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Overcoming barriers to the conservation and use of banana seed germplasm

Boek - Dissertatie

The intrinsically low intraspecific diversity of clonal crops such as banana, and continued reliance on existing cultivars and landraces, means that there is an increased threat of epidemic disease infection and spread. Climate change will likely exasperate the problem further, as disease spread could be greater under warmer conditions. Bananas may come under further pressure as climate change causes drought stress or storm damage to crops. When a host and pest/pathogen exist together, over time, coevolution can occur. Pathogens impose selection pressure for resistance (and associated costs) on hosts in arms-race interactions. It therefore makes sense for breeders to search for disease resistance, from sexually reproducing populations, in the native ranges of both the pathogen and host. For clonal parthenocarpic crops such as bananas and plantains, this in essence means crop wild relatives. Wild relatives of cultivated bananas have been used to breed for disease resistance. Most notably has been the wild diploid Musa acuminata subsp. burmannica Simmonds var. 'Calcutta 4'. Calcutta 4 is highly resistant to black leaf streak, has shown some resistance to Fusarium wilt race 1 and 4, and burrowing nematode (Radopholus similis (Cobb.) Thorne). Because of these properties, Calcutta 4 has been used in several breeding programmes. Other Musa acuminata and related cultivars ('Pisang lilin' and 'Pisang jari buaya') have been used to introgress resistant genes to pathogenic fungi and nematodes. Further, the other progenitor of the cultivated banana Musa balbisiana Colla., and its derivatives, are thought to show some resistance to Bunchy Top. Several constraints exist in our ability to make use of such Musa crop wild relatives. The research I propose, aims to address some of these constraints in relation to seed germplasm, as seeds can be the most efficient means of collecting and storing the greatest range of genotypes, if constraints are overcome. 1. Musa seeds cannot be consistently germinated, effectively meaning that breeding using banana seeds requires embryo rescue techniques, which is time consuming and requires laboratory facilities 2. Optimal storage conditions and lifespan of Musa seeds in storage is not known, so expensive collecting programme can result in quickly aging or dying seeds; 3. We do not know how best to sample Musa germplasm to ensure maximum genetic capture of genetic diversity. The aim of this study is to investigate approaches to ex situ conservation of Musa germplasm in the following areas. 1. To determine Musa seed dormancy type and optimise dormancy breaking protocols 2. To assess optimal storage conditions for Musa seeds and an indication of longevity 3. To describe Musa genetic structure and diversity 4. To model best sampling approaches to genetic diversity and structure.
Jaar van publicatie:2022
Embargoed until:05/04/2023