Primary Host Interaction of Root Parasite Sandalwood (Santalum album L): Morphological and Biochemical Responses during Interaction with Legume Host Cajanus and Non-Legume Host Alternanthera

摘要

Sandalwood (Santalum album L.), a root hemiparasite, endemic to Southern India, is a tree of great commercial value globally. Considering the growing demand and the diminishing supply of sandalwood from its natural habitat, there is a great potentialfor cultivating sandal trees in agricultural land, home gardens and other agro forestry systems. The cultivation of sandalwood is challenging because of the poor understanding of host parasite relationship as sandalwood is a root parasite. In this context a study was carried out to understand the relationship of sandalwood with its two primary hosts, Cajanus (legume) and Alternanthera (nonlegume). The results showed that sandalwood grown with Cajanus (T_3) have greater plant height (176.57 cm), stem girth (12.01 cm) chlorophyll content (3.29 mg/g FW of leaves) in contrast to sandalwood grown with Alternanthera (T_2) and control (T_1) without a host. The variations in activity of SOD, Peroxidase (POX) and accumulation of phenols, flavonoids, proline insandalwood indicates differences in sandalwood response at molecular level towards the two hosts. There was a clear shift in SOD isozyme bands in sandalwood when it interacted with Cajanus as compared to Alternanthera (T_2) and control (T_1). The increase in peroxidases observed in T_3 (11.30mug/mg protein) was significantly higher compared to the T_2 and T_1. The same trend was observed for the phenols, flavonoids and prolines. The greater reduction in defense response in the host plant Cajanus in comparison to Alternanthera when planted with sandalwood signifies the deliberate vulnerability of Cajanus towards sandalwood parasitism, making it a superior host. Indeed, a polybag experiment to evaluate the direction of root growth shows a clear preference of sandalwood root to Cajanus, as compared to Alternanthera. Overall from the phenotypic observations and also from the biochemical estimations, the leguminous host Cajanus was found to be a better primary host than Alternanthera in the field condition. The insights gained from the present investigation can be used for sandalwood cultivation in large scale in the natural habitat as well as in other agroforestrty region.