Influence of photoperiod response on the expression of cold hardiness in wheat and barley

Abstract

Vernalization and photoperiod requirements regulate the timing of the vegetative/reproductive transition in plants. Cereals adapted to cold winter climates regulate this developmental transition mainly through vernalization requirements, which delay transition from the vegetative to the reproductive growth stage. Recent research indicates that vernalization requirements also influence the expression of low-temperature (LT) tolerance genes in cereals exposed to acclimating temperatures. The objective of the present study was to determine if LT tolerance expression was also developmentally regulated by photoperiod response. The nonhardy, short day (SD) sensitive, wheat (Triticum aestivum L. em Thell) cultivar AC Minto, the LT tolerant, highly SD sensitive barley (Hordeum vulgare L.) cultivar Dicktoo, and a barley selection with very low sensitivity to SD were subjected to 8-h (SD) and 20-h (LD) days at cold acclimating temperatures over a period of 98 d. Final leaf number (FLN) was used to measure photoperiod sensitivity and determine the vegetative/reproductive transition point. The LT tolerance of the less SD sensitive barley genotype was similar for LD and SD treatments. In contrast, a delay in the transition from the vegetative to the reproductive stage in AC Minto and Dicktoo grown under SD resulted in an increased level and/or longer retention of LT tolerance. These results support the hypothesis that not only the level, but also the duration of gene expression determines the degree of LT tolerance in cereals. Consequently, any factor that lengthens the vegetative stage, such as vernalization or photoperiod sensitivity, also increases the duration of expression of LT tolerance genes. Key words: Triticum aestivum L., Hordeum vulgare L., low-temperature tolerance, photoperiod, developmental regulation

Changes in requirements on vernalization of winter wheat varieties in the Czech Republic in 1950-2000

“…In spring, a short pre-spring day does not enable a premature transition into the generative stage, and hence, plants are not damaged by frost. Mahfoozi et al (2000) even presents that a short day raises the level of the lethal temperature, or it maintains resistance values attained for a longer time. To be a winter crop does not automatically mean frost hardiness or winter hardiness.…”

“…through a correlation with the tendency to winter killing Schmütz (1977), and for some varieties indirectly, e.g. Mahfoozi et al (2000), who stress the regulative effect of a short day in the relation to over wintering. Also a relation to the time of restoring of spring vegetation, when varieties with a finished vernalization and a specific sensitivity to a short day restore the spring vegetation earlier, they can form the base of the ear for a longer time, and they are more demanding of early regenerative fertilization, which is already connected with forming of yield elements.…”

Regulation of low-temperature tolerance in barley under field conditions in northwest Iran

“…Long days accelerate floral initiation and heading by reducing the number of leaves in vernalized or spring barley plants (Pinthus and Nerson 1984). Under SD regimes, DR formation is delayed in sensitive genotypes (Lucas 1972;Mahfoozi et al 2000) and the plants produce more leaves rather than a reproductive inflorescence (Holmes 1973;Mahfoozi et al 2001) until a genetically determined maximum leaf number is attained (Pinthus 1985).…”

“…Low-temperature (LT) acclimation in cereals is a cumulative process characterized by a rapid initial response followed by a gradual reduction in rate of change until vernalization (Fowler et al 1996) and/or photoperiod (Mahfoozi et al 2000) requirements have been met. A close association between the vegetative/reproductive transition and the start of a decline in LT tolerance has demonstrated the regulatory influence that developmental genes have over LT-induced genes in cereals grown under controlled conditions (Fowler et al 1999;Mahfoozi et al 2001).…”

The relationship between frost tolerance and generative induction in winter wheat (Triticum aestivum L.) under field conditions

“…Furthermore, short day conditions, or the absence of a long photoperiod, have also been found to delay the transition from a vegetative to a generative stage of development (Slafer and Rawson 1996;Mahfoozi et al 2000Mahfoozi et al , 2001aDanyluk et al 2003). Danyluk et al (2003) hypothesized that vernalization makes the cells of the apex become competent to phase change, while long day conditions promote the activation of these cells to initiate the formation of flower primordia.…”