Scion Cultivars Research Articles

Four Diaporthe species associated with grapevine nursery plants and commercial vineyards in Uruguay

AbstractDiaporthe species cause Diaporthe dieback (DD) in many grape‐growing countries causing general vine decline, shoot dieback and dead spurs, with perennial cankers and internal trunk necrosis. These pathogens are also the causal agents of Phomopsis cane and leaf spot, a common foliar disease affecting grapevine around the world. In this study, we specifically investigated DD affecting nursery vines and commercial vineyards in Uruguay. A collection of 59 Diaporthe isolates obtained from symptomatic and asymptomatic wood samples of commercial grapevines (nine cultivars) and nursery vines (including cuttings of four scion cultivars and two rootstocks, and six scion–rootstock combinations of grafted plants), was characterized based on DNA phylogenetic analysis, phenotypical characteristics and pathogenicity tests. Diaporthe ampelina was the most frequent species (86%), followed by D. foeniculina (9%), D. eres (3%) and D. terebinthifolii (2%). All species were isolated from nursery material, but D. ampelina was the only one found in field vines. The pathogenicity of all species was confirmed, with D. ampelina being the most virulent, causing the longest necrotic lesions on both green shoots and lignified canes. Further studies are needed to comprehend the epidemiology of DD and to better understand its relationship with Phomopsis cane and leaf spot in order to design a management programme to prevent the disease development.

Rootstock affects phytotechnical attributes, gas exchange, and carbohydrate accumulation in mango scion

ABSTRACT The market demand for grafted mango seedlings is increasing because they provide uniformity and precocity for orchards and gain in productive performance. However, studies on suitable rootstocks for mango seedling production of the main mango cultivars of economic interest in the Sao Francisco Valley, Brazil, are incipient. In this context, the objective of the present study was to evaluate growth, gas exchange, and carbohydrate accumulation in the 'Palmer', 'Tommy Atkins', 'Kent', and 'Keitt' mango scions grafted onto polyembryonic rootstocks ('Capucho', 'Coquinho', and 'Espada'). The experiment was carried out under nursery conditions, with 50% shading. A randomized block experimental design was used, in a 3 × 4 factorial arrangement, consisting of three mango rootstocks ('Espada', 'Capucho', and 'Coquinho') and four mango scion cultivars ('Palmer', 'Keitt', 'Kent', and 'Tommy Atkins'), with five replications and five plants per plot. Graft success was evaluated 28 days after grafting (DAG) to determine the effects of the rootstocks on each scion. Growth, photosynthetic parameters, and total soluble carbohydrate (TSC) and starch content were evaluated 227 DAG. The rootstocks used affected the growth, photosynthetic pigments, contents of TSC and starch, and gas exchange of the mango scions. The higher graft success percentages were found for the cultivars 'Keitt', 'Palmer', and 'Kent' grafted on 'Espada' rootstocks. The cultivar 'Tommy Atkins' showed the highest graft success percentages when grafted on 'Espada' and 'Capucho' rootstocks. 'Capucho' rootstocks showed higher performance for most of the analysed variables, mainly when using 'Palmer' and 'Tommy Atkins' cultivars as scions.

The rootstock genotype shapes the diversity of pecan (Carya illinoinensis) rhizosphere microbial community.

Pecans (Carya illinoinensis), one of the most valuable native North American nut crops, are commonly propagated through grafting to preserve the desired characteristics from parent trees. Since successful cultivation of pecan trees relies on the interplay among scion varieties, rootstocks, and soil conditions, this study investigated the microbial change to communities in the soils and roots of southern (87MX5-1.7) and northern (Peruque) rootstocks in a rootstock test orchard. Both grafted with the 'Pawnee' scion cultivar. Bacterial 16S ribosomal RNA and fungal ITS were amplified from both roots and rhizosphere soils of the two 10-year-grafted trees, then sequenced and annotated into trophic and nutrient-related groups to characterize the rhizosphere microbiota. The Peruque roots had a higher relative abundance of saprotroph fungi, while 87MX5-1.7 exhibited higher levels of symbiotroph fungi and nitrogen fixation-related bacteria. Among them, the presence of symbiotroph fungi, particularly ectomycorrhizal fungi, notably differed between these two rootstocks, with a significantly higher presence observed in the root of 87MX5-1.7 compared to Peruque. This variation likely leads to divergent pathways of nutrient translocation: Peruque was in favor of multiple fungi (Russula and Inocybe) to gain nutrition, while 87MX5-1.7 preferred a specific domain of fungi (Tuber) and nitrogen fixation-related bacteria (Bradyrhizobia) to form beneficial symbiosis. Moreover, the presence of pathogens suggested a potential risk of Fusarium patch and snow molds in 87MX5-1.7, while canker and black foot disease pose threats in Peruque. The findings of this study suggest that rootstocks from different origins shape rhizosphere microbes differently, potentially affecting nutrient uptake and nut yield. Exploring rootstock-microbe combinations could provide insights into optimizing scion growth and ultimately increasing nut yield. By understanding how different rootstock-microbe interactions influence pecan tree development, growers can strategically select combinations that promote beneficial symbiotic relationships, enhancing nutrient uptake, disease resistance, and overall tree vigor.

Evaluation of brinjal and tomato scions for enhancing yield and quality attributes in grafted brimato plants

To meet the growing demand for fresh produce in cities, promoting peri-urban and urban farming is essential to reduce reliance on rural areas for vegetables. One innovative approach developed at ICAR-IIVR, Varanasi (2019-2022), is the dual grafting of brinjal and tomato on a single brinjal plant, termed 'Brimato' (Brinjal + Tomato). Using the vigorous, waterlogging and salinity-tolerant brinjal rootstock IC 111056, four brinjal cultivars (Kashi Sandesh, Kashi Uttam, Kashi Manohar, Kashi Vijay) and three tomato cultivars (Kashi Aman, Kashi Chayan, Vani) were selected as scions. Over three years, experiments showed that scion cultivars significantly impacted Brimato productivity. Kashi Manohar combined with Kashi Aman or Kashi Chayan yielded the highest brinjal fruit numbers, while Kashi Aman combined with hybrid brinjal Kashi Sandesh resulted in the highest tomato fruit numbers. The highest fruit yields were observed with the Kashi Sandesh + Kashi Chayan combination, yielding 2.58 kg/plant. The Kashi Aman + Kashi Sandesh combination produced a cumulative yield of 5.98 kg/plant. Physiological traits like photosynthetic rate and chlorophyll fluorescence yield varied significantly among scion cultivars, with Kashi Manohar and Kashi Aman scions exhibiting the highest photosynthetic rates. Grafted Brimato plants showed enhanced fruit quality, particularly in vitamin C and β-carotene content. These findings highlight the potential of Brimato plants for urban agriculture, offering a viable solution for sustainable fresh produce supply.

Rootstock Effects on Fruit Yield and Quality of 'BRS Tainá' Seedless Table Grape in Semi-Arid Tropical Conditions.

In viticulture, choosing the most suitable rootstock for a specific scion cultivar is an efficient and cost-effective way to increase yield and enhance the physicochemical characteristics of the fruit. The objective of this study was to evaluate the agronomic performance of the 'BRS Tainá' grapevine on different rootstocks under the conditions of the Sub-Middle São Francisco Valley. The main experimental factor consisted of eight rootstocks (IAC 313, IAC 572, IAC 766, 101-14 MgT, Paulsen 1103, Ramsey, SO4, and Teleki 5C), arranged in randomized blocks with four replicates. The experiment was conducted over four production cycles, from 2021 to 2023, in a commercial crop area in Petrolina, PE, Brazil. There were significant effects of rootstocks for the yield and number of bunches per plant, as well as berry length and firmness. 'BRS Tainá' achieved the highest yield (22.2 kg per plant) when grafted onto the Paulsen 1103 rootstock, which was superior to the yield on 101-14 MgT, IAC 313, and IAC 572 rootstocks. The highest number of bunches (88) was obtained with 'BRS Tainá' grafted on Paulsen 1103, while the lowest number (63) was obtained on IAC 572; both these rootstocks were not significantly different from the other rootstocks. For all scion-rootstock combinations, the mean values for soluble solid (SS) content, titratable acidity (TA), and the SS/TA ratio were similar to those previously described for 'BRS Tainá', meeting the commercialization standard. The results for the yield and number of bunches per plant indicate the suitability of grafting 'BRS Tainá' on Paulsen 1103 under the semi-arid tropical conditions of the São Francisco Valley.

‘Rootpac R’ for Apricots? Yes!

The rootstock ‘Rootpac R’ is not used for apricots. The aim of this study was to evaluate the characteristics of ‘Rootpac R’ in comparison to the widely used ‘Myrobalan 29C’ rootstock. The evaluation of the rootstocks was conducted in combination with 16 scion cultivars to assess their effects on vegetative traits and mortality. The total height of the trees on ‘Rootpac R’ initially surpassed the ‘Myrobalan 29C’ trees. By the end of the fourth year, both rootstocks showed comparable heights with ‘Rootpac R’ standing at 317 cm and ‘Myrobalan 29C’ standing at 307 cm. Both rootstocks exhibited comparable TCSA values of 5 cm2 initially; ‘Rootpac R’ surpassed 35% compared to ‘Myrobalan 29C’. Canopy space occupancy assessments revealed that ‘Rootpac R’ initially demonstrated superior space utilization, occupying 8% of the designated volume compared to 4% for ‘Myrobalan 29C’. By the fourth year, ‘Rootpac R’ exhibited a higher occupancy rate of 65% compared to 50% for ‘Myrobalan 29C’. For apricot cultivars, such as ‘Bergeron’, ‘C. óriás’, ‘Gönci magyarkajszi’, ‘Lady Cot’, ‘Tardif de Valance’, and ‘Tom Cot’, ‘Rootpac R’ exhibited survival rates beyond the fourth season, highlighting its effectiveness for these varieties. Based on these results, ‘Rootpac R’ rootstock could be useful in apricot growing.

Vulnerability of pear (Pyrus) genetic resources in the U.S.

AbstractPears (Pyrus) represent an important part of consumer diets, and have the fourth highest production of non-citrus fruits, measured by fresh weight, in the U.S. They are maintained clonally and grown as composite plants, consisting of a scion (fruit bearing) cultivar grafted onto a rootstock cultivar. Up to 98% of existing production relies on only a few scion and rootstock cultivars, leaving the standing crop vulnerable to threats. Pears are faced with a wide range of biotic and abiotic threats and production vulnerabilities, some of which can be limited by integrating resistance and horticultural traits from wild and cultivated materials from around the world. The National Clonal Germplasm Repository (NCGR Corvallis), part of the USDA-ARS National Plant Germplasm System, maintains a large Pyrus collection from across the globe, consisting of 2793 Pyrus accessions from 37 species. The collection represents an important resource for preservation, research, and breeding efforts for pears. The crop vulnerability status of pears in the U.S. is currently moderate to high, with increasing threats and challenges. Breeding and preservation efforts, along with genetic, crop protection and production research are, however, actively targeting these needs.

The Combination of Citrus Rootstock and Scion Cultivar Influences Trioza erytreae (Hemiptera: Triozidae) Survival, Preference Choice and Oviposition.

Trioza erytreae (Del Guercio, 1918) (Hemiptera: Triozidae) is a citrus pest which produces gall symptoms on leaves and transmits bacteria associated with the citrus disease Huanglongbing, 'Candidatus Liberibacter' spp. In the present work, the biology and behaviour of T. erytreae were studied in different rootstock-cultivar combinations. Six rootstocks were used, Flying dragon (FD), 'Cleopatra' mandarin (CL), Carrizo citrange (CC), Forner-Alcaide no.5 (FA5), Forner-Alcaide no.517 (FA517) and Citrus macrophylla (CM), and six scion cultivars: 'Star Ruby', 'Clemenules', 'Navelina', 'Valencia Late', 'Fino 49' and 'Ortanique'. Survival and oviposition were evaluated in a no-choice trial, and preference in a choice trial, all of them under greenhouse conditions. Trioza erytreae did not show a clear settle preference for any citrus combination. However, it was able to lay more eggs in 'Fino 49' grafted on CC than on FD. In terms of survival, 'Ortanique' grafted onto FA5 was more suitable than when grafted onto FA517, and in the case of 'Valencia Late', when it was grafted onto CM rather than CC. Our results showed that T. erytreae behave differently depending on the citrus combination.

Both the scion and rootstock of grafted grapevines influence the rhizosphere and root endophyte microbiomes, but rootstocks have a greater impact

BackgroundSoil microorganisms play an extensive role in the biogeochemical cycles providing the nutrients necessary for plant growth. Root-associated bacteria and fungi, originated from soil, are also known to influence host health. In response to environmental stresses, the plant roots exude specific molecules influencing the composition and functioning of the rhizospheric and root microbiomes. This response is host genotype-dependent and is affected by the soil microbiological and chemical properties. It is essential to unravel the influence of grapevine rootstock and scion genotypes on the composition of this microbiome, and to investigate this relationship with plant growth and adaptation to its environment. Here, the composition and the predicted functions of the microbiome of the root system were studied using metabarcoding on ten grapevine scion-rootstock combinations, in addition to plant growth and nutrition measurements.ResultsThe rootstock genotype significantly influenced the diversity and the structure of the bacterial and fungal microbiome, as well as its predicted functioning in rhizosphere and root compartments when grafted with the same scion cultivar. Based on β-diversity analyses, 1103P rootstock showed distinct bacterial and fungal communities compared to the five others (RGM, SO4, 41B, 3309 C and Nemadex). The influence of the scion genotype was more variable depending on the community and the investigated compartment. Its contribution was primarily observed on the β-diversity measured for bacteria and fungi in both root system compartments, as well as for the arbuscular mycorrhizal fungi (AMF) in the rhizosphere. Significant correlations were established between microbial variables and the plant phenotype, as well as with the plant mineral status measured in the petioles and the roots.ConclusionThese results shed light on the capacity of grapevine rootstock and scion genotypes to recruit different functional communities of microorganisms, which affect host growth and adaptation to the environment. Selecting rootstocks capable of associating with positive symbiotic microorganisms is an adaptation tool that can facilitate the move towards sustainable viticulture and help cope with environmental constraints.

Rootstocks on the Nutritional Status of Seedlings of the Main Mango Cultivars of the São Francisco Valley

ABSTRACT Mango is the fruit most exported by Brazil, with a significant increase in cultivated area in recent years. However, the orchards have been made up of seedlings produced by the grafting process, but without identifying the most suitable rootstock for each cultivar, which affects the competitiveness of mango farming, since the rootstock affects, among other factors, the growth and nutrient absorption from the canopy cultivar. The objective of this study was to evaluate the nutritional status and mineral nutrition of ‘Palmer,’ ‘Tommy Atkins,’ ‘Kent’ and ‘Keitt’ mango seedlings grafted onto the polyembryonic rootstocks Capucho, Coquinho and Espada. The experiment was carried out between October 2019 and May 2020 at the Fruit Growing Nursery of the Agricultural Sciences Campus of the Federal University of Vale do São Francisco (UNIVASF), in Petrolina-PE, in a 3 × 4 factorial scheme, corresponding to three polyembryonic rootstocks (Espada, Capucho and Coquinho) and four crown cultivars (‘Palmer,’ ‘Keitt,’ ‘Kent’ and ‘Tommy Atkins’), with five replications of ten plants each. Leaf contents of macronutrients (N, P, K, Ca), micronutrients (Cu and Fe) and silicon depend on the scion (Tommy Atkins, Palmer, Keitt and Kent) x rootstock (Espada, Capucho and Conquinho) combination. The leaf contents of S, Mg, B, Mn and Mo in the scion are affected by the rootstock adopted for mango propagation In general, for macro and micronutrient absorption purposes, the sword rootstock and the ‘Keitt’ cultivar are the best combination for most of the variables analyzed in the research. The effect of rootstock on the nutritional status of scion cultivars (Tommy Atkins, Palmer, Keitt and Kent) must be taken into consideration when interpreting crop nutrition.

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.

Walnut growers want rootstocks that can resist diseases

Abstract: English walnuts are the walnut species of choice for nut production. In the United States, edible English walnuts are almost exclusively produced in California, using soil and water resources on more than 370,000 acres. Scion cultivars of English walnuts are grafted onto rootstocks. Traditional rootstocks are seedling populations of so-called Paradox hybrids generated from crosses of black walnut with English walnut. These rootstocks are susceptible to soil-borne diseases, including crown gall, Phytophthora root and crown rot, and plant-parasitic nematodes. Strategies to respond to these diseases include the use of newly developed clonal walnut rootstocks with genetic resistance. In a survey conducted during 2020 through 2021, walnut growers revealed their willingness to pay higher prices for clonal walnut rootstocks with some disease resistance. The survey showed that they were most concerned with crown gall and nematodes, and were willing to pay significant price premiums for rootstocks that are resistant to these pathogens.

Rootstock effects on leaf function and isotope composition in apple occurred on both scion grafted and ungrafted rootstocks under hydroponic conditions.

Rootstocks are used in modern apple production to increase productivity, abiotic and biotic stress tolerance, and fruit quality. While dwarfing for apple rootstocks has been well characterized, the physiological mechanisms controlling dwarfing have not. Previous research has reported rootstock effects on scion water relations. Root architecture and variability in soil moisture across rooting depths can also contribute to these differences among rootstocks in the field. To exclude these effects on rootstock behavior, scions were grafted onto four different rootstocks with varying effects on scion vigor (B.9, M.9, G.41 and G.890). Non-grafted rootstocks were also grown to examine whether the effects of rootstock occurred independently from scion grafting. Plants were grown in a greenhouse under near steady-state hydroponic conditions. Carbon (δ13C), oxygen (δ18O) and nitrogen (δ15N) isotope composition were evaluated and relationships with carbon assimilation, water relations, and shoot growth were tested. Rootstocks affected scion shoot growth, aligning with known levels of vigor for these four rootstocks, and were consistent between the two scion cultivars. Furthermore, changes in water relations influenced by rootstock genotype significantly affected leaf, stem, and root δ13C, δ18O, and δ15N. Lower δ13C and δ18O were inconsistently associated with rootstock genotypes with higher vigor in leaves, stems, and roots. G.41 had lower δ15N in roots, stems, and leaves in both grafted and ungrafted trees. The effects of rootstock on aboveground water relations were also similar for leaves of ungrafted rootstocks. This study provides further evidence that dwarfing for apple rootstocks is linked with physiological limitations to water delivery to the developing scion.

Thermotolerance of tomato plants grafted onto wild relative rootstocks.

Heat stress is a major environmental constraint limiting tomato production. Tomato wild relatives Solanum pennellii and S. peruvianum are known for their drought tolerance but their heat stress responses have been less investigated, especially when used as rootstocks for grafting. This study aimed to evaluate the physiological and biochemical heat stress responses of tomato seedlings grafted onto a commercial 'Maxifort' and wild relative S. pennellii and S. peruvianum rootstocks. 'Celebrity' and 'Arkansas Traveler' tomato scion cultivars, previously characterized as heat-tolerant and heat-sensitive, respectively, were grafted onto the rootstocks or self-grafted as controls. Grafted seedlings were transplanted into 10-cm pots and placed in growth chambers set at high (38/30°C, day/night) and optimal (26/19°C) temperatures for 21 days during the vegetative stage. Under heat stress, S. peruvianum-grafted tomato seedlings had an increased leaf proline content and total non-enzymatic antioxidant capacity in both leaves and roots. Additionally, S. peruvianum-grafted plants showed more heat-tolerant responses, evidenced by their increase in multiple leaf antioxidant enzyme activities (superoxide dismutase, catalase and peroxidase) compared to self-grafted and 'Maxifort'-grafted plants. S. pennellii-grafted plants had similar or higher activities in all antioxidant enzymes than other treatments at optimal temperature conditions but significantly lower activities under heat stress conditions, an indication of heat sensitivity. Both S. pennellii and S. peruvianum-grafted plants had higher leaf chlorophyll content, chlorophyll fluorescence and net photosynthetic rate under heat stress, while their plant growth was significantly lower than self-grafted and 'Maxifort'-grafted plants possibly from graft incompatibility. Root abscisic acid (ABA) contents were higher in 'Maxifort' and S. peruvianum rootstocks, but no ABA-induced antioxidant activities were detected in either leaves or roots. In conclusion, the wild relative rootstock S. peruvianum was effective in enhancing the thermotolerance of scion tomato seedlings, showing potential as a breeding material for the introgression of heat-tolerant traits in interspecific tomato rootstocks.

Productivity and Physicochemical Properties of the BRS Isis Grape on Various Rootstocks under Subtropical Climatic Conditions

Brazil has emerged as a significant producer of seedless grapes due to high consumer demand. This has led to increased production of seedless grapes in non-traditional cultivation regions, such as subtropical areas. To meet this demand, the search for new grape varieties suitable for these conditions, such as the ‘BRS Isis’ variety, has become an option for growers. The interaction between grape cultivars and rootstocks is specific, and their adaptability to climatic conditions can result in uneven performance. Therefore, the choice of rootstock should be considered before making any recommendations. The purpose of this study was to assess the productive performance, physical-chemical, and biochemical properties of the ‘BRS Isis’ vine grafted onto rootstocks (‘IAC 572’, ‘IAC 766’, and ‘Paulsen 1103’) in two production cycles. The experimental design consisted of randomized blocks, with seven blocks and three plants per plot, for a total of 63 vines. Thus, the vine’s income components, physical qualities of bunches and berries, chemical profile, bioactive substances, and antioxidant activity were assessed. The Tukey test (5% probability) was used to compare means between rootstocks. The data on scion cultivar and rootstock pairings were further evaluated using principal component analysis (PCA). There were substantial variations in the rootstocks, with ‘IAC 572’ and ‘IAC 766’ producing more bunches, generating more fresh mass, and having a longer bunch length than ‘Paulsen 1103’. However, phenolic compounds and flavonoids were greater in ‘BRS Isis’ grapes than in ‘Paulsen 1103’. ‘BRS Isis’ shows good adaptation to subtropical environments when employing the IAC 572 and IAC 766 rootstocks due to their higher yield and bioactive component accumulation compared to grapes grafted onto ‘Paulsen 1103’. However, regardless of the rootstock utilized, ‘BRS Isis’ grapes perform well commercially in subtropical environments.

Effects of Rootstock and Location on Open Field ‘BHN 589’ and ‘Nebraska Wedding’ Grafted Tomato Yield

Grafted tomato (Solanum lycopersicum) production is popular, particularly in high tunnels, because grafted plants can mitigate soilborne disease incidence in highly infested soils and increase water and nutrient use efficiency and crop yield and quality. However, these potential benefits are not as well documented in open field production systems with less disease pressure. The objective of this study was to quantify the effect of tomato grafting on fruit yield, number, and size across 2 years (2018 and 2019) and three diverse open-field production environments in Nebraska (Lincoln, North Platte, and Dwight). At each location, a scion from one of two determinant fresh market tomatoes, ‘Nebraska Wedding’ (heirloom) or ‘BHN 589’ (commercial hybrid), were grafted onto one of two rootstocks, ‘Estamino’ and ‘Maxifort,’ and the nongrafted scion cultivars were controls. In year 2, a fertilizer treatment was introduced (0 and 50 kg·ha−1 N). Ripe tomatoes were harvested weekly, sorted as marketable or cull, counted, and weighed fresh. No marketable or total yield benefits of grafting were observed in 2018 for any scion by rootstock combination across locations. Marketable yield of grafted plants was reduced by 32% in Lincoln. However, grafted ‘Nebraska Wedding’ plants (regardless of rootstock) in North Platte (with coarse-textured, lower organic matter soil) increased fruit number (but not yield) by 50% to 63%. In 2019, grafting ‘BHN 589’ to ‘Maxifort’ increased total tomato yield by 24% across all locations. The heirloom variety Nebraska Wedding did not benefit from grafting in 2019. ‘Estamino’ rootstock did not increase tomato yield, number, or size for either scion variety in either year. Nitrogen fertilizer increased yield as expected in 2019, but grafted plants did not perform better than nongrafted under reduced nitrogen fertility. Results from this study suggest that grafting is not consistently beneficial to ‘BHN 589’ and ‘Nebraska Wedding’ in open field production systems in Nebraska, particularly if there are no known soilborne disease issues.

Rootstock mediated alteration in morphology and photosystem in sweet orange (Citrus sinensis) scion cv. Pusa Sharad under NaCl stress

There is a dearth of rootstock studies on how salinity stress imparts tolerance to the scion cultivar in citrus [Citrus sinensis (L.) Osbeck]. The impact of sodium chloride on sweet orange cv. Pusa Sharad (PS) grafted on 11 different rootstocks i.e. Jatti khatti (JK), X–639 (X9), CRH–12 (C12), NRCC–1 (N1), NRCC–2 (N2), NRCC–3 (N3), NRCC–4 (N4), NRCC–5 (N5), Troyer citrange (TC), CRH–47 (C47) and Cleopatra mandarin (CM) was evaluated at the nursery unit of ICAR-Indian Agricultural Research Institute, New Delhi, during 2019–22. Irrigation water containing 30 and 60 mM of sodium chloride (NaCl) was applied to scion/rootstock combinations in comparison to control (without NaCl) till the onset of salt injury symptoms i.e. 42 days. Under salinity stress, the PS scion grafted onto CM, X9, C47, N1, and N3 rootstocks exhibited minimum reduction in the scion height, leaf area ratio, root to shoot ratio, total chlorophyll content, total carotenoid content, transpiration rate, photosynthesis rate, internal CO2 concentration and stomatal conductance as compared to PS scions grafted onto JK, C12, N2, N4, N5, and TC rootstocks under 60 mM NaCl stress. Results showed that specific rootstock can enhance salt-tolerance potential by increasing pigment content and strengthening the photosystem. PS scions grafted onto CM, C47, X9, N1, and N3 demonstrated greater NaCl tolerance compared to those grafted onto JK, C12, N2, N4, N5, and TC and hence recommended for areas having salinity level up to 60 mM.

Rootstock influence on performance of different citrus scion cultivars: A review

Citrus is one of the most important fruit crop of Pakistan in terms of area and production. Pakistan ranks 7th according to area and 13th according to production. While comparing with leading citrus producing nations like Brazil, USA, China and Spain, citrus production of Pakistan is far behind and increasing at an average annual rate of only 5%. Brazil holds the 35% share in total citrus production of world while share of Pakistan is only 1.46%. Citrus cultivars are propagated asexually through grafting and budding on specific rootstocks. Rootstocks play very important role in Citriculture industry and decide success or failure of citrus cultivation. Under a specific and uniform set of climatic and soil conditions, citrus rootstocks tend to vary in their compatibility with a specific scion cultivar. The rootstocks have significant influence overall growth of tree including vegetative growth, mineral uptake, physiological performance of scion cultivar and reproductive growth of scion cultivars. The role of rootstocks in manipulating or improving the performance of citrus scion cultivars has been discussed in present review. Keywords: Citrus, rootstocks, physiology, vegetative, reproductive

Relative contribution of season, site, scion and rootstock genotype, and susceptibility to European canker to the variability in bacterial and fungal communities in apple leaf scar tissues

AbstractNeonectria ditissima infects apple trees through wounds, causing European canker. In the UK, the most important entry site for N. ditissima is leaf scar. Specific apple endophytes may contribute to cultivar resistance/tolerance to the pathogen. We assessed the relative effect of location, sampling time (season), and rootstock/scion genotype on bacterial and fungal endophyte communities in the apple leaf scar tissues of current‐season extension shoots and identified Operational Taxonomic Units (OTUs) with differential abundance between canker resistant and susceptible scions, and between rootstocks. Leaf scar tissues were sampled from two orchards at three times (10/2018, 06/2019 and 10/2019) for eight scion cultivars, each grafted onto two rootstocks, for profiling 16S and ITS rRNA regions. Endophyte composition was primarily affected by season (autumn vs. spring) and location (sites and blocks within site). There was a significant reduction in the community size in the spring, particularly for fungi, and species turnover between autumn and spring. This seasonal dynamics suggest that to protect leaf scars from N. ditissima infection in the autumn specific endophytes suppressing canker may have to be augmented annually around the leaf‐fall time. Scion and rootstock genotypes had limited effects on the endophyte community. A group of resistant cultivars differed from a group of susceptible ones in the relative abundance of many bacterial and fungal OTUs, most of which had low reads numbers. Nevertheless, several OTUs with high reads numbers differed in their relative abundance between resistant and susceptible scions, including OTUs from Sphingomonas, Methylobacterium, Vishniacozyma and Rhodotorula babjevae, and warrant further investigation for their potential role in host resistance/tolerance against N. ditissima.

Germplasm Diversification in Citrus Orchards in a Mesothermal Climate in Brazil

The limited scion-rootstock combinations used in sweet orange orchards in Brazil reduce the commercial potential of citrus and lead to greater susceptibility to pests and diseases. Aiming to provide germplasm diversification, the research evaluated the Folha Murcha (FM) and Charmute de Brotas (CB) orange trees grafted onto ‘Rangpur’ lime (RL) and ‘Swingle’ citrumelo (SC) rootstocks. The study was conducted in the southern center of the state of São Paulo, in the subtropical region of southeastern Brazil. The grafted trees were planted in September 2016. The field experiment was conducted over two seasons. The combinations were evaluated based on the duration in days and degree-days of the phenological intervals, growth and yield performance, alternate bearing, fruit ripening, and quality. The trees of the two scion cultivars grafted onto RL had the shortest crop cycle, the earliest fruit ripening, and the largest canopy volume. SC produced fewer alternate bearings with greater production efficiency. The CB/SC combination produced fruits with a better color index, higher total soluble solids content, and a higher technological index. This assessment can be useful in planning orchards for dual-purpose markets, such as table fruit and the juice industry.