Highland banana (Musa AAA-EA) has a narrow genetic base, making it susceptible to several pests and diseases including weevils, black sigatoka, nematodes and bacterial wilt. Since 1994, the Ugandan National Agricultural Research Organization (NARO) has spearheaded development of conventionally bred varieties resistant to these pests and diseases as a priority intervention option in response to these problems. However, most highland banana cultivars (including the five most popular ones) are infertile and therefore cannot be improved conventionally. Around 2000, it was decided that a biotechnological approach should be applied to improve the popular but infertile cultivars. A consortium of donors, including the Rockefeller Foundation, accepted to provide resources to support improvement of these banana types through application of biotechnological tools.

The current method of choice when introducing new traits into a banana involves inserting the genes in a cell suspension. The biggest hurdle in this process is developing the banana cell suspensions. The standard method of developing cell suspensions was optimized with a highland banana (Nakyetengu) at Kawanda. Since 2003, cells have been regenerated into plants that were planted out in the field and have been confirmed to be true to type. This implies that a system through which highland banana can be improved through genetic engineering is now in place. The same method is now being applied to other highland banana cultivars and cell suspension initiation and regeneration have been achieved for Nakinyika, Mbwazirume and Sukali Ndizi (Musa AAB). Optimization experiments for transformation of banana cell suspensions using marker genes through particle bombardment have been initiated. Transient GUS expression was achieved after 2 days. Similar transient expression results were observed in cells transformed using Agrobacterium tumefaciens.

Donors in the consortium support different but interlinked biotechnology activities. Technical coordination has been achieved with support from the Rockefeller Foundation through a grant to support a visiting scientist, who in addition to coordinating the biotechnology activities is executing a study aimed at identifying markers for parthenocarpy. A segregating population for parthenocarpy was developed from Cal 4 (seeded) and Psang Lilin (non-seeded). F1 hybrids (which will be used for DNA fingerprinting to identify markers for parthenocarpy) have been planted out in the field. The scientist also executed activities aimed at quickening ploidy-based selection using cytometry. Hybrids generated through conventional breeding crosses were screened to ascertain their exact ploidy through ploidy analysis. Results obtained show that 4x by 2x crosses yielded mainly 88% triploids, 8% diploids and 4% tetraploids while 3x by 2x crosses yielded mainly 99% tetraploids and 1% diploids. Field planting for early evaluation is now routinely done according to desired ploidy. This report highlights progress achieved in the last 2 years.