Taking stock of banana breeding

Leila_Er-rachiq Tuesday, 25 January 2011

Ivan W. Buddenhagen’s introduction to a new book on the progresses made in breeding bananas. The book covers all aspects of breeding and genetics, including biotechnology.

Cover of the book: 'Banana breeding: progress and challenges'
Finally we have a book centering on banana breeding. It is even entitled “Banana Breeding”. This is a most welcome addition to the classical books by N.W. Simmonds on Bananas and Banana Evolution, now some 50 years old.

The book is a wide-ranging compilation of chapters by various authors, covering plant morphology, Origin, Genetic Resources, Reproductive Biology, Diseases, Pests, Quality Improvement, propagation, Distribution to Farmers, as well as the central focus chapters covering breeding, genetics and biotechnology. There is even a final chapter comparing breeding with three other major clonal tropical crops.

When one considers that banana breeding based on modern science is now some 90 years old and yet farmers are still mainly growing the diverse clones selected by villagers thousands of years ago from their natural environment, one must ask why. How could so many diverse and excellent clones have arisen by purely natural events of pollination, seed set, seed germination, and then selection?

The answers are complex, but things must have been very different then. Indeed, in an excellent chapter by Fortescue and Turner on Reproductive Biology, it is made very clear that low seed set and germination today are major detriments to breeding progress and that little research has been applied to understand the physiological/biochemical reasons for ovule abortion/low seed set. When early Man first found and brought into cultivation parthenocarpic plants, they were probably quite fertile. Thus, as plants were moved about, encountering genetically diverse bananas, seed set was probably abundant. With time, seed set was negatively selected and, hence, present day sterility. Yet some parthenocarpic clones are still quite fertile, but exploration and evaluation for this character has been neglected. Even our understanding of parthenocarpy itself and its inheritance go back to work now 50 years old.

But the breeding programs themselves have waxed and waned as support changed and objectives changed. There are six existing breeding programs outside the center of origin of Musa. Only two efforts in India and none at all in the Southeast Asia center of diversity where wild bananas still exist and clones are still being domesticated. Research on coevolved pathosystems is neglected and no feedback from the natural systems into breeding exists.

Many chapters in this book reveal the enormity of molecular research applied to bananas and the attempts to apply molecular techniques to banana breeding itself. Molecular assisted selection is still in its infancy and much dynamism continues in the molecular field.

Breeding techniques and breeding philosophies are expertly detailed in a chapter by Tenkouano et al. It is clear that much has been learned to direct the future of breeding. Excellent bibliographies in many chapters provide a valuable documentation of the diverse and enormous scattered research activity on bananas of the last 50 years.

Breeding bananas started with the simple objective of a Fusarium wilt-resistant Gros Michel. Breeding objectives changed and proliferated as new programs started and local farmer needs were addressed. Objectives are now very diverse and complex and they differ in different regions. Much has been learned of banana evolution through molecular science. Yet breeders still use only a very limited pool of parents compared with the great natural diversity existing. It is clear that much research is still needed to assess and to reduce reproductive barriers.

A perusal of these chapters with the literature and experience on which they are based, reveals a wealth of knowledge and views not readily available elsewhere. It is an excellent new resource on bananas and banana breeding.

Reprinted with the kind permission of the publisher. Banana breeding: progress and challenges was edited by Pillay, M., Tenkouano, A. and is published by Taylor and Francis.

Ivan W. Buddenhagen is Professor Emeritus at the University of California in Davis, USA.