Leaf Epinasty in Chrysanthemum: Enabling Breeding Against an Adverse Trait by Physiological Research

Abstract

Breeding for a certain trait is only possible when the phenotypic variation that is caused by genotypic variation can be estimated. For traits that strongly depend on environmental conditions, this can be extremely difficult and knowledge and collaboration with experts from other disciplines becomes essential. A wellknown example is breeding for disease resistance. Here, we describe a similar approach to assist breeding against adverse leaf deformations that severely reduce the ornamental value of some chrysanthemum (Dendranthema × grandiflora) genotypes during greenhouse cultivation in winter. These leaf deformations occur rather unpredictably, but seem to be related to the increased use of assimilation light. To breed against this trait knowledge is needed (i) about inductive environments in which sensitive and insensitive genotypes are distinguishable, and (ii) about the physiological background associated with leaf epinasty. In this paper hypothetical physiological factors and mechanisms are discussed, which may mediate effects of light spectrum and greenhouse climate on leaf epinasty. One factor involved could be starch accumulation, since leaf epinasty usually aggravates after disbudding -a practice that most probably alters the sink-source balance. Additionally, light spectra can affect the circadian clock and thereby disturb starch synthesis and breakdown resulting in accumulation. Both within and independent of this process, plant hormones such as auxin and ethylene may play a role in leaf epinasty. This theoretical framework will be used to further investigate the physiological background of leaf epinasty and to come up with a test in which susceptibility for leaf epinasty can be assessed.

From a different angle: genetic diversity underlies differentiation of waterlogging-induced epinasty in tomato

“…The downwards bending of leaves (epinasty) reduces canopy cover, thereby limiting transpirational water losses ( Else et al., 1995 ) and possible deleterious effects of photo-inhibition when carboxylation has ceased ( Pastenes et al., 2005 ; Van Geest et al., 2012 ) during waterlogging. As such, epinasty and its recovery are part of the morphological adaptation to increase survival under low-oxygen stress conditions.…”

Leaf ontogeny steers ethylene and auxin crosstalk to regulate leaf epinasty during waterlogging of tomato

“…This nastic movement has been observed in several crops such as tomato (Jackson & Campbell, 1976), potato (Tonneijck et al, 1999), sunflower (Kawase, 1974) and cotton (Wiese & Devay, 1970). It is hypothesized that epinasty is an avoidance strategy to minimize intense solar radiation (Van Geest et al, 2012) and reduce plant transpiration (Else et al, 2009; Grichko & Glick, 2001).…”