Dog Ridge Research Articles

Bio-efficacy and Phytotoxicity of Gibberellic Acid (GA3) Technical 90% for Improving Yield and Quality in Grapes (Vitis vinifera L.)

The experiment was conducted on Thompson Seedless grapevines grafted on dog ridge rootstock to study its response towards the application of gibberellic acid (GA3) Tech. 90% at different time intervals. The experiment was designed in a randomized block design (RBD) having five treatments with four replications were carried out at Maharashtra Rajya Draksha Bagaitdar Sangh, Pune during 2020-2021 & 2021 - 2022. Significant differences were observed with the applications of GA3 at different developmental stages (pre-bloom and fruit set) resulted in to increased bunch weight, berry weight, berry length, berry size, pedicel thickness, rachis length, and quality parameters viz. total soluble solids along with the highest yield per vine exogenous application of different concentrations of GA3 at different time interval schedules was beneficial for the quality and yield of Thompson Seedless grapevines.

Evidence that methoxypyrazine accumulation is elevated in Shiraz rachis grown on Ramsey rootstock, increasing ‘green’ flavour in wine

Background and Aims ‘Green’ sensory characters in Shiraz wines were observed in wines produced from different rootstocks. The compounds responsible were investigated as these attributes are generally seen as negative. Methods and Results GC/MS-olfactometry and stable isotope dilution analysis methods were used to identify and quantify a range of volatile compounds associated with ‘green’ sensory characters in Shiraz wine made from grapes grafted on Ramsey and Dog Ridge rootstocks. These wines were higher in this character compared to wines from Merbein 6262, a low vigour rootstock. GC-olfactometry identified the compound responsible for this intense ‘green’ aroma to be 3-isobutyl-2-methoxypyrazine, which was not detected in Shiraz grape berries but was found at significantly higher concentration in rachis tissue from bunches grown on Ramsey rootstock compared to own-roots. Conclusions Grape rachis inclusion is the most probable cause of the 3-isobutyl-2-methoxypyrazine concentration in the Shiraz wines, and rootstocks can influence the accumulation of methoxypyrazines in the rachis. Significance of the Study Methoxypyrazines in rachis tissues have the potential to impart ‘green’ sensory characters in wines of cultivars not known to produce methoxypyrazines in the berries. Other volatile aroma compounds were found to be affected by rootstocks which may also be useful in targeting rootstocks to give a desired wine style.

Rootstock effects on growth and fruit composition of low‐yielding winegrape cultivars grown in a hot Australian climate

Background and Aims The use of rootstocks to enhance the performance of low-yielding wine cultivars grown under hot irrigated conditions was studied. Methods and Results Field performance and grape composition of low-vigour cultivars (Chasselas, Egiodola, Ehrenfelser, Gamay, Perdea, Reichensteiner and Roussanne) grown as own roots or grafted on rootstocks (1103 Paulsen, Dog Ridge, Ramsey, Schwarzmann and SO4) were assessed over three seasons. Across all cultivars, yield of own roots, SO4 and Schwarzmann was similar. Ramsey and 1103 Paulsen produced a higher yield without a major effect on juice composition. Dog Ridge produced excessive vigour and poor grape composition. Across the scion–rootstock combinations, high vine vigour, yield and berry mass were associated with high juice pH, K+ and malic acid and low tartaric acid. Rootstock effects on juice K+, tartaric and malic acid were stable and independent of the scion cultivar. Conclusions The performance of low-vigour cultivars was enhanced by grafting on 1103 Paulsen and Ramsey. ‘Scion conferred root vigour’ was found under field conditions. Significance of the Study The genetic diversity of cultivars available for wine production can be broadened by adoption of rootstocks for low-vigour cultivars. Rootstock selection requires knowledge of inherent scion vigour and conferred rootstock vigour.

Rootstocks Improve Blanc Du Bois Vine Performance and Fruit Quality on Alkaline Soil

Summary Goals: Blanc Du Bois is the most widely planted Pierce’s Disease (PD) tolerant white wine grape variety in Texas. However, on alkaline soils, which are widespread across the state, nutritional deficiencies have been observed in own-rooted vines. This work evaluated the impact of rootstock on Blanc Du Bois vine growth, nutritional status, and fruit composition on an alkaline vineyard site in the Texas Gulf Coast. Ten rootstocks representing common rootstocks in Texas (Paulsen 1103, Kober 5BB, Teleki 5C), nematode resistant rootstocks (UCD-GRN1, UCD-GRN2, UCD-GRN3, UCD-GRN4 and UCD-GRN5), and rootstocks with believed tolerance to cotton root rot (Phymatotricopsis omnivorum) (Ramsey, Dog Ridge) were studied over a four-year period. Key Findings: UCD-GRN1 rootstock performed poorly as a result of severe magnesium and iron deficiency. Ramsey maintained the most favorable nutritional status and consistently produced the highest pruning weights. Own-rooted Blanc Du Bois had lower fruit quality when compared to most rootstocks (Ramsey, Dog Ridge, UCD-GRN2, UCD-GRN3, UCD-GRN4, UCD-GRN5, Paulsen 1103, Kober 5BB), although vine size (pruning weight) and crop load (yield:pruning weight) were generally comparable. In 2015 and 2016, juice pH positively correlated with juice potassium with concentrations of potassium varying by an average of approximately 20% across rootstocks. On average, own-rooted Blanc Du Bois tissue samples contained 323% more sodium than grafted vines. Impact and Significance: This study demonstrated that Blanc Du Bois can benefit from grafting onto rootstocks on alkaline soils. Own-rooted Blanc Du Bois vines were generally less productive than Paulsen 1103, Dog Ridge, UCD-GRN3, and Ramsey likely as result of nutritional status. Own-rooted Blanc Du Bois also had lower soluble solids at harvest than most rootstocks as a result of diminished nutritional status, although titratable acidity and pH were not consistently different. Delaying harvest did not result in a further increase in soluble solids, although acidity continued to decrease, suggesting that own-rooted Blanc Du Bois was not simply behind in physiological maturity, but rather produced lower quality fruit than most of the rootstocks under study. The poor performance of UCD-GRN1 throughout the study suggests that it is not adapted to alkaline soils.

Evaluation of Grapevine Rootstocks on Slightly Acidic and Strongly Alkaline Texas Hill Country Soils

Summary Goals: Rootstock selection is usually dictated by vineyard site conditions such as pest and disease pressure, soil, and climate. This work evaluated the impact of rootstock on ‘Sangiovese’ vine size, nutritional status, and fruit composition at two sites in the Texas Hill Country, one with a slightly acidic (pH 6.58 ± 0.05) loamy fine sand soil and the other with a moderately to strongly alkaline (pH 8.48 ± 0.06) clay loam soil. Eleven rootstocks representing common rootstocks in Texas (‘Paulsen 1103’, ‘Kober 5BB’, ‘Teleki 5C’), nematode resistant rootstocks (‘UCD GRN-1’, ‘UCD GRN-2’, ‘UCD GRN-3’, ‘UCD GRN-4’ and ‘UCD GRN-5’), and rootstocks with possible tolerance to cotton root rot (Phymatotricopsis omnivora) (Ramsey, Dog Ridge, Florilush) were studied over a five-year period. Key Findings: At the Real County test site, in an alkaline clay loam soil, the rootstocks ‘Dog Ridge’ and ‘Teleki 5C’ maintained the most favorable nutrient status resulting in higher vine vigor and dormant cane pruning weights with pruning weights averaging 0.52 kg/vine and 0.37 kg/vine, respectively, versus 0.09 kg/vine for own-rooted ‘Sangiovese’. The rootstocks ‘Florilush’, ‘UCD GRN-1’, ‘UCD GRN-5’, and own-rooted ‘Sangiovese’ performed poorly at the Real County test site as a result of nutritional deficiency. At the Gillespie County site, in a slightly acidic loamy fine sand soil, all rootstocks performed acceptably with respect to vine size, nutrition, and fruit composition, although average dormant pruning weights over five years ranged across rootstocks from 0.52 to 0.87 kg/vine. Petiole potassium and magnesium were inversely correlated across rootstocks, with the strongest relationship (R2 = 0.58) observed in late summer at the Gillespie County site. Own-rooted ‘Sangiovese’ maintained the lowest petiole potassium and highest petiole magnesium concentrations over the study, as well as the lowest juice potassium and pH at the Gillespie County site. Juice potassium and pH were positively correlated (R2 = 0.57 and 0.76) across rootstocks in two out of three years of study at the Gillespie County site. Impact and Significance: This study demonstrated the importance of rootstock selection on a moderately to strongly alkaline soil versus a slightly acidic soil. Out of the eleven rootstocks tested, only ‘Dog Ridge’ and ‘Teleki 5C’ produced an acceptably sized (0.25 and 0.16 kg/m canopy) mature vine (fourth leaf) likely as a result of nutrition. All rootstocks under study resulted in petiole iron concentrations below recommended values, but the severity of shoot tip chlorosis, which is associated with iron deficiency, was highly rootstock dependent. The rootstocks with the lowest pruning weights and vigor ratings at the Real County site (own-rooted ‘Sangiovese’, ‘Florilush’, ‘UCD GRN-1’, and ‘UCD GRN-5’) generally expressed the most shoot tip chlorosis. Addressing this apparent nutritional deficiency with targeted fertilizer applications may have improved vine performance, but this research suggests that proper rootstock selection is a more viable option. The impact of rootstock was less apparent on slightly acidic loamy fine sand soil. All rootstocks and own-rooted ‘Sangiovese’, conferred acceptable pruning weights, nutritional status, and fruit composition. Basic juice chemistry did vary by rootstock while own-rooted ‘Sangiovese’ having the lowest juice potassium and pH, but the risks of growing own-rooted V. vinifera likely outweigh this potential benefit on sites where climate, soil conditions, pests, or disease may be limiting.

Standardization of surface sterilization protocol for <em>in vitro </em>mass multiplication of grape rootstock dog ridge (<em>Vitis champini </em>P.)

To standardize surface sterilization protocol in grape Dog Ridge rootstock, two types of explants viz., axillary buds and shoot tips were subjected to surface sterilization with sodium hypochlorite (0.25% and 0.5%) for three different duration (5,10 & 15 minutes). Prior to surface sterilization, the explants were pretreated with Carbendazim (0.3% and 0.5%) for 30 min. Pre-treatment of the axillary buds with 0.5% Carbendazim for 30 minutes and surface sterilization with 70% ethanol for 30 seconds followed by 0.5% sodium hypochlorite for 10 minutes under laminar air flow chamber resulted in the highest survival rate (68.33%) with least contamination (15.00%) and mortality (16.67%). However, in shoot tips, the highest survival rate (56.67%) with least contamination (30.00%) and mortality (13.33%) was recorded by pre-treating with 0.3% Carbendazim for 30 minutes and surface sterilization with 70% ethanol for 30 seconds followed by 0.25% sodium hypochlorite for 10 minutes.

Standardization of micropropagation protocol for grape rootstock dog ridge

In the present study, attempt was made to standardize in vitro micropropagation protocol of grape rootstock Dog Ridge. Among two explants compared (axillary bud and shoot tip), axillary buds registered superior shoot proliferation response (75.81%) compared to shoot tips (40.38%) during January to March in Coimbatore conditions. Full strength Murashige and Skoog (MS) medium supplemented with 6-Benzylaminopurine (BAP) 2.0 mg l−1 produced the highest bud sprouting response of explants. Addition of 0.2 mg l−1 1-Naphthaleneacetic acid (NAA) along with BAP 2.0 mg l−1 was found effective for producing maximum number of lengthier multiple shoots within short time and MS medium fortified with BAP 2.0 mg l−1 and gibberellic acid (GA3) 0.5 mg l−1 resulted in elongated shoots. Half-strength MS medium with 2.0 mg l−1 Indole-3 butyric acid (IBA) and 200 mg l−1 activated charcoal resulted in the maximum in vitro root induction of 83.00% within 11.74 days. For hardening of in vitro rooted plantlets, a combination of pot mix (1:1:1 of sand +soil +farm yard manure) and vermicompost in 1:1 proportion was found to be optimum (86.67% ex vitro survival).

Comportamento agronômico de porta-enxertos de videira com resistência ao declínio de plantas jovens nas condições do estado de Santa Catarina

Abstract – Young vine decline caused by the joint action of ground pearl or margarodes (Eurhizococcus brasiliensis) and pathogenic fungi (Cylindrocarpon, Phaeoacremonium and others) is a major problem in many vineyards of the South of Brazil. Resistant rootstocks can be used to reduce the losses caused by this phytosanitary problem; however, these rootstocks are not used on a large scale in the South of Brazil. This study evaluated the agronomic characteristics of the cultivar Moscato Embrapa grafted on these rootstocks, and compared to Paulsen 1103 and R99, which were used as reference. Tropical rootstocks IAC 313 Tropical, IAC571-6 Jundiai and IAC 766 Campinas induced early bud break when compared to Paulsen 1103, unlike VR043- 43 and Dog Ridge. Even tropical rootstocks with no winter dormancy behave as normal rootstocks when grafted. IAC 572 Jales has the advantage of not inducing early bud break but causes excessive vigor, requiring special management practices to control vegetative development

Conversion to Mechanical Pruning in Vineyards Maintains Fruit Composition while Reducing Labor Costs in ‘Merlot’ Grape Production

A field study was conducted for three consecutive seasons in the hot climate of central California to assess the performance of ‘Merlot’ grapevine (Vitis vinifera) grafted onto ‘Freedom’ [Fresno 1613-59 × Dog Ridge 5 (27% V. vinifera hybrid)] during training system conversion to facilitate mechanization. The traditional head-trained and cane-pruned (CP) system was either retained or converted either to a bilateral cordon-trained, spur-pruned California sprawl training system (HP), or to a bilateral cordon-trained, mechanically box-pruned single high-wire sprawling system (SHMP). After the conversion, SHMP sustained greater yield with more clusters per vine and smaller berries without affecting the canopy microclimate. This was due to a higher number of nodes retained after dormant pruning. The SHMP canopies, compared with CP and HP; filled allotted canopy space earlier based on photosynthetically active radiation (PAR) transmitted through the canopies, populating the space allotted per vine, favoring higher production efficiency. There were no adverse effects of training systems on berry composition or flavonoid concentration, during or after conversion to mechanical management. However, experimental year effect was obvious on anthocyanin composition of ‘Merlot’ berries, increasing trihydroxylated (i.e., delphinidin-based) anthocyanins in the latter years of the experiment. Our results also provided evidence that earlier canopy growth coupled with sufficient reproductive compensating responses allowed for increased yields while reaching commercial maturity without a decline in anthocyanin content with the SHMP. Converting CP to SHMP reduced labor operations costs by 90%. Furthermore, the SHMP had greater gross revenue and resulted in greater net income per acre even when the conversion year was taken into account. Therefore, SHMP is recommended for growers within the hot climate of the central San Joaquin Valley as a means to maintain productivity of vineyards while not sacrificing berry composition at the farm gate.

Performance of Thompson Seedless Grape and ITS Clones on Dog RIDGE Rootstock

Afield trial was conducted at the RD NO 3 -N status was more and K status less after back pruning in Sonaka. Fruitfulness of buds as indicated by the cluster/cane ratio was more resulting in more clusters/vine in Sonaka, though the canes/vine was less. Yield increase in Sonaka was mediated through more cane diameter, shoot length on the 45 th day and shoot growth rate during 30-45 days after back pruning; less number of shoots/vine and shoot length at veraison. Results of this trial revealed that Sonaka is the best variety on Dog Ridge for obtaining high yield of quality grapes and that the viticultural practices that increase the cane diameter, shoot length on the 45 th day and shoot growth rate during 30-45 days after back pruning; and reduce the number of shoots/vine and shoot length at veraison might help increase the yield in Thompson Seedless and Tas-A-Ganesh.

Effect of rootstock-scion interaction on petiole nutrient content, bud break, and yield of three commercial grape cultivars

An experiment was conducted to study the influence different rootstocks (1103 P, SO4 and Dog ridge) on petiole nutrient content (%), bud break (days) and fruit yield (kg ha−1) of commercial grape varieties (Thompson Seedless, Flame Seedless and Kishmish Chorni). The study revealed that there was often rootstock, scion and rootstock x scion interaction effect on mineral nutrient content, yield components and yield. In general, across scion cultivars higher petiole N content was recorded with Dogridge rootstock at full bloom, while the pronounced effect on increasing petiole K content was recorded with Dogridge at bud differentiation stage. Considerable effect in increasing phosphorus (P) content was recorded with 1103 P which was comparable to own rooted vines during both the stages. Across rootstocks, Thompson Seedless cultivar recorded higher nitrogen (N) and P and Kishmish Chorni recorded higher potassium (K) content. Early bud break was observed with 1103P and own rooted vines among rootstocks and with Kishmish Chorni among cultivars. Yield per vine was higher in Thompson Seedless on own root which was on par with Kishmish Chorni on Dogridge which recorded comparable yields with 1103 P and own rooted vines. Irrespective of the scion varieties, higher bunch weight was recorded on Dogridge.

Variation in nutrient absorption tendency of Thompson Seedless grape on own root and Dog Ridge rootstock

A Study of the variation in the absorption of major nutrients on Thompson Seedless on its own roots and Dog Ridge rootstock, showed no correlation between soil and petiole nutrients, indicating strong interference of other nutrients. Path coefficient analysis was employed to assess the direct and indirect effects of nutrients on other nutrients in Thompson Seedless on its own roots and Dog Ridge rootstock. Correlation observed between any two nutrients is the outcome of direct effect modified by the indirect effects via other nutrients. The direct and indirect effects of nutrients on the absorption of a particular nutrient were different in Thompson Seedless vines on Dog Ridge rootstock compared to vines on their own root. Variation in the indirect effect of a pair of nutrients on the absorption of different nutrients was attributable to the complexity of the interrelationship among nutrients, relative abundance of nutrients, preferential absorption of roots, mobility of nutrients and ionic balance in foliar tissues. The direct and indirect effects indicated that restricting the application of P and K can limit the absorption of N in vines on their own root; whereas restricting the input of P and application of sulphur on Dog Ridge rootstock. Phosphorus absorption could possibly be increased by limiting the application of potash to vines on their own roots and foliar application of Mg to those on Dog Ridge in soils with high levels of available K and Na. Absorption of soil K by Thompson Seedless on own roots can be increased by higher rates of application of N, S and Mg, and reducing the application of P; and growing in soils with low levels of Na. Higher petiole N and P levels and soil S levels were found to restrict Na absorption.

Variation in the Interactions among soil K+, Ca++, Mg++ and Na+ ions as influenced by the variety and rootstock in grape

A nutritional survey was conducted to study the influence of variety and rootstock on interactionamong K+, Ca++, Mg++and Na+ ions in grape during 2012-14. Soil cation contents did not correlatewith their respective contents in petioles indicating a strong antagonism among them. Quadraticrelationship of soil cations with the absorption (ratio of petiole content to soil content) of otherions revealed that the antagonism among cations was observed in case of soil K+ with Ca++ andNa+ absorption on 110R and Dog Ridge rootstocks, soil Ca+ with K+ and Mg++ and Na+ in Sonakavariety and Na+ in own rooted vines, soil Mg++ with Ca++ and Na+ also in own rooted vines; andNa++ with Ca++ and Mg++ respectively in 2A clone and Dog Ridge. Contrarily, increased absorptionof K+ by soil Ca++ on 110R, Na+ and K+ by soil Mg++ respectively in Sonaka and 110R, and Ca++by soil Na+ on Dog Ridge was also observed. All the soil cations together influenced K+ absorptionmost in Sonaka followed by Mg++ absorption in 2A clone, but Ca++ absorption on Dog Ridgefollowed by K+ on 110R.

Variation in the Interactions among soil K+, Ca++, Mg++ and Na+ ions as influenced by the variety and rootstock in grape

A nutritional survey was conducted to study the influence of variety and rootstock on interactionamong K+, Ca++, Mg++and Na+ ions in grape during 2012-14. Soil cation contents did not correlatewith their respective contents in petioles indicating a strong antagonism among them. Quadraticrelationship of soil cations with the absorption (ratio of petiole content to soil content) of otherions revealed that the antagonism among cations was observed in case of soil K+ with Ca++ andNa+ absorption on 110R and Dog Ridge rootstocks, soil Ca+ with K+ and Mg++ and Na+ in Sonakavariety and Na+ in own rooted vines, soil Mg++ with Ca++ and Na+ also in own rooted vines; andNa++ with Ca++ and Mg++ respectively in 2A clone and Dog Ridge. Contrarily, increased absorptionof K+ by soil Ca++ on 110R, Na+ and K+ by soil Mg++ respectively in Sonaka and 110R, and Ca++by soil Na+ on Dog Ridge was also observed. All the soil cations together influenced K+ absorptionmost in Sonaka followed by Mg++ absorption in 2A clone, but Ca++ absorption on Dog Ridgefollowed by K+ on 110R.

Variation in the Determination of Macronutrient Absorption by Micronutrients in Certain Stionic Combinations of Grape

Investigations were carried out through a survey of vineyards of Thompson Seedless and 2A clone on their own root and Dog Ridge rootstock to identify those micronutrients which have positive relationship with major nutrient absorption and the stionic combinations in which such relationship exists. Relationship of major nutrient absorption with micronutrient status was highly complex, which could be attributed to variation in their absorption due to their relative abundance, variety and rootstock, and interactions among them. Results of the investigations indicated that none of the micronutrients could influence the absorption of N in any stionic combination. Fe, Mn, Zn and Cu together determined the absorption of Na highest in 2A clone on Dog Ridge rootstock, followed by the determination of P and S in Thompson Seedless on Dog Ridge. Mn contributed most towards the determination of P, K, Ca, Mg, S and Na across the stionic combinations. P absorption increased with higher levels of Mn and Cu respectively above 66.0 and 111.9 ppm, but decreased above 121.1 ppm of Zn in TS/DR. It increased with increasing levels of Mn above 129.8 ppm in 2A/OR and Zn levels above 121.2 ppm in 2A/DR. Higher levels of petiole Cu above 105.4 ppm and of Mn below 435.9 ppm increased K absorption in TS/DR. Levels of Mn above 210.2 ppm in 2A/OR, of Cu above 155.6 ppm and Mn at any level in 2A/DR were also associated with higher absorption of K. Calcium absorption increased with Fe levels above 116.7 ppm and Mn levels above 106.3 ppm in TS/OR. The increase in Ca absorption was limited to 466.7 and 500 ppm respectively of Fe and Mn in 2A/DR. Fe levels above 100 ppm resulted in increased Ca absorption in 2A/OR. Increased Mg absorption was associated with petiole Zn levels above 65.2 ppm in TS/OR, with any level of Mn and Zn levels up to 96.7 ppm in 2A/OR. It also increased with Zn levels above 112.9 ppm, but Mn levels up to 650 ppm in 2A/DR. Sulphur absorption increased with increasing contents of petiole Mn to any level and Cu levels above 149.3 ppm, but its increase was limited to 118.8 ppm of Zn in 2A/OR. Reduced absorption of Na was associated with increasing levels of Mn above 209.6 ppm in TS/OR, and with increasing levels of Fe, Mn and Zn respectively above 63.6, 257.1 and 117.1 ppm in 2A/OR. Increasing levels of Fe an Mn respectively above 516.6 and 380.8 ppm, but Zn levels below 66.7 ppm also reduced Na absorption in 2A/DR. Management of micronutrient levels above their threshold levels and below optimum levels corresponding to major nutrient absorption could help in increased absorption of P, K, Ca, Mg and S but reduced absorption of Na in different stionic combinations.

Variation in the Relationship of Major Nutrients with Micronutrient Absorption in Grape due to Variety and Rootstock

A survey of vineyards of Thompson Seedless and Its clone 2A on their own root and Dog Ridge rootstock was conducted with an aim to elucidate the variation in the absorption (ratio of petiole to soil contents) of Fe, Mn, Zn and Cu in relation to major nutrient contents of soil and petioles, and thereby evolve guidelines for major nutrient application for efficient absorption of micronutrients in these stionic combinations. Among the four micronutrients studied, the order of sensitivity to soil and petiole nutrient contents in the four stionic combinations surveyed was Mn>Zn>Cu>Fe. Fe was more sensitive in TS on DR. The sensitivity of Mn was in the order of 2A on DR > TS on DR > 2Aon OR > TS on OR, whereas TS on DR>2A on OR >TS on OR = 2A on DR was the order of sensitivity of Zn. Sensitivity of Cu was in the order of 2A on OR > 2A on DR > TS on OR = TS on DR. Absorption of micronutrients, mainly Mn and Zn was affected most by majority of the major nutrients by Dog Ridge rootstock, particularly in combination with Thompson Seedless and least affected by 2A on own root. Variation in the relationship of major nutrient contents of soil and petioles with the absorption of micronutrients was attributed to the variation in the available soil nutrient contents, rootstock affinity for nutrients and physiological need of varieties. Hence management of micronutrients assumes greater importance in Thompson Seedless on Dog Ridge rootstock. The levels of major nutrients associated with minimum absorption, threshold levels for increasing absorption and the optimum values of major nutrients for maximum absorption of each micro nutrient were identified. The results of the investigation will guide in the application of major nutrients for efficient absorption of Fe, Mn, Zn and Cu in Thomson Seedless and its clone 2A on Dog Ridge rootstock.

Association of mineral imbalance with leaf chlorosis under saline irrigation in Sharad seedless grapes raised on Dog Ridge rootstock

Under saline irrigation, development of leaf chlorosis/discoloration beginning from the upper leaves has been found to cause severe reduction in productivity and life span of the Sharad Seedless grape (Vitis vinifera L.) and its mutants grafted on Dog Ridge rootstock. In the present study, mineral accumulation in vine tissues over the years under saline irrigation and association of mineral imbalance with chlorosis/necrosis was investigated during the two pruning seasons in Sharad Seedless vines grafted on Dog Ridge rootstock. The contents of nitrogen, phosphorus, potassium, calcium and magnesium were significantly lower and sodium and chloride contents were found significantly higher in upper leaf lamina of symptomatic vines. Lamina N, P, K and Ca and Mg contents were positively correlated, whereas sodium and chloride contents were negatively correlated with chlorophyll content. Significant negative correlation was observed between chloride and phosphorus and nitrogen concentration in leaf tissues. Principal component analysis revealed a negative interaction between N, P, K and Na and Cl−content in leaf tissues. Principal components (PCs) explained 91.7% of total variation in leaf lamina and were designated as PC1 (N+P+K-Na-Cl) and PC2 (N+P+K+Ca+Mg). Symptomatic vines accumulated higher sodium (>5.0 g−1/kg) than potassium content in the leaf tissues and mean potassium content in symptomatic leaf lamina was <5.0 g−1/kg. Increased accumulation of Na+ and Cl− in the chlorotic leaf tissues revealed that ability of Dog Ridge rootstock to exclude these salts diminished over time and long term studies are needed for identifying salt tolerant rootstocks.

The effect that indolebutyric acid (IBA) and position of cane segment have on the rooting of cuttings from grapevine rootstocks and from Cabernet franc ( Vitis vinifera L.) under conditions of a hydroponic culture system

Abstract The present study aimed at determining the effect of indolebutyric acid (IBA) and of the part of cane from which the cuttings were taken on the rooting ability of three rootstocks and of a grapevine variety using a hydroponic system employing water as the culture medium. Under hydroponic conditions, three different auxin treatments (control water, 120 and 250 ppm IBA) were applied on the three rootstocks, namely 1103 Paulsen, SO4, Dog Ridge and cv Cabernet franc ( Vitis vinifera L.). The treatments were applied annually for a period of two (2) years and, more specifically, in 2014 and 2015, using a completely randomized design. The cuttings were collected from the Experimental Vineyard, Laboratory of Viticulture, Agricultural University of Athens. The study continued by evaluating the effect of that three factors, rootstock/variety, cane part donating the cuttings, and IBA concentration had on the following: percentage of callogenesis, percentage of rhizogenesis, average diameter of roots, average number of roots per cutting, total surface of roots, and total length of roots. The results of the experiment revealed that treatment with 250 ppm IBA and cuttings coming from the middle part of the cane yielded the highest rhizogenesis percentages. At the same time, the highest callogenesis percentage was observed in the basal cuttings of rootstock 1103 P that underwent the same treatment. Following the 120 ppm IBA treatment, the basal cuttings of rootstock Dog Ridge presented the highest average number of roots. Under the 250 ppm IBA treatment, the basal, middle and middle cuttings of the Dog Ridge rootstock respectively presented the highest average diameter, surface, and length of roots. The experiment led to the conclusion that, under hydroponic conditions and when treated in low IBA concentrations, the grapevine variety and the rootstocks under study can give rooting results which are quite satisfactory. Based on those results, a hydroponic system employing water as its culture medium may prove practical and economical when it comes to vine propagation.

The Performance of Chenin blanc Grafted onto Different Rootstock Cultivars on a Dundee Soil in the Montagu District

The performance of Chenin blanc grafted onto 15 different rootstock cultivars and clones, established on a sandy alluvial soil in the Montagu district, was investigated. Over the eleven years of the trial, the highest mean yields were obtained with 99 Richter (Clone: RY 13), Constantia Metallica, Dog Ridge, Ramsey and 101-14 Mgt. The mean yield of99 Richter (Clone: RY 13) was significantly higher than that of the other 99 Richter clones and selections. The highest pruning masses were found with 143-B Mgt, Dog Ridge, Constantia Metallica and Ramsey. The crop-to-pruning-mass ratio of 143-B Mgt was, however, lower than that of the other graft combinations, which suggests that this graft combination was undercropped and that potentially higher yields could have been obtained. Moderate growth was obtained with the cultivars 101-14 Mgt and 3306 Coucerc. These cultivars showed potential as growth-limiting cultivars as they consistently produced relatively high yields with satisfactory grape composition, associated with low pruning masses.

The Influence of Water and Gas Exchange Parameters on Grafted Grapevines Under Conditions of Moisture Stress

Among the four grape varieties that were subjected to moisture stress, Flame Seedless and Thompson Seedless recorded the highest relative water content, osmotic potential and water potential compared to Sharad Seedless and Tas-A-Ganesh. Similarly, Flame Seedless and Thompson Seedless recorded the maximum rate of photosynthesis, the minimum transpiration rate, and thus increased water-use efficiency. Sharad Seedless on its own root had the lowest water-use efficiency. Budding the respective four varieties on different rootstocks and subjecting them to moisture stress resulted in significant differences in various physiological parameters that influence water-use efficiency. When Sharad Seedless was budded on Dog Ridge rootstock and subjected to moisture stress, it resulted in increased water potential, osmotic potential and water use efficiency compared to other rootstocks. This suggests that rootstocks have an influence on the physiological mechanisms of scion leaves. Hence, the genotypic selection of rootstocks for establishing vineyards under drought conditions is of great importance