Crop improvement strategies against plant diseases are critical to ensure food security and sustain agricultural productivity. Plant diseases lead to significant yield losses, affecting farmers’ livelihoods and affecting food availability for a growing global population. To combat these challenges, agricultural scientists and researchers have developed various strategies to enhance the immunity of major crops. In this discussion, we will draw insights from notable case studies involving major agricultural crops and explore various approaches used for crop improvement against diseases. These studies will highlight innovative solutions and advances in the field of plant pathology and biotechnology, demonstrating the critical role of science in protecting our food supply and addressing global agricultural challenges.
There are several strategies for crop improvement against plant diseases, including:
Breeding for disease resistance
Plant breeding for disease resistance is an important part of modern agriculture and involves creating plant varieties that are resistant or tolerant to diseases caused by pathogens such as viruses, bacteria, fungi and nematodes.
Traditional plant breeding methods
Traditional plant breeding methods have been used for centuries to develop disease-resistant plant varieties. This process involves selecting plants with desirable traits such as disease resistance and crossing them with other plants to produce offspring with those traits. This process is repeated over several generations, and plants with desired traits are selected for further breeding. This method is also known as conventional breeding.
For example, in the development of Fusarium head blight-resistant wheat varieties, traditional breeding methods were used to incorporate resistance traits from wild wheat relatives into domesticated wheat varieties. Resistance traits were identified by observing the phenotypes of wild relatives, and desirable traits were selected and bred with domesticated wheat. This process was repeated over several generations until the desired resistance traits were successfully incorporated into the bred wheat variety (Buerstmayr et al., 2009).
Marker-assisted selection
Marker-assisted selection (MAS) is a modern plant breeding technique that identifies genetic markers linked to disease resistance genes and uses those markers to select plants with desired traits. This approach allows breeders to more efficiently and accurately select resistant plants without the need for time-consuming and expensive phenotypic screening.
For example, in the development of rice varieties resistant to bacterial blight, MAS has been used to select plants containing the Xa21 gene that confers resistance to the bacterial pathogen. The Xa21 gene was linked to a genetic marker, and this marker was used to screen rice plants for the presence of the Xa21 gene. This allowed breeders to more efficiently and precisely select plants with the desired resistance trait compared to traditional breeding methods (Singh et al., 2001).
Genetic engineering
Genetic engineering is a plant breeding technique to induce or improve disease resistance in a plant. To do this, disease resistance genes from other plants or organisms are inserted into the target plant, or the plant’s own genes are used to strengthen its natural defense mechanisms. This strategy has resulted in the development of resistant transgenic crops, including papaya resistant to papaya ringspot virus and potatoes resistant to late blight.
For example, genetic engineering was used to transfer the coat protein gene of papaya ringspot virus (PRSV) into the papaya genome to create papayas resistant to PRSV. As a result, a transgenic papaya plant resistant to PRSV infection was developed (Fitch et al., 1992).
Genetic editing
Genome editing is a new plant breeding technique that allows precise and targeted changes to be made to a plant’s DNA. This technique can be used to introduce or improve disease resistance by editing genes associated with immunity or by altering the plant’s immune system.
For example, in the development of rice varieties with broad-spectrum disease resistance, the CRISPR system was used to edit the OsSWEET14 gene, which is essential for the growth and development of bacterial pathogens. By disrupting this gene, engineered rice plants became resistant to several bacterial pathogens (Jiang et al., 2018).
Crop rotation:
Crop rotation is a traditional agricultural practice that involves systematically rotating different crops on a given plot of land over time. This is an effective strategy for improving soil health and reducing plant disease stress. By changing crops, soil-borne pathogens lose their host plant and their populations decline over time, reducing the risk of disease outbreaks.
Several studies have demonstrated the effectiveness of crop rotation in reducing the incidence of plant diseases. For example, in a study of potato late blight, researchers found that a 2-year crop rotation with non-host crops reduced disease impact by up to 90% compared to a continuous potato crop caused by Phytophthora infestans (Harrison et al., 2014). Similarly, in a study of Fusarium wilt of banana, a devastating fungal disease, crop rotations with non-host crops reduced disease impact by up to 80% compared to continuous banana cropping (Talbot et al., 2018).
- Cultural Practices: Cultural practices like proper watering, fertilizing and pruning help reduce plant stress and make them less susceptible to disease.
- Use of biocontrol agents: Biocontrol agents are natural enemies of plant pathogens such as bacteria, fungi or insects. These agents can be used to control diseases without the use of chemical pesticides.
- Chemical control: Chemical pesticides can be used to control diseases in crops, but their use must be carefully managed to prevent negative impacts on human health and the environment.
- Molecular techniques: Molecular techniques such as gene editing and RNA interference are used to modify crops for disease resistance. These techniques are still in development but hold promise for improving disease resistance in crops.
