Suckers collected from different populations of Musa acuminata ssp. malaccensis were found to be highly resistant to race 4 of Fusarium oxysporum f. sp. cubense (FOC) suggesting that local wild banana populations co-evolved with the pathogen. Seedlings from these wild banana plants segregated for resistance to the pathogen. The infected seedlings were characterized based on external and internal symptoms and the variable response to FOC was mainly due to the genetic factors. Using the technique of random amplified polymorphic DNA (RAPD), 96 major amplification products from 15 primers were identified. Only 10 out of 96 markers were monomorphic and shared among the seed progenies, whereas the remaining 86 were highly polymorphic. Three primers showed banding patterns specific to resistant or susceptible seedlings. These results showed the great potential of the wild Musa acuminata ssp. malaccensis as a source for banana improvement and also for the synthesis of segregating populations for linkage mapping, gene cloning and DNA markers related to FOC resistance.

No abstract

Fourteen populations of Musa acuminata ranging from populations in the lowlands of northern (ssp. siamea) to central Malaysian region (ssp. malaccensis) and highland banana (ssp. truncata) were characterized based on chromosome number and 46 morphological characters. A large amount of variation was observed within the populations. However, only highland bananas appeared morphologically distinct. Lowland populations both from northern and central Malaysia were found to be overlapping and no distinguishing pattern was observed. The morphological characters found variable within these populations were related to developmental changes and mutations. The results obtained in this study were not revolutionary. However, the survey of a large number of characters treated with multivariate techniques further sharpened the existing groupings of the Musa acuminata subspecies.

Mutagens cause random changes in the nuclear DNA or cytoplasmic organelles, resulting in gene, chromosomal or genomic mutations and hence, create variability. In this study, flow cytometry (FCM) was used to determine ploidy levels and DNA content in gamma-irradiated variants of mutated Pisang Berangan (cv. Intan, AAA) -a local banana genotype. Induced variants such as short plant stature (stunted growth), late flowering plants (late maturity) and abnormalities in bunch characters were selected to study possible changes at the DNA level. The study showed that DNA content of mutated plants differed from non-irradiated control and that irradiation had the most effect at high doses (40 and 60 Gy). The increase of DNA content in 20 Gy and 30 Gy treated plants was not more than that of the control plants. The values of genomic DNA content of gamma-irradiation variants decreased as the dose of irradiation increased from 20 to 60 Gy, indicating that the high dose of gamma-irradiation had a significant effect on the genome of the plants.The analysis further showed that phenotypic variation due to mutagenesis was reflected in the DNA content of the plants. The results also showed that ploidy levels were not affected by gamma-irradiation even at high doses.

The male buds of 16 Musa species (Musaceae) populations were investigated by HPLC for the occurrence of anthocyanins. The investigation was based on the presence of 6 anthocyanins. The 16 Musa samples could be classified into three distinct species i.e. Musa acuminata, Musa violascens and Musa balbisiana. Musa acuminata could be divided into two subspecies : malaccensis (lowland) and tmncata (highland) according to their constituents and content of major anthocyanins. No variation was observed in the composition of the anthocyanins of Kedah type ssp. siamea and Selangor types ssp. malaccensis. The classification of M. acuminata into two subspecies based on anthocyanin data further supported the current taxonomic grouping of the species.