Reserve nutrient status of Vitis graft material and the relationship with graft combination success during the callus period

Project Number
WW 12-03

Project title
Reserve nutrient status of Vitis graft material and the relationship with graft combination success during the callus period

Project leader
Hunter, J J

Team members
Volschenk, C G
Fouché, G W
Adams, L F

Project description
During the 1995-96 season the relationship between starch content, mineral composition of graft material, and callus development, was investigated during the callus period. Based on this, K, Zn, and K-Zn fertilisation were applied to 99 Richter and 101-14 Mgt and the effect on starch content, callus development and nursery performance determined. Means of the past two years showed that, in spite of little change in starch content, K and Zn (for 99R) and K, Zn and K + Zn (for 101-14 Mgt) fertilisation increased callus performance. The effect will probably be greater under less favourable soil conditions. The results also indicated that the rootstock had an effect on scion metabolism from as early as the callus period. Poor callus formation is probably the result of physiological deficiencies in both the rootstock and scion cultivar. The Zn and K + Zn fertilisation for 99R and Zn fertilisation for 101-14 Mgt increased the root and cane mass of the nursery vines. The results indicate that supplying in the fertilisation needs of the rootstocks can have a positive effect on callus and nursery success. This part of the project is concluded.

Using leaf removal and shading, the starch content of 99R graft material after callusing was reduced. This was, however, not correlated with callus performance. An improvement in both root and shoot growth of the flat growing rootstock was found with leaf removal and shading. This is a strange phenomenon. Hormone imbalances most probably played a role. The investigation showed that leaf removal and shading of flat growing rootstocks in the mother blocks will most probably not affect the performance of stocks in the nursery. This part of the project is concluded.

A summary of data obtained over the last three years on the seasonal growth pattern, starch accumulation, and mineral consumption by rootstock parent material (99R and 101-14 Mgt) was presented. Data from two seasons in February of Ramsey, 110R and US 8-7 were included. Graft shoot production of the different rootstocks differed clearly. A reasonably stable growth pattern occurred until January/February, after which it decreased. Leaf fall occurred earlier for 101-14 Mgt (April) than for 99R (May). In contrast to vineyard experience, 101-14 Mgt grew more vigorous than 99R and again point to a mutual effect of scion and rootstock. The results highlighted the positive effect of lateral shoots on the growth of rootstock parent material. Main shoot growth decreased in the order of Ramsey, 110R, 101-14 Mgt, 99R, and US 8-7. On the basis of starch content, the results indicated that lateral shoots may also be used as graft shoots in the case of 99R, 101-14 Mgt, Ramsey and US 8-7. In the case of 110R the risk of using lateral shoots will be higher. Lateral shoots of the aforementioned rootstocks should also be used with care, particularly under unfavourable conditions. The mineral content of the different rootstocks showed little variation and leaf and petiole levels were mostly comparable to those of bearing vines. The mineral levels in the main and lateral shoots were, except for low N and Ca contents, also comparable to the leaf norms of bearing vines. As no obvious deficiency symptoms occurred, these mineral levels can probably be considered normal. Calcium and N are important for graft shoot growth and for callus development and these aspects should nevertheless be investigated. Transport of minerals to graft shoot growth should be stimulated by judicious management practices. An analysis of the mineral requirements of rootstocks for the production of one ton of graft shoots and of a 28 cm length graft shoot showed that Ramsey, 110R and 101-14 Mgt had the highest mineral levels. The results indicate that soils may be over- or under-exploited, depending on the rootstock used. That will eventually lead to differential fertilisation in order to ensure optimum soil utilisation and cost efficiency and to restrict soil and water pollution.

In an effort to elevate density and shade in the canopies of the rootstocks and to increase the starch content of main shoots, lateral shoot removal led to a slight decrease in the starch content of 99R and 101-14 Mgt; the mineral content of the graft shoots and nursery stocks was not affected. The percentage Class I stocks in the nursery was, however, noticeably reduced by lateral removal. The lateral shoots therefore contribute, as in the case of production vineyards, to photosynthetic activity and carbohydrate production capacity during the second phase of the growth period in particular, when main leaves already started senescing. Labour inputs for this practice cannot be justified. This part of the project is concluded.

Investigating the optimum time for graft shoot collection, it was found that early collection of 101-14 Mgt was more critical that in the case of 99R to ensure maximum starch content in graft shoots. In the case of 99R, 101-14 Mgt, Ramsey, 110R and US 8-7 collection should preferably start before June. Results indicated an almost 50 % loss in starch during the storage period, which shows that a high starch content before storage is crucial in order to support callus development after grafting. The nursery performance of the stocks showed that rootstocks differ in terms of optimum collection time. The percentage Class I stocks decreased from April to July. According to that, 101-14 Mgt must be collected as soon as possible, whereas 110R can be collected up to June, US 8-7 early or late, and 99R and Ramsey over the whole collection period. Root and shoot results after the nursery phase concurred with this. High volumes of quality vines are important for economic sustainability. To limit risks, producers muststill strive for early collection. The investigation continues with the use of 140 Ruggeri, 1103 Paulsen, SO4, 143 B and US 2-1.

Application of hot water treatment in order to investigate the role of starch reserves in stock resistance to unfavourable conditions resulted in a general loss of water from the shoots of scion cultivars (Chenin blanc, Malbec, Red Muscadel, Ruby Cabernet, Sémillon, Tinta Roriz, Tinta Francisca, Touriga Nacional, Viognier). That will require more care during the callus and nursery periods to sustain the water content of graft material. Defoliation decreased the starch content of only T. Roriz, T. Francisca, T. Nacional and Viognier. Hot water treatment resulted in starch losses of up to 60%. Callus performance of the different cultivars was mostly decreased. The results imply that untimely loss of leaves, in combination with hot water treatment, may indeed affect the quality of graft combinations and lead to losses in the nursery, specially because huge starch losses also occur during the callus period. This part of the project is concluded.

Results regarding the set-up of a starch and mineral reference source, indicated that the starch content of scions was higher than that of rootstocks. The starch content of the scions and rootstocks (101-14 Mgt, 99R, 110R, Ramsey, US 8-7, Chardonnay, Sauvignon blanc, Pinotage, Shiraz and Merlot) decreased from February to July. That of Ramsey, Merlot, Pinotage and Sauvignon blanc did not decrease sharply. The starch content of the rest of the cultivars, however, decreased drastically and implies that these cultivars must be collected as soon as possible after the growth season. Scions and rootstocks displayed similar mineral contents; fertilisation requirements are probably also similar. This part of the project is being continued with other cultivars, namely SO4, 3306 Couderc, 1103 Paulsen, 140 Ruggeri, 143 B, Pinot noir, Sémillon, Ruby Cabernet, Colombar and Cabernet Sauvignon.

A titration method for easy determination of starch in graft material was developed. A comparison of this method with the normal enzyme method showed that the titration method is probably more successful in the case of rootstocks than in the case of scions. Cultivars also differed. The analyses will be repeated during the following year. The investigation is being continued.

An investigation into the effect of desiccation (before cutting) and water absorption (after cutting) of graft shoots just after collection on callus and nursery success, was started during the past season. Desiccation resulted in a loss of water, but this is reasonably recovered with an overnight period in water. Submersion in water (without prior desiccation) for different periods resulted in a higher water status in the material, but callus formation of only 99R was stimulated. The callus percentage is negatively affected by desiccation without an overnight water absorption period; with a water absorption period, callus was stimulated. Submersion of cut stocks (without prior desiccation) for different periods stimulated the callus formation of only 99R. Desiccation of the graft shoots led to less in the case of 99R, but to more Class I vines in the case of 101-14 Mgt, after the nursery phase. Desiccation followed by overnight water absorption led to an increase in the number of Class I stocks in the case of 99R, but to a decrease in the case of 101-14 Mgt. Apparently, only a long period of water absorption (more than 48 hours) (without prior desiccation) increased the percentage Class I stocks; root growth was stimulated, whereas cane mass was decreased. An interaction between callus formation, root growth and shoot growth probably occurred. It is possible that the treatments led to changes in hormone balances. These interactions between the growing areas of the stock must be investigated by means of hormone analyses.

Poster(s)
Hunter J J, Volschenk, C G and Le Roux, D J. 2001. Reserve nutrient status of Vitis graft material, as related to growth during callusing. National Congress of the South African Society for Enology and Viticulture Congress, November, Somerset West.

Hunter, J J, Volschenk, C G, Fouche, G W and Adams, L F. 2001. Mineral absorption of rootstock mother material, National Congress of the South African Society for Enology Congress, November, Somerset West.

Hunter, J J, Volschenk, C G, Fouche, G W and Adams, L F. 2001. Reserve nutrient status of Vitis graft material, as related to growth during callusing. National Congress of the South African Society for Enology and Viticulture Congress, November, Somerset West.

Presentation(s)
Hunter, J J. 1995. Reserve nutrient status of Vitis graft material and the relationship with graft combination success during callus period. KWV, 27 July, Paarl.

Hunter, J J. 1995. Reserves in graft material. SAPO visitors, 19 September, Nietvoorbij, Stellenbosch.

Hunter, J J. 1996. Report on reserves in graft material and thickness of graft stocks. VIB meeting, 8 February, Nietvoorbij, Stellenbosch.

Hunter, J J. 1997. Investigation into the reserve nutrient status of Vitis graft material and the relationship with performance during the grafting period. Winetech Technology Transfer Meeting, 24 July, Nietvoorbij, Stellenbosch.

Hunter, J J. 1997. Quality of mother material. Seminar Mother Block Producers, KWV, 30 October 1997, Paarl.

Hunter, J J. 1997. Quality of mother material. Seminar Nurserymen, KWV, 18 November, Paarl.

Hunter, J J. 1998. Physical and physiological quality of graft material. Nursery Seminar, Vine Improvement Association, 22 April, KWV, Paarl.

Hunter, J J. 1999. Physical and physiological quality of graft material. Nursery Seminar, Vine Improvement Association, 14 April, KWV, Paarl.

Hunter, J J. 1999. Quality of graft material. Winetech Technology Transfer Meeting, 25 May, KWV, Worcester.

Hunter, J J. 1999. Establishment strategies and canopy management for higher grape and wine quality. Lutzville Cellars, 9 December, Lutzville.

Hunter, J J. 2001. Handling of graft material. Nursery Seminar, 25 April, Paarl.

Article
Hunter, J J, Ruffner, H P, Volschenk, C G. 1995. Starch concentrations in grapevine leaves, berries and roots and the effect of canopy management, South African Journal of Enology and Viticulture, v. 16 (2) (p. 35-40)

FinalReport.pdf

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