Indian sandalwood (Santalum album L, Santalaceae) is one of the high traded medicinal tree species of India having ecological and conservation value. It is a hemi-root parasite and requires suitable host plants for its successful regeneration and establishment (Rai 1990). The global distribution of the sandal family is between 30° North and 40° South from Indonesia in west to Juan Fernandez Island in the north to New Zealand in the south. These species are mainly found in India, Indonesia, Australia, Timor, Hawaii etc (Subasinghe 2013). Sandalwood trees are found in southern tropical dry deciduous forests of India (sub types 5A/C₂ and 5A/C₃) ie from south (Karnataka, Tamil Nadu and Kerala) to other parts of the country viz Andhra Pradesh, Maharashtra, Madhya Pradesh, Orissa, Rajasthan, Uttar Pradesh, Bihar, Gujarat and Manipur (Luna 1996).

Sandal is prized for its aroma in the heartwood and the wood is used for carving which fetches good price in the national and international markets. Sandalwood oil is used in perfumes, cosmetics, aromatherapy and pharmaceuticals (Ambasta 1986), therefore, great demand for heartwood of sandalwood. Farmers from different parts of the country are already cultivating this species on their farmlands in blocks or agroforest plantations.

Sandalwood improvement programme has alreadybeen initiated in the country to improve the quality and quantity of wood biomass and oil content (Radomiljac et al 1998). For breeding tree species, knowledge of reproductive biology including phenology is veryessential that eventually helps in production of quality germplasm for large scale seedling production and plantation programme (Zobel and Talbert 1984). Therefore, this study was undertaken to understand the pattern of flowering and fruiting phenology in sandalwood.

This study was carried out at the campus of Forest Training Institute, Gungaragatti, Dharwad, Karnataka. Sandalwood is naturalized in the campus and adjoining areas. Several bird species visit the sandalwood trees hence, the natural regeneration of sandalwood is found to be medium to abundant under tree plantation, bamboo plantation, medicinal plants garden and natural forests within the campus (Hanumantha et al 2012). Phenological variation was initially observed among trees in sandalwood at the campus. Therefore, detailed study was undertaken by selecting 15 trees distributed in the research plot of sandalwood to record the reproductive phenological pattern during 2010-11. Trees were visited at fortnightly intervals and methodology was followed as per Gunaga and Ramesh (2002a, 2002b).

Tree to tree variation for time of flowering and fruiting was recorded in the study (Figs 1, 2). All the marked trees flowered during Jan to Mar. Many marked individuals showed peak flowering (>70% of crown bloomed) twice in a year, the first during Jul-Aug and the second during Dec-Jan as shown in Fig 1. One of the individuals showed peak flowering during Sept and Nov (Tr-08). Tree bearing number Tr-05 showed peak flowering thrice in a year (Aug, Dec and end of Feb) followed by Tr-08. However, in Tr-12, second peak flowering occurred during Feb-Mar. The similar pattern of variation was also recorded for fruiting phenology. Continuous fruiting except during Jun-Jul, was observed in the sandalwood as presented in Fig 2. Peak fruit collection period would be Apr-May and Sept-Oct for large scale propagation of seedlings in the nursery.

Knowledge of breeding system and patterns of gene flow among forest trees are more informative for planning of seed collection as well as designing and managing seed orchards to maintain genetic diversity of breeding population (Zobel and Talbert 1984). The reproductive phenology also plays a vital role for incorporating diverse clones while establishing seed orchard to avoid asynchronous flowering and to improve the quality and quantity of seed output in the clonal orchard (Nagarajan et al 1998, Gunaga and Ramesh 2002a).

The present study showed the different patterns of phenology in terms of flowering and fruiting in sandalwood. In general, two peak flowerings were recorded and such observation was also reported in sandalwood (Kulkarni and Muniyamma 1998, Annapurna et al 2005, Ratnaningrum and Indrioko 2015, Krishnakumar and Parthiban 2017). Patterns of flowering within a site or provenance would be attributed by genotypes, however, time of flowering is mainly influenced by genotype, temperature and photoperiod (Iannucci et al 2008, Ramesh and Gunaga 2012). In sandalwood, annual climatic conditions like temperature and rainfall alter the flowering behaviour, maturity of sexual organs, fruit set, seed quality and yield (Annapurna et al 2005, Ratnaningrum and Indrioko 2015). Kulkarni and Muniyamma (1998) documented the reproductive cycle in sandalwood where period required from bud initiation to fruit ripening was recorded to be 110-140 days. Fig 1 determines the asynchronous flowering pattern among 15 individuals and such pattern was also reported by Kulkarni and Muniyamma (1998) in sandalwood where asynchronous flowering and duration required for completion of blooming for each inflorescence varied among genotypes. They also noticed that one of the studied trees flowered throughout the year and yielded maximum seed output than other morphotypes. In this study, accession Tr 07 fruited almost throughout the year and peaks were achieved twice – first during early May and another during late October. From ecological point of view, it can be said that presence of such individuals in the ecosystem may be useful for birds (Hanumantha et al 2012) and/or bees (Tamla et al 2012) that visit sandalwood for their food.

The tree to tree variation for flowering and fruiting phenology was observed. Trees produce fruits throughout the season that helps birds for their food. Moreover, two peak fruitings were recorded which would be useful in large scale seedling production in the nursery. Study implies that before establishment of CSO, the reproductive phenology of selected genotypes (plus trees or clones) must be known while incorporating clones from local or distance geographic regions into CSO in order to match the flowering synchrony among clones for production of quality seeds in large quantity.

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