Climate Change Is Increasing Pressure On Crop Breeding

Climate change is strongly influencing agricultural production and cultivation practices of all major crops with various and heterogeneous effects, which critically depend on geographical areas. Among the climate variables that affect agricultural production, the rapid increase in CO2 levels and temperatures and the increasing frequency and magnitude of extreme weather events have the greatest impact.

Recent studies have demonstrated the simultaneous negative effect of high temperatures and drought on the growth, development and reproduction of cereals, thus affecting productivity. Water deficit is a growth- and yield-limiting factor for crops worldwide. It has been reported that water scarcity deeply influences flowering, pollination and grain-filling of most grain crops; on the other hand, abundant rainfalls may have a positive impact on yield and end-use quality but they may damage plants because of higher relative humidity, which predisposes to the outbreak of diseases. Drought also has a major impact on crop yield, however it has been demonstrated that the severity of the stress depends on the phenological status of the plant.

Impact of extreme heat waves has been analyzed in wheat, rice, maize and soybean. It has been noted that an increase of 1°C of seasonal temperatures determines a decrease in yield ranging from 7. 4% in maize to 3. 1% in soybean. The increase of atmospheric CO2 has conflicting effects on crops: on one hand it determines an increase in plant photosynthesis and growth, on the other hand it negatively affects the nutritional quality of crops as well as their health status. As an example, an increase in barley yellow dwarf virus infections has been observed in wheat under elevated CO2 levels. Elevated temperatures combined with drought reduced the performance of grapevine in the Mediterranean basin, but elevated levels of CO2 could mitigate such damaging effects.

All these developing threats are leading to an increase in the incidence of weeds, pests and pathogens, which generally were confined in particular geographical areas. At present, they are thriving worldwide because of warming temperatures and increasing levels of humidity. Because of the relevance of crop diseases, combining disease risks with climate changes has led to the development of predictive models. It is expected that between 2050 and 2100, Fusarium oxysporum spp. will be the main cause of plant disease in European, Middle Eastern and North African regions, posing risks to a number of cash crops.

In this challenging scenario, it is clear that we need miscellaneous strategies to expedite the rate of genetic gains with the purpose of developing climate-resilient cultivars. The understanding of the physiological, genetic, and molecular mechanisms that allow the plant to adapt/respond to climate change and the investigation of adaptation traits to variable environmental conditions triggered by climate change are among the main objectives of next generation breeding.

Next generation breeding lays on the availability of large plant breeding populations and germplasm collections, efficient high-throughput technologies, big data management tools and downstream biotechnology and molecular breeding activities. It is allowing and will allow the scientific community to define, in a smaller time frame, one or more ideotypes in order to satisfy the breeding demand and to discover superior alleles/haplotypes to be used in breeding programs. Furthermore, recent advances in genomic knowledge and the increasing availability of information on genes as well as on in vitro regeneration technologies allow to develop and use second-generation biotechnologies, based on cisgenesis and genome editing to produce a diverse array of novel, value-added products that are indispensable to address future challenges associated with sustainable agriculture.

Genome editing has already been established as a powerful tool in research and can breathe new life into plant breeding strategies. Indeed, genome editing is opening up novel opportunities for the precise and rapid modification of crops to boost yields, protect against pests, diseases and abiotic stressors. The great potential of the genome editing techniques relies on make crop breeding faster and more precise at lower production costs.