Identification of the genomic constitution of Musa L. lines (bananas, plantains and hybrids) using molecular cytogenetics

Abstract

The genomic constitutions of some Musa L. lines (bananas, plantains and artificial hybrids) were identified using molecular cytogenetic techniques. Double target in situ DNA:DNA hybridization to chromosome spreads using as probes, total genomic DNA isolated from diploid Musa lines of known AA (labelled with biotin-11-dUTP) and BB (labelled with digoxigenin-11-dUTP) genome constitution was carried out. The use of 60% acetic acid combined with heating over a flame gave high quality chromosome spreads free of cytoplasm for in situ hybridization. Total genomic A DNA labelled broad centromeric regions of all 22 chromosomes of the diploid line, Calcutta 4 ( M. acuminata Colla. ssp. burmanniccoides ; A genome) with some chromosomes showing stronger hybridization. Labelled DNA from the B genome hybridized strongly to the centromeric regions of all 22 chromosomes of Butohan 2 ( M. balbisiana Colla; B genome). The two satellited chromosomes of genome B labelled strongly with genomic A DNA. In situ hybridization of labelled A and B genomic DNA to metaphase chromosomes of triploid AAB and ABB cultivars discriminated between A and B genome chromosomes. The plantains Agbagba, Obino l'Ewai and Mbi Egome showed 22 genome A and 11 genome B chromosomes while the cooking bananas Bluggoe and Fougamou showed 11 genome A and 22 genome B chromosomes. Hybridization of labelled A and B genomic DNA to chromosomes of the hybrids showed that TMP2x 2829-62 has all 22 genome A chromosomes while TMPx 4698-1 has 33 genome A and 11 genome B chromosomes. In situ hybridization of labelled total genomic DNA to chromosomes has immense potential for identification of chromosome origin and can be used to characterize cultivars and hybrids produced in Musa breeding.