Development of Integrated Techniques for Induced Genetic Diversity and Improvement of Vegetatively Propagated and Horticultural Tree Crops

In the current proposal, we aim to develop novel genetic resources, methodologies and tools for accelerated breeding for productivity improvement in vegetatively propagated (cassava) and perennial horticultural tree (olive) crops by using mutation induction and associated in vitro micropropagation techniques. The research focus is on developing, optimizing and/or validating protocols for tissue culture-based induced mutagenesis, the dissociation of chimera and the regeneration of plantlets of putative stable mutants of these two crops with tolerance to Cassava Brown Streak Disease (CBSD) and Olive Quick Decline Syndrome Disease (OQDSD) respectively. Towards this end, the CRP, with the expected participation of the National Agricultural Research Systems of countries where the crops are grown extensively, some advanced institutions and the CGIAR centres with the respective mandates, shall over a period of four to five years, generate stable mutant clones, that are free-of-chimeras and characterized in genetic and molecular terms for traits of interest and publication of protocols for phenotyping and genomic analysis.  Based on the predominance of the two crops in FAO/IAEA Member States, the CRP contracts will be distributed 70:30 between cassava and olive.
Cassava and olive crops play an important role in food security and income and represent significant agricultural opportunities in most  of the globe. But their improvement have been very slow due to their limited genetic diversity, as they cannot be easily self or cross-pollinated to produce seed or to expand variation, due to vegetative propagation and/or long breeding cycles making progress in breeding programs through conventional methods (i.e., generations of crossing and selection) time-consuming. Climate change further worsens this situation by causing serious production losses from other factors including intensifying and transboundary spread of pests and pathogens.
Plant breeding using induced genetic diversity is an established, safe and highly effective mean to generate heritable variation in crops relevant for breeding programs and farmers, and therefore holds great promise to unlock further the genetic bases of cassava and olive crops to enhance their adaptation to the pressures of climate change, especially regarding the frequent emergence of new pests and pathogens. It has already played an important role in the development of many crops, mostly seed propapagated.  Improvement of vegetatively propagated crops (VPCs) and perennial horticultural tree crops (HTCs) using induced genetic diversity has intrinsic limitations, and only a pragmatic approach to optimize  cell and tissue culture methodologies for chimera-free regeneration can make this technology feasible. To date, very few VPCs and HTCs improved or developed through breeding based on induced genetic diversity have been released, relative to seed propagated crops.
 Developing efficient methodologies and protocols capable of overcoming the limitations associated with plant breeding using induced genetic diversity in cassava and olive has become increasingly imperative if we are to meet the rising demands for food and nutrition without adverse environmental footprints. Tissue culture has the potential for improving effectiveness of inducing genetic variation for the improvement of VPCs and HTCs, as it offers a wide choice of plant material for treatment (in vitro axillary buds, organs, tissues, and cells) that are more suited for the induction of novel genetic diversity.. Tissue culture also allows for the cost-effective handling of large populations for mutagenic treatment and selection of variants.
With the recent technological advances, in particular the advent of NGS (Next Generation Sequencing), and the continuous development of cheaper and more affordable approaches, the efficiency of improvement of VPCs and HTCs using induced genetic variation could be enhanced through the use of genomic resources. Functional genomics tools can help establish gene-to-phenotype associations thus providing information of the underlying molecular bases for traits that can then be used in marker-assisted breeding or gene editing.