Use of genome editing confers resistance to Banana Xanthomonas wilt. Photo Credit IITA

New gene editing tool promises quicker banana breeding

By Murimi Gitari

[rt_dropcap_style dropcap_letter=”D” dropcap_content=”ESPITE being a staple for millions of people worldwide, banana has long been plagued by various genetic issues, including low genetic variability in germplasm, protracted production cycles, and the sterility of many cultivars.”]

A report by the Centre for Agriculture and Bioscience International (CABI) shows that over 50 million people in East Africa depend on highland bananas for their food or income. Annually, the crop’s production is worth around $4.3 billion. The lack of quality banana varieties, pests and diseases associated with nutrient deficiencies and drought stress continues to affect average productivity of this African staple.

Over the last 50 years, there have been attempts to increase banana production by increasing the land area under cultivation, but this is not sustainable since available arable land area is limited. The low productivity is also linked to challenges such as poor management and production constraints, including low soil fertility, drought, pests and diseases.

Nevertheless, researchers are making strides in the improvement of the banana varieties through by using the transformative genome editing technique to enhance disease resistance and increased yield potential, for example. Genome editing has developed rapidly in the last decade and has transformed researchers’ ability to manipulate various organisms’ genomes.

CRISPR/Cas9 has emerged as the most popular technique for functional genomics and crop improvement due to its ease of use, design flexibility, high efficiency, and multiplexing. CRISPR-Cas9 is a unique technology that enables researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence.

A study by the International Institute of Tropical Agriculture (IITA) in partnership with Demeetra AgBio Inc has unveiled another similar technology purposely for banana genome editing aimed at improving varieties and disease resistance. The technology, Cas-CLOVER is a novel, precise and highly efficient genome editing tool for banana.

The findings of this study intend to revolutionise banana cultivation by addressing critical challenges faced in traditional breeding. The study titled “A new and novel high- fidelity genome editing tool for banana using Cas-CLOVER” found that Cas- CLOVER is an efficient genome editing technology in banana for boosting crop development to enhance the yield and income of smallholder farmers.

Dr Leena Tripathi, a plant biotechnologist and the Director of the Eastern Africa Hub of IITA, says the move to explore Cas-CLOVER as an alternative genome editing approach to the CRISPR/Cas9 system was prompted by the need to avoid the complex intellectual property (IP) issues surrounding the latter. With CRISPR/Cas 9, it is difficult to obtain licensing for growers, for example.

The Cas-CLOVER system, for its part, has the efficiency of CRISPR/Cas9 and improved fidelity but due to its clear IP and simple licence, it has the potential to facilitate the development of genome- edited crops quickly and with full commercial freedom. “Cas-CLOVER uses a different nuclease protein called Clo51, achieving greater precision by using two guide Ribonucleic acids (gRNAs) and a nuclease activity requiring the dimerization of subunits associated with each guide gRNA,” Dr Tripathi says.

“While CRISPR/Cas9 has earned its reputation as the go-to technique for functional genomics and crop enhancement due to its user- friendliness, design flexibility, high efficiency, and multiplexing capabilities, our study demonstrates the remarkable potential of the Cas-CLOVER system in editing the genome of the banana for the first time.”

Dr Tripathi says that they are still on the research phase of the genome editing. But the application of this genome editing technology may well be the key to addressing some of the most pressing challenges of global agriculture today. Due to its precision and versatility, the Cas-CLOVER tool promises to usher in a new era of crop enhancement, offering hope for increased yields, improved disease resistance, and enhanced income for banana farmers.

The findings of this study promise to revolutionise banana cultivation by addressing critical challenges faced in traditional breeding. The research on the banana genome editing started in the year 2021 and with the unveiling of the Cas-CLOVER tool as a highly efficient genome editing tool is not only a great breakthrough for the scientists but also for the sector in regards to combating the hurdles that have plagued the genetic improvement of bananas.

Dr Tripathi notes that the final product from the bananas cannot be classified as GMOs. This is because in genome editing there is no introduction of a foreign organism in the genome of the bananas. Bananas are an indispensable part of life in the East and Central Africa (ECA), providing up to one-fifth of the total calorie consumption per capita.

The average daily per capita energy from banana consumption in ECA is 147 kcal: 15 times the global average and 6 times the African average. The region has over 50 percent of its permanent cropped area under banana; this is around half of the total area under banana cultivation across Africa. ECA countries (Burundi, DR Congo, Kenya, Rw anda, Tanzania, and Ug anda) produce annually 21 million tons of banana with a value of US$4.3 billion.

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