (DelDel x LA 1177) served only as orientation bout the linkage Del-fd. As far as we know the location of aud and mua on chromosome 12 is not yet fixed. According to the frequency of recombination in BC1P2 (DelDel x La 1171) Del is situated very near to fd. The distance between them is about 2 crossover units (Table 2). The linear order of the two markers and of the gene studied could be Del-fd-aud or fd-Del-aud. In the first case the locus of Del will be situated at position 29 and in the second case - at position 33. The gene aud should have to be at position 50-52 (Fig. 1).
Table 1. Phenotype segregation
____________________________________________________________ Combination Segregation ____________________________________________________________ Del+fl+ Del+fl Del fl+ Del fl BC1P2/DelDel x LA1171/ 65 2 10 45 F2/DelDel x LA1171/ 125 22 0 61 Del+aud+ Del+aud Del aud+ Del aud BC1P2/DelDel x LA1171/ 51 15 1 54 F2/DelDel x LA1171/ 125 23 0 60 Del+alb+ Del+alb Del alb+ Del alb BC1P2/DelDel x LA1171/ 40 21 15 53 Del+mua+ Del+mua Del mua+ Del mua BC1P2/DelDel x LA1171/ 44 18 16 54 ____________________________________________________________The data from BC1P2 (DelDel x LA 1177) suggest that Del is located 27 units from alb. This result is very close to the result for the first combination in linear order Del-fd-aud. Therefore we accept that Del is located at the 29 and not at the position 35. As far as the position of mua is concerned according to the crossing-over percentage alb-mua, it should be located about the position 44 and according to the crossing-over percentage Del-mua the latter is 26 units from Del, i.e. on position 55. Probably mua should be located between position 44 and 55 on chromosome 12.
Table 2. Frequency of recombination
______________________________________________________________ Combination Genes No of No. of reco Distance plants mbinations ______________________________________________________________ BC1P2(DelDel x LA1171) Del-fd 122 3 2,46+\-1,91 Del-aud 122 (22 + 3) 20,49+\-1,33 F2(DelDel x LA1171) Del-fd 208 1 0,48+\-2,30 Del-aud 208 (22 + 1) 11,05+\-4,72 BC1P2(DelDel x LA1171) Del-alb 132 (25 + 11) 27,27+\-1,50 Del-mua 132 (23 + 11) 25,75+\-2,45 alb-mua 132 (25 + 23) 43,93+\-4,76 ______________________________________________________________Figure 1. Linkage map of chromosome 12
Chalukova, M. and P. Stoeva 1988. Plant Breeding, 100:230-234.
Chalukova, M., Z. Vulkova-Atchkova, E. Lukarska 1990. TGC Report, 40:8.
Rick, C. 1974. Hilgardia, 42:493-510.
Soost, R., 1956. TGC Report, 6:28-33.
Tomes, M. 1963. Bot. Gaz., 124:180-185.