8 - Frost Tolerance and Genetic Improvement in Barley

Abstract

Frost is an important stress factor both at vegetative and reproductive stages of barley. Frost, otherwise known as low temperature stress, damages leaf and stem, causes floret sterility, increases screenings, and reduces grain yield and germination causing substantial loses. To curb these problems, numerous studies have been undertaken elsewhere on frost tolerance in barley both at vegetative and reproductive stages. These studies used field or controlled environments, or a combination of field and controlled environments to understand response of barley genotypes to frost. At the vegetative stage, percentage survival, electrolyte leakage, ABA content, cold induced protein contents, and molecular markers as diagnostic tools have been used to distinguish between barley cultivars for frost tolerance. Reproductive stage traits used to distinguish between barley genotypes for frost tolerance include floret sterility, grain damage, and grain yield and associated molecular markers. Measurement for frost tolerance at reproductive stages has been reported to be complex. Despite substantial research efforts to understand frost tolerance in barley, improvement for this stress at the reproductive stage of development remains challenging. This is in contrast to vegetative stage frost tolerance in winter barleys that not only tolerate but also require low temperature to transit from the vegetative stage to the reproductive stage. Recent developments in barley genomics may help to exploit high genotypic variation in barley for frost tolerance at the reproductive stage. Frost tolerance genes already mapped on various chromosomes would play key roles in improving commercial barley varieties for reproductive stage frost tolerance. This chapter is an overview of barley genotypic variation, methods used in frost tolerance studies, and genetic factors reported elsewhere to be associated with frost tolerance.