Spontaneous structural rearrangements in Solanum phureja Juz. et Buk. 2. Meiotic behaviour and identification of interchange chromosomes using primary trisomics

Abstract

Meiosis was studied in two diploid (2n = 2x = 24) siblings of Solanum phureja Juz. et Buk. and in 11 disomic and 2 trisomic descendants. The diploid siblings carry the same heterozygous interchange and either one or two inversions. The frequency of quadrivalents at diakinesis/metaphase I in these clones was 0.56 and 0.62 per pollen mother cell. In two plants from the first inbred generation (I1) this frequency was about the same but in some other I1plants and a full sib the frequency was substantially lower, varying from 0.00 to 0.16. Most quadrivalents, 78–83%, were rings. A variety of quadrivalent configurations at diakinesis and metaphase I was observed, giving rise to balanced and unbalanced gametes. The absence of ring quadrivalents in trisomic descendants of one of the siblings implied that tertiary trisomics or primaries being homozygous for the interchange were present in the I1generation. Regular chromosome distribution (12–12) at anaphase I occurred in 46.5 and 73.2% of the pollen mother cells studied in the two original clones. Irregularities, such as 11–13 distribution, lagging chromosomes, and a bridge and fragment, were detected on average in 2.7, 3.3, and 32.5%, respectively, of the anaphase I cells analysed. In hybrids from crosses between 6 primary trisomics as females with the interchange heterozygote, the involvement in the interchange of chromosomes 3 and 12 was clearly demonstrated.Key words: Solanum phureja, interchange heterozygote, chromosome identification, interchange trisomic, meiosis.