High-precision phenotyping under controlled versus natural environments

Abstract

Multiple abiotic stresses such as drought, heat, cold, frost, salinity, high light intensity, and many other challenges affect the growth of crop plants during the life cycle leading to substantial yield losses every year. These challenges are becoming more serious under the current scenario of climate change. Therefore, it is required to develop climate-resilient crops using various conventional and genomic approaches. Now physiological, biochemical, and molecular mechanisms responsible for tolerance to the above abiotic stresses are well known, and many morphophysiological traits have been identified which impart tolerance to these abiotic stresses. These traits are either constitutive, i.e., express under both stressed and non-stressed conditions, or adaptive which express exclusively when stress is commenced and are only important for plants survival. Breeders used successfully constitutive traits (i.e., water-use efficiency, root-based traits, phenology, ABA accumulation, stay-green character, leaf area index, delayed senescence, canopy temperature depression, stomatal conductance, fertility of reproductive parts, chlorophyll fluorescence, etc.) in improving yield of crop plants. However, relationship of adaptive traits (i.e., osmotic adjustment, proline accumulation, remobilization of reserve carbohydrates from stems and leaves, membrane stability, lethal leaf water potential, and many other morphophysiological traits) during stress conditions towards improving yield is still questionable. In spite of this, focus has also been given on the past years for harnessing the potentiality of adaptive traits indirectly towards the development of abiotic stress-tolerant genotypes. Currently, genetic diversity for both type of traits is available in exiting germplasm of diverse crop species. Therefore, it provides enormous opportunities for developing stress-tolerant cultivars. However, it is required effective phenotyping methods that are rapid and reliable to screen the large number of genotypes. These traits can be screened under both natural and controlled conditions. Although high-precision phenotyping can be done for many traits related to abiotic stresses under natural conditions, there are many other traits that are only screened under controlled conditions. Moreover, certain traits are essential to screen because they are positively associated with yield or tolerance to abiotic stress and their measurement can only be possible in controlled conditions. Because the environment plays an important role in the growth and development of crop plants, crop plants face two different conditions during the phenotyping of interested traits. As a result each environmental condition has its own limitations. In this chapter, we discussed the precision phenotyping of traits of agronomic importance under the controlled and natural environments.