Abstract
Abstract Indian sandalwood ( Santalum album L.) is an expensive wood that requires reproducible method for mass propagation to ensure consistent production and sustainable use of sandalwood. For mass propagation of sandalwood, plant organogenesis requires different combinations of the tissue culture medium. The media is composed of exogenous phytohormones which decides the explant's morphological stages such as shooting or rooting induction. Early prediction of morphological stage from explant can potentially help in selecting the exogenous phytohormones combinations thereby saving time and resources for mass sandalwood propogation. An efficient protocol for the direct and indirect organogenesis (up to shooting development phase) of sandalwood were developed using Woody Plant Media (WPM). WPM supplemented with various concentrations of 6-Bezylaminopurine (BAP) and 1-Naphthaleneacetic acid (NAA) were tested for direct organogenesis, while different treatments consisting of various levels of 2,4-dichlorophenoxyacetic acid (2,4-D), NAA, BAP, Adenine sulphate (ADS), glycine and potassium nitrate were tested for indirect organogenesis. Three stages of leaf development were selected viz. , the leaf just after inoculation in WPM media, initial stage of callus formation from leaf and shoot formation for expression pattern analysis. The targeted genes were Alternative oxidase ( ao ), Late embryogenesis abundant ( lea ), Cytochrome P450 ( cyt-p450 ), ABC transporter ( abct ), and Serine-threonine phosphatase ( stp ) which are associated with in vitro organogenesis. The expression patterns were evaluated to identify a transcription marker. During the initial stages of organogenesis, ao , cyt-p450 and abct showed no/little change in expression in the direct pathway but up-regulation of ao and abct and downregulation of cyt-p450 were observed in the indirect pathway. Expression of lea was increased up to 70-fold during direct and dropped to half during indirect organogenesis.
Highlights
Indian sandalwood (Santalum album L.) is one of the tree species popularly known as ‘The Royal Tree’ of the plant kingdom (Subasinghe 2013)
The shoot induction media for direct organogenesis was comprised of Woody Plant Medium (WPM) (Lloyd and McCown 1981) supplemented with various combinations of 6-Benzylaminopurine (BAP) and 1-Naphthaleneacetic acid (NAA) and 3% w/v sucrose (Table 1) while the shoot induction media for indirect organogenesis was comprised of Woody Plant Media (WPM) supplemented with various combinations of Glycine, Adenine Sulphate (ADS), Potassium nitrate KNO3), NAA, BAP, 2,4-Dichlorophenoxyacetic acid (2,4-D) and 3% w/v sucrose (Table 2)
Treatments SD14 and SD7 came up with potential numbers of shoots formation per explant after 120 days but considering the overall efficient health SD14 dominated over SD7. These observational analyses were in correlation with the report by Singh et al (2013) where they used WPM supplemented with 2.5 mgL-1 BAP and 0.2 mgL-1 NAA and obtained a bud frequency of 79.16%, whereas incongruent with results of Mujib (2005) who reported the BAP concentration as low as 0.5 mgL-1 without incorporating NAA
Summary
Indian sandalwood (Santalum album L.) is one of the tree species popularly known as ‘The Royal Tree’ of the plant kingdom (Subasinghe 2013). Sandalwood has the capacity to grow under diverse conditions, viz. The major constraints in growing sandalwood are long seed dormancy period (ranges from 2 months to 12 months and normally take 4-8 weeks for the germination) and flowering usually occurs after 3–4 years in only 60% plants (Srimathi et al 1995). Since the conventional breeding methods is one of the techniques for creating consistency in production. It is an expensive and difficult process because sandalwood has long generation time and heterozygous in nature (Rugkhla and Jones 1998)
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