Estimation of Vascular Discontinuity between Rootstocks and Scions of Rambutan and Durian Using Isotope Techniques at the Nursery Stage

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1 Jpn. J. Trop. Agr. 49(3) : , 2005 Short Report Estimation of Vascular Discontinuity between Rootstocks and Scions of Rambutan and Durian Using Isotope Techniques at the Nursery Stage Ismiyati SUTARTO1, Soertini GANDANEGARA1, ARWIN1 and Nobuo SUGWANIA2,* 1 Center for Research and Development of Isotope Radiation and Technology, Box 7002, Jakarta, Indonesia 2 The University of Tokyo, Bunkyo-ku, Tokyo , Japan * Corresponding author Key Words: Durio zibethinus L., Interstock, Nephelium lappaceum L., Radiophosphate, Rootstock, Scion Introduction Fruit trees are usually propagated by budding and grafting. The ability of two different plants when grafted to successfully produce a composite plant is called graft compatibility. Some specific combinations of scions and rootstocks are incompatible, that is, grafted plants show abnormalities in growth or do not make successful graft unions (Feucht, 1988; Hartmann et al., 1990). Different plant species are often used as rootstocks because specific influences on the performance of scions, such as dwarfing characteristics or disease resistance, are expected (Hartmann et al., 1990). Therefore, it is important to clarify the combinations of plants capable of producing permanent and successful graft unions. However, there is no definite rule to predict the exact outcome of the combinations of rootstocks and scions. For example, the Japanese plum cv. Beauty can be successfully grafted on almond trees, while the combination of cv. Santa Rosa and almond trees leads to the failure of successful grafting (Hartmann et al., 1990). It is considered that graft incompatibility occurs due to anatomical abnormalities of vascular bundles, adverse physiological responses between rootstocks and scions, and pathogen transmission (Hartmann et al.,1990). If there is discontinuity in the vascular bundles, the translocation of water and nutrients is inhibited. Magnetic resonance imaging, which can measure bound water in tissues, has been reported to be a useful tool for Received Apr. 30, 2004 Accepted July 2, 2005 detecting the discontinuity of apple bud unions (Warmund et al., 1993). However, magnetic resonance imaging is very expensive, and not easily used for experiments in Indonesia. Therefore, we examined whether the isotopic method could be used instead to elucidate the easiness of the translocation of nutrients, i.e., vascular discontinuity, between roostocks and scions. Materials and Methods The use of interstocks on rambutan propagation Rambutan seeds cv. Sinyonya were sown in 5-liter pots containing growth medium in February 1993, in a glasshouse at the Cipaku Experimental Station, Bogor. The growth medium consisted of soil, rice husks and manure (1:1:1 on a volume basis). Scions (cvs. Binjai, Rapiah, Lebak Bulus and Simacan) were budded on rootstocks cv. Sinyonya or march-grafted on interstocks cv. Sitangkue in July 1993, i.e., five months after sowing. For double working, the composite plants were separated after the formation of graft unions, and the scion cultivars were budded 10 cm above the graft union between the rootstocks and interstocks in October 1993, i.e., three months after marched grafting. The experiment was arranged in a factorial randomized block design with 6 replications, i.e., operation of interstocks (with and without interstock) combined with 4 different scion cultivars (Binjai, Rapiah, Lebak Bulus, and Simacan). Each replication included 5 plants. The 32P movement in rootstocks, interstocks and scions was traced in January 1994, i.e., 11 months after sowing. Isotope 32P in the form of

2 234 Jpn. J. Trop. Agr. 49 (3) 2005 KH232PO4 was injected into 3 holes in the growth medium at a depth of 5 cm and 3 cm from the grafted plants. Each hole received 1 ml KH232PO4 solution with a total activity of 5.55 ~106 Bq. One week later, the plants were removed from the growth medium, and separated into rootstock, interstock and scion parts. The union parts were cut 2cm each from interface. Thus, the union between the rootstocks and interstocks, interstocks, and the union between the interstocks and scions were collected from double worked trees, while the union between rootstocks and scions was collected from trees without interstocks. Each part was dried in an oven at 70 Ž for 24 hours, ashed in a furnace for 8 hours at 500 Ž and then dissolved in 1 mol liters HCI. The activity of the 32P was measured by the Cerenkov technique using a liquid scintillation spectrometer (Beckman LS 1801). The results are expressed as the specific activity of 32P (log cpm 32P/g of samples). The use of interstocks on durian propagation Seeds of a local cultivar (LK) were sown in 5-liter pots containing growth medium at the experimental farm of the Research Institute for Fruits in April In December 1994, ecirik Kudo 1 f (Ck 1), ecirik Kudo 2 f (Ck 2) and e Chanee f (Ch) were budded on an 8-month old LK cultivar. For double working, the Ch cultivars were budded on Ckl, Ck 2 and Ch interstocks that had been budded on a LK cultivar in October 1994, i.e., 3 months before double working. The 32P movement in the rootstocks, interstocks and scions was traced in January Isotope 32P was injected into 3 holes in the growth medium at a depth of 5 cm and 3 cm from the plants. Each hole received 1 ml KH232P04 with a total activity of 6.66 ~106 Bq. One week later, the plants (consisting of rootstock, interstock and scion parts) were removed from the growth medium, dried in an oven at 70 Ž for 24 hours, ashed in a furnace for 8 hours at 500 Ž and then dissolved in 1 mol liter-1 HCI. The parts used for the measurement of the 32P activity were the same as those in the rambutan experiments. The union part was cut 2 cm from each interface. The activity of 32P was measured by the Cerenkov technique using a liquid scintillation spectrometer (Beckman IS 1801). The results are expressed as the specific activity of 32P (log cpm 32P/g of samples). Results The use of interstock on rambutan propagation There is no significant difference in the 32P activity in the rootstocks among the scion cultivars although the insertion of interstocks reduced the 32P activity in the rootstocks irrespective of the scion cultivars (Table 1). The 32P activity in leaves was influenced by the scion cultivars, with cvs. Simacan and Lebak Bulus showing a higher activity than cv. Binjai (Table 2). The insertion of an interstock did not affect the 32P activity in the leaves. The scion cultivars did not affect the 32P activity in the interstocks, the union between rootstocks and interstocks or the union between interstocks and scions when the interstocks were inserted between the rootstocks and scions (Table 3). On the other hand, the 32P activity in the part between the rootstocks and scions was higher in the cv. Rapiah than in the cv. Lebak Bulus unless the interstocks were used (Table 3). The use of interstock in durian propagation The 32P activity in the scions and rootstocks was higher when a Ck 1 scion was budded on Lk rootstocks than when a Ch scion was budded Table 1 Effect of scion cultivars on the activity of 32P expressed cpm/g dry matter in rootstock cv. Sinyonyaz as log z Means indicated by different letters within columns or rows are significantly different based on Duncan's multiple range test at the 5% level.

3 Sutarto et al.: Vascular discontinuity in rambutan and durian 235 Table 2 Effect of scion cultivar on the activity of 32P, expressed as log cpm/g dry matter, in leaves of rambutan scionsz Z Means indicated by different letters within columns or rows are significantly different based on Duncan's multiple range test at the 5% level. Table 3 Effects of scion cultivar on the activity of 32P, expressed as log cpm/g dry matter, in the different union parts in double budding, and in the union between rootstocks and scions without interstocks Z Means indicated by different letters within columns are significantly different based on Duncan's multiple range test at the 5% level. Table 4 Effects of scion and interstock cultivars on the activity of 32P expressed as log cpm/g dry matter, in different parts of durian plants Table 5 Effects of scion cultivar on the activity of 32P, expressed as log cpm/g dry matter, at the union between rootstocks and scions Z Rootstocks/Scions or Rootstocks/Interstocks/Scions y Means indicated by different letters within columns are significantly different based on Duncan's multiple range test at the 5% level. Z Rootstocks/scions y Means indicated by different letters within columns are significantly different based on Duncan's multiple range test at the 5% level. (Table 4). However, there were no significant differences in the 32P activity when the Ch scions were budded on the Ch, Ck 1 or Ck 2 interstocks. The 32P activity in the union between the rootstocks and scions was higher when the Ck 1 scions were budded on the Lk rootstocks than when the Ch or Ck 2 scions were budded (Table 5). On the other hand, the 32P activity in the union between the rootstocks and interstocks was lower when Ck 1 was used as the interstocks. No significant differences in the 32P activity were found in either the interstocks or unions between the interstocks and scions, regardless of the interstock cultivar (Table 6). Discussion In the rambutan experiment, the 32P activity at the graft union between the rootstocks and scions was higher for the combination of esinyonya f rootstocks and erapiah f scions than for the combination of esinyonya f rootstocks and elebak f

4 236 Jpn. J. Trop. Agr. 49 (3) 2005 Table 6 Effects of interstock cultivars on the activity of 32P, expressed as log cpm/g dry matter, at the union between rootstocks and interstocks, interstocks and the union between interstocks and scions Z Rootstocks/Scions or Rootstocks/Interstocks/Scions y Means indicated by different letters within columns are significantly different based on Duncan's multiple range test at the 5% level. Bulus' scions (Table 3). However, there were no significant differences among the scion cultivars of the 32P activity for the union between the rootstocks and interstocks or between the interstocks and scions at double grafting. This suggests that the 32P movement at the union between the erapiah f cultivar and esinyonya f rootstocks is more restricted than that at the union between the other cultivars and rootstocks, and the insertion of an interstock, cv. Sitangkue, can diminish the negative effect of the erapiah f cultivar on the 32P movement. In the durian experiment, the scion cv. Ck 1 contained higher amounts of 32P when grafted on the Lk rootstocks. On the other hand, there is no difference in the 32P activity in scions among the interstock cultivars when cv. Ch is top-budded. Bukovac et al. (1958) found that 32P transport from roots to scions parallels the plant vigor, that is, large amounts of isotopes are transported to scions budded on vigorous rootstocks. However, the result of the present study suggests that the scion cv Ck 1 stimulates the 32P mobilization. This possibility is supported by the fact that (1) a higher amount of 32P was detected in any part for the combination of the Ck 1 scions and Lk rootstocks, and (2) the 32P activity in any part was not different among the interstock cultivars if the scion cv. Ch was topbudded. Therefore, it is likely that the 32P movement was not restricted in any part for the combination of the Lk rootstocks and Ck 1 scions. Two major types of incompatibility in the grafting of fruit trees have been proposed, i.e., translocatable incompatibility and localized incompatibility (Hartmann et al.,1990). The insertion of a mutually compatible interstock does not overcome the translocatable incompatibility because some labile influence can move across the interstocks and cause phloem degradation. On the other hand, a localized incompatbblity is caused by the vascular discontinuity at the graft union, and incompatible combinations between rootstocks and scions become compatible when mutually compatible interstocks are used. Chen (1964) hypothesized that compatible grafts show a smooth translocation of 32P 35S and 45Ca from the rootstocks to scions, and tried to detect the compatibility of citrus trees, i.e., Tankan (Citrus Tnkan Hayata), Ponkan (Citrus reticulate Blanco) and satsuma mandarins (Citrus unshiu Marc.), at the nursery stage. She considered that the trifoliate orange (Poncitrus trifoliate Ref.) rootstocks are more compatible with scions than Sunki (Citrus sunki hort. ex Tanaka) rootstocks because large amounts of isotopes per unit dry mass were found in scions grafted on trifoliate oranges. However, Tankan and Ponkan grafted on trifoliate oranges grow much more slowly in fields than when grafted on Sunki rootstocks. Therefore, the possibility that nutrient mobilization is affected by plant vigor was not ruled out in the experiment of Chen (1964). In the present study, the performance of grafts was not checked. Therefore, it remains unclear whether graft incompatibility can be estimated by the accumulation of 32P at the graft union. However, the results of the present study suggested that double grafting techniques should be used for the detection of vascular discontinuities by measuring the distribution of radioisotopes in plants.

5 Sutarto et al.: Vascular discontinuity in rambutan and durian 237 References Bukovac, M.J., S.H. Witter and H.B. Tukey Effect of stock-scion interrelationships on the transport of 32P and 45Ca in the apple. J. Hort. Sci. 33: Chen, C.C Studies on absorption and translocation of nutrient on Citrus as influenced by stock-scion relationship using 32P, 35S and 45Ca as tracers. China Horticulture 10: Feucht, W Graft incompatibility of the tree crops: An overview of the present scientific status. Acta Hort. 227: Hartmann, H.T., D.E. Kester and ET. Davies Plant Propagation, Principle and Practise. Prentice Hall (New Jersey) p Warmund, M.R., B.H. Barritt, J.M. Brown, K.L. Schaffer and B.R. Jeong Detection of vascular discontinuity in bud unions of ejonagold fapple on mark rootstock with magnetic resonance imaging. J. Amer. Soc. Hort. Sci. 118: