In-vitro seed germination of citrus rootstocks and micro-grafting studies in sweet orange (Citrus sinensis)
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Date
2019
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CCSHAU
Abstract
Citrus is one of the world’s most economically important fruit crops and belongs to family Rutaceae. It is the third most cultivated fruit crop in the world after mango and banana. Citrus produces more citric acid per unit area as compare to other fruit crops and is major source of Vitamin-C in many countries. Conventionally, plants are propagated through budding but virus can easily transmit through budding. Viral infection transmitted through budding is the major cause of citrus decline in India. Due to diseased planting material, there is a need to develop an alternate method of propagation. Therefore, Meristem Culture and Micro-grafting technique can be used for the mass production of true-to-type, disease free quality planting material of sweet orange cv. Jaffa. In the present investigation, experiments were conducted to develop an efficient procedure for in-vitro seed germination of citrus rootstocks and micro-grafting of sweet orange (Citrus sinensis). Nodals explants were sterilized using bavistin (0.2%) and streptocycline (0.4 %) for 90-120 minutes followed by treatment with HgCl2 (0.1%) for 5-6 minutes. Sterilized explants were inoculated on MS basal supplemented with various concentration of BAP (0.25 - 2.0 mg/l) and established successfully. The regenerated explants were further used in taking shoot tips (0.2-0.4 mm). The maximum regeneration (100%) was reported on medium (CEE4) (MS basal medium with BAP-1.00 mg/l). The surface sterilized seeds of four citrus rootstocks, viz. Rough lemon, Rangpur lime, Pectinifera and Cleopatra mandarin were aseptically inoculated using three different medium. Rough lemon was found to be most responsive amongst all other rootstocks with 100% seed germination in 7.1 days with maximum 2.5 seedlings per seed and maximum 4.0 cm shoot length on medium CSG2 (MS basal medium + BAP 0.5 mg/l + NAA 1.0 mg/l + GA3 4.0 mg/l). The micro-grafting was carried out using seedling of different ages (20, 24, 28 and 32 days) of rootstocks and excised shoot tip (0.2-0.4 mm) of sweet orange cv. Jaffa. Rough lemon was found to be easiest rootstock for micro-grafting as it showed maximum micro-grafting success (33.3%) on 20 and 24 days old seedlings and took minimum days (19.4) for graft union in micro-grafted plants of sweet orange cv. Jaffa.
Successfully micro-grafted plantlets were successfully hardened in green house using sterilized mixture of cocopeat, perlite and vermiculite in the ratio of 1:2:1 and finally transferred to field. The procedure will be very useful for further production of disease free budwood stock.
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