Self-grafted Seedlings Research Articles

Bitter Melon (Momordica charantia L.) Rootstock Improves the Heat Tolerance of Cucumber by Regulating Photosynthetic and Antioxidant Defense Pathways.

High temperature is considered a critical abiotic stressor that is increasing continuously, which is severely affecting plant growth and development. The use of heat-resistant rootstock grafting is a viable technique that is practiced globally to improve plant resistance towards abiotic stresses. In this experiment, we explored the efficacy of bitter melon rootstock and how it regulates photosynthesis and the antioxidant defense system to alleviate heat stress (42 °C/32 °C) in cucumber. Our results revealed that bitter-melon-grafted seedlings significantly relieved heat-induced growth inhibition and photoinhibition, maintained better photosynthesis activity, and accumulated a greater biomass than self-grafted seedlings. We measured the endogenous polyamine and hydrogen peroxide (H2O2) contents to determine the inherent mechanism responsible for these effects, and the results showed that heat stress induced a transient increase in polyamines and H2O2 in the inner courtyard of grafted seedlings. This increment was greater and more robust in bitter-melon-grafted seedlings. In addition, the use of polyamine synthesis inhibitors MGBG (methylglyoxal bis-guanylhydrazone) and D-Arg (D-arginine), further confirmed that the production of H2O2 under heat stress is mediated by the accumulation of endogenous polyamines. Moreover, compared with other treatments, the bitter-melon-grafted seedlings maintained high levels of antioxidant enzyme activity under high temperature conditions. However, these activities were significantly inhibited by polyamine synthesis inhibitors and H2O2 scavengers (dimethylthiourea, DMTU), indicating that bitter melon rootstock not only maintained better photosynthetic activity under conditions of high temperature stress but also mediated the production of H2O2 through the regulation of the high level of endogenous polyamines, thereby boosting the antioxidant defense system and comprehensively improving the heat tolerance of cucumber seedlings. Taken together, these results indicate that grafting with a resistant cultivar is a promising alternative tool for reducing stress-induced damage.

Grafted organic seedling production of tomato and watermelon

Grafting is used as a common tool to increase tolerance of vegetables against biotic and abiotic stresses. However, grafted organic seedling production is not present in Turkey. This study was conducted to determine the crop performance of organically grown grafted tomato and watermelon seedlings. Rootstock and scion seeds of both species were sown in vermicompost:local peat (1:1.5 v/v) mixture. After germination in growth chamber (24/24°C, 80% relative humidity (RH) for 3 days), plants were moved to a greenhouse. When seedlings had 3-4 fully opened leaves, tomato (Lycopersicon esculentum) scion 'Melis' were grafted with tube grafting method on two interspesific (L. esculentum × L. hirsutum) rootstocks, 'Beaufort' and 'Sarafin'; watermelon (Citrullus lanatus) scion 'Asbal' was grafted with slide cut grafting method on three rootstocks, 'Argenterio' (Lageneria siceraria), 'Jumbo' (Cucurbita maxima) and 'Flexifort' (C. maxima × C. moschata). Self-grafted seedlings were used as control. Grafted seedlings were left in a healing unit at 24-26°C, 80-90% RH, 16 h LED lighting/8 h dark for 10 days. Seedlings were placed again into greenhouse after healing for adaptation and watermelon and tomato grafted seedlings stayed there 14 and 21 day, respectively. Ten seedlings from each replicates were harvested from for seedling performance (root, rootstock and scion length, root and shoot diameter, shoot and root fresh and dry weight). It was concluded that among the tested rootstocks, 'Beaufort' for tomato and 'Flexifort' for watermelon were found more appropriate as rootstock compared to the others due to the higher performance in root and stem length and diameter of rootstocks and scions and shoot and root fresh and dry weights.

Comparative transcriptome profiling of chilling stress responsiveness in grafted watermelon seedlings

Rootstock grafting may improve the resistance of watermelon plants to low temperatures. However, information regarding the molecular responses of rootstock grafted plants to chilling stress is limited. To elucidate the molecular mechanisms of chilling tolerance in grafted plants, the transcriptomic responses of grafted watermelon under chilling stress were analyzed using RNA-seq analysis. Sequencing data were used for digital gene expression (DGE) analysis to characterize the transcriptomic responses in grafted watermelon seedlings. A total of 702 differentially-expressed genes (DEGs) were found in rootstock grafted (RG) watermelon relative to self-grafted (SG) watermelon; among these genes, 522 genes were up-regulated and 180 were down-regulated. Additionally, 164 and 953 genes were found to specifically expressed in RG and SG seedlings under chilling stress, respectively. Functional annotations revealed that up-regulated DEGs are involved in protein processing, plant-pathogen interaction and the spliceosome, whereas down-regulated DEGs are associated with photosynthesis. Moreover, 13 DEGs were randomly selected for quantitative real time PCR (qRT-PCR) analysis. The expression profiles of these 13 DEGs were consistent with those detected by the DGE analysis, supporting the reliability of the DGE data. This work provides additional insight into the molecular basis of grafted watermelon responses to chilling stress.

The effects of grafting on glycolysis and the tricarboxylic acid cycle in Ca(NO3)2-stressed cucumber seedlings with pumpkin as rootstock

In this research, we investigated the effects of grafting on intermediate metabolites and key enzymes of glycolysis and the tricarboxylic acid (TCA) cycle in self-grafted and salt-tolerant pumpkin rootstock-grafted cucumber seedlings supplied with nutrient solution and subjected to 80 mM Ca(NO3)2 stress for 6 days. Ca(NO3)2 stress induced accumulation of 3-phosphoglycerate (3-PGA) and phosphoenolpyruvate (PEP) in the leaves of self-grafted cucumber seedlings and enhanced the activities of phosphoenolpyruvate carboxylase (PEPC) and enolase (ENO). Succinic acid and malic acid contents and isocitrate dehydrogenase, succinate dehydrogenase (SDH), and malate dehydrogenase (MDH) activities in self-grafted seedlings were significantly decreased by Ca(NO3)2 stress. In addition, activities of PEPC, ENO, SDH, and MDH and contents of glycolysis intermediate metabolites (citric, succinic, and malic acids) were significantly higher in leaves of rootstock-grafted seedlings compared with those in self-grafted seedlings under saline conditions. Furthermore, leaf adenosine triphosphate (ATP) content of rootstock-grafted seedlings was relatively higher than that in self-grafted plants under salt stress, with an opposite effect observed on adenosine diphosphate content. These results indicate that rootstock grafting alleviates Ca(NO3)2 stress-induced inhibition of the glycolytic pathway and the TCA cycle in cucumber seedling leaves, which may aid the respiratory metabolism of cucumber seedlings and help maintain a high ATP synthesis level, thereby increasing the biomass of cucumber seedlings and enhancing their salt tolerance.

Effects of grafting with pumpkin rootstock on carbohydrate metabolism in cucumber seedlings under Ca(NO3)2 stress

This study investigated the effects of grafting on the carbohydrate status and the enzymes of carbohydrate metabolism in self-grafted and grafted cucumber seedlings using the salt-tolerant pumpkin rootstock ‘Qingzhen 1’ (Cucurbita maxima × Cucurbita moschata) under 80 mM Ca(NO3)2 stress for 6 d. The growth of self-grafted seedlings was significantly inhibited after the treatment of Ca(NO3)2 stress, whereas the inhibition of growth was alleviated in pumpkin rootstock-grafted seedlings. Ca(NO3)2 stress increased the contents of the total soluble sugar, sucrose and fructose, but decreased the starch content in rootstock-grafted leaves. However, compared with self-grafted plants, rootstock-grafted seedlings were observed with a higher content of sucrose and total soluble sugar (TSS) under salt stress. Rootstock-grafted seedlings exhibited higher activities of acid invertase (AI), neutral invertase (NI) and phosphate sucrose synthase (SPS) of sucrose metabolism in leaves than that of self-grafted seedlings under salinity. Moreover, the activities of fructokinase (FK), hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) of glycolysis were maintained at a higher level in leaves of rootstock-grafted seedlings after Ca(NO3)2 stress. Additionally, rootstock-grafting decrease the high percentage enhancement of key enzymes gene expression in glycolysis in the scion leaves of cucumber seedlings induced by salt stress. These results suggest that the rootstock-grafting improved salt tolerance, which might play a role in elevated sucrose metabolism and a glycolytic pathway regulated by the pumpkin rootstock.

CRESCIMENTO DE CAFEEIROS ENXERTADOS CULTIVADOS EM SOLUÇÃO NUTRITIVA

The use of grafting in coffee, and give greater tolerance for nematodes, have shown influence on the growth of coffee, so the purpose of this study was to evaluate the growth of different varieties of Coffea arabica L. grafted into Apoata IAC 2258 ( Coffea canephora ). The experiment was installed in a greenhouse, using the method of cultivation in nutrient solution. It used a factorial 7 x 3 + 2, and seven cultivars of C. arabica L. (Palma II, Catucai 2SL, Oeiras MG 6851, Obata IAC 1669-20, Acaua, Topazio MG 1190 and Paraiso MG H 419-1), three types of seedlings (coffee cultivars grafted on ‘Apoata IAC 2258’, self grafted, meaning a cultivar was grafted on a rootstock of the same cultivar and no grafting) and two additional treatments (Apoata self grafted and Apoata no grafting). The technique of grafting did not disadvantage the development of seedling trees. Cultivars Acaua, Paraiso MG H 419-1 and Catucai 2SL had better perform when grafted. The development of the root system of the plants self-grafted and non-grafted seedlings was better then grafted seedlings. Cultivars Palma II, Obata IAC 1669-20 and Oeiras MG 6851have potential to promote the root system development similar to Apoata self-grafted seedlings.

Bottle gourd rootstock-grafting affects nitrogen metabolism in NaCl-stressed watermelon leaves and enhances short-term salt tolerance

The plant growth, nitrogen absorption, and assimilation in watermelon (Citrullus lanatus [Thunb.] Mansf.) were investigated in self-grafted and grafted seedlings using the salt-tolerant bottle gourd rootstock Chaofeng Kangshengwang (Lagenaria siceraria Standl.) exposed to 100mM NaCl for 3d. The biomass and NO3− uptake rate were significantly increased by rootstock while these values were remarkably decreased by salt stress. However, compared with self-grafted plants, rootstock-grafted plants showed higher salt tolerance with higher biomass and NO3− uptake rate under salt stress. Salinity induced strong accumulation of nitrate, ammonium and protein contents and a significant decrease of nitrogen content and the activities of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate synthase (GOGAT) in leaves of self-grafted seedlings. In contrast, salt stress caused a remarkable decrease in nitrate content and the activities of GS and GOGAT, and a significant increase of ammonium, protein, and nitrogen contents and NR activity, in leaves of rootstock-grafted seedlings. Compared with that of self-grafted seedlings, the ammonium content in leaves of rootstock-grafted seedlings was much lower under salt stress. Glutamate dehydrogenase (GDH) activity was notably enhanced in leaves of rootstock-grafted seedlings, whereas it was significantly inhibited in leaves of self-grafted seedlings, under salinity stress. Three GDH isozymes were isolated by native gel electrophoresis and their expressions were greatly enhanced in leaves of rootstock-grafted seedlings than those of self-grafted seedlings under both normal and salt-stress conditions. These results indicated that the salt tolerance of rootstock-grafted seedlings might (be enhanced) owing to the higher nitrogen absorption and the higher activities of enzymes for nitrogen assimilation induced by the rootstock. Furthermore, the detoxification of ammonium by GDH when the GS/GOGAT pathway was inhibited under salt stress might play an important role in the release of salt stress in rootstock-grafted seedlings.