Improvement of Horticultural Crops for Abiotic Stress Tolerance: An Introduction

Abstract

Improvement of horticultural crops has traditionally focused on enhancing a plant’s ability to resist diseases or insects. That is evidenced by the large number of disease- or insect-resistant cultivars or germplasm released and used. Research on crop resistance or tolerance to abiotic stresses (heat, cold, drought, flood, salt, pH, etc.) has not received much attention. However, that is changing as a result of the research and publicity of global warming. ‘‘Adaptive research’’ aiming at adapting the horticultural industry to climate changes is becoming popular and is now one of the emphasis areas of funding agencies. Vegetable Breeding and Stress Physiology working groups of the American Society for Horticultural Sciences cosponsored a colloquium, ‘‘Improvement of Horticultural Crops for Abiotic Stress Tolerance,’’ at the society’s 2010 annual conference in Palm Desert, CA. With its summer heat and dry weather, Palm Desert was a perfect place to discuss the topic. Papers on pages 1068–1097 of this issue are based on presentations at the colloquium. Although there are still different opinions and modeling results regarding how much the planet will warm up, global warming is widely accepted as fact. The warmer climate threatens the production of many horticultural crops, especially those cool-season species. Growing crops above their optimal temperature range may lead to cellular damages and the development of physiological disorders. Even warm-season crops may be affected by heat stresses during critical periods. Forecasts show that warming over the next several decades will take place irrespective of what actions we take today. Therefore, adapting horticultural crops to the changing environments may be the single most important step for us to take to mitigate the adverse effects of climate change. Plant breeding is a long-term process, often taking more than 10 years to develop a new variety, especially for tree crops. Therefore, there is an urgent need to mitigate these abiotic stresses through development of new heat-tolerant vegetable, fruit, nut, nursery, and ornamental crop varieties that will thrive in future conditions. Climate change may affect agriculture more through water availability than temperature. Scientists predict that the altered hydrologic cycles will change the pattern of precipitation and cause wet areas becoming wetter while dry areas become drier. Global warming may cause reduced precipitation, less snow pack, and earlier snow melt, leading to drought conditions. As global temperatures rise, we are experiencing fewer but heavier rains, which may cause a host of problems such as flooding, soil erosion, leaching chemicals from fields, compaction and low oxygen levels in the soil, and delayed planting. Warmer weather will also accelerate water transpiration from plants and evaporation from soil. According to Dr.