Strategies to avoid salinity and hydric stress of pepper grafted plants

Sweet pepper is one of the most important vegetable crops in arid and semiarid regions. Grafting has been proposed as an interesting strategy that improves the responses of crops under the salinity and hydric deficits occurring in these areas. In a previous work, we selected Capsicum spp accessions with different degrees of salinity and hydric stress tolerance to be used as rootstocks (the highest to lowest): Capsicum chinense Jacq. ‘ECU-973’ (code 12), Capsicum baccatum L. var. pendulum ‘BOL-58’ (code 14) and Capsicum annuum L var. ‘Serrano’ (code 5). The behavior of commercial cultivar seedlings grafted onto these rootstocks was compared during 14 days under water stress (5% polyethylene glycol) and salinity (40 mM NaCl) in hydroponic culture. Different physiological parameters were measured to test the hypothesis that tolerance might be related to the role of rootstock in altering the stress perception by the scion and to identify differences in pepper-grafted plants adaptation mechanisms in response to salt and osmotic stresses. At a similar osmotic pressure of the solution, grafted plants onto the 12 and 14 rootstocks activated tolerance mechanisms based on ion specific responses under salinity, whereas osmotic adjustment based on proline accumulation was performed under water stress. The maintenance of the scion's homeostasis under salinity was achieved through the restriction of Cl- transport to leaves and to diminished Na+ loading in roots and leaves, thus favouring K+ uptake. Under both stresses, a minor negative impact on photosynthesis, nitrate reductase activity and lipid peroxidation in scion leaves grafted onto 12 and 14 rootstocks was observed. In conclusion, the results of these works reinforce that the use of tolerant pepper rootstocks is a promising strategy to provide salinity and water stress tolerance and can consequently improve crop yield

Relation of carbohydrate reserves with the forthcoming crop, flower formation and photosynthetic rate, in the alternate bearing Salustiana sweet orange (Citrus sinensis L.)

[EN] The aim of this work was to assess the relation between carbohydrate levels and flower and fruit production, as well as the role of carbohydrates on CO(2) fixation activity, by analysis of leaves, twigs and roots from the alternate bearing 'Salustiana' cultivar of sweet orange (Citrus sinensis [L.] Osbeck). A heavy crop load (on year) did not affect photosynthesis activity when compared to non-fruiting trees (off year). Fruiting trees accumulated most of the fixed carbon in mature fruits, whilst no accumulation was observed in roots before harvest. Non-fruiting trees transported part of the fixed carbon to the roots and mobilize it for growth processes and, at the end of the season (December), store it as reserves. Reserve carbohydrates accumulation in leaves started by early December for both tree types, showing the same levels in on and off trees until spring bud sprouting. A heavy flowering after an off year caused the rapid mobilization of the stored reserves, which were exhausted at full bloom. We found no evidence on carbon fixation regulation by either fruit demand or carbohydrate levels in leaves. Carbohydrate reserves played little or no role over fruit set, which actually relied on current photosynthesisWe thank Ing. Agr. J.M. Torres (ANECOOP, Valencia, Spain) for providing the orchard facilities and logistic help, the R + D + i Linguistic Assistance Office at the Universidad Politecnica de Valencia for their help in revising this article and Y. Bordon for her cooperation in some experiments. Thanks are due also to Dr. Olivares for the critical review of the manuscript. This research was funded by grants from the Conselleria de Agricultura, Pesca y Alimentacion (GV-CAPA00-11) and the Conselleria diEmpresa, Universitat i Ciencia, Generalitat Valenciana (Grupos 04/059).Monerri Huguet, MC.; Fortunato De Almeida, A.; Molina Romero, RV.; González Nebauer, S.; García Luís, MD.; Guardiola Barcena, JL. (2011). Relation of carbohydrate reserves with the forthcoming crop, flower formation and photosynthetic rate, in the alternate bearing Salustiana sweet orange (Citrus sinensis L.). Scientia Horticulturae. 129(1):71-78. https://doi.org/10.1016/j.scienta.2011.03.009S7178129

Strategies to Avoid Salinity and Hydric Stress of Pepper Grafted Plants

AbstractSweet pepper is one of the most important vegetable crops in arid and semiarid regions. Grafting has been proposed as an interesting strategy that improves the responses of crops under the salinity and hydric deficits occurring in these areas.In a previous work, we selected Capsicum spp accessions with different degrees of salinity and hydric stress tolerance to be used as rootstocks (the highest to lowest): Capsicum chinense Jacq. ‘ECU-973’ (code 12), Capsicum baccatum L. var. pendulum ‘BOL-58’ (code 14) and Capsicum annuum L var. ‘Serrano’ (code 5). The behavior of commercial cultivar seedlings grafted onto these rootstocks was compared during 14 days under water stress (5% polyethylene glycol) and salinity (40mM NaCl) in hydroponic culture.Different physiological parameters were measured to test the hypothesis that tolerance might be related to the role of rootstock in altering the stress perception by the scion and to identify differences in pepper-grafted plants adaptation mechanisms in response to salt and osmotic stresses.At a similar osmotic pressure of the solution, grafted plants onto the 12 and 14 rootstocks activated tolerance mechanisms based on ion specific responses under salinity, whereas osmotic adjustment based on proline accumulation was performed under water stress. The maintenance of the scion's homeostasis under salinity was achieved through the restriction of Cl- transport to leaves and to diminished Na+ loading in roots and leaves, thus favouring K+ uptake. Under both stresses, a minor negative impact on photosynthesis, nitrate reductase activity and lipid peroxidation in scion leaves grafted onto 12 and 14 rootstocks was observed.In conclusion, the results of these works reinforce that the use of tolerant pepper rootstocks is a promising strategy to provide salinity and water stress tolerance and can consequently improve crop yield

Evaluation for salt stress tolerance of pepper genotypes to be used as rootstocks

Salinity is a major environmental constraint on crop productivity and grafting can be a sustainable strategy to enhance plant tolerance under adverse growth conditions. Screening different graft combinations under field conditions can be a slow and expensive processes. In this study, plants of 18 genotypes of Capsicum spp. were evaluated during 5 months to select salt tolerant plants to be used as rootstocks in greenhouse under controlled conditions. Their net photosynthetic rate was used as a rapid and sensitive methodology for screening their tolerance to salt stress conditions. The germination potential of some genotypes was also tested under different salinity conditions to see if it would be useful to accelerate the screening process. According to photosynthesis rate, the commercial rootstock ‘Tresor’ and the genotypes ‘Serrano’ (C. annuum), ‘ECU-973’ (C. chinense) and ‘BOL-58’ (C. baccatum) were the most tolerant during this period. Nevertheless, the evaluation of pepper genotypes for salinity tolerance based on the germination performance and chlorophyll fluorescence parameter Fv/Fm ratio were not good indicators of the sensitivity along plant ontogeny. Finally, the selected genotypes as salt-tolerant were validated under field conditions as rootstocks of two interesting pepper cultivars, concluding that using the rootstocks selected by the net photosynthetic rate improved the salt tolerance of the scion in terms of marketable yield and fruit quality