performances of different scion-rootstock combinations in grafted litchi trees. In this study, scions of different cultivars ('Guiwei', 'Nuomici' and 'Feizixiao') were.
Shoot Growth from Scions Top-Grafted on Different Litchi Cultivars G.B. Hu, H.B. Chen and X.M. Huang* Physiological Lab for South China Fruits College of Horticulture South China Agricultural University Guangzhou 510642 China *Corresponding author
J.H. Bu Huaxiang Orchard, Rutong, Yangxi Guangdong China
Keywords: Litchi chinensis Sonn., graft compatibility Abstract Changing cultivars in established litchi (Litchi chinensis Sonn.) orchards is commonly carried out by top-grafting. However, there is little information about performances of different scion-rootstock combinations in grafted litchi trees. In this study, scions of different cultivars (‘Guiwei’, ‘Nuomici’ and ‘Feizixiao’) were top-grafted onto branches about 1 cm in thickness in trees of different cultivars (‘Baitangying’, ‘Baila’, ‘Feizixiao’, ‘Heiye’ and ‘Shuangjianyuhebao’) in the summer of 2006, and the length of shoots developed from the scions were measured 8 month later on June 7, 2007. The results showed that scions of ‘Guiwei’ grew vigorously on ‘Baitangying’ and ‘Baila’, but less vigorously on ‘Heiye’, while the growth was stunted when grafted onto ‘Shuangjianyuhebao’ and ‘Feizixiao’. ‘Nuomici’ scion grew most vigorously on ‘Baitangying’, less vigorously on ‘Baila’ and least vigorously on ‘Shuangjianyuhebao’. ‘Feizixiao’ shoot grew very well on ‘Heiye’. The results showed a poor compatibility between ‘Guiwei’ and ‘Feizixiao’ and that ‘Shuangjianyuhebao’ might serve a dwarfing rootstock for ‘Guiwei’ and ‘Nuomici’. INTRODUCTION Litchi is a subtropical fruit cultivated widely in regions with a warm subtropical climate. In most producing countries, litchi is propagated via air-layers due to difficulty in grafting operation and low success rate (Mitra and Ray, 2005). However, in China, grafting and/or budding have been extensively used in litchi propagation for hundreds of years (Tong, 1983). Despite the long history of grafting application, systemic studies on litchi grafting including scion/rootstock relations is lacking and there is little information concerning compatibility among cultivars. Practice of litchi grafting is largely based on trials and errors, which has led to a general principle of ‘early cultivars grafted on early cultivars, late cultivars on late cultivars’. Hence, seedlings of ‘Huaizhi’ are widely used rootstock for ‘Nuomici’ and ‘Guiwei’, while ‘Heiye’ seedlings are used for ‘Feizixiao’ and ‘Dazao’ (See Huang, 2005). Incompatibility of scion and rootstock is one of the major obstacles in propagation via grafting. It includes complete incompatibility, scion overgrowing rootstock and delayed incompatibility (scion dies 1 or 2 years after grafting) (Murray and Murray, 1994). After the rapid expansion in litchi production in the late 1980s and throughout the 1990s in China, seasonal overproduction during harvesting season turned out to be the major problem in the industry. Major commercial cultivars such as ‘Heiye’ and ‘Huaizhi’, which used to account for two thirds of litchi production in China, have become much less profitable than before. Hainan is a relatively new litchi production region, where ‘Feizixiao’ is the major player and is marketed much earlier than other regions, taking up considerable market share from the traditional ‘Feizixiao’ regions. Many growers in Guangdong and Guangxi tend to replace their low-profit traditional cultivars including ‘Heiye’, ‘Feizixiao’ and ‘Huaizhi’ with better-priced cultivars such as ‘Guiwei’ and ‘Nuomici’. Instead of replanting, top-grafting is a common practice to change cultivars. Due to the issue of incompatibility, scions from these cultivars may perform differentially Proc. 3rd IS on Longan, Lychee & Other Fruit Trees in Sapindaceae Family Eds.: Qiu Dongliang et al. Acta Hort. 863, ISHS 2010
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when top-grafted on different cultivars. There is an urgent need to investigate the performance of different scion/rootstock combinations. MATERIALS AND METHODS The investigation was conducted in 2007 in Huaxiang Orchard, Yangxi, Guangdong Province. The orchard had a number of litchi cultivars including ‘Feizixiao’ (F), ‘Shuanjianyuhebao’ (S), ‘Baila’ (BL), ‘Baitangying’ (BT), ‘Guiwei’ (G) and ‘Heiye’ (H). Top-grafting was carried out in summer of 2006. Scions of ‘Nuomici’ (N) and ‘Guiwei’ (G) were top-grafted on BT, BL, S, H or F, and those of ‘Feizixiao’ on ‘Heiye’, giving 9 scion-rootstock combinations including G/BT (‘Guiwei’ on ‘Baitangying’), G/BL, G/S, G/H, G/F, N/BT, N/BL, N/S and F/H. Segments of bud woods with 2 nodes were grafted onto 0.8-1 cm thick stems of heavy pruned one-year-old trees of relevant cultivars. After grafting, new growth of flushes of the rootstock cultivars were all removed to encourage the growth of the scion shoots. Performance of shoots grown from the scions was investigated in June 2007. Lengths of all shoots from the graft union were measured and grafted trees photographed. RESULTS Length of shoots from ‘Guiwei’ scions top-grafted on different cultivars followed the order of G/BT > G/BL > G/H > G/S > G/F (Fig. 1). Hence, scions of ‘Guiwei’ grew most vigorously on ‘Baitangying’ and ‘Baila’, but less vigorously on ‘Heiye’, while their growth was stunted when grafted onto ‘Shuangjianyuhebao’ and ‘Feizixiao’. Similarly, shoot length of ‘Nuomici’ showed the same pattern: N/BT > N/BL > N/S (Fig. 1), suggesting ‘Nuomici’ scion grew most vigorously on ‘Baitangying’, less vigorously on ‘Baila’ and poorly on ‘Shuangjianyuhebao’. ‘Feizixiao’ shoot grew very well on ‘Heiye’. G/B, G/BL, G/H, N/BT, N/BL and F/H all produced perfect grafting healing; G/S and N/S showed slightly swollen grafting union; and G/F produced swollen and vertically cracked conjunction (Figs. 2 and 3). Trees of G/F failed to grow and remained stunted. G/S and N/S trees tended to produce a lower canopy than the remaining combinations (Figs. 2 and 3). The results showed a strong incompatibility between ‘Guiwei’ and ‘Feizixiao’ and a poor compatibility between ‘Shuangjianyuhebao’ and ‘Guowei’ or ‘Nuomici’. ‘Guiwei’ has also a poor compatibility with ‘Heiye’ as compared to with ‘Baitangying’ and ‘Baila’. Both ‘Guiwei’ and ‘Nuomici’ are highly compatible to ‘Baitangying’ and ‘Baila’, so is ‘Feizixiao’ to ‘Heiye’. DISCUSSION ‘Guiwei’ and ‘Nuomici’ are of top quality among the commercial cultivars in China. They are mostly cultivated in the Pearl River Delta. Due to their high price, growers in other regions are trying to replace their less profitable traditional local cultivars like ‘Heiye’ and ‘Baila’ with ‘Guiwei’ or ‘Nuomici’. ‘Feizxiao’ used to be a competitive mid-season cultivar in the Pearl River Delta and west Guangdong. However, due to rapid development of this cultivar in Hainan, where climate is warmer and ‘Feizixiao’ fruit are marketed earlier, ‘Feizixiao’ in Guangdong is no longer a profitable cultivar and is being replaced by ‘Guiwei’ and ‘Nuomici’. Top grafting is the most efficient way to quickly establish canopy of the desirable cultivars without time- and labor-taking tree removal and replanting. Because the performance of scion cultivars is subjected to the strong influence of rootstock, it is very important to know the compatible with cultivars to be grafted on. Based on this study, ‘Guiwei’ is not the suitable scion for top grafting on ‘Feizixiao’, but it performed well when top-grafted on ‘Baitangying’ and ‘Baila’. Compatibility of ‘Guiwei’ to ‘Shuangjianyuhebao’ was lower than to ‘Baitangying’, ‘Baila’ and ‘Heiye’, but higher than to ‘Feizixiao’. ‘Nuomici’ can also be top-grafted on ‘Baitangying’ and ‘Baila’. When top-grafted on ‘Shuangjianyuhebao’, ‘Guiwei’ and ‘Nuomici’ tended to grow slowly and produce a small canopy. Perhaps ‘Shuangjianyuhebao’ can serve as a dwarf rootstock for ‘Guiwei’ and ‘Nuomici’. Long-term performances of G/S and N/S combinations are under investigation.
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There is fragmental information about scion-rootstock compatibilities in litchi (Zhang, 2000; Mitra and Ray, 2005; Huang and Li, 2007). It is generally believed that compatibility between scion and rootstock is closely related to genetic similarity of the two parts. According to the study by Liu and Mei (2005), genetic similarity to ‘Guiwei’ based on DNA finger printing followed the order of ‘Nuomici’ > ‘Heiye’ > ‘Baitangying’ > ‘Baila’ > ‘Feizixiao’, which is basically in agreement with their grafting compatibility. A genetic similarity analysis among litchi cultivars will help to find compatible scion-rootstock combinations. Further studies are necessary to understand the mechanisms behind grafting compatibility. ACKNOWLEDGEMENTS This study has been supported by Ministry of Agriculture of China (Project No. nyhyzx08-031 and 2006G31) and Ministry of Science and Technology China (2006BAD01A17). Literatures Cited Huang, D.Y. and Li, E.P. 2007. Key techniques in litchi top-grafting. South China Fruits 36(3):45-46. Huang, X.M. 2002. Litchi production in China. p.41-54. In: M.K. Papademetriou and F.J. Dent (eds.), Lychee Production in the Asia-Pacific Region. FAO Press. Mitra, S.K. and Ray, P.K. 2005. Propagation. p.35-48. In: C.M. Menzel and G.K. Waite (eds.), Litchi and longan: Botany, production and uses. CAB International. Murray, V.G. and Murray, R.D. 1994. Confronting plant diversity when propagating Litchi chinensis. Proc. Fla. State Hort Soc. 107:354-358. Tong, P.Y. 1983. History of fruits in China. Agricultural Press, Beijing p.362. (in Chinese) Zhang, X.L. 2000. Internal and external factors affecting grafting success in litchi. Rural Practical Techniques 3:18-19.
Figures 140
Shoot length (cm
120 100 80 60 40 20 0 G/BT G/BL
G/S
G/H
G/F
N/BT N/BL
N/S
F/H
Scion/Rootstock combination
Fig. 1. Shoot growth in different scion-rootstock combination. G/BT: ‘Guiwei’ grafted on ‘Baitangying’; G/BL: ‘Guiwei’ grafted on ‘Baila’; G/S: ‘Guiwei’ grated on ‘Shuangjianyuhebao’; G/H: ‘Guiwei’ grafted on ‘Heiye’; G/F: ‘Guiwei’ grafted on ‘Feizixiao’; N/BT: ‘Nuomici’ grafted on ‘Baitangying’; N/BL: ‘Nuomici’ grafted on ‘Baila’; N/S: ‘Nuomici’ grafted on ‘Shuangjianyuhebao’; F/H: ‘Feizixiao’ grafted on ‘Heiye’.
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Fig. 2. Tree canopies and graft unions of ‘Guiwei’ top-grafted on different cultivars. Prof. Guibing Hu served as reference. Pictures were taken on June 7, 2007, one year after top grafting. G/BT, G/BL, G/H, G/S and G/F represent ‘Guiwei’ top-grafted on ‘Baitangying’, ‘Baila’, ‘Heiye’, ‘Shuangjianyuhebao’ and ‘Feizixiao’, respectively.
Fig. 3. Tree canopies and graft unions of ‘Nuomici’ and ‘Feizixiao’ top-grafted on different cultivars. Prof. Guibing Hu served as reference. Pictures were taken on June 7, 2007, one year after top grafting. N/BT, N/BL, N/S and F/H represent ‘Nuomici’ top-grafted on ‘Baitangying’, ‘Baila’ and ‘Shuanjianyuhebao’, and ‘Fezixiao’ on ‘Heiye’, respectively.
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