Studies on Propagation of Grapefruit (Citrus paradisi Macf.) by Bud Grafting

Abstract

Experiments were carried out at the greenhouses of the Date palm Company, Shambat Research Station, Khartoum North, to evaluate the potential effects of some growth regulators (BAP , Sangral) pesticides (Furadan,Glyphosate, Seven and Stroby) and plant extracts (Rocket, Spinach and Garlic) on scion bud-take and subsequent scion shoot growth and development of grapefruit (Citrus paradisi Macf.),cv. “Redblush”. All experiments were conducted using scion bud-wood obtained from a single 10-yearsold "Redblush" grapefruit tree grown in the open fields of the Department of Horticulture, Ministry of Agriculture and Forestry, Al-Mogran (Latitude 35 15 N; Longitude 33 32 E), selected on the basis of uniformity of fruiting and vigorous growth habit. Sour orange (Citrus aurantium L.) seedlings, 9- month -old and 60 cm in height were used as rootstock. The effect of soaking scion buds in different concentrations of benzyl-amino-purine (BAP), as a pre- budding treatment, on bud-take and subsequent scion shoot growth and development was examined. Scion buds responded best to 400 mg/l BAP and this response was reflected on the highest values obtained with all growth variables measured. Soaking of scion buds in Sangral at a concentration of 200 mg/l resulted in a positive effect on percent scion bud-take and number of leaves. The highest number of leaves and the bud-take ii percentage was obtained with scion buds soaked in 200 mg/l Sangral concentration. Shoot elongation was not significantly affected by all Sangral concentrations relative to the control. The values recorded with the 200 mg/l Sangral were similar to those obtained with the 400 mg/l Sangral, denoting the presence of a cytokinin-like effect in Sangral which is used in commercial horticultural nurseries for rooting of plant cuttings. Thus sangral exhibits considerable potential as an agent for promoting scion bud-take in grapefruit. The results of the 200 mg/l of Sangral and topping showed that the combination was optimum for all parameters measured compared with the other treatments. The Sangral/topping combination treatment significantly increased leaf formation and scion bud-take compared to the soaking in sangral or topping treatments. Again, shoot elongation was not significantly affected by any of the other treatments. Concentrations of furadan, sevin, glyphosate and stroby chemical compounds were tested each alone, in order to determine their influence on scion bud-take and subsequent scion shoot growth efficiencies. Because of scarcity and availability, only one concentration, (50 mg/l) of each of furadan, sevin and glyphosate was tested in one experiment. Stroby is available in the market and was thus tested in different concentrations in a separate experiment. Positive effects on leaf number and scion bud-take of iii equivalent magnitude were obtained with furadan and sevin treatments whereas, shoot length was largely unresponsive to any of the two treatments. The 50 mg/l glyphosate concentration treatment caused injury to the scion buds resulting in the browning of all budded scions and consequently failure of the scion bud-take process. Scion buds responded best to relatively high concentrations of stroby where the largest number of leaves and the highest percentage of scion bud-take were obtained with scion buds soaked in 200 mg/l stroby concentration. Although differences between treatments were not significant in shoot length, the longest shoots were obtained in 200 mg/l stroby concentration. It is difficult to give an explanation for the effects of these chemical compounds at the moment. Nevertheless, the results demonstrated that relatively low concentrations of all of the four chemical compounds tested in this study enhanced growth and development of budded scion buds of grapefruit denoting a growth regulators-like effect. All rocket leaf extract concentrations tested increased leaf formation, shoot length and percent scion-bud take relative to the control. The 10% rocket leaves extract concentration resulted in high values of all growth parameters with no significant difference among treatments. Spinach leaf extract concentrations improved all parameters relative to the control. The 5% concentration treatment effectively enhanced leaf formation, shoot iv elongation and scion bud-take percentage with no significant difference among treatments. Neither leaf number nor scion shoot length were affected by garlic extract concentrations but the values obtained for both measures were non-significantly higher with scion buds treated by soaking in 5% garlic extract concentration than the other treatments. Bud-take however, responded differently to garlic extract concentrations . All concentrations of garlic significantly increased scion bud-take percentage over the control. The highest bud-take percentage was obtained with 5% garlic concentration .