By Dr Ratna Kumria, Director, Biotechnology Alliance for Agri Innovation (AAI)
Gene editing offers an accurate, predictable, quick, and economical method for crop improvement. Due to its precision, it offers the opportunity to increase nutrient levels, decrease anti-nutrients, and improve the shelf life of food to preserve quality and nutrition. This technology cannot provide solutions for all farming challenges or plant breeding bottlenecks, but it can certainly streamline the process towards greater efficiency. It provides an opportunity to address hunger and malnutrition regionally using traditional, local crops. It can also enable local solutions to conserve biodiversity and resources, moving towards better agriculture.
Gene editing refers to making changes in the genome of an organism using various nucleases with distinct specificities and modes of action. The nucleases are programmed to target particular sequences for cutting, although the repair mechanisms can either be random or designed with external templates. While traditional nucleases cut both strands of DNA, some have been adapted to cut a single strand and utilise RNA as a template for making alterations. The selection of the appropriate gene editing tool is based on the target’s cost and feasibility. As new nucleases are being discovered and editing tools developed, gene editing is finding diverse applications. Although currently used in therapeutics, it is expected to have far-reaching effects on crop improvement and agriculture.
Humans have been selectively breeding plants and animals for centuries, long before the field of genetics was established. Today’s cultivated crops, whether ornamental or used for food, as well as domesticated animals are very different from their wild counterparts. For example, maize was selected and bred from its ancestor teosinte and likewise the fibrous, blander version of ancient watermelon fruits, as also other food crops were bred for a better flavour and texture that is more palatable to humans. Domesticating plants and animals are a painstaking and repetitive process that has been ongoing for hundreds, and sometimes thousands, of years.
Advancements in genetics have accelerated plant breeding and crop improvement over the past century. With the knowledge of genetics, breeders were able to identify variations and select for new genetic combinations that were better suited for cultivation and consumption. In addition to identifying variations, breeders have also been using chemicals or radiation to induce random mutations that result in beneficial genetic modifications. This mutation breeding has led to the creation of over 3000 new varieties of crops across the globe, during the last few decades. As a result of these plant breeding efforts, cereal crop production has tripled during this period, with only a 30 per cent increase in land under cultivation. India’s green revolution, which transformed it from a food-deficient nation to a food-surplus one, owes much of its success to plant breeding efforts.
However, the haphazard nature of mutation-generation makes selecting the relevant modifications an expensive, time-consuming, and laborious process. Conventional breeding is a lengthy process that depends on the number and duration of growing seasons per year, as well as the time it takes for plants to mature. This process can be even more prolonged when dealing with trees, perennials or assembling multiple traits through multi-stage crossing, selection, and testing. Additionally, the randomness of induced mutagenesis adds another dimension to the selection and testing required for large-scale screening. To make the breeding process more efficient over time, various technological interventions have been introduced, including molecular markers, double haploids, genome-wide association studies (GWAS), and other prediction tools.
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