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- QTL analysis for stomatal functioning in tetraploid Rosa × hybrida grown at high relative air humidity and its implications on postharvest longevityPublication . Carvalho, Dália R. A.; Koning-Boucoiran, Carole F. S.; Fanourakis, Dimitrios; Vasconcelos, Marta W.; Carvalho, Susana M. P.; Heuvelink, Ep; Krens, Frans A.; Maliepaard, ChrisHigh relative air humidity (RH >= 85 %) during leaf development disturbs stomatal functioning leading to excessive water loss in conditions of high evaporative demand, resulting in severe reduction in postharvest longevity. In roses, this effect depends on the genotype, opening the possibility for breeding cultivars with more responsive stomata. In this study, we aim at identifying genomic regions associated with the control of water loss following growth at high RH. The F1 generation (108 offspring) and the two parents (P540 and P867) of a tetraploid cut rose population grown at high (85 %) RH were phenotyped for stomatal control to water loss by assessing the relative water content after 4 h of leaflet desiccation (RWC_4 h). The RWC_4 h varied between 7 and 62 % across the 110 studied individuals, with parents P540 and P867 showing 51 and 20 % RWC_4 h, respectively. Based on these data, a quantitative trait locus (QTL) analysis was performed. The impact of the identified QTLs on postharvest longevity of ten selected offspring was further evaluated. Three QTLs were identified: two major [positioned on linkage group 5 of the integrated consensus map (ICM 5) of both parents and on ICM 2 of the parent P867] and one putative minor (mapped to ICM 6 of both parents), explaining 32 % of the variability in the RWC_4 h. Low RWC_4 h was found to be a good proxy for eliminating the offspring with short vase life. This study constitutes a first step toward identifying the most likely regions for genes of interest controlling stomatal functioning in high RH-grown plants.
- Root-to-shoot ABA signaling does not contribute to genotypic variation in stomatal functioning induced by high relative air humidityPublication . Carvalho, Dália R. A.; Fanourakis, Dimitrios; Correia, Maria J.; Monteiro, José A.; Araújo-Alves, José Pedro L.; Vasconcelos, Marta W.; Almeida, Domingos P. F.; Heuvelink, Ep; Carvalho, Susana M. P.High relative air humidity (RH 85%) during leaf expansion hampers stomatal responsiveness to closing stimuli, a genotype-dependent effect. Genotypes with reduced stomatal closure in response to closing stimuli (i.e., sensitive genotypes) show low bulk leaf abscisic acid concentration ([ABA]). We hypothesized that the amount of ABA produced in the roots and delivered with the transpiration stream to the leaves is a critical step for a proper stomatal functioning in high RH-grown plants. Ten genotypes from a cut rose tetraploid population were grown at moderate (62%) or high (89%) RH. Stomatal anatomy and responsiveness to desiccation or ABA feeding were evaluated. Root and leaf petiole xylem sap [ABA] were quantified, and ABA delivery rate from root-to-shoot was estimated. High RH reduced stomatal responsiveness to both closing stimuli in the sensitive genotypes, whereas it had a nonsignificant effect in the tolerant ones. Estimates of [ABA] in root xylem sap at transpirational flow rate were not related to the genotypic differences in the sensitivity to high RH. However, high RH increased this concentration irrespective of the genotype, probably due to a reduced dilution of the [ABA] in the xylem sap as a result of a lower transpiration rate compared to moderate RH-grown plants. Leaf petiole xylem sap [ABA] was neither related to the genotypic differences in the sensitivity to high RH nor it was affected by RH. We concluded that genotypic differences in the stomatal sensitivity to high RH cannot be explained by changes in the [ABA] delivered with the transpiration stream from the roots to the leaves