Growth and Corm Production of Amorphophallus at Different Shading Levels in Indonesia. Edi SANTOSA, Nobuo SUGIYAMA*, Miki NAKATA and 0 New LEE

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1 Jpn. J. Trop. Agr. 50 (2) : 87-91, 2006 Growth and Corm Production of Amorphophallus at Different Shading Levels in Indonesia Edi SANTOSA, Nobuo SUGIYAMA*, Miki NAKATA and 0 New LEE Graduate School of Agricultural and Life Sciences, The University of Tokyo Abstract Amorphophallus paeoniifolius (Dennst.) Nicolson (elephant foot yam) and A. muelleri Mill. are commonly cultivated under tree canopies. They are usually harvested two to three years after the planting of one-year-old corms. However, information about suitable cultivation periods and shading levels is limited. The present study was conducted in a field located in Bogor, West Java, over a period of three years at four shading levels: control (0%), 25, 50 and 75%. Regardless of the shading level, the fresh mass of the corms increased exponentially in a year in elephant foot yams, while linearly in A. muelleri. Leaf size increased with the increase in the shading level, resulting in the production of large daughter corms at a low light intensity. About half of the A. muelleri plants flowered in the third year under the 75% shading condition, while no elephant foot yam plants flowered under the same condition. Daughter corms reached a commercial size two years after planting in A. muelleri and three years after planting in elephant foot yams under the 75% shading condition. These results suggested that both species are shade-loving plants and that A. muelleri could be harvested one year earlier than elephant foot yams under shading conditions. Key Words: Agroforestry, Amorphophallus muelleri, Amorphophallus paeoniifolius, Low light intensity, West Java Introduction In Java, Indonesia, edible Amorphophallus species such as Amorphophallus paeoniifolius (Dennst.) Nicolson (elephant foot yam) and A, muelleri Mill. are commonly cultivated under tree canopies in home gardens and timber plantations, or between other crops in upland fields (Jansen et al., 1996; Santosa et al., 2002, 2003). They provide important sources of additional income and carbohydrates for households in villages close to timber plantations in Java (Santosa et al., 2003). Although Amorphophallus species are considered to be suitable crops for agroforestry, the effects of shading vary among the species. Pushpakumari and Sasidhar (1992) reported that the yield in elephant foot yams decreased by 66% if the light intensity was reduced to 25% of full sunlight, while Inaba (1984) stated that the dry mass of A. konjac corms increased by shading (50% of full sunlight). There are no reports on the effect of the light intensity on the growth of A. muelleri. Elephant foot yams and A. muelleri are usually harvested when corms reach a commercial size (950 g), but before they flower. Flowering usually occurs three to four years after the planting of one-year-old corms. However, it remains to be determined whether Received Jan. 26, 2006 Accepted Mar. 11, 2006 * Corresponding author Bunkyoku, Tokyo , Japan anobuo@mail.ecc.u-tokyo.ac.jp the light intensity affects the time to flower. The objective of the present study was to determine at which time corms could be harvested when elephant foot yams and A. muelleri plants were grown at different light intensities. Materials and Methods The present study was conducted in a field located at the Cikabayan Experimental Farm, Bogor Agricultural University, Indonesia (6 36 ŒS; ŒE; 240 m above sea level). The soil type was a Latosol with a ph ranging from 5.8 to 6.5, and with a structure consisting of 12.8% sand, 29.1% silt and 58.1% clay. Corms of elephant foot yam and A. muelleri plants were cultivated once a year from September to July (during the rainy season) in 2002/2003, 2003/2004 and 2004/2005. In the first planting (2002), one-year-old corms (40.3 }5.7 g for elephant foot yams and 49.4 } 7.4 g for A. muelleri) were used. The one-year-old corms were raised from cormels for elephant foot yams and from bulbils for A. muelleri. Seed corms were harvested in July 2002 and stored at room temperature until they were planted in September In the second and third year plantings, seed corms harvested in the first and second year plantings, respectively, were used. From harvest to planting, corms were stored in a storage house at temperatures ranging between 27 and 29 Ž and at a relative humidity of 70-85%. The experiment was designed as a randomized complete block with four replications. Shading nets,

2 88 Jpn. J. Trop. Agr. 50 (2) 2006 which reduced the light intensity by 25, 50 and 75%, were spread over the plot before planting. No shading net was used for the control treatment. In each replication, 20 corms with their buds at the top were planted at a spacing of 50 cm ~50 cm in a cm raised bed at a depth of cm. Based on preliminary observations, some plants showed a severe reduction in growth or died under full sunlight. Therefore, the number of plants in the control treatment was increased to ensure the necessary number of corms in the third year. At planting, about 500 g of rice husk was applied below the corms to reduce corm rot. The corms were then covered with a mixture of soil and goat manure (3:1, v/v). The monthly rainfall (average, minimum and maximum values), average daily temperatures, and relative humidity in the first, second, and third years are shown in Table 1. Irrigation was carried out at a rate of 2-31 per plant if there was no rainfall for 7 days. Leaf numbers and petiole lengths were measured every week, and plants were harvested in mid-july of each year after they had entered dormancy. The diameter, height, and fresh mass of the daughter corms were measured after the cormels had been detached. Numbers and fresh mass of the cormels were also recorded. The dry mass of the daughter corms was measured after oven-drying at 65 Ž for 3 days. In the third year harvest (2005), corms displaying any disease and corms formed after flowering were examined. Results and Discussion Both species were damaged by full sunlight, under which conditions necrosis and curling at either the edge or the tip of the leaflets were observed, and in severe cases, the plants died. In A. muelleri, 50, 55 and 60% of the plants died in the first, second and third and 75% shading treatments in either species. It is likely that the leaves of the A. muelleri plants were more sensitive to direct sunlight than those of elephant foot yam plants. The life span of the leaves was longer under shading conditions than under the control condition, irrespective of the year (data not shown). Inaba and Chonan (1984) also reported that leaves grown under full sunlight exhibited a shorter life spans than those grown under 50% shade (40 days in the control vs. three months under 50% shading). The number of leaves differed significantly in two of three years between the treatments for the elephant foot yam and A. muelleri plants. Shading treatments significantly decreased the leaf number in both elephant foot yam and A. muelleri plants, although there were no significant differences between the 25, 50 and 75% shading conditions (Table 2). In agreement with these results, Caesar (1980) reported that Xanthosoma and Colocasia plants showed a smaller number of leaves under shading conditions than under full sunlight. The short life span of the leaves might lead to the production of new leaves, resulting in a larger number of leaves under full sunlight. Shading treatments significantly affected the length of the petioles and rachis in both species in all the three years,except for the rachis length of the elephant foot yam plants in 2004/2005 (Table 3). Control plants displayed the shortest petioles, while the longest petioles were produced under 75% shading. Leaf size increased year by year because large seed corms produced large leaves. Restricted leaf sizes under full sunlight was also reported in the case of A. konjac: the Table 2 Number of leaves of elephant foot yam and A. muelleri plants grown under different shading conditions over a three-year period years, respectively. However, only 25, 30 and 30% of elephant foot yam plants were lost due to damage by strong light in the first, second and third years, respectively. No damage was observed in the 25, 50 Table 1 Average monthly rainfall, daily mean temperature and relative humidity (RH) during the experiment z Figures in parenthesis denote the minimum and maximum values. z Means followed by different letters within columns in each species are significantly different based on the least significant difference method at the 5% level.

3 Santosa et al.: Amorphophallus growth under different shading levels 89 Table 3 Petiole and rachis length, corm fresh mass, and weight and number of cormels of elephant foot yam and A. muelleri plants grown at different shading levels over a three-year period z Leaf 1 was the first to emerge.y Average of all the harvested corms including infected and flowering corms. x Means followed by different letters within columns in each year in each species are significantly different based on the least significant difference at the 5% level. w No cormels were formed. leaf sizes increased by 30% when the light intensity was reduced to 30-70% of full sunlight (Inaba, 1984). The fresh mass of elephant foot yam corms was significantly smaller under full sunlight than under the 75% shading condition in the second and third years, while that of the A. muelleri corms was significantly smaller under full sunlight than under shading conditions in all the three years (Table 3). Fresh mass of both elephant foot yam and A. muelleri corms increased with the decrease in the light intensity: 75% shading led to the formation of the largest corms. Pushpakumari and Sasidhar (1992) reported that the yield was reduced by 66% under a 75% shading condition in elephant foot yams. Such a response to shading might depend on the landraces used, as reported in the case of potato (Roberts-Nkrumah et al., 1986). Miura and Watanabe (1985) reported that the ratios of the fresh mass of daughter corms to that of seed corms were 6.6, 4.8, and 3.9 in one-, two- and three-year-old corms, respectively. The ratios decreased with the increase in the corm age in A. muelleri ( and in oneand two-year-old corms, respectively), but not in elephant foot yams ( and in one- and twoyear-old corms, respectively) in the present study. Furthermore, these ratios were higher in A. muelleri than in elephant foot yams in the second year, but lower in the third year. This was because the fresh mass of the corms increased exponentially with time in the elephant foot yam plants, but linearly in the A. muelleri plants, regardless of the light intensity (data not shown). Although a decrease in the light intensity increased the fresh mass of daughter corms in both

4 90 Jpn. J. Trop. Agr. 50 (2) 2006 species, the effect was more evident in A. muelleri. In elephant foot yams, although the fresh mass of the cormels was not significantly different between the treatments in any year, the number of cormels was lower under 50% shading than under the control treatment in the first and third years, for unknown reasons. On the other hand, Douglas et al. (2005) reported that the number of A, konjac cormels increased by 52% under 50% shading compared with full sunlight. No cormels were formed in A. muelleri plants during the experiments. Over the duration of the study period, some corms were found to be infected by pathogens such as Rhizoctonia solani, Fusarium and Sclerotium sp. When corms were infected, their infected parts became black and spongy, and the corms underwent rot. Although the light intensity did not affect the occurrence infected corms in elephant foot yams (Table 4), 50% of the A. muelleri corms became infected under the control condition, while no infection was found under the 75% shading condition. In elephant foot yams, most corms reached a commercial size (950 g) or larger size in the third year under the 75% shading condition, whereas only 34% of the corms reached such a size under the control condition (Table 4). In A. muelleri, most corms reached a commercial size by the end of the second year under 75% shading, and at the end of the third year under 50% shading (Tables 3 and 4). In elephant foot yams, no plants produced Table 4 Percentage of infected corms, corms of marketable size and flowering corms in elephant foot yams and A. muelleri plants grown at different shading levels when measured on July 19, 2005 of inflorescences in the third year, regardless of the light conditions. However, in A. muelleri, 10% and 45% of the plants produced inflorescences in the third year under 50% and 75% shading conditions, respectively (Table 4). Because corms fetch a low price after flowering (Santosa et al., 2003), they should be harvested prior to flowering. To produce corms with a commercial size in the absence harvested of flowering, A. muelleri should be two years after the planting of one-year-old corms, i.e., one year earlier than elephant foot yams. Based on the pattern of increase in the fresh mass of corms and flower induction, it is possible that the physiological stage of A. muelleri plants is more advanced than that of elephant foot yams. Goodwin et al. (1995) reported that flowering in Blanfordia grandiflora occurred less frequently in the plants grown under full sunlight than in the plants grown under shade. In agreement with these results, A. muelleri plants did not produce inflorescences under full sunlight in the third year. It is well known that the bulb size is the main factor which determines the capacity to flower in bulbous plants (Le Nard and De Hertogh, 1993). Therefore, it is possible that flower induction depends on the corm size in Amorphophallus. However, it remains to be determined whether differences in flowering among the treatments are related to differences in corm size, or result from the a direct effect of the light intensity on flower induction. Acknowledgements This study was supported by the Core University Program between the Japanese Society for Promoting Science (JSPS), and the Directorate General of Higher Education (DGHE), Indonesia. References z Corm surface infected by pathogens, e.g., Rhizoctonia solani and Sclerotium sp. y Size larger than 950 g. x Means followed by different letters within columns in each species are significantly different based on the least significant difference method at the 5% level. Caesar, K Growth and development of Xanthosoma and Colocasia under different light and water supply conditions. Field Crop Res. 3: Douglas, J.A., J.M. Follett and J.E. Waller Research on konjac (Amorphophallus konjac) production in New Zealand. Acta Hort. 670: Goodwin, P. B., P. Dunstan and P. Watt The control of flowering in Blandfordia grandiflora. Sci. Hort. 62: Inaba, K Effect of shading on leaf anatomy in konjak plants (Amorphophallus konjac K.Koch). Jpn. J. Crop Sci. 53: * Inaba, K and N. Chonan The effect of light intensity on the ultrastructure of chloroplasts in konjak (Amorphophallus konjac K.Koch). Jpn. J. Crop Sci. 53: * Jansen, P.C.M., C. van der Wilk and W.L.A. Hetterscheid Amorphophallus Blume ex Decaisne. In: PROSEA 9: Plant yielding non-seed carbohydrates. (Flack, M. and F. Rumawas eds.). Backhuys Publ. (Leiden)

5 Santosa et al.: Amorphophallus growth under different shading levels 91 Le Nard, M. and A.A. De Hertogh Botanical aspects of flower bulbs. In: The physiology of flower bulbs. (De Hertogh, A.A. and M. Le Nard eds.). Elsevier (Amsterdam) Miura, K. and K. Watanabe Effect of seed-corm age and weight on the efficiency of corm tuberization in konjak plants (Amorphophallus konjac K. Koch). Jpn. J. Crop Sci. 54: 1-7.* Pushpakumari, R. and V.K. Sasidhar Yield variations of yams and aroids as influenced by shade intensities. Indian J. Plant Physiol. 34: Roberts-Nkrumah, L.B., L.A. Wilson and T.U. Feruson Responses of four potato cultivars to levels of shade: 2. Tuberization. Trop. Agric. 63: Santosa, E., N. Sugiyama, S. Hikosaka and S. Kawabata Cultivation of Amorphophallus muelleri Blume in timber forests of east Java. Jpn. J. Trop. Agric. 47: Santosa, E., N. Sugiyama, A.P. Lontoh, Sutoro, S. Hikosaka and S. Kawabata Cultivation of Amorphophallus paeoniifolius (Dennst.) Nicolson in home gardens in Java. Jpn. J. Trop. Agric. 46: (*: in Japanese with English summary)