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Ch. SUNITHA*, B. UMA BHARANI, D. MANOHAR PRASAD, P. VINOD KUMAR AND B. MANJU VANI
Department of Fruit Science, Horticultural College, Dr YSR Horticultural University, Rajendranagar, Hyderabad.
The aim of the study was to determine the effects of cytokinins and silver nitrate on success of graft union of Thompson Seedless grape (Vitis vinifera L.) cuttings on Salt Creek. Set of two experiments were conducted in Completely Randomized Design in open condition and another in poly house conditions. The treatments included concentrations of BAP (150 ppm, 250 ppm and 350 ppm), kinetin (150 ppm, 250 ppm and 350 ppm), silver nitrate (50 ppm, 100 ppm and 150 ppm) and control. IBA 2000 ppm was commonly treated for all the basal end of the rootstock cuttings. The treated cuttings were grafted and analyzed for various growth parameters. Among the treatments, cuttings treated with kinetin 250 ppm followed by BAP 250 ppm recorded beneficial effect on the early graft union and subsequent improvement in growth parameters of grafts grown under polyhouse condition compared to open conditions.
Callusing, Grafting, Kinetin, 6- Benzyl Amino Purine, Indole 3- Butyric Acid, Silver nitrate, Grapevine cuttings.
Grape (Vitis vinifera L.) is one of the most important commercial subtropical vine crop grown all over the world, except at few places with high altitude and extreme temperatures. Grape is mainly propagated by cuttings, but productivity of grapes showed reduction on its own roots due to salinity in soil, chlorides in irrigation water, drought and also nematodes. In order to sustain the grape production under these adverse conditions, grafting is adopted by using appropriate rootstocks. Salt Creek imparts vigour to scion, although rooting is difficult but readily graft and promote bud proliferation. It performs well with table and raisin varieties. Thompson Seedless grafted on Salt Creek recorded maximum total dry matter in secondary cordon of Salt Creek and significantly higher N was recorded in canes (1.96%) and recorded the high levels of amino acids in fruits the time of harvest (Somkuwar et al., 2009 and Jogaiah et al., 2010).
Successful grafting of plant species and cultivars is related to the production of callus, which is essential for graft union formation (Hartman 1990). The plant growth regulators such as auxins and cytokinins induce the initiation and proliferation of callus and new vascular tissue by promoting cell division and/or cell development
(Bonner and Galston, 1952; Rost et al., 1984; Raven et al., 1992; Salisbury and Ross, 1992; Preece and Read, 1993). The graft union takes place as a result of formation of callus on the two components. Kinetin in the presence of auxin produces callus. Auxin increases cambial activity causing callus formation and it differentiates into phloem. The prime role of plant growth regulators contributed for success in graft union has been reported in many crops (Nanda and Kochar, 1985).
It is postulated that simultaneous rooting, union of scion and rootstock is considered to result in poor root development (Purushotham, 1982). Hence, it is reiterated that auxins like IBA when used can increase root formation while cytokinins like Kinetin and BAP stimulate rapid proliferation of callus between the scion and rootstock. AgNO3, having antisenescence effect can help in delaying the abscission by inhibiting ethylene synthesis and enhancement of callus formation and shoot regeneration (Elif et al., 2005; Mercy et al., 2010; Steephen et al., 2010).
The experiment was conducted to evaluate the success of graft union on Thompson seedless grape in
poly house and open condition at Grape Research Station, Dr. YSRHU, Hyderabad (17°20′ N, 78°25′ E) India.
Open conditions
In open conditions there was no control over environmental factors and grafted plants were kept in sunken beds and partial shade was maintained initially for 30 days.
The propagation of grape was done in naturally ventilated polyhouse admeasuring 20 × 28 m with a height of about 6 m. The temperature and relative humidity of the polyhouse was maintained at 28- 30°C and 80-85 per cent. The glazing material used was 200 µ U.V stabilized polythene sheet.
Planting materials one year old healthy woody cuttings of Vitis vinifera L. (Thompson seedless) and root stock Salt Creek. Black polythene bags were filled with potting mixture of vermicompost: FYM: sand at a proportion of 1:1:1 along with 1 g of carbendizim per cubic meter. The filled bags were kept in sunken beds under open and polyhouse condition. Two holes of 0.5 cm were made on either side of the polythene bag to facilitate water absorption.
The cut grafting surfaces of both the scion and rootstock were treated with different concentrations of BA, Kinetin and AgNO3 as detailed T1 – 150 ppm BAP, T2 – 250 ppm BAP, T3 – 350 ppm BAP, T4 – 150 ppm Kinetin, T5 – 250 ppm Kinetin, T6 – 350 ppm Kinetin, T7
– 50 ppm AgNO3, T8 – 100 ppm AgNO3, T9 – 150 ppm AgNO3, T10 – Control. The cut basal 3-4 cm portion of Salt Creek hard wood cuttings were treated with IBA 2000 ppm.
The samples were cut into 25 cm length with five internodes for rootstocks and 8 cm length with two- bud pieces for scion. Buds of rootstock cuttings were then removed with a knife. Grafting was done giving a vertical slit cut (V notch) of about 4 to 5 cm downward from the cut end of the stock. At the basal end of the scion, the bark on two opposite sides was removed with sharp knife and made into a wedge shape of 3 to 4 cm without damaging cambium layer. The pith of the basal portion of the scion was exposed. The cut grafting surfaces of
both the scion and rootstock each were first dipped into BAP, Kinetin and AgNO3 solution for 20 seconds. BAP and kinetin were applied at concentrations of 150, 250 and 350 ppm and AgNO3 was applied at rates of 50, 100 and 150 ppm. The basal portion of the rootstock cuttings were dipped in IBA of 2000 ppm concentration for promoting rooting. After dipping, cuttings were air dried for 10 minutes and the wedge shaped scion was inserted into the vertical slit on the rootstock. The stock and scion were tied firmly with polythene strips. There should not be any air space left while tying the graft joint by plastic strip. These grafted cuttings were placed in poly bags with potting mixture and were maintained in open and polyhouse condition as per experiments and success of graft was observed.
Grafted cuttings were then evaluated for number of days required for bud sprouting of scion was recorded by counting the days taken from grafting to initiation of first sprout from nodal region of successful grafts, The total number of roots per graft after 60 days of grafting was counted and their average was computed. Number of grafts survived at 60 days after grafting were recorded and percentage survival of grafts was calculated by number of grafts survived/ total number of grafts ×100. Stock: Scion ratio was by measured one cm below the graft union (stock girth) and at one cm above the graft union (scion girth) with the help of Vernier callipers for five observational plants after 60 days of grafting and the average ratio was computed. The experiment used a completely randomized design with three replications, 10 treatments in each replication and 30 grafts per treatment. The data was subjected to statistical scrutiny by the method of Analysis of variance outlined by Panse and Sukhatme (1989). Statistical significance was tested by F value at 5 per cent level of probability and wherever the F value was found significant critical difference was worked out at 5 per cent level of probability and the values were furnished.
Effects of different concentrations of kinetin, BAP and silver nitrate on graft union of cuttings are summarized in the table. Treatments significantly reduced number of days taken for bud sprouting of scion when compared to untreated cuttings , the cuttings treated with BAP 250 ppm (T2) sprouted earlier (16.83) which was on a par with kinetin 250 ppm (T5) (18.75) in poly house conditions. Maximum stock: scion ratio was recorded in cuttings treated with kinetin 250 ppm (T5) (0.84) followed by BAP 250 ppm (T2) (0.81) in poly house conditions. Cuttings treated with kinetin 250 ppm (T5) recorded maximum number of roots (27.76) followed by BAP 250 ppm (T2) (25.11) in open conditions. On 60th day, kinetin 250 ppm (T5) showed maximum survival percentage of 63.33 which were on a par with BAP 250 ppm (T2) (62.67) in poly house conditions where in open condition 54.67 percent with kinetin 250 ppm (T5). Data pertaining to number of days required for bud sprouting of scion, percentage survival of grafts, stock/ scion ratio were best recorded in polyhouse conditions than open conditions. This might be due to the comparatively higher relative humidity, moderate light intensity as well as moderate temperatures maintained under polyhouse condition when compared to open conditions. High relative humidity promotes the low rate of transpiration, keeps the guard cells turgid and the stomata open which might have resulted in production and accumulation of carbohydrates, protein and earlier completion of other physiological processes involved in development of rapid callus formation between the stock and scion (Baghel et al., 2000). Number of roots produced were comparatively high under open conditions than the grafts under polyhouse conditions. This might be due to the fact that evapotranspirational loss of water from shoots is more in open conditions. To meet the requirement of water, more number of roots were developed to absorb water from deeper layers (Hartmann et al., 2007). Better root development was recorded compared to control with kinetin 250 ppm and BAP 250 ppm. Better root development was obtained when both cytokinin and auxin were used which could be due to better organogenesis caused by their combination. These results are in harmony with those obtained by Saeed et al. (2004).
In terms of the effects of different concentrations of kinetin, BAP and AgNO3 on initiation and proliferation of callus at the grafting point, 250 ppm kinetin and BAP 250 ppm yielded best results in polyhouse. The reason may be attributed to cytokinins (Kinetin and BAP) promoting both initiation and proliferation of callus at the grafting point. The formation of callus is a good indication of graft success, since the callus provides the initial pathway for water until vascular connections are formed between the rootstock and scion (Hartmann et al., 1997). Kinetin and BAP application dramatically improved callus structure with organization into dense circular layers. These results are in close conformity with
the findings of Kose & Muharrem (2006). The likely reason for this is that cytokinins promote cell division, cell development and formation of vascular connections among plant parts (Salisbury & Ross 1992). With respect to number of days required for bud sprouting of scion, cuttings treated with kinetin 250 ppm and BAP 250 ppm sprouted earlier in poly house condition. It may be due high temperature inside polyhouse, favouring the bud swell thus bud sprout were earlier in comparison to open field conditions (Sharma and Yousuf Dar, 2006).
In viticulture growth observations are strongly related to the graft union which has been linked to rootstock-scion incompatibility (Biolatti et al., 1921). The ratio of scion trunk diameter to rootstock trunk diameter was a good indicator of potential problems for productivity in grafted vines. In present study for stock: scion combinations, it was clear that there were differences in the growth behavior of grafted vines with different treatments and rootstocks. (Satisha et al., 2010). Kinetin can be used as an inductive cytokinin to produce callus in the presence of auxin. Among the growth regulators and chemicals tested, it was found that kinetin 250 ppm and BAP 250 ppm remarkably improved the graft take under poly house condition. Similar results were observed in veneer grafting of mango (Mathad, 1983; Ramakrishna, 1985). The promotary effect of kinetin and BAP in the present study may be attributed to its role in cell division, cell elongation and formation of callus for which it is all known (Murashige and skoog, 1962). Cytokinins are also known for their role in delaying senescence. It is commonly observed that scions which fail to graft take, wilt and wither very early. In other words, if their senescence could be avoided or atleast delayed graft take can be improved. Kinetin, BAP and AgNO3 treatments could have acted in this way there by improving the graft take. Similar improvement was observed on graft take in mango with BAP and AgNO3 by Amarnath Reddy (1987). Percentage survival of grafts was observed to be highest in cuttings treated with kinetin 250 ppm. Similar results were obtained by Kose and Muharrem (2006) in grape. Among the two growing conditions under study, highest percentage survival of grafts was observed inside the poly house condition. The results were similar with Sulkeri et al. (1997) in sapota and Raghavendra (2008) in wood apple.
In conclusion, significant increase in number of days taken for bud sprout, number of roots, stock: scion ratio and percentage survival of grafts showed that kinetin 250
ppm and BAP 250 ppm may have potential to improve the grafttake in grapevine in polyhouse conditions compared to open conditions. Further studies need to be conducted to find out the optimal doses of chemicals and growth regulators in different rootstocks with commercial varieties in of problematic soils for improving both graft union.