Tolerant Rootstocks Research Articles

Humic acid and grafting as sustainable agronomic practices for increased growth and secondary metabolism in cucumber subjected to salt stress

Salinity stress poses a significant treat to crop yields and product quality worldwide. Application of a humic acid bio stimulant and grafting onto tolerant rootstocks can both be considered sustainable agronomic practices that can effectively ameliorate the negative effects of salinity stress. This study aimed to assess the above mentioned ameliorative effects of both practices on cucumber plants subjected to saline environments. To attain this goal a factorial experiment was carried out in the form of a completely randomized design with three replications. The three factors considered were (a) three different salinity levels (0, 5, and 10 dS m−1 of NaCl), (b) foliar application of humic acid at three levels (0, 100, and 200 mg L−1), and (c) both grafted and ungrafted plants. Vegetative traits including plant height, fresh and dry weight and number of leaf exhibited a significant decrease under increasing salinity stress. However, the application of humic acid at both levels mitigated these effects compared to control plants. The reduction in relative water content (RWC) of the leaf caused by salinity, was compensated by the application of humic acid and grafting. Thus, the highest RWC (86.65%) was observed in grafting plants with 0 dS m−1 of NaCl and 20 mg L−1 of humic acid. Electrolyte leakage (EL) increased under salinity stress, but the application of humic acid and grafting improved this trait and the lowest amount of EL (26.95%) was in grafting plants with 0 dS m−1 of NaCl and 20 mg L−1 of humic acid. The highest amount of catalase (0.53 mmol H2O2 g−1 fw min−1) and peroxidase (12.290 mmol H2O2 g−1 fw min−1) enzymes were observed in the treatment of 10 dS m−1 of NaCl and 200 mg L−1 humic acid. The highest amount of total phenol (1.99 mg g−1 FW), total flavonoid (0.486 mg g−1 FW), total soluble carbohydrate (30.80 mg g−1 FW), soluble protein (34.56 mg g−1 FW), proline (3.86 µg g−1 FW) was in grafting plants with 0 dS m−1 of NaCl and 200 mg L−1 of humic acid. Phenolic acids and phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) enzymes increased with increasing salinity and humic acid levels. Contrary to humic acid, salt stress increased the sodium (Na+) and chlorine (Cl−) and decreased the amount of potassium (K+) and calcium (Ca2+) in the root and leaf of ungrafted cucumber. However, the application 200 mg L−1 humic acid appeared to mitigate these effects, thereby suggesting a potential role in moderating physiological processes and improving growth of cucumber plants subjected to salinity stress. According to the obtained results, spraying of humic acid (200 mg L−1) and the use of salt resistant rootstocks are recommended to increase tolerance to salt stress in cucumber. These results, for the first time, clearly demonstrated that fig leaf gourd a new highly salt-tolerant rootstock, enhances salt tolerance and improves yield and quality of grafted cucumber plants by reducing sodium transport to the shoot and increasing the amount of compatible osmolytes.

Oxidative stress dynamics revealed the role of H2O2 in citrus rootstocks sensitivity to Phytophthoranicotianae

Phytophthora nicotianae is a devastating pathogen in citrus and tolerant rootstocks are required for its management. Seven Jatti Khatti (JK, a rough lemon strain; susceptible) × Poncirus trifoliata (PT; tolerant) hybrids were screened against P. nicotianae. In feeder root rot based evaluation, three hybrids were found moderately tolerant (MT) while four were moderately susceptible (MS). The H2O2 in plant pathogen interactions contributes in resistance/susceptibility to the biotrophic/necrotrophic pathogens. To comprehend its role in citrus against Phytophthora (a hemi-biotrophic pathogen), H2O2, lipid peroxidation, and peroxidase (POD) activity were determined in Phytophthora inoculated and non-inoculated roots of JK, PT, three MT and one MS hybrids at 10, 20 and 30 days post inoculation (dpi). The tolerant parent, PT and MT hybrids exhibited lower or stable H2O2 content in Phytophthora inoculated plants at 20 or 30-dpi. Their POD activity increased at 10-dpi, depicting its role in H2O2 homoeostasis. At 30-dpi, JK and MS hybrid showed significantly higher H2O2 content (4.10 and 3.62 μmol g−1 FW), compared to 1.88 μmol g−1 FW in PT. The lipid peroxidation content significantly increased in JK or MS hybrid at 20 or 30-dpi. The susceptible or MS individuals displayed significantly higher (18–25 % higher) electrolyte leakage than their control. A strong positive association (r = 0.89) was found between electrolytes leakage and H2O2 accumulation at 30-dpi. The POD activity and H2O2 at 10-dpi showed strong negative correlation (r = −0.86). Results infer that high H2O2 causes cellular death and contributes to Phytophthora susceptibility in citrus. It can serve as a biomarker for predicting relative sensitivity to Phytophthora.

Diagnosis and distribution of Citrus tristeza virus in northern Veracruz, Mexico

Objective: of the research was to know the incidence of CTV to try to associate it with the yellowing and death of citrus trees. Design/ Methodology/ Approach: the presence of the virus was diagnosed in seven citrus-producing municipalities in northern Veracruz. A total of 804 samples from citrus trees were collected in 90 locations belonging to the municipalities of Álamo, Castillo de Teayo, Cazones, Chicontepec, Ixhuatlán, Papantla and Tihuatlán. Results: out of all the samples, 380 were positive for CTV; 68% corresponded to attenuated variants and 40% to severe variants. The following symptoms were observed in all the municipalities: death of branches (68%), yellowing of shoots (41%), trees with small leaves (38%), and debarking of the trunk (32%); the incidence of small fruits was 31%, and finally, generalized yellowing (19%). Limitations/ Implications of the study: to manage the disease there are various alternatives, the most frequent is the use of tolerant rootstocks, however, with the existence of severe variants there may be tree deaths even with tolerant rootstocks, so it is necessary to search for and implement other far-reaching options. Findings/ Conclusions: the results show that even with the regulations for the production and mobilization of plants, the virus is widely distributed in the seven municipalities of northern Veracruz.

Rootstocks for the Mediterranean citrus industry: current choices and new releases

Modern citriculture relies on the use of rootstocks to guarantee adaptability to environmental and biotic constraints and to speed up the establishment of a potentially unlimited number of homogeneous plants of a specific clone, which in turn ensures uniformity in the production of high-quality fruit. In this contribution, the status of rootstock availability for the Mediterranean citrus industry is described along with its evolution during the last decades. The major turning points in rootstock choice were caused by the spread of new diseases, such as Citrus Tristeza Virus (CTV), that hastened the use of resistant or tolerant rootstocks. In Italy, the growers decisions on rootstock replacement were facilitated by information from rootstock trials performed for more than 70 years in several areas of southern Italy, as well as information from other countries. However, there is still the need to find alternatives to sour orange (which was the most commonly used rootstock before the CTV outbreak), especially for cultivation under suboptimal growing conditions. Nowadays, the process of replacing standard rootstocks with new ones with better performance should be assisted by a long-term evaluation strategy, since negative characteristics can become evident after many years of evaluation in combination with specific scion varieties. Ongoing rootstock breeding programs in different parts of the world and in Italy are critically described.

The effect of grafting on vegetative and reproductive traits of tomato

Relevance. Tomato (Solanum lycopersicum L.) is one of the most important vegetables in the world. Every year the number of identified viruses and diseases increases, infection with which causes significant crop losses and significantly worsens the quality of agricultural products, especially in tomatoes. Material and methods. In the present study we compared the growth of the vegetative and reproductive traits of tomato plants ‘Dokia’, ‘TY Red 250’ and ‘Pilabi’ grated onto bacterial wilt (caused by Ralstonia solanacearum) and Fusarium wilt (Fusarium oxysporum) diseases tolerant rootstock “Spider” (Takii seed, Japan). The non-grafted (control - CT) and grafted tomato plants (GR) were transplanted on 4 March of 2021 to the four season (vinyl) greenhouse on substrate perlite (mixture of perlite no. 1 and no. 3) and cultivated until September 20. Results. The results showed that responses of the tomato cultivars to grafting combination was different, where agronomical traits depends on the each cultivar’s features can be ranged. The reduction of the values of stem diameter (SD), leaf length and width (LW), fresh fruit weight (FFW), fruit diameter (FD), fruit pericarp thickness (FPT) and fruit hardness (FH) with aging of plants and rising ambient temperature was detected. However, fruit soluble solids among all cultivars regardless of treatments were slightly increased. The index of fruit yield per truss (FYT) significantly decreased among all cultivars after 10th truss regardless of the treatments when the daily temperature increased from July to August. In grafted tomato ‘TY Red 250’ were identified the highest fruit yield per plants (FYP) than in CT plants, whereas in other tomatoes did not found similar differences between CT and GR plants.

Oxidative stress as markers in identification of aluminum-tolerant peach tree rootstock cultivars and clonal selections

ABSTRACT Peach rootstock and scion cultivars are selected in breeding programs considering resistance to pests and diseases, salt tolerance, drought tolerance, and vigor. However, rootstock tolerance to aluminum (Al), which is markedly present in tropical and subtropical soils of the world, is not considered. Thus, it is essential to define potential markers that can contribute to the selection of Al-resistant or Al-tolerant peach rootstocks. The objective of this study was to identify Al-tolerant peach tree rootstock cultivars and clonal selections using physiological and oxidative stress variables. A completely randomized experimental design was used in a 13 (rootstock cultivars and clonal selections) × 2 (with and without Al) factorial arrangement, with three replications. Nursery peach trees of own-rooted ‘BRS Mandinho’ (without rootstock) and nursery trees of ‘BRS Mandinho’ grafted on different rootstock cultivars and clonal selections were grown in a hydroponic system, consisting of two treatments, with and without 100 mg L -1 of Al. Dry biomass, photosynthetic variables, pigment concentration, hydrogen peroxide content, membrane lipid peroxidation, and activity of the antioxidant enzymes were evaluated. The total dry matter production of the own-rooted ‘BRS Mandinho’ trees and the SS-CHI-09-39 and SS-CHI-09-40 selections is affected by the Al presence, representing a decline of 35.4, 37.2, and 24.4 %, respectively, compared to the treatment with Al. The highest total dry matter production in Al presence was observed for the ‘Sharpe’ rootstock. ‘Capdeboscq’, DB-SEN-09-23, FB-ESM-09-43, JB-ESM-09-13, JAH-MAC-09-77, SAS-SAU-09-71, and VEH-GRA-09-55 rootstock selections are tolerant to Al. The use of physiological and biochemical variables shows potential for the selection of clonal rootstocks tolerant or resistant to Al.

Photosynthetic gas exchange and functionality in different grapevine cultivars and their cross grafted combinations in response to bicarbonate-induced Fe deficiency

Iron (Fe) deficiency-induced chlorosis can be a serious problem in grapevine cultivation. Measuring genotypic tolerance to this disorder is of vital importance in rootstock selection. In this research, different sources of Fe (FeSO4·7H2O and FeEDTA) were used and their effects were evaluated on the response of a tolerant (‘Thompson Seedless’) and a sensitive (‘Flame Seedless’) grape cultivar. Also, their cross-grafted combinations [‘Flame Seedless’/’Thompson Seedless’ (FS/TS) and ‘Thompson Seedless’/‘Flame Seedless’ (TS/FS)] were evaluated for tolerance to Fe deficiency. Bicarbonate (30 mM) was used for inducing iron deficiency in the plants. Despite the negative effects of bicarbonate, the ‘Thompson Seedless’ maintained a significant chlorophyll index, compared to the ‘Flame Seedless’ cultivar. Gas exchange measurements showed that the bicarbonate had more adverse effects on photosynthesis and water-use-efficiency (WUE) in the ‘Flame Seedless’ cultivar. Despite the bicarbonate toxicity, the photosynthetic system of the FS/TS graft combination showed no significant change in FV/FO, whereas adverse effects occurred significantly in ‘Thompson Seedless’, ‘Flame Seedless’, and their TS/FS graft combination. Bicarbonate decreased the performance index in ‘Flame Seedless’. In conclusion, scions of the susceptible cultivar performed well when grafted on tolerant rootstocks. Such grafting combinations can help plants to cope with the negative effects of bicarbonate toxicity on grapevine.

Enhancing salinity tolerance in cucumber through Selenium biofortification and grafting

BackgroundSalinity stress is a major limiting factor for plant growth, particularly in arid and semi-arid environments. To mitigate the detrimental effects of salinity stress on vegetable production, selenium (Se) biofortification and grafting onto tolerant rootstocks have emerged as effective and sustainable cultivation practices. This study aimed to investigate the combined effects of Se biofortification and grafting onto tolerant rootstock on the yield of cucumber grown under salinity stress greenhouse conditions. The experiment followed a completely randomized factorial design with three factors: salinity level (0, 50, and 100 mM of NaCl), foliar Se application (0, 5, and 10 mg L-1 of sodium selenate) and grafting (grafted and non-grafted plants) using pumpkin (Cucurbita maxima) as the rootstock. Each treatment was triplicated.ResultsThe results of this study showed that Se biofortification and grafting significantly enhanced salinity tolerance in grafted cucumbers, leading to increased yield and growth. Moreover, under salinity stress conditions, Se-Biofortified plants exhibited increased leaf relative water content (RWC), proline, total soluble sugars, protein, phenol, flavonoids, and antioxidant enzymes. These findings indicate that Se contributes to the stabilization of cucumber cell membrane and the reduction of ion leakage by promoting the synthesis of protective compounds and enhancing antioxidant enzyme activity. Moreover, grafting onto pumpkin resulted in increased salinity tolerance of cucumber through reduced Na uptake and translocation to the scion.ConclusionIn conclusion, the results highlight the effectiveness of Se biofortification and grafting onto pumpkin in improving cucumber salinity tolerance. A sodium selenate concentration of 10 mg L-1 is suggested to enhance the salinity tolerance of grafted cucumbers. These findings provide valuable insights for the development of sustainable cultivation practices to mitigate the adverse impact of salinity stress on cucumber production in challenging environments.

Physiological and Morphological Responses of Three Grapevine Rootstocks to Water Stress

Water deficit stress is one of the most frequent environmental stresses affecting the physiological and growth responses of plants, especially grapevines. However, grapevine varieties and species differ in their tolerance to water stress. To identify the most tolerant grapevine rootstock, a factorial randomised block design with two factors was used. The first factor included the susceptible cv. Sultana (V. vinifera L.) scion grafted onto three rootstocks (Yaghouti, Kolahdari and 140 Ru), and the second factor was water stress potential at three levels (control, -1 MPa and -2 MPa). The physiological parameters, such as malondialdehyde (MDA), electrical leakage (EL), proline, soluble sugar, protein, photosynthetic pigments, and antioxidant enzymes were investigated. Our results revealed that increasing water stress enhanced H2O2, MDA, EL, proline, soluble sugar, and soluble protein, while decreasing chlorophyll (Chl) and carotenoid contents, growth parameters, and plant dry weight. The glutathione peroxidase (GPX) activity was enhanced in response to water deficiency, whereas catalase (CAT) and ascorbate peroxidase (APX) enzymes exhibited higher activity at -1 MPa, which was then reduced under the lowest water potential (-2 MPa). In addition, 140 Ru rootstocks exposed to water stress had lower levels of MDA, H2O2, EL, and higher Chl (a, b), carotenoid, APX, and GPX activity, as well as higher shoot dry weight. Overall, the physiological and morphological responses of the three rootstocks propose that grafting the commercial Sultana cultivar onto drought-tolerant rootstocks such as 140 Ru is an effective strategy for improving drought stress tolerance.

Optimal treatment against Athelia rolfsii rot in processing tomatoes using pesticide and rootstock against key stages of the disease

The soilborne fungus Athelia rolfsii (synonym Sclerotium rolfsii) causes stem or collar rot in tomato (Lycopersicon esculentum Mill.). We aimed to develop an optimal treatment for A. rolfsii in processing tomatoes in Israel through an understanding of the key developmental stages of the plant that are susceptible to disease development. We tested two approaches: best timing for pesticide application, and grafting onto a tolerant rootstock. The fungus attacked processing tomatoes at two stages: (i) immediately after planting, when the root neck is attacked and the young plant wilts, and (ii) in the last month of growth, when the humidity under the foliage increases, temperatures are high, and the root neck, shoot and fruit, which are lying on the ground, are susceptible to pathogen attack. The number of infected plants was significantly reduced after incorporating azoxystrobin at 2.5 and 5 L a. i./ha in the soil preplanting, and applying the combination fungicide Nativo (a.i. tebuconazole and trifloxystrobin) at 0.75 kg/ha in the drip-irrigation system (chemigation) once, 60–90 days after planting. This treatment enhanced total yield by up to 35.2% and marketable yield by up to 33.7% relative to untreated plots. Grafting to a resistant rootstock significantly reduced plant wilting in the first weeks of growth to less than 1% of the plants, and enhanced fruit yield up to four fold. In soil with a history of infestation, A. rolfsii infection should be treated during the plants’ susceptible stages: preventive azoxystrobin treatment preplanting, and a single treatment of Nativo later on to prevent infection and decay, especially for late harvest; grafting to a resistant rootstock can also reduce infection in the early stages of growth and enhance yield. In this study, we show for the first time that A. rolfsii infection in processing tomato can be dramatically decreased with minimal pesticide application against key stages of the disease and rootstocks.

Plant Physiological Assessments on Promising New HLB-Tolerant Citrus Rootstocks after Inoculation with the Phytopathogenic Ascomycete Rosellinia necatrix

Citriculture is considered the most important fruit industry and involves the cultivation of several fruit varieties, which are susceptible to many plant pathogens. In this sense, soil-borne pathogenic fungi, such Rosellinia necatrix, threaten citrus fruit production worldwide because they can cause fruit loss. Therefore, we assayed the physiological reaction of novel citrus rootstocks against white root rot disease during long-term management. Data from above-ground symptoms and chlorophyll content were periodically obtained during the experimental process. In addition, plant leaf area and percentage of biomass reduction were determined for each rootstock when the experiment finished. The behavior of the inoculated tolerant rootstocks was as follows: the lowest symptom rate of SAUDPC was achieved by B11R5T25 and N40R3T25; AMB+CZO manifested the highest disease incidence; B11R5T25 and A+VOLK × Orange 19-11-8 displayed the highest and the lowest chlorophyll content, respectively; AMB+CZO and A+VOLK × Orange 19-11-8 showed the highest biomass reduction, and the lowest was detected in B11R5T25 and N40R2T19; concerning the leaf area, N40R1T18, N40R3T25 and N40R2T19 showed the lowest response, and 2247 × 2075-01-2 achieved the highest rate. In summary, B11R5T25 and N40R3T25 displayed the lowest disease rate.

Exogenous calcium improves growth and physiological responses of pistachio rootstocks against excess boron under salinity

Although boron (B) is necessary for plant growth and development, excessive concentrations of it can be harmful. Toxicity due to boron can occur naturally in the soils of arid and semiarid areas. Soluble forms of Ca were applied as foliar sprays at 1.1 and 2.2 g L−1 on three pistachio rootstocks, namely Pistacia vera L. ‘Ghazvini’, P. vera L. ‘Badami-Riz’ and P. atlantica subsp. Atlantica. Effects of the foliar sprays were assessed on growth and physiological responses of the three rootstocks while an excess of B was added to the irrigation water under saline soil (ECe ≅12 dS/m). Four-month plants were irrigated with water containing B as boric acid (20 and 40 mg L−1). Calcium treatments occurred either as aminochelate or chloride, and were sprayed on the foliage once a week. The experiment lasted for 12 wk and terminated when 50% of the plants showed symptoms of B toxicity. Excess B retarded growth and affected physiological parameters including plant height, leaf number, leaf area, leaf dry weight, stem diameter, shoot dry weight, root length, root dry weight, leaf proline content, SPAD value and RWC. Boron concentrations increased in the plant tissues, due to the boric acid in the irrigation water, while foliar sprays of calcium reduced B content in the leaves, stems and roots. Applications of Ca-Chelate and CaCl2 (2.2 g L−1 each) significantly improved growth and physiological responses of all rootstocks. The Ca-Chelate was more effective than CaCl2 in ameliorating B toxicity. In terms of rootstock tolerance to B toxicity, ‘Ghazvini’ and ‘Atlantica’ were more tolerant than ‘Badami’. The results indicate that foliar sprays of Ca are effective in mitigating excess boron symptoms in pistachio rootstocks grown under saline conditions.

Transcriptome analysis showed that tomato-rootstock enhanced salt tolerance of grafted seedlings was accompanied by multiple metabolic processes and gene differences.

Grafting is a commonly used cultural practice to counteract salt stress and is especially important for vegetable production. However, it is not clear which metabolic processes and genes are involved in the response of tomato rootstocks to salt stress. To elucidate the regulatory mechanism through which grafting enhances salt tolerance, we first evaluated the salt damage index, electrolyte permeability and Na+ accumulation in tomato (Solanum lycopersicum L.) leaves of grafted seedlings (GSs) and nongrafted seedlings (NGSs) subjected to 175 mmol·L- 1 NaCl for 0-96h, covering the front, middle and rear ranges. Compared with the NGS, the GSs were more salt tolerant, and the Na+ content in the leaves decreased significantly. Through transcriptome sequencing data analysis of 36 samples, we found that GSs exhibited more stable gene expression patterns, with a lower number of DEGs. WRKY and PosF21 transcription factors were significantly upregulated in the GSs compared to the NGSs. Moreover, the GSs presented more amino acids, a higher photosynthetic index and a higher content of growth-promoting hormones. The main differences between GSs and NGSs were in the expression levels of genes involved in the BR signaling pathway, with significant upregulation of XTHs. The above results show that the metabolic pathways of "photosynthetic antenna protein", "amino acid biosynthesis" and "plant hormone signal transduction" participate in the salt tolerance response of grafted seedlings at different stages of salt stress, maintaining the stability of the photosynthetic system and increasing the contents of amino acids and growth-promoting hormones (especially BRs). In this process, the transcription factors WRKYs, PosF21 and XTHs might play an important role at the molecular level. The results of this study demonstrates that grafting on salt tolerant rootstocks can bring different metabolic processes and transcription levels changes to scion leaves, thereby the scion leaves show stronger salt tolerance. This information provides new insight into the mechanism underlying tolerance to salt stress regulation and provides useful molecular biological basis for improving plant salt resistance.

Study on the Mechanism of Grafting to Improve the Tolerance of Pepper to Low Temperature

Pepper is a horticultural crop that does not tolerate low temperatures. To investigate how the grafted pepper responds to low temperature stress in the short term, transcriptome analysis was performed on grafted seedlings treated with low temperature for 1 h, 4 h, 12 h and 24 h compared with those treated for 0 h. The results showed that genes related to CAM4, MPK8, RbohD and OXI1 might be related to the response of grafted seedlings to low temperature stress in the short term. To investigate how low temperature tolerant rootstocks can improve the low temperature tolerance of grafted peppers, morphological and physiological indices of self-rooted and grafted seedlings were analyzed under low temperature conditions for different days. The results showed that the degree of wilting, REL and MDA content of grafted seedlings were significantly lower than those of self-rooted seedlings, and the antioxidant enzyme activities were significantly higher than those of self-rooted seedlings under low temperature stress. The results indicated that grafted pepper would activate ROS-related genes in a short period of time after low temperature stress and produce a large amount of ROS in response to the low temperature stress. When ROS accumulated to a certain level, the grafted pepper could increase the enzyme activity of antioxidant system to remove the ROS produced in the body, and help the pepper seedlings adapt to low temperature stress through osmoregulation mechanism, so as to resist the damage caused by low temperature. The results of the study provide ideas for growing pepper in low temperature environment.

Determination of the Microspore Development Concerning Floral Morphology for Improving Drought Tolerant Citron Watermelon (Citrullus lanatus var. citroides) Rootstocks Via Androgenesis.

The negative effects of abiotic stress factors (especially drought and salinity) that arise due to global climate change are increasing in today’s agricultural production. To eliminate the negative effects of these stress factors, some cultural practices have been implemented such as the breeding of tolerant cultivars and rootstock, exogenous applications of PGPR, AMF, and chemical substances, etc. Contrary to exogenous applications, providing tolerance with breeding methods has an important role in efficient and sustainable agriculture. Androgenesis is a phenomenon for the induction and development of microspore-derived pure lines, as initial material for F1 cultivar breeding, in different vegetable crops. Success in microspore embryogenesis is considerably related to the culture of microspores at an appropriate developmental stage. There is no standard protocol for the anther culture in citron watermelon (Citrullus lanatus var. citroides). Thus, a relation between floral morphology (bud length and width, bud index, sepal position, petal color), and microspore development (microspore diameter, uninucleated and binucleated phases) was investigated in citron. The male flower buds were collected at different sizes and microspore development was observed in both light and fluorescence microscopy. A strong positive relationship was detected between flower bud morphology and the specific stages of microspore development. To the author’s knowledge, this is the first report to indicate that the microspore developmental stage can be estimated by flower bud morphology, and applied in the anther/microspore culture of citron watermelon.

Produção e qualidade de frutos de goiaba ‘Paluma’ com porta-enxerto tolerante a nematoides irrigados no semiárido

ABSTRACT Using nematode-resistant and/or -tolerant rootstock is a strategy that has maintained guava cultivation feasible in the irrigated perimeters of the Brazilian semi-arid region. The objective was to evaluate the production, gas exchange, and fruit quality of ‘Paluma’ guava with and without nematode-tolerant rootstock under different irrigation depths and production periods. The experimental design was randomized blocks, in the mixed 2 × 4 × 2 factorial scheme, corresponding to two forms of cultivation of ‘Paluma’ guava (without and with nematode-tolerant rootstock), four irrigation depths (60, 80, 100, and 120% of crop evapotranspiration - ETc), and two production periods, with four replicates. Guava plants were evaluated for physiological, production and post-harvest quality parameters. Gas exchange in ‘Paluma’ guava leaves was higher in the second production cycle, under irrigation depths above 100% ETc, not differing with the use of the rootstock. The use of the rootstock ‘BRS Guaraçá’ promotes a greater number of fruits and production with the increase of the irrigation depth, mainly in the second half of the year, with the increase of soluble solids and titratable acidity in the fruits.

Metabolomic exhibits different profiles and potential biomarkers of Vitis sp co-cultivated with Fusarium oxysporum for short, medium, and long times.

Differential rootstock tolerance to Fusarium sp. supports viticulture worldwide. However, how plants stand against the fungus still needs to be explored. We hypothesize it involves a differential metabolite modulation. Thus, we performed a gas chromatography coupled with mass spectrometry (GC-MS) analysis of Paulsen P1103 and BDMG573 rootstocks, co-cultured with F. oxysporum (FUS) for short, medium, and long time (0, 4, and 8 days after treatment - DAT). In shoots, Principal Component Analysis (PCA) showed a complete overlap between BDMG573 CNT and FUS at 0 DAT, and P1103 treatments showed a slight overlap at both 4 and 8 DAT. In roots, PCA exhibited overlapping between BDMG573 treatments at 0 DAT, while P1103 treatments showed overlapping at 0 and 4 DAT. Further, there is a complete overlapping between BDMG573 and P1103 FUS profiles at 8 DAT. In shoots, 1,3-dihydroxyacetone at 0 and 4 DAT and maltose at 4 and 8 DAT were biomarkers for BDMG573. .For P1103, glyceric acid, proline, and sorbitol stood out at 0, 4, and 8 DAT, respectively. In BDMG573 roots, the biomarkers were β-alanine at 0 DAT, cellobiose and sorbitol at both 4 and 8 DAT. While in P1103 roots, they were galactose at 0 and 4 DAT and 1,3-dihydroxyacetone at 8 DAT. Overall, there is increase in amino acids, glycolysis, and TCA components in tolerant Paulsen P1103 shoots. Thus, it provides a new perspective on the primary metabolism of grapevine rootstocks to F. oxysporum that may contribute to strategies for genotype tolerance and early disease identification. This article is protected by copyright. All rights reserved.

Sodicity stress differently influences physiological traits and anti-oxidant enzymes in pear and peach cultivars.

The growth and physiological responses to sodicity stress of pear and peach are poorly understood. Insights into how sodicity stress alters tree physiology remain vital to developing salt tolerant scion and rootstock cultivars. The effects of sodicity stress (soil pHs ~8.8) on tree growth and physiological traits of field grown trees of pear cultivars Punjab Beauty and Patharnakh, and peach cultivars Partap and Shan-e-Punjab were recorded using standard procedures. Sodicity-induced changes in oxidative stressors, proline, anti-oxidant enzymes and leaf ions were measured to draw inferences. Sodicity-induced reductions in vegetative growth were particularly marked in Patharnakh pear and Partap peach compared with other cultivars. Although sodicity stress triggered a significant increase in leaf malondialdehyde (MDA) and hydrogen peroxide (H2O2), their levels relative to controls were much higher in peach than in pear; reflecting that peach suffered from greater oxidative stress. Interestingly, MDA and H2O2 levels did not seem to be deleterious enough to trigger proline-induced osmotic adjustment in pears. The activities of anti-oxidant enzymes strongly varied with the cultivar; specifically, the sodicity-induced increases in CAT and SOD activities were much higher in Punjab Beauty pear and Shan-e-Punjab peach. Principal Component Analysis revealed an explicit convergence between CAT and SOD activities in Punjab Beauty and Shan-e-Punjab cultivars in response to sodicity-induced oxidative stress. Correlation analysis revealed that leaf Na+ strongly inhibited tree growth in peach than in pear. Leaf K+ and proline were found to be the major osmolytes in sodicity-stressed pear and peach cultivars, respectively. We have for the first time studied the effects of sodicity stress on important tree growth and physiological traits of commercially important pear and peach cultivars. Our findings revealed a marked suppressive effect of sodicity stress on tree growth in peach than in pear. The sodicity-induced upticks in leaf malondialdehyde, hydrogen peroxide and Na+ seemed to induce proline-mediated osmotic adjustment in peach but not in pear. The overall better sodicity tolerance in pear compared to peach was ascribed to increased activities of anti-oxidant enzymes catalase and superoxide dismutase enzymes together with restricted Na+ uptake and better leaf K+ levels. Further investigations are needed to elucidate the effects of sodicity stress on genetic and transcriptional changes, and on fruit yield and quality.

A Water Stress–Tolerant Pepper Rootstock Improves the Behavior of Pepper Plants under Deficit Irrigation through Root Biomass Distribution and Physiological Adaptation

The use of rootstocks tolerant to water stress in pepper crops is a complementary technique for saving irrigation water without affecting yields by means of particular rootstock physiological traits, which changes the scion’s perception stress. The present study aimed to analyze the morphological and physiological adaptation of the ‘Cuerno’ pepper cultivar grafted onto tolerant rootstock NIBER® subjected to capacitance sensor-based deficit irrigation. The stomatal conductance, relative water content and leaf water potential parameters were used to confirm the degree of crop stress. Leaf dry weight and root volume were higher in the grafted plants under the control irrigation and stress treatment conditions. Total fresh root biomass and root volume percentage of grafted plants under water stress were 24% and 33% higher, respectively, than the ungrafted plants. The grafted plants subjected to both water stress and control conditions had a higher marketable production than the ungrafted plants. The higher yields obtained using tolerant rootstocks were explained by the reduced blossom-end rot incidence.

Transcription factors MhDREB2A/MhZAT10 play a role in drought and cold stress response crosstalk in apple.

Drought and cold stresses seriously affect tree growth and fruit yield during apple (Malus domestica) production, with combined stress causing injury such as shoot shriveling. However, the molecular mechanism underlying crosstalk between responses to drought and cold stress remains to be clarified. In this study, we characterized the zinc finger transcription factor ZINC FINGER OF ARABIDOPSIS THALIANA 10 (ZAT10) through comparative analysis of shoot-shriveling tolerance between tolerant and sensitive apple rootstocks. MhZAT10 responded to both drought and cold stresses. Heterologous expression of MhZAT10 in the sensitive rootstock 'G935' from domesticated apple (Malus domestica) promoted shoot-shriveling tolerance, while silencing of MhZAT10 expression in the tolerant rootstock 'SH6' of Malus honanensis reduced stress tolerance. We determined that the apple transcription factor DEHYDRATION RESPONSE ELEMENT-BINDING PROTEIN 2A (DREB2A) is a direct regulator activating the expression of MhZAT10 in response to drought stress. Apple plants overexpressing both MhDREB2A and MhZAT10 genes exhibited enhanced tolerance to drought and cold stress, while plants overexpressing MhDREB2A but with silenced expression of MhZAT10 showed reduced tolerance, suggesting a critical role of MhDREB2A-MhZAT10 in the crosstalk between drought and cold stress responses. We further identified drought-tolerant MhWRKY31 and cold-tolerant MhMYB88 and MhMYB124 as downstream regulatory target genes of MhZAT10. Our findings reveal a MhDREB2A-MhZAT10 module involved in crosstalk between drought and cold stress responses, which may have applications in apple rootstock breeding programs aimed at developing shoot-shriveling tolerance.