Novel Prunus rootstock somaclonal variants with divergent ability to tolerate waterlogging

Abstract

Plants require access to free water for nutrient uptake, but excess water surrounding the roots can be injurious or even lethal because it blocks the transfer of free oxygen between the soil and the atmosphere. Genetic improvement efforts in this study were focused on the increased tolerance in roots to waterlogging. Among a pool of clones generated in vitro from leaf explants of rootstock Mr.S.2/5 of Prunus cerasifera L., the S.4 clone was flood tolerant whereas the S.1 clone was sensitive. The S.4 clone formed adventitious roots on exposure to flooding. Moreover, the chlorophyll content and mitochondrial activity in the leaf and root, soluble sugar content, alcohol dehydrogenase activity and ethylene content were different between the clones. The sorbitol transporter gene (SOT1) was up-regulated during hypoxia, the alcohol dehydrogenase genes (ADH1 and ADH3) were up-regulated in the leaves and down-regulated in the roots of the S.4 clone during hypoxia, and the 1-aminocyclopropane-1-oxidase gene (ACO1) was up-regulated in the leaves and roots of the S.4 clone during hypoxia and down-regulated in the wild-type roots. In addition, in the S.4 root, hypoxia induced significant down-regulation of a glycosyltransferase-like gene (GTL), which has a yet-undefined role. Although the relevant variation in the S.4 genome has yet to be determined, genetic alteration clearly conferred a flooding-tolerant phenotype. The isolation of novel somaclonals with the same genomic background but with divergent tolerance to flooding may offer new insights in the elucidation of the genetic machinery of resistance to flooding and aid in the selection of new Prunus rootstocks to be used in various adverse environments.

Physiological Responses to Hypoxia and Manganese in Eucalyptus Clones with Differential Tolerance to Vale do Rio Doce Shoot Dieback

“…Prunus cerasifera L. clones (Pistelli et al, 2012) tolerant and sensitive to hypoxia had high total antioxidant capacity in the leaves when the roots were under hypoxia. Lacerda (2013) demonstrated that the damage caused by hypoxia in the roots of these same clones was faster and more intense than the damage under high Mn concentrations.…”

Plant water stress: Associations between ethylene and abscisic acid response

“…Several types of tropical and subtropical fruit trees show anatomical or morphological adaptations to flooding stress, such as the development of hypertrophied stem lenticels, adventitious rooting or the formation of porous aerenchyma tissue (Schaffer et al, 2006). Aerenchyma formation in response to low oxygen availability has been reported as an anatomical adaptation to facilitate gas diffusion (like O 2 ) between hypoxic/ anoxic roots and the aerial environment, including Prunus rootstocks (Garthwaite et al, 2008;Pistelli et al, 2012). Under hypoxia, aerenchyma formation involves cell death caused by an enhanced rate of ethylene synthesis (Jackson, 1985;He et al, 1994;Gunawardena et al, 2001).…”

“…Epinasty, a common response in flooded plants, results from accumulation of the ethylene precursor ACC in roots; basically, ACC is transported through the transpiration stream to the aerial part of the plant, where the presence of oxygen allows it to be converted into ethylene, triggering petiole epinasty (Jackson, 2008;Vidoz et al, 2010). In Prunus cerasifera Ehrh., while the wild-type was sensible to flooding, showing epinasty and leaf senescence, the L clone showed an increase in ethylene synthesis (mainly in leaves) and ACC oxidase (ACO) gene expression (Pistelli et al, 2012). In Citrus, water-stress induced leaf abscission was associated with ACC expression accompanied by a concomitant increase in ethylene (Gómez-Cadenas et al, 1996).…”

“…Ethylene under water logged conditions is also associated with adventitious root formation (Steffens et al, 2006;Vidoz et al, 2010;Pistelli et al, 2012); adventitious roots are able to maintain plant growth during waterlogging by maintaining nutrient and water uptake (Sairam et al, 2008). In rice, waterlogging induced adventitious root formation mediated by ethylene that also appeared to facilitate aerenchyma formation (Justin and Armstrong, 1991).…”

EVALUATION OF GAS EXCHANGES IN DIFFERENT Prunus SPP. ROOTSTOCKS UNDER DROUGHT AND FLOODING STRESS

“…Although, plants need free access to water for nutrient absorption, excess water around roots can be harmful or even lethal, since it reduces drastically the transfer of free oxygen between the soil solution and the atmosphere (PISTELLI et al, 2012). This condition, decreasing the oxygen levels in the environment around the roots, inducing root asphyxia and greatly damaging critical periods of the crop, as it is the case of the blossoming period and beginning of sprouting (MARTINAZZO et al, 2013).…”