During a cytological investigation of a number of crop plants, a chromosome number of tomato was found which may not have been previously reported in Lycopersicum esculentum or in the genus Lycopersicum. About 60 plants of the variety FLORA-DADE, grown from Queensland certified seed, were all found to have the chromosome number 2 n = 26. Among chemically treated plants of this variety a tetraploid with 52 chromosomes, a triploid with 39 chromosomes and a trisomic with 27 chromosomes were also found. The chromosome numbers of the two polyploids is strong confirmation that the n chromosome number in this variety is 13. Furthermore preliminary meiotic examination of FLORA-DADE revealed 13 bivalents at metaphase I. There also appear to be 13 pairs of chromosomes at pachytene.
Following identical cytological methods of examination as those used for FLORA-DADE, VF 36 as well as GROSSE LISSE were found to have the expected chromosome number 2 n = 24.
The chromosome numbers of the original line of FLORA-DADE imported to Australia from Florida as well as some varieties related to FLORA-DADE were also determined. This line of FLORA-DADE and its parental varieties WALTER and Florida 2153 were also found to have the chromosome number 2 n = 26. The related varieties TROPI-RED, FLORIDA 1A and NC 507 were also found to have the chromosome number 2 n = 26.
In his comprehensive review of chromosome numbers in flowering plants Fedorov does not cite any reports of a chromosome number 2 n = 26 in any of the species of Lycopersicum. A computerized library search of more recent literature failed to reveal any reports of tomatoes with this chromosome number. The results presented here indicate that the chromosome number 2 n = 26 may be widespread among subtropically adapted commercial varieties of tomato. FLORA-DADE itself accounts for about 90% of the fresh fruit marketed in Australia. The chromosome number of several other varieties is being investigated.
Information about the relatives of FLORA-DADE was provided by Dr. R. Volin, University of Florida. Seed was provided by M. Herrington, Redlands Horticultural Research Station, Ormiston, Queensland.