Aspects of the pollination and fuit production of teak (Tectona grandis Linn.f )

Vol 3, No. 2, May - Aug 2010 Aspects of the Pollination and Fruit Production of Teak 61 Research Articles Aspects of the pollination and fuit production of teak (Tectona grandis Linn.f ) Manas Titayavan 1 and D. Michael Burgett 2 Abstract Aspects of the pollination and fruit production of Teak(Tecona grandis Linn. F.) were investigated utilizing three middle aged (ca. 25 years) grown in mixed forest condition in northern Thailand. The first bloom phenology began early in July and carried on for 3 to 4 weeks. The average inflorescence produced 485.5 blooms with an average of 20.2 new blooms per panicle per day. Teak is shown to be a polyphilic species. Daily observations of flower visitors which were made from 10:00 to 14:00 hrs yielded 39 insect species representing: Lepidoptera (64.10%), Hymenoptera (25.64%), and Diptera (10.26%) as potential pollinators. The relative effectiveness of sting-less bees, Trigona laeviceps and T. pagdeni as potentially managed pollinators of teak was investigated by the daily introduction of controlled numbers of worker bees into individually bagged blooms. The trials were 2x3 factorial experiments in a randomized complete block design: open-pollination, bagged with no bees, 4 bees, 8 bees, and 12 bees per inflorescence. All trials were replicated three times for each of two species of bees. The highest fruit production was 19.3 fruits per panicle observed under the conditions of open pollination. The lowest rate was 3.7 fruits per panicle under closed pollination conditions. The maximum fruit production by sting-less bees was 10.7 fruits per panicle under the trial of 12 bees per inflorescence. There were no statistically significant differences between means relative effectiveness of these bees. Keywords: Tectona grandis, Trigona laeviceps, Trigona pagdeni, pollination, northern Thailand, polyphilic species, stingless bee, anthophilus insect, pollinator 1 School of Agriculture and Natural Resources, Naresuan University, Phayao Phayao 56000, Thailand 2 Department of Horticulture, Oregon State University, Corvallis, OR 97331, U.S.A. Received : 25 Februay 2010 ; Accepted : 18 August 2010

62 Titayavan M and Burgett M Naresuan Phayao Journal Introduction Teak (Tectona grandis Linn. F.) is an important hardwood commodity in Thailand and has been a commercial tree species since the early 1800 s [1]. Although the species perform very impressively in its natural habitat, the annual teak planting program in Thailand is still limited [2]. One restraining factors is seed production [1, 3,10,11]. Like many hermaphroditic species [3], teak produces a low fruit production rate when compared to the number of flowers produced due to self incompatibility [4]. A high natural abortion rate may contribute to the overall low seed production [5]. We suggest that less than optimum pollination is another contributing factor to the low Fruit and seed production. At the present time there is an insufficient quantity of seed for large scale plantation teak planting in Thailand. As previous suggested by Kaosa-ard (1995), insects are the major pollinating agents for teak, but little research is available concerning the general subject of teak pollination. The insect guilds associated with the full annual bloom phenology are still unclear. Thus, understanding of which pollinator cohorts are of primary importance in overall fruit and seed production. We conducted the research program that will examine various aspects of teak fruit production in northern Thailand and improve knowledge in the area of managed pollination, which can contribute to an improvement in teak fruit and seed production. This study reports on (1) the relative effectiveness of sting-less bees species (Trigona spp.) as potentially managed pollinators of teak, and (2) the polyphilic nature of teak and the association of anthophilus insect pollinators. The expected output are (1) a realization of the potential of sting-less bees species as managed pollinators, and (2) more complete knowledge base of the keystone pollinator species. Materials and Methods The potential of sting-less bees as teak pollinators (Trigona spp.) was investigated utilizing three middleaged (ca.25 years) teak tree grown in mixed forest plantations on the campus of Chiang Mai University in northern Thailand. This was done by the daily introduction of controlled numbers of worker bees into individually bagged blooms. The trials were: open pollination- bagged with no bees 4 bees 8 bees and 12 bees per inflorescence. Bees were introduced at 10:00 hr on each of 25 days. All trials were replicates three times for each of the two species of sting-less bees chosen for study. The species used are indigenous to northern Thailand and were Trigona laeviceps and T. pagdeni. Total fruit production per inflorescence was used as the parameter to measure pollination efficacy. Data analysis from this experiment was by the analysis of variance of 2x3 factorial experiments in a randomized complete block design. It was followed by the Duncan Multiple Range Test (DMRT) for the evaluation of all possible pairs of treatment means. Daily quantification of bloom rates was conducted during the primary bloom periods. Scaffolding was erected to allow observers access to teak blooms. Individual panicles were carefully observed with 27 replicates to provide meaningful statistical analyses. Concurrent with pollinator observations, an additional cohort of teak blossoms was used to construct a bloom phenology during the period 5 29 July. It was the second of three major teak bloom periods in northern Thailand. Daily observations and collections of flower visitors were made from 10:00 to 14:00 hrs. Results Total fruit set per inflorescence was observed under the conditions of pollination. The highest fruit production was 19.3 fruits per panicle observed under conditions of open pollination. The lowest fruit production rate was 3.7 fruits per panicle under the conditions of complete pollinator exclusion or closed-pollination. The maximum fruit set by T. laevicep was 10.7 fruit per panicle under the trial of 12 bees per inflorescence. Number of fruit set for open-pollinated flowers measured 30 d after pollination differed significantly (P< 0.01) from closedpollinated flowers. Only 1.19% of closed-pollinated flowers set fruits where as 4.18% of open-pollinated flowers set

Vol 3, No. 2, May - Aug 2010 Aspects of the Pollination and Fruit Production of Teak 63 fruits. There were no significantly differences between the relative effectiveness of Trigona laeviceps and T. pagdeni as potentially managed pollinators of teak. The results of this experiment are shown in Table 1. Bloom phenology and pollination requirements for fruit production in teak were begun from July 4 through July 26. July is the second of three major teak bloom periods in northern Thailand. The average inflorescence produced 485.5 blooms with an average of 20.2 new blooms per panicle per day. Flowering began from the lower to the upper part of the panicle. The cycle of flowering period for each panicle was 4 weeks. The phenology during this period is shown in Figure 1. Teak is shown to be a polyphilic species as concerns pollinators and in excess of 39 species, representing 64.10% Lepidoptera (butterflies), 25.64% Hymenoptera (wasps, bees, ants), and 10.26% Diptera (flies) were recorded as flower visitors (Table 2). Discussion In our study many factors may have contributed to the relatively low fruit production. Fruit set under the condition of open-pollination was much greater (4.18%) than closed-pollination (1.19%). Mean fruit size and number of seeds per fruit as suggested by Tangmitchareon and Owens (1997) were not determined in this study. The un-pollinated flowers fell off either in the evening or the next morning of the flowering day as reported in earlier studied [6,7,8,9]. High fruit set after open pollination may probably be resulted from high density of 39 insect species of potentially pollinators. Daily observations of flower visitors were made from 10:00 to 14:00 hrs because of the earlier field work has shown that anthophilus species rarely visit teak bloom prior to 10:00 or after 14:00 hrs (Kaosa-ard 1998, pers.comm.). In our study insufficient insect pollinators and their effectiveness appear to be major causes for limited fruit set in teak. This agrees with studies by Tangmitchareon and Owens (1997) [4]. Teak provides both pollen and nectar as foraging rewards to pollinating insects [10]. It was observed that insects foraged mostly among the inflorescence of the same tree or nearly relatives which may contribute to inbreed fruit and lacks of heterozygonity, consequently low seed production [11]. Representative samples of all pollinating group were collected and are undergoing formal identification with assistance from Thai Ministry of Agriculture Insect Museum in Bangkok. Data from both of keystone pollinator trials suggested that higher density of controlled number (12 bees per inflorescence) had always a greater tendency to increase in fruit set via increased in pollen load by supplementary pollination. The potential of insects as teak pollinators should be investigated in more detail. Among the flower visitors of 39 insect species which were abundant throughout the experiments, ants (Pheidole spp.) were found to persistently associate with panicles. However, their exact pollinating habits were not observed. Thus far our investigations have shown the importance of insect fauna as vectors of teak pollen. Effective of insect pollination is obviously pre-requisite condition not only for satisfactory fruit yields but also for the maintenance of the special characteristics of Tectona grandis [12] Acknowledgments This study was funded by the MRI (Midwest Research Institute, MO, U.S.A.). Research support was also provided by the Department of Horticulture, Oregon State University, Corvallis, OR. U.S.A. We thank the Chiang Mai University, Thailand for providing the collection site, field and laboratory facilities.

64 Titayavan M and Burgett M Naresuan Phayao Journal Table 1 Number of fruit set for the trial of bees/type of pollination Number of bees/type of pollination Mean number of fruit set for bees Trigona pagdeni Trigona laeviceps 0 4.3 b 3.7 b 4 4.7 b 4.0 b 8 4.7 b 7.7 b 12 6.3 b 10.7 a b Open-pollination 21.3 a 19.3 a Mean of each variable followed by the same superscript are not significantly different (P< 0.01) as determined by the Duncan Multiple Range Test. Table 2 List of 39 insect species of potential pollinators of teak observed from floral visitation Flower visitors Lepidoptera Cyana coccinea Moore Euploea coregodartii Lucas Euploea mulciber mulciber (Cramer) Danus genutia genutia (Cramer) Badamia exclamationis Fab. Anthena emolus emolus (Godart) Hypolycaena erytus himavantus Fruh Moduza procris procris (Cramer) Catopsilia pomona pomona Fab. Catopsilia pyranthe pyranthe Linn. Bilbasis harisa harisa Moore Graphium doson evemonides (Honrath) Asota caricae Bosid Caltoris tenuis Evans Hyblae puera Cramer Spindasis lohita senama (Frushtorfer) Athyna perius perius (Linn.) Cethisia cyane evanthes Frushtorfer Hypolymnas bolina bolina (Linn.) Neptis hylas papaja Moore Phalanta phalanta phalanta (Drun) Precis hierta hierta (Fab.) Precis lemonias lemonias (Linn.) Yoma sabina Cramer Cheritra freja freja (Fab.) Frequency

Vol 3, No. 2, May - Aug 2010 Aspects of the Pollination and Fruit Production of Teak 65 Flower visitors Hymenoptera Trigona spp. Apis dorsata Fab. Apis florea Fab. Xylocopa sp. Scolia ruficeps Smith Vespa affinis (Linn.) Pheidole sp. Megachile sp. Polistes stigma Fab. Eumenes petiolata Fab. Diptera Sarcophaga albiceps Meigen Sarcophaga nathani (Lopes) Chrysomya sp. Tachina sp. Frequency

66 Titayavan M and Burgett M Naresuan Phayao Journal Literature cited 1. Piananuruk, P. Teak (Tectona grandis Linn.f.) plantation stands at Maegar- Phayao seed orchard. The informative presentation prepared for course No. 106510 (Integrated Natural Resources Management). School of Agriculture and Natural Resources, Nresuan University at Phayao. February 17, 2009. 2. Tangmitcharoen S, Takaso T, Sioripatanadilox S, Tasen W, Owens JN. Insect biodiversity in flowering teak (Tectona grandis L.f.) canopies comparison of wild and plantation stands. Forest Ecology Management 2006 Feb 15; 222: 99-107. 3. Bryndum K, Hedegart T. Pollination of teak (Tectona grandis L.f.). Silvae Genetica 1969; 18: 77-80. 4. Kaosa-ard A. Teak (Tectona grandis Linn. f.) domestication and breeding. UNDP/FAO/RAS/91/ 004 June 1995. 5. Tangmitcharoen S, Owens JN. Pollen viability and pollen- tube growth following ontrolled pollination and their relation to low fruit production in teak (Tectona grandis Linn. f.). Annals of Botany 1997; 80 : 401-410. 6. Hedegart T. Pollination of teak (Tectona grandis L. f.). Silvae Genetica 973; 22: 124-128. 7. Egenti LC. Preliminary studies on pollinators of teak (Tectona grandis L. f.). Research Paper Forest Services, Federal Department of Forest Research, Nigeria 1974. 8. Siripatanadilox S. Development of teak flower (Tectona grandis L. f.). Forest Research Bulletin 31. Faculty of Forestry, Kasetsart University 1974. 9. Kertadikara PD. Genetic structure and mating system in teak (Tectona grandis L. f.). Silvae Genetica 1995; 44:2-3 10. Tangmitcharoen S, Takaso T, Siripatanadilox S, Tasen W, Owens JN. Behavior of major Insect pollinators of teak (Tectona grandis L. f.) : A comparison of clonal seed orchard versus wild trees. Forest Ecology and Management 2006 Feb 15; 222: 67-74. 11. Tangmitcharoen S, Owens JA. Floral biology, pollination, pistil receptivity and pollen- tube growth of teak (Tectona grandis L. f.). Annals of Botany 1997; 79: 227-241. 12. Mathew G, Koshy MP, Mohanadas K. Preliminary study on insect visitors to teak (Tectona grandis Linn. f.) inflorescence in Kerela,India. Indian Forest 1987; 113: 61-64.