UNDERSTANDING AND ENHANCING POTENTIAL VASE LIFE OF ROSA HYBRIDA: FROM PRE-HARVEST CONDITIONS TO POST-HARVEST LONGEVITY

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QTL analysis for stomatal functioning in tetraploid Rosa × hybrida grown at high relative air humidity and its implications on postharvest longevity

Publication . Carvalho, Dália R. A.; Koning-Boucoiran, Carole F. S.; Fanourakis, Dimitrios; Vasconcelos, Marta W.; Carvalho, Susana M. P.; Heuvelink, Ep; Krens, Frans A.; Maliepaard, Chris

High 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.

2015Journal article

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Moderate salinity improves stomatal functioning in rose plants grown at high relative air humidity

Publication . Carvalho, Dália R. A.; Vasconcelos, Marta W.; Lee, Sangseok; Vreugdenhil, Dick; Heuvelink, Ep; Carvalho, Susana M. P.

Plants grown at high relative air humidity (RH ≥ 85%) show hampered stomatal closure in response to closing stimuli. We hypothesized that a moderate salinity during growth could trigger a stress response and stimulate stomatal functioning due to an increased leaf abscisic acid concentration ([ABA]). Cut rose ‘Prophyta’ was grown at moderate (63%) or high (89%) RH combined with three electrical conductivities (EC) in the nutrient solution (2, 4 and 6 dS m−1; adding NaCl). High RH resulted in higher pore area per leaf area in intact leaves, and higher stomatal conductance (gs) both in leaves subjected to desiccation and to light/dark transition, as compared to moderate RH. Increasing EC in high RH-grown plants lead to higher stomatal density but it enhanced stomatal closure in response to leaflet desiccation. This enhanced stomatal functioning was associated with increased [ABA] and [ABA + metabolites]. Nonetheless, plants grown at EC6 showed a significantly lower chlorophyll content, total plant dry weight and total leaf area. This negative effect on plant growth is related to ionic stress as the sodium and chloride concentrations increased in plants grown at EC6 compared to EC2 (up to 111- and 14-fold, respectively). This is the first study on the interactive effects of RH and salinity on stomatal functioning and anatomy during leaf development. It is shown that, when these two environmental factors that influence stomatal responsiveness in an opposite way are combined, moderate EC is able to improve stomatal responsiveness to leaflet desiccation in high RH-grown plants due to increased leaf [ABA].

2017Journal article

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Gene expression and physiological responses associated to stomatal functioning in Rosa×hybrida grown at high relative air humidity

Publication . Carvalho, Dália R.A.; Vasconcelos, Marta W.; Lee, Sangseok; Koning-Boucoiran, Carole F.S.; Vreugdenhil, Dick; Krens, Frans A.; Heuvelink, Ep; Carvalho, Susana M. P.

tHigh relative air humidity (RH ≥ 85%) during growth disturbs stomatal functioning, resulting in excessivewater loss in conditions of high evaporative demand. We investigated the expression of nine abscisic acid(ABA)-related genes (involved in ABA biosynthesis, oxidation and conjugation) and two non-ABA relatedgenes (involved in the water stress response) aiming to better understand the mechanisms underlyingcontrasting stomatal functioning in plants grown at high RH. Four rose genotypes with contrasting sen-sitivity to high RH (one sensitive, one tolerant and two intermediate) were grown at moderate (62 ± 3%)or high (89 ± 4%) RH. The sensitive genotype grown at high RH showed a significantly higher stomatalconductance (gs) and water loss in response to closing stimuli as compared to the other genotypes. More-over, high RH reduced the leaf ABA concentration and its metabolites to a greater extent in the sensitivegenotype as compared to the tolerant one. The large majority of the studied genes had a relevant role onstomatal functioning (NCED1, UGT75B2, BG2, OST1, ABF3 and Rh-APX) while two others showed a minorcontribution (CYP707A3 and BG1) and AAO3, CYP707A1 and DREB1B did not contribute to the tolerancetrait. These results show that multiple genes form a highly complex regulatory network acting togethertowards the genotypic tolerance to high RH.

2016Journal article

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Root-to-shoot ABA signaling does not contribute to genotypic variation in stomatal functioning induced by high relative air humidity

Publication . 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

2016Journal article

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Avaliação do contributo da expressão genética na tolerância à desidratação em Rosa × hybrida cultivada em humidade relativa elevada

Publication . Carvalho, D. R. A.; Vasconcelos, Marta; Koning-Boucoiran, C. F. S.; Krens, F. A.; Heuvelink, E; Carvalho, S. M. P.

Cultivation of cut flowers with high postharvest longevity is of extreme importance for consumer’s satisfaction. A negative water balance is indicated as the most important factor reducing longevity. This problem is more severe in plants grown at high relative air humidity (i.e. RH > 85%) mainly due to a poor stomatal functioning associated to lower abscisic acid (ABA) concentrations, leading to higher water loss. In this paper it is analysed whether a sensitive cut rose cultivar to high RH show different gene expression related to ABA metabolism when grown at moderate (60%) or high (90%) RH. RNA was isolated from fully developed leaves, harvested 180 min after the beginning of the dark period (stomatal closing stimulus) and the relative gene expression was evaluated in genes involved in: biosynthesis (AAO3 and NCED1), oxidation (CYP707A1 and CYP707A3) and conjugation (UGT75B2) of ABA. The stomatal conductivity in the dark period was 5.6-fold higher in intact plants developed at high RH compared to moderate RH-grown plants, showing the reduced closure capacity of the stomata during darkness. After 4 h of leaflet desiccation, leaflets grown at high RH showed a relative water content (RWC) 69% lower than the moderate RH-grown leaflets, validating the sensitivity of K023 to high RH during growth. At last, from the five studied genes only the expression of CYP707A3 was significantly reduced by high RH, without significant differences found in the other genes. In conclusion, the sensitivity of the genotype K023 to high RH cannot be explained by the expression of the genes evaluated in this study, using leaves harvested 180 min after the beginning of the dark period (closing stimulus). We expect that after transferring the plants to the postharvest conditions, inducing water stress, a more contrasting gene expression among RH levels will appear.

2014Conference object

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