Dr. (Mrs.) Anamika Sharma ICAR Research Complex for NEH Region, Jharnapani, Nagaland Propagation is an art of multiplication of plants. Citrus can be multiplied sexually as well as asexually also. 1. Sexual propagation: Multiplication of plants by seed is known as sexual propagation. It is a simple and cheap method of propagation. In citrus polyembryony exists. For example all the varieties of citrus except pumalo (Citrus grandis), tahati lime (C. latifolia) and turanj (C. medica) give rise to more than one seedling from one seed. Polyembroynic varieties can therefore, be propagated by seeds. The rootstocks upon which the fruit varieties are budded or grafted are usually obtained by sexual propagation for e.g. rangpur lime is generally used as rootstock in citrus. 2. Asexual / vegetative propagation: Mitosis is the basic process of normal vegetative growth, regeneration and wound healing which make possible the vegetative propagation techniques like cuttings, grafting, layering, separation, and divisions. These methods of propagations are important because they permit a large-scale multiplication of genetically identical individual plants. For many plant species , rootstocks are available which tolerate unfavorable conditions such as heavy, wet soil or which resist soil–borne pest or disease organism. For e.g. trifoliate orange and its hybrid citranges are resistant to citrus nematode. These can be used as rootstock in citrus nematode affected areas. a) Propagation by layering: Layering is the method of propagation in which roots are developed on a stem while it is still attached to parent plant. After proper rooting, the stem is detached and becomes a new plant for growing on its own roots. The high success of layering is obtained by ringing or wounding, etiolation (absence of light), use of rooting hormone (IBA, NAA) and favorable environmental conditions (temp. and humidity). Air layering is most commonly used in citrus. Air Layering: In this method, roots are formed in the aerial part of plant. The stem is girdled and rooting hormone is applied to upper part of cut. Moist rooting medium (mass grass) is wrapped with the help of small polythene strip ( 200-300 gauze, transparent).( In case mass grass is not available 50% well rotten cow dung and 50% garden soil should be mixed well , then some water is to be added so that balls can be prepared).This method is commonly known as goottee. Lemon, kagzi limes can be propagated by this method. May to July is the ideal period for air layering. Rooting in air layers generally commences within 25-30 days and layers are ready for transplanting within 3 months. b) Propagation by cuttings: In this method, cutting of plant parts (specially stem, leaf or root) are used for propagation. Hard wood and semi hard wood cuttings are generally used for propagation. Semi hard wood cuttings are mostly used in evergreen fruit plants like lemons etc. Available shoots during June- July have not attained the full maturity and are 5-9 months old. Such shoots are used for propagation purpose. Length of cuttings should be 7-20 cm. It is better to retain 2-4 leaves on the top of cuttings. Treating cuttings with 5000 ppm IBA gives better results. Commercial formulations of IBA are available in the name of Rootex, Rootbin, Seradex etc. c) Propagation by budding: Budding is cheaper, easier, quicker and better method of propagation than grafting. Budding utilizes only one bud and a small section of bark with or without wood. Budding method usually depends upon the slipping of bark when the bark can be easily separated from wood. It denotes the period of the year when the plant is in active growth and cambium cells are actively dividing. It is important to use vegetative bud than flower bud. Vegetative buds are usually small and pointed while flower buds are large and plumpy. Spring budding : Budding in spring ( March –April) as soon as active growth of rootstock begins and bark separates easily from wood. This period is very limited and budding should be completed soon. Bud wood is collected while it is still dormant before there is any evidence of bud swelling. As this dormant bud is INSERT IGNOREed and rootstock is in active growth, the bud sprouts and develops easily. It is commonly found in citrus Shield or “T” budding: As the name indicates “shield” is the shape of the bud and “T” is the shape of cut given on rootstock for operation. In case of citrus, budding should be done along with wood to avoid rupture of bud. This method is mostly used in oranges. Micropropagation: It refers to propagation of plants from very small plant parts, tissues grown aseptically in a test-tube or container under controlled nutritional and environmental conditions. This method is gaining popularity because of production of virus free seedlings. But this method can not be used by small farmers.
