MICROPROPAGATION OF 'TROYER' CITRANGE [PONCIRUS TRIFOLIATA (L.) RAT. × C. SINENSIS (L.) OSBECK

Abstract

In Citrus, the success of the scion largely depends upon the rootstock on which it has been grafted. 'Troyer' citrange is an important rootstock used worldwide for high density planting. It is also one of the most promising rootstock for several Indian scion varieties such as 'Nagpur' mandarin, 'Kinnow' mandarin, grapefruits, acid lime, 'Satsuma' sweet orange and 'Mosambi' sweet orange. In addition, it has high resistance to tristeza virus, which causes Citrus decline, and has good adaptability for acidic soil. Commercial rootstock cultivars are commonly propagated by seeds. However, seeds of many Citrus varieties are moderately recalcitrant and also face loss of viability within a short period. The plants grown from seeds exhibit extended juvenility (4 to 10 years), thus making vegetative propagation and micropropagation a desirable method of propagation. The present study focuses on developing an efficient micropropagation protocol for the production of clonally uniform plants through axillary branching method of slow growing rootstock variety, 'Troyer' citrange. Multiple shoots can be obtained from single nodes of field grown trees cultured on Murashige and Skoog's (MS; 1962) medium containing Benzylamino purine (BA; 1.11 μM), Kinetin (Kn; 1.1625 μM), and 3% sucrose. A shoot multiplication fold of 3.86 every four weeks was achieved. Proliferated shoots were rooted on half strength MS medium with Naphthalene acetic acid (NAA; 0.5 μM) and plantlets were transferred to a mixture of soil and agropeat. 100% survival was observed during hardening of the rooted plantlets. The comparative analyses of the DNA fingerprinting profiles confirmed the genetic stability of the regenerated plantlets. The results of this study have enormous commercial application for the propagation of healthy disease-free Citrus rootstocks to meet the ever-growing demand for superior quality planting material.