Rootstock Trial Research Articles

Effects of extra potassium supply and rootstocks indicate links between water, solutes and energy in Shiraz grapevines (Vitis vinifera) pericarps.

Potassium (K) is essential for the development of grapevines (Vitis vinifera ), accumulating into berries during maturation. Elevated K has been associated with high sugar and low acidity in juice. Characterising the accumulation patterns of K and other components in pericarps treated with various experimental factors may indicate potential regulators of berry K levels. A soil fertiliser trial using nutrient solutions with two K supply rates was conducted on potted Shiraz vines during berry ripening. Doubled-K supply increased L-malic acid content in the early-ripening phase, and increased K and magnesium concentrations in the late-ripening phase. Doubled-K supply reduced the ratio of K to sodium in later ripening phases, suggesting that the accumulation of K relative to sodium was limited in more mature berries supplied with extra K. Pericarp water percentage, sugar, K and ATP were correlated in both treatments, indicating links between hydration, solute transport and energy in maturing berries. In a separate rootstock trial over the two growing seasons, Shiraz scions grafted onto 420-A rootstock produced berries with lower K concentration and content than those grafted onto Ramsey or Ruggeri-140 rootstocks and own-rooted vines. This study demonstrated that the K supply and berry ripening phase impacted the berry K level.

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.

Rootstocks Alter the Seasonal Dynamics and Vertical Distribution of New Root Growth of Vitis vinifera cv. Shiraz grapevines

Minirhizotron tubes were installed to monitor root growth dynamics of mature Shiraz grapevines in a rootstock trial established in the hot climate Riverina region of New South Wales, Australia. The vertical root distribution and seasonal root growth dynamics of Shiraz on own-roots and Shiraz grafted on the rootstocks Ramsey, 140 Ruggeri and Schwarzmann was studied for five seasons across a seven-year period to a depth of 60 cm. New root production was significantly influenced by genotype, soil depth, season, growth stage and year. Soil moisture and soil temperature were monitored at 10, 30 and 60 cm in the last two seasons. Soil moisture at 30 cm and soil temperature at all three depths were significant predictors of root growth. New root numbers were significantly higher in 140 Ruggeri than the other rootstocks. To the depth studied, 140 Ruggeri roots were evenly distributed from the topsoil down, whereas the majority of roots of Schwarzmann and Shiraz were located at intermediate depths in the 10–40 cm ad 20–40 cm zones respectively, while Ramsey roots were found at 20 cm or below. Depending on genotype, root growth occurred across several phenological stages but tended to peak at flowering. In some years we observed root growth in early and late winter at rates exceeding that of autumn, and this was associated with warmer temperatures during this period. In general, the seasonal dynamics of root growth attributes were found to be influenced by abiotic factors, but mainly determined by genotype. The insights gained from this study can help us better understand the interplay between rootstock, environment, and management, and predict how different rootstock genotypes may perform under changing climatic conditions.

Decision support system for selecting the rootstock, irrigation regime and nitrogen fertilization in winemaking vineyards: WANUGRAPE4.0

We aim to develop and transfer to the wine sector a decision support system (DSS) in the frame of WANEGRAPE4.0 project that, integrated into a geographic information system, helps wine growers in i) selecting the most suitable rootstock given some agroecological conditions and oenological objectives; and ii) managing irrigation and nitrogen fertilization in the most suitable way for the selected rootstock and agroecological conditions. The following goals have been achieved. First, the modular structure and information flow of the DSS has been defined. Second, the main algorithms of the water balance module (DSS core part) have been formulated and the module coded in a spreadsheet. Third, this water balance module has been tested with data from field experiments in several regions of Spain. Fourth, the relationships between grapevine water status and production and harvest quality variables have been established, revealing an always-significant effects of the decrease in water stress on vegetative development, yield, and grape composition. Fifth, the nitrogen fertilizer effects on vine performance has been assessed. Sixth, the effects rootstocks have on 5 parameters of vine production and grape quality for winemaking have been established too by doing another meta-analysis of rootstock trials. Seventh, a rootstock selection module has been defined. The WANUGRAPE4.0 project goes on with the integration of all its modules, their coding in a World Wide Web language and their publication on an Internet portal.

X-ray imaging of 30year old wine grape wood reveals cumulative impacts of rootstocks on scion secondary growth and Ravaz index.

Annual rings from 30year old vines in a California rootstock trial were measured to determine the effects of 15 different rootstocks on Chardonnay and Cabernet Sauvignon scions. Viticultural traits measuring vegetative growth, yield, berry quality, and nutrient uptake were collected at the beginning (1995 to 1999) and end (2017 to 2020) of the lifetime of a vineyard initially planted in 1991 and removed in 2021. X-ray Computed Tomography (CT) was used to measure ring widths in 103 vines. Ring width was modeled as a function of ring number using a negative exponential model. Early and late wood ring widths, cambium width, and scion trunk radius were correlated with 27 traits. Modeling of annual ring width shows that scions alter the width of the first rings but that rootstocks alter the decay of later rings, consistently shortening ring width throughout the lifetime of the vine. Ravaz index, juice pH, photosynthetic assimilation and transpiration rates, and instantaneous water use efficiency are correlated with scion trunk radius. Ultimately, our research indicates that rootstocks modulate secondary growth over years, altering physiology and agronomic traits. Rootstocks act in similar but distinct ways from climate to modulate ring width, which borrowing techniques from dendrochronology, can be used to monitor both genetic and environmental effects in woody perennial crop species.

Establishment performance of the 2017 NC-140 vigor-limiting peach rootstock trial across ten sites in North America

Establishment performance of the 2017 NC-140 vigor-limiting peach rootstock trial across ten sites in North America

EUFRIN apple rootstock trials: first results across Europe

EUFRIN apple rootstock trials: first results across Europe

Influence of Citrus Rootstocks on Scion Growth, Hormone Levels, and Metabolites Profile of ‘Shatangju’ Mandarin (Citrus reticulata Blanco)

Dwarfing rootstocks are a valuable genetic resource for managing high-density plantations. The selection of the appropriate scion/rootstock combination is key to improving crop performance and sustainable production in a particular environment and specific training systems. ‘Shatangju’ mandarin scion cultivar grafted onto ‘Flying Dragon’ rootstock tends to be dwarfing and develops short stature plants. To obtain insight into potential mechanisms underlying rootstock-induced dwarfing effects, we conducted a rootstock trial to examine the influence of 11 different rootstocks based on their growth vigor, antioxidants, and hormonal levels of the scion cultivar. The phenotypic observations revealed that size reduction in the ‘Flying Dragon’ rootstock is due to lower node number, shorter internodal length, and a reduced trunk diameter of the scion compared with more vigorous rootstocks. Antioxidant analysis showed that ‘Shatangju’ mandarin grafted onto ’Flying Dragon’ and ‘Trifoliate Orange’ rootstock had significantly lower peroxidase (POD) activity than other tested rootstocks. The hormonal analysis indicated that there were markedly lower amounts of abscisic acid (ABA) in ‘Shatangju’ mandarin grafted with ‘Flying Dragon’ rootstock. In addition, trees grafted with ‘Sour Pummelo’ and ‘Flying Dragon’ depicted minimum amounts of gibberellins (GA24). Moreover, several metabolites associated with organic acids, flavonoids, amino acids, and alkaloids responded differently in plants grafted with ‘Flying Dragon’ (dwarfing) and ‘Shatang Mandarin’ (vigorous) rootstocks. This study concluded that ‘Flying Dragon’ rootstock with a strong dwarfing effect has been proposed to improve high-density cultivation methods. These findings will provide useful insights for future research associated with rootstock-mediated dwarfing mechanisms of citrus rootstocks.

Using rootstocks to lower berry potassium concentrations in 'Cabernet Sauvignon' grapevines

Potassium is the most abundant cation in grape berries. It has important roles in grapevine physiology and winemaking. This study investigates the feasibility of using rootstocks to lower berry potassium concentrations ([K]) in 'Cabernet Sauvignon' grapevines. The ultimate target is to achieve lower pH and higher titratable acidity (TA) in grape juice so as to bring down the cost of acid adjustment during winemaking. The specific objective here is to provide new insights into the potential of particular rootstocks to modify K uptake by 'Cabernet Sauvignon' grapevines and their partitioning and accumulation into grape berries. The vineyard soils of a replicated rootstock trial located in the Limestone Coast of South Australia were characterised. Petiole, berry and juice nutrient content were assessed at oenological maturity of 'Cabernet Sauvignon' grown on eight different rootstocks. Rootstock had an impact on cations of the vegetative tissue of 'Cabernet Sauvignon', with Merbein 5512 having the lowest petiole [K]. The concentrations of major cations in the berry were, however, not altered by rootstock. While no particular rootstock stood out in limiting 'Cabernet Sauvignon' berry K accumulation, berries grown on the 'Borner' rootstock tended to have slightly lower concentrations (< 10 %) relative to vines on their own roots. Across the rootstocks, juice pH tended to increase with greater juice [K], while juice TA tended to decrease with greater juice [K]. It was found that juice TA was higher for the rootstocks 140 Ruggeri and 110 Richter, and juice pH tended to be lower for the rootstocks 110 Richter, 140 Ruggeri, Merbein 5512 and Merbein 5489. There was no effect of rootstock on total soluble solids.

Breeding for Plum pox virus resistant rootstocks by interspecific hybridization of Prunus species – state of the art and preliminary results of rootstock trials

Breeding for <i>Plum pox virus</i> resistant rootstocks by interspecific hybridization of <i>Prunus</i> species – state of the art and preliminary results of rootstock trials

Rootstock breeding for resistance to grapevine decline and dieback in southern Brazil

Grapevine decline and dieback is a serious problem for grape production in southern Brazil. It is characterized by a set of symptoms that lead to the weakening and death of affected plants. The main causes are a root scale, the ground-pearl (Eurhizococcus brasiliensis), associated with soil fungi (Cylindrocarpon, Fusarium, Phaeacrimonium and others), and high-clay-content soils. Apparently, the root wounds caused by ground-pearl under poorly aerated soil conditions allow the entrance of root decay fungi, resulting in plant death. The creation of grape rootstocks resistant to root decay fungi is one objective of the grape breeding program at Epagri, the Agricultural Research Enterprise of Santa Catarina State, Brazil. The first step was the identification of resistance sources. In rootstock trials carried out in areas where high mortality rates were previously observed, all traditional rootstocks were highly susceptible. Vitis caribaea hybrids showed a high level of resistance but also some defects, such as excessive vigor and absence of winter dormancy. Some genotypes of Vitis shuttleworthii and Vitis palmata, originating from the waterlogged soil conditions of the Everglades (Florida, USA), also showed a high level of resistance. However, the performance of these genotypes and their descendants under dry soil conditions was very poor, and more generations of crossing will be necessary to eliminate undesirable characters. The most promising breeding lines resulted from self pollination of the rootstock IAC 572 (V. caribaea × 101-14Mgt). The selection process started from 840 seedlings and resulted in 23 selections that showed no symptoms of vine decline at three different sites. These selections are being evaluated now for productivity and fruit quality in rootstock trials with different scion cultivars.

Prunus rootstock testing for peach tolerance to Pseudomonas and Armillaria diseases in South Carolina

New commercial rootstocks for peach include P. persica seedlings as well as many Prunus interspecific hybrids and plum species. However, no rootstock has been successful in replant infected soils that have the Peach Tree Short Life Syndrome (PTSL) that includes both Pseudomonas syringae canker disease and Armillaria spp. root rot. Four rootstock trials consisting anywhere from 5 to 16 out of 18 total rootstocks were budded with 4 scion cultivars, ‘Flameprince’, ‘Crimson Lady’, ‘Julyprince’ and ‘Fireprince’ and planted in 2012, 2013, 2013, 2015, respectively, in either Edgefield or Oconee Counties in South Carolina, USA. Tree death from bacterial canker (P. syringae) occurred in all sites planted before 2015. Trees on the hybrid or plum species rootstocks except MP-29 had the highest mortality. P. munsoniana selections “1, 2, 3, and 4” had tree death of (24-63%) from either incompatibility or bacterial canker in the 2012 test. Trees on these rootstocks were also ~40 to 50% smaller than the controls after 4 years. Hybrid rootstocks Replantpac, Tempropac, Densipac and Purplepac had PTSL-related mortality of 50, 63, 67, and 33%, respectively for the 2013 ‘Crimson Lady’ planting. Several ‘Julyprince’ trees on Densipac and Tempropac rootstocks have also died from PTSL. The plum hybrid MP-29 had a high survival and semi-dwarfing effect (~50% standard) on the “2” test sites in which it was planted in 2013. Lovell and Guardian® have had minimal PTSL death from bacterial canker but Armillaria has started to kill trees in the 2012 planting site. Another 3-5 years will be necessary to determine Armillaria tolerance, but the new rootstocks appear to have less resistance to bacterial canker than their commercial standard counterparts.

New cherry rootstock and cultivar interactions directly affect orchard profitability

Due to increased production costs, Wasco County Oregon, USA cherry growers have found it difficult to remain profitable in recent years. Despite production increases in the last 30 years, average yields ha(-1) have actually fallen slightly to 10.5 t ha(-1). A newly developed cost of production study determined that at the average price received (US$ 2.14 kg(-1)), the break-even yield for ‘Bing’ cherries is 14 t ha(-1). New scion and rootstock cultivar releases have provided growers with the means to exceed this economic benchmark. In a rootstock trial in The Dalles, Oregon, ‘Bing’ cherries on ‘Krymsk 5’ rootstock yielded 21.0 t ha(-1) and ‘Krymsk 6’ yielded 21.7 t ha(-1) (5th-8th leaf). A new, productive, dwarfing rootstock series released by Michigan State University, named CoretteTM, consisting of five rootstocks: ‘Cass’, ‘Clare’, ‘Clinton’, ‘Lake’ and ‘Crawford’, also showed potential to significantly increase yields. The average number of flowers per leader cross-sectional area for ‘Bing’ on ‘Gisela 6’ was about 10 flowers cm(-2), but ‘Lake’, ‘Clare’ and ‘Crawford’ all had significantly more flowers with ‘Lake’ producing more than 20 flowers cm-2. However, in order to produce quality fruit, fruit on all five rootstocks were thinned to obtain a standard crop load. No differences in average fruit size were found between the five Corette™ rootstocks and the ‘Gisela 5’ and ‘Gisela 6’ controls in 2012 and 2013. The Krymsk rootstocks produced sufficient yields for growers to exceed all costs of production and the Corette™ rootstocks have similar potential. In addition to rootstock effects on yield, differences between cultivars also have a direct effect on profitability. Newly released cultivars offer growers an alternative to low-producing cultivars. Data from a cultivar evaluation trial in The Dalles, Oregon is presented.

Improving profitability: assessment of new rootstocks and planting systems

For over 25 years, rootstocks for sweet cherries are evaluated in different locations in the german federal state of Rhenania Palatinate. They are situated in a vine growing climate and have medium-heavy soils. Replant disease of stone fruit plays a significant role in most orchards. In general, all trees in the rootstock trials are trained as central leader and planted 4.0 to 4.5 m by 2.0 to 3.0 m depending on the expected vigour. In addition to the common performance parameters, tree health, anchorage and tendency for root suckers are observed. In 2013 a new rootstock trial has been established including, inter alia, the new Weigi series and some recent Gisela numbers. In the experimental orchard of Oppenheim, replanted soil can be compared to new land. Up to now, Weigi 2 is slightly more dwarfing but also less productive in this trial what is no disadvantage regarding the fruit size. In the group of semi-dwarfing rootstocks Weigi 1, Weigi 3, Gisela 13 and Gisela 17 seem to be similar both in vigour and yield efficiency. In this group there is an interest to replace PiKu 1 which turned out to be not winter hardy enough and susceptible to heavy soils and bark beetles under German conditions. Training trials revealed that also with low tree forms, yields and qualities comparable to the spindle can be obtained. The picking performance can be improved in many cases. Mechanical pruning only makes sense if it is combined with manual correction pruning. An exclusive mechanical pruning reduces the fruit size and can also reduce the picking performance.

Application of a MITE Citrus apomixis marker in the Australian rootstock breeding program

Australia's citrus breeding efforts are small by international standards, and unashamedly focused on conventional approaches. Molecular markers had not yet been used in the program because they failed to meet our four essential criteria of being: linked to a trait of economic significance; technically difficult to phenotype by conventional methods; temporally difficult to phenotype by conventional methods and; likely controlled by a simple genetic mechanism. This situation changed dramatically with the 2017 publication of a miniature inverted-repeat transposable element (MITE) marker that co-segregated with the Citrus apomixis trait. This met all of the above four criteria and was quickly verified on local germplasm. Application of this MITE marker is now a standard screening procedure in our rootstock breeding research. An extensive network of field rootstock trials is used to identify parents for rootstock breeding, and the resulting segregating populations are nursery-screened within 18 months of sowing for tolerance to phytophthora, resistance to CTV, and salt exclusion using conventional screening techniques. Hybrids that survive this screening are then assessed for apomixis using the MITE marker. Monoembryonic and polyembryonic hybrids are both useful for future breeding, but those with apomixis have more immediate commercial application. Consequently, putative apomictic hybrids are propagated in greater numbers (via cuttings) to maximise replication and data precision in rootstock field trials. Use of the MITE marker has enabled maximum replication of putative apomictic hybrids, dramatically reducing the size and cost of field trials and hastened the establishment of seed-source trees. We consider it to be the first useful molecular marker in citrus breeding.

Evaluation of Rootstocks on Harvest Metrics of ‘Pinot Noir clone 02A’ Wine Grapes in Maritime Western Washington

The Puget Sound American Viticulture Area (AVA), located west of the Cascade Mountain Range in Washington State, is a large and uniquely situated area with diverse topography and mesoclimates. Given the young age of the AVA, little formal information exists on the appropriate rootstock–scion combination in wine grapes (Vitis vinifera) for the region. This project reports on a series of rootstock trials from 2003 to 2007, which evaluated the influence of ‘420A Millardet et de Grasset’, ‘3309 Couderc’, ‘101-14 Millardet et de Grasset’ (all Vitis hybrids), and a self-rooted control on basic harvest metrics of the wine grape scion ‘Pinot noir clone 02A’. At the warmer site in Everson, WA, rootstocks had no effect on final juice harvest metrics measured by soluble solids, titratable acidity (TA), and pH. At the cooler site in Mount Vernon, WA, the use of rootstocks did not always influence soluble solids or pH but did reduce final harvest TA, a desired effect for the region that is typified by low sugar–high TA wines. Even with a reduction in TA in some rootstock–scion combinations, overall, TA remained at the upper end or above the range typically desired for many wine styles.

Ultra-high-throughput DArTseq-based silicoDArT and SNP markers for genomic studies in macadamia.

Macadamia (Macadamia integrifolia, M. tetraphylla and hybrids) is an Australian native nut crop and has a significant economic value in the food industries worldwide. Long juvenility along with traditional breeding strategies impede quick genetic improvement of this crop. The existing cultivars constitute only second to fourth generation of the wild germplasm in the rainforest. The utilisation of molecular markers for genomic selection and genome-wide association studies may accelerate genetic gains. Identification of a robust, reproducible, and cost-effective marker system is instrumental in increasing the efficiency of genomic studies. This study is the first to report the potential of two ultra-high-throughput diversity array technology (DArT) markers (silicoDArT and SNP) in macadamia. Both markers were used to identify the genetic diversity and population structure in 80 macadamia cultivars. Parentage analysis of 25 scions in a rootstock trial was conducted to confirm plant identity where recorded identities did not corroborate with phenotypic field observations. A total of 22,280 silicoDArT and 7,332 SNP markers were reported, of which 11,526 silicoDArT and 3,956 SNP markers were used for analyses after screening with quality control parameters including >95% call rate, >95% reproducibility, and >0.05 one ratio. The average polymorphic information content (PIC) values of silicoDArT and SNP markers were 0.29 and 0.21, respectively. Genetic variance among the cultivars ranged from 0.003 to 0.738 in silicoDArT and 0.004 to 0.412 in SNP markers. Four distinct population groups were identified from SNP data analysis. Most of the accessions used in this study were descended from two or more populations. Cluster analysis clearly separated genotypes of distinct origins, such as the Hawaii Agricultural Experiment Station and Hidden Valley Plantation accessions. Two wild accessions of Macadamia jansenii and M. ternifolia were found to be distantly related to the cultivars. Wild germplasm individuals and their hybrids with cv. ‘660’ formed separate clusters, suggesting that crossing between wild and cultivated genepools can extend genetic diversity. DArTseq-based SNP markers were successfully utilized to confirm the genetic identity of 25 scions in a rootstock trial. Our study suggests that DArT platforms are a robust system for the facilitation of genomic studies with regard to macadamia.

Apple rootstock trials at Warsaw University of Life Sciences-SGGW, Poland

valuation of 22 dwarfing and semi-dwarfing apple rootstocks for several scion cultivars was conducted on fertile soil in the years 1995–2010. It was found that most of the new rootstocks performed similarly to M.9 EMLA with respect to vigour, yield, cropping efficiency and fruit mass. These rootstocks would not be, therefore, a good replacement for M.9 in Polish climatic conditions. The most promising rootstock was B 9 and some of its derivatives, e.g., B 146, B 396, P 59 and P 60. However, their suitability may be limited to particular cultivars grown under similar soil conditions.

English

Plant species of Solanaceae family are affected by numerous pathogens worldwide. Among them is the root-knot nematode which hinders the establishment of crops in the field, reducing their production capacity. This work aims to select Solanaceae species tolerant or resistant to root-knot nematode under the climatic conditions of Fortaleza, Cear&aacute;. Two experiments were performed. For both, the followings were evaluated: &#39;Santa Clara&#39; tomato, hybrid &#39;T92&#39;, cherry &#39;Carolina&#39; and &#39;Laranja&#39;; gilo &lsquo;Comprido Grande Rio&rsquo;; eggplant &lsquo;Comprida Roxa&rsquo;; Pepper &#39;Cayenne&#39;; and chili &#39;All Big&#39;. Each treatment had six replicates. In the first trial, the number of twigs and egg masses per root, the aboveground height and fresh root weight at 60 days after inoculation (DAI) were evaluated. In the second trial, the reproduction factor of the 130 DAI, total number and weight of fruits, as well as productivity were evaluated. The tomato &lsquo;Santa Clara&#39;, &#39;Carolina&#39;, &#39;Laranja&#39;, the eggplant and gilo had the major infestations of Meloidogyne incognita; however, only tomato &#39;Santa Clara showed decreased productivity among all the cultivars. On the other hand, in the hybrid &#39;T92&#39; and chili, there was no nematode reproduction, no eggs mass and reproduction factor was zero. Thus, it is concluded that Pepper &#39;Cayenne&#39;, &#39;All big&#39; Chili &#39;All Big&#39; and &#39;T92&#39; hybrid tomato are immune to Meloidogyne incognita, so they can be tested in resistant rootstock trials for susceptible commercial tomato plants. &nbsp; Key words: Root-knot nematode, Solanum lycopersicum, Solanum melongena, Capsicum annuum, Solanum gilo, Meloidogyne incognita.

The Effect of Three Rootstock Cultivars, Potassium Soil Applications and Foliar Sprays on Yield and Quality of Vitis vinifera L. cv. Ronelle in South Africa

The early black cultivar Ronelle is the major export table grape produced in the northern summer rainfall area of South Arica. In a rootstock trial at Roodeplaat near Pretoria, low yield, poor quality and low export mass as well as typical potassium (K) deficiency symptoms were observed for Ronelle grafted onto 110 Richter, despite K saturation percentages of 6,3% and 6,0% in the topsoil and subsoil respectively. The effect of 500 kg ha-1 and 1 000 kg ha-1 soil-applied K combined with a 0,02% foliar application of K was investigated for Ronelle grafted onto 110 R (V. rupestris x V. Berlandieri), 101-14 Mgt (Y. riparia x V. rupestris) and 143 B Mgt (v. riparia x V. vinifera). The K fertilizer treatments were applied only once, before budbreak. Three foliar sprays were applied annually, at two-week intervals, commencing at 15 cm shoot length. Results after two seasons showed that neither high levels of K fertilizer, nor K foliar sprays improved yield or quality of Ronelle on 110 R. The K content of leaves was not significantly affected by any of the K treatments. Leaf K levels of 110 R were significantly lower compared to those of 143 Mgt, but the leaf K content of all three graft combinations was above the minimum norm. Apparently there is no effective cure for established Ronelle/110 R vineyards with K deficiency problems and it is recommended that the Ronelle/110 R graft combination is not used in future.