Abiotic stresses such as drought (water stress), excessive watering (water logging), extreme temperatures (cold, frost and heat), salinity and mineral toxicity can adversely affect crop and other plant growth, development, yield and seed quality.

Climate change is becoming more intense, necessitating farmers to find crops that can withstand these extreme conditions. One way of accomplishing this goal is through plant breeding.

What is plant breeding for stress environments?

Plant breeding for stress environments is the process of cultivars with increased tolerance to environmental stresses such as drought, suboptimal temperatures, salinity or mineral deficiency and toxicity (Blum 1988).

Plant breeders have historically relied on trial-and-error to select varieties for their crops. Their goal has been to create high yielding varieties that thrive in certain conditions and at certain times of year for production.

Food demand and climate change are increasing, making the environmental milieu more challenging for our crop plants. This includes heat/cold extremes, salt accumulation, droughts, floods and aridity in some regions as well as nutrient shortages and pest infestations elsewhere.

Therefore, our crops' ability to withstand abiotic stresses caused by climate change is an essential requirement for maintaining food security and safety in an increasingly volatile world.

Over the past two decades, molecular biologists and genomic researchers have highlighted their potential in this area; while agronomy research and breeding for biotic stress resistance have highlighted the need to address stress problems within breeding programs in an organized and specific way. As a result, an inherent conflict has arisen between these disciplines.

Why is plant breeding for stress important?

Plants, particularly crop plants, are constantly exposed to various biotic and abiotic stresses due to shifting climate conditions. These changes can result in significant losses of yield for these crops due to heat, drought, salinity and other abiotic stressors [1].

Crop plants sense external stresses through sensors located on their cell surfaces or cytoplasm, and respond by producing appropriate cellular responses which make them tolerant against the stress. This may take the form of biochemical and physiological changes or specific transcriptional alterations.

Cellular responses to stresses are dependent on transcription factors and signaling pathways which activate multiple genes at once, providing plant tolerance against stresses. These gene activation cascades may be initiated by hormones like ethylene, jasmonic acid (JA), salicylic acid (SA), etc.

Breeding for stress tolerance is the simplest and most efficient way to do it: select a high-yielding variety and screen for the trait. Additionally, it is possible to pyramid stable quantitative trait locuses controlling multiple traits together, which can greatly enhance the results of one breeding program by decreasing cross numbers made and increasing genetic diversity within populations.

Is plant breeding for stress environments safe?

Plants possess the capacity to develop strategies that address stress conditions, both biotic and abiotic. These tactics involve the utilization of metabolites – highly beneficial compounds for plant nutrition and structure that have antimicrobial properties.

Environmental conditions that impact plant growth include drought, high temperature, low nitrogen (N), salinity and chemical toxins. Unfortunately, some of these conditions are also linked to pests which may harm or even destroy the plant if left unchecked.

Climate change has compounded these difficulties by increasing aridity and warmer temperatures in some regions, which can adversely impact crop production.

These issues necessitate expertise in breeding solutions for stressful environments. Over the last several decades, agricultural productivity has kept up with population growth due to advances in crop breeding that improve plants' biotic and environmental tolerances.

However, it has become evident that this approach is inadequate to manage the growing complexity of environmental stress. Particularly, breeding crops tolerant to water scarcity presents a major challenge.

As a result, the plant breeding community has recognized the need to address these stresses head-on and with precision. This book offers guidance to assist in this endeavor.