The contribution of the gibberellin-insensitive semi-dwarfing (Rht) genes to genetic variation in wheat seedling growth in response to osmotic stress

Abstract

SU MMARYThe effects of various gibberellin-insensitive semi-dwarfing (Rht) alleles and background genotypes on the growth response of wheat seedlings to simulated low water potential were investigated. Four sets of near-isogenic lines, each consisting of six members (Rht-B1a+Rht-D1a (rht), Rht-B1b, RhtB1c, Rht-D1b, Rht-B1b+Rht-D1b and Rht-B1c+Rht-D1b), and one set of five members (rht, RhtB1b, Rht-B1c, Rht-B1d and Rht-D1b) were germinated in the presence of polyethylene glycol (PEG). The growth responses were assessed by measuring the lengths of the longest root, coleoptile and longest leaf (shoot) and calculating the root length :shoot length ratio and a tolerance index (TI). Seedling growth was significantly affected by the allelic status at the Rht loci, background genes and the water potential. The PEG treatment had major effects on root and shoot growth. Coleoptile growth was mainly affected by the Rht alleles. There were significant interactions of the Rht allele and variety on the growth response to low water potential. Genotypes with longer roots, coleoptiles and shoots when grown in water, as determined by the Rht allelic status (rht, Rht-B1b and Rht-D1b) and varietal background, had the highest TI and maintained this advantage under stress, while genotypes with smaller seedlings (Rht-B1c and Rht-B1c+Rht-D1b) when grown in water were more strongly affected.

Changes in Water Status, Membrane Stability and Antioxidant Capacity of Wheat Seedlings Carrying Different Rht‐B1 Dwarfing Alleles under Drought Stress

“…It was shown in our earlier study that growth of Rht‐B1c dwarf seedlings was more strongly restrained under stress than that of the tall counterpart Rht‐B1a having relatively greater growth potential (Landjeva et al. ). Essentially, growth inhibition might have adaptive significance under stress as smaller plants have lower requirements for resources and are thereby able to survive in adverse environments where resources are limited (Harberd et al.…”

“…Following stress, the seedlings growth was more strongly restrained in the presence of the severe dwarfing allele Rht‐B1c than in the tall ( Rht‐B1a ) or the semidwarf ( Rht‐B1b ) genotypes having relatively greater growth potential (Landjeva et al. ). These earlier results suggest that better tolerance of dwarf plants is derived from their relatively smaller size and slower growth rate.…”

“…There is only limited evidence that height-reducing genes have impact on cellular osmotic potential under optimal growth conditions (Hoogendoorn et al 1990). Studies on the possible contributions of Rht genes to plant response to water deficiency are focused mostly on their effects on plant growth, biomass, leaf area, water balance and osmotic adjustment in juvenile plants (Blum et al 1997, Landjeva et al 2008, or on grain yield at adult stage (Alghabari et al 2013). Using a set of wheat Rht near-isogenic lines, growth reduction by dehydration was shown to be inversely related to plant size.…”

Correlation of drought resistance in grass pea (Lathyrus sativus) with reactive oxygen species scavenging and osmotic adjustment

“…The symptoms of drought stress, salinity or low temperature are mainly caused by osmotic stress and result from limited water absorption (Caruso et al 2008). Application of polyethylene glycol (PEG), a non-toxic and nonpenetrating, osmotically active polymer, is a successful laboratory simulation of drought stress (Kocheva et al 2005;Landjeva et al 2008). In these laboratory tests, the osmotic potential of the medium can be easily controlled and much of the environmental noise associated with field experiments can be avoided (Kocheva et al 2009).…”

Response of coleoptiles to water deficit: growth, turgor maintenance and osmotic adjustment in barley plants (Hordeum vulgare L.)

“…Final coleoptile length is under the control of many genes and regulated by environment. The expression of these genes is differentially affected by the drought stress applied [2]. Heat-stress was associated with a decrease in the rate of growth and in the final length of barley and wheat coleoptiles [3,4] Osmotic adjustment is becoming increasingly recognised as an efficient drought tolerance mechanism in cultivated plants [5,6], exerting a positive effect-either directly or indirectly-on the productivity of plants that grow under drought conditions [7].…”