Clonal Variation for Loranthus infestation in Teak (Tectona grandis L.f.)

Abstract

Dendrophthoe falcata var. pubescens, commonly known as Loranthus is one of the important epiphytic parasites of Teak plantations, which can cause substantial economic losses. It is generally observed that certain clones harbour a higher number of Loranthus than others. However, susceptibility of different Teak clones to Loranthus infestation has not been documented in India. Here we report on the clonal variation for this aspect in one of the Teak clonal seed orchards (CSOs) of Karnataka. All the ramets in the CSO (n=625) were scored for the number of mistletoes on them. A weighted score was developed to assess clonal variation for Loranthus infestation, considering percent ramets infested and the number of mistletoes per individual. Around 37 percent of the ramets in the CSO were infested by at least one parasite, which is akin to the infestation levels among neighboring Teak plantations. However, significant variation for the Loranthus infestation was observed among 24 clones studied. Clones- MySS1 and MySS2 were found to be least infested (i.e. 3.8 and 4.0% ramets), whereas clone- MyHaV2 showed highest Loranthus infestation of 48.1%. Although the influence of origin of clone on the Loranthus infestation was significant, provenancial effect on the trait was weak. Based on the score developed, four clones (viz., MySS1, MySS2, MyHaD2 and MyHaD1) were classified as ‘tolerant’, five clones were under ‘highly susceptible’ (viz., MyHuT4, MyHuT5, MyHuT8, MyHaV4 and MyHaV2) and rest of the 15 clones were ‘susceptible’. None of the clones were absolutely resistant against Loranthus infestation. Perhaps this is the first report on clonal variation for Loranthus infestation in Karnataka. We discuss the plausible reasons for such clonal variation.