Breeding Hawaiian Taros for the Future

Author: John J. Cho, Department of Plant and Environmental Plant Sciences, Agricultural Research Center, University of , POB 269, Kula, Maui, Hawaii 96790, USA. Abstract A program has been initiated in 1998 to improve commercial taros through breeding by increasing resistance to pests such as taro leaf blight and aphids, increasing plant vigor and yield, and. developing new and exciting varieties for the restaurant and landscape trade. In this program, Hawaiian taro cultivars are being used to incorporate different corm colors, low acridity, soft rot tolerance, early maturation, and brilliant colors. Hawaiian taros have been found to be closely related genetically based on RAPD studies conducted in Hawaii, thereby limiting their usefulness for our breeding program. Therefore we have introduced taro varieties from where they originated where we should expect greater genetic diversity. Introduced taro cultivars from Micronesia, Palau, Indonesia, Papua New Guinea, Thailand and Nepal are being used to increase resistance to taro leaf blight. Our approach is to incorporate 2 to 3 different sources of resistance into our improved taros to increase the durability of resistance. Tolerance to aphids are being incorporated into commercial taros using cultivars from Micronesia that reduce the longevity of aphids or reduce the number of offspring and cultivars from Indonesia and Micronesia that reduce longevity and offspring. Several new F1 hybrids and backcross F1 hybrids have been generated, evaluated for commercial potential in 2002 and a few are currently being advanced tested on on-farm tests. INTRODUCTION Around the 4th or 5th century A.D. a large double-hulled voyaging canoe originating from the Marquesas Islands laden with taro, breadfruit and other crops made landfall in Hawaii. These were the first Hawaiians. Although only a few different taro varieties were thought to have been brought into Hawaii by the first Hawaiians, over 300 hundred varieties have been documented and represent a reasonable number that were present prior to the arrival of Captain Cook in 1778 (Handy, 1940, Handy, et al. 1972). It has been suggested that the large number of varieties may have been derived from genetic crosses made by old Hawaiians and/or selection and propagation of mutant clones. The number of varieties by far outnumbered any found in Polynesia where it came from. The chiefs or ali’i selected many of the varieties for specific characters such as Lehua and Pi’i ali’i that were favored and the low acrid varieties, Lauloa and Haokea, favored as medicinal or ceremonial taros. Moreover many new varieties were selected for their adaptability to different microenvironments encountered with the expansion of agricultural production beyond the banks of rivers and streams.

It was in Hawaii where taro was brought to the highest state of cultivation and played an important role in the diet of the people. Upon the arrival of the first Hawaiians in Hawaii, taro or kalo, was first planted along the seacoast in marshes near the mouths of rivers (Krauss, 1993). With an increase in population to what was estimated to be about 200,000 Hawaiians, an intensification of agricultural production occurred to fulfill the demand for food. Accordingly, land in the valleys were cleared developing an elaborate system of plant production under flooded conditions in banked and terraced plots called lo’i, which required delegation of labor and movement of large amounts of water. Taro was not only cultivated under irrigated wetland conditions that are in evidenced today but archeological studies indicate that large plantings along with sweet potato probably occurred on the leeward sides of Maui and Hawaii under dry land conditions (Kirch 1985). This production system was a key component of a resource management system of land units known as the ahupua’a. Taro production was not merely an activity of food production but was tightly interwoven into the Hawaiian culture and their legends about creation. Genetic improvement of commercial taros are needed to increase resistance to adverse environmental conditions (i.e. high salt and soil pH, low rain fall) and pests, to increase plant vigor and yield, and to develop new and exciting varieties with different colors and tastes for the growing Hawaii regional cuisine restaurant trade. Further, a few taro varieties are being grown for the ornamental-landscape marketplace and a breeding program designed to introduce new and colorful taro varieties is needed. Several of the Hawaiian taros have desirable attributes which could be combined in a number of different combinations to produce superior varieties compared with those that are presently grown commercially. For example, there are different corm flesh colors available including the orange-yellow corm found in Mana Ulu, dark purple or red found in the Lehua varieties, and white found in Moi and Haokea. Two of the varieties (Lehua and Moi) are grown commercially for the red and gray poi market. There may be a place for the development of white and yellow poi varieties. The Kai and Wehiwa varieties are known to be very tolerant or resistant to soft rots as compared to the major commercial varieties. Currently, wetland growers are experiencing severe crop losses due to a type of soft rot called pocket rot. Development of wetland poi varieties with Kai or Wehiwa variety attributes may be useful in reducing future pocket rot losses. The irritating or acrid factor that is associated with many of the major commercial varieties is one of reasons that has impeded wider acceptance and utilization of taro. Lauloa, Kalalau, and Haokea varieties are relatively non-acrid and could be used in the development of low acrid commercial varieties. Other useful attributes that could be used to improve commercial taros include early maturation (Piko Elele), and brilliant color (Ulaula Kumu). Recent biochemical and genetic evaluations are beginning to provide a basis for distinguishing Hawaiian varieties and understanding the history of taro in Hawaii and the Pacific. Hawaiian and Polynesian taros showed very low genetic variation based upon isozyme variation (Lebot and Aradhya 1991). On the other hand, variation based upon DNA sequence using RAPD (random amplified polymorphic DNA) markers could be used to distinguish between varieties (Irwin et al. 1998). However, the majority of the Hawaiian taros were found to be closely related with about 80% DNA similarity. The narrow genetic base found in Hawaiian varieties makes sense since they were derived from only a few introduced taros. The geographic region from India to Southeast Asia is the center of genetic diversity for taro (Chang 1958, Coates et al. 1988, Yen and Wheeler 1968). Introduction of taro varieties from the center of diversity will provide different genes that could be used in a breeding program to broaden the genetic base of Hawaiian taros. Plant breeders have used genetic diversity in other crops that can be credited for at least one-half of a doubling in yields of rice, barley, soybeans, wheat, cotton, and sugarcane; a threefold increase in tomato yields; and a fourfold increase in yields of corn, sorghum and potato (World Resources Institute, Agriculture and genetic diversity.

2 www.wri.org/wri/biodiv/agrigene.html#risks). Also many genes for resistance to pests and tolerance to adverse environmental stress have been introduced into cultivated crops from related wild plants from its center of diversity. For example, several sources of taro leaf blight resistance appear to be available. This disease caused by the fungus, Phytophthora colocasiae is the most important disease in Hawaii and the major taro growing regions worldwide. In Southeast Asia several taro varieties are reported to either resistant or immune to the disease (Deshmukh and Chibber 1960, Paharia and Mathur 1964). In the Solomon Islands breeding program, Patel and Liloqula (1985) have developed advanced materials generated from a cross between TLB resistant and susceptible materials and indicate that a single dominant gene confers resistance. Vasquez (1990) in the Philippines reports three taro accessions moderately resistant and one accession highly resistant to TLB when inoculated with P. colocasiae 2 to 4 months after planting. In the Papua New Guinea breeding program, intrageneric crosses have been made between cultivated and wild genotypes with TLB resistance (Ivancic and Kokoa, personnel communication). They indicate that single and multiple gene(s) confer TLB resistance. Greenough et al. (1996) have evaluated several taro lines from Micronesia in American Samoa and Hawaii and confirmed resistance of a few lines (personal communication). Importation of the available resistant varieties for breeding purposes is warranted. MATERIALS AND METHODS Germplasm: In 1997 we started to assemble a collection of 298 taro genotypes to be used in a genetic improvement program. Several genotypes were first obtained from the University of Hawaii’s Taro Germplasm Nursery located in Kauai. These included about 70 Hawaiian varieties collected by Whitney et al. (1939), and several accessions from Asia, Indonesia, Polynesia, and Melanesia collected by Lebot (Lebot and Aradhya 1991). Table 1. Taro (number of accessions and country of origin) used in Hawaiian breeding program. Region Number Region Number • Country • Country North America Far East • USA/Hawaii 63 • India 2 • Nepal 3 Southeast Asia Polynesia • Thailand 56 • Cook Islands 4 • Vietnam 14 • Easter Island 6 • Indonesia 11 • Niue 1 • Myanmar 2 • Samoa 28 Micronesia Melanesia • Guam 4 • Fiji 2 • Palau 15 • New Caledonia 2 • Pohnpei 6 • Papua New Guinea 5 • Rota 5 • Vanuatu 22 • Saipan 6 Asia • Tinian 4 • China 5 20 • Yap 6 • Japan 3 • Philippines

3 Many of the Indonesian accessions were shown to be TLB resistant (Java 48, Java 74, Java 75, Kuat, Ketan 36). Furthermore, several taro leaf blight (TLB) resistant genotypes were introduced in Hawaii including 2 accessions (PH15, PH21) from Papua New Guinea (Kokoa & Darie 1992) and a wild type (Bangkok) originating from Thailand (Patel and Liloqula 1985) in 1997, 7 accessions (Thailand, Pwetepwet, Gilin, Kugfel, Oglang, Ol, Sushi) from Micronesia (Wall and Wieko 1998), 1 accession (C81081) from Nepal, and 15 accessions (Ngesuas-P1, Terrekakl-P2, Ongdibel-P3, Homestead-P4, Ochab-P5, Kerdeu-P6, Ochelochel-P7, Moalech-P8, Ngeruuch- P10, Merii-P12, Dirraiuosch-P13, Moded-P15, Meltalt-P16, Ngetmadei-P19, Dirratengadik-P20) from Palau (Hamasaki et al., Trujillo 1996) in 1999. In 2000, 4 aphid tolerant taro accessions that either reduces aphid longevity (Likay), reduces the number of offspring (Saipan, Rumung 1) or both (Japon) were introduced from Guam (Miller and Wall, personal communication). Ketan 36 was also shown to reduce aphid longevity and fecundity. Also many accessions from Southeast Asia were secured during a collecting trip in 1999. Table 1 summarizes the number of accessions and country of origin assembled for our genetic improvement program. Genetic crosses: The major objectives of our breeding program are to develop higher yielding, good tasting food taros and brilliantly colored ornamental taros with increased disease and insect resistance and increased genetic complexity. Our breeding strategy uses a modified backcross and recurrent selection approach. In this approach we first develop first generation F1 hybrids by making genetic crosses between commercial Hawaiian taro varieties and different TLB resistant taro accessions. The F1 progeny are then evaluated, selections are made for desirable horticultural characteristics, and selected BC1s are evaluated for TLB resistance, yield, and taste quality in on farm trials. Genetic crosses will be made between selected BC1 progeny with different sources of TLB resistance in an attempt to combine 2 and more sources to create more durable resistant commercial taros. In general, the commercial type taros are used as pollen donors. The male portion of the spadix is removed when pollen is shed and applied to emasculated pest resistant recipient at anthesis by either brushing stigmas with pollen or placing the male spadix between the female flowers and the spathe. Seeds are collected from successful crosses about 1 month following pollination and germinated in peat moss trays. Fifty to one hundred germinating seedlings from each cross are then randomly selected from each cross and transplanted first into 2.5 cm Speedling flats containing peat moss, and after about 2 months, seedlings are transplanted into field plots located on the island of Maui. Approximately 6 to 8 months after transplanting, field transplants are evaluated and individuals exhibiting the best horticultural characters based upon commercial standards are selected. RESULTS AND DISCUSSION 1998 Crosses: Genetic crosses were made between three TLB resistant taro accessions (Bangkok, PH15, PH21) and seven different commercial type taro varieties (Table 2). All crosses were successful resulting in viable progeny. About 12% of the progeny were selected for further genetic improvement. Those selected produced short or no stolons, 3 to 12 suckers, and well- shaped corms. However, none of the selected F1 progeny were considered suitable for commercial production because of the small corm size. Average mature corm weights for 8 F1 (Bangkok x Niue Waula) progeny ranged from 0.7 kg to 1.9 kg, 1.2 kg for 1 F1 (Red Moi x PH15); 0.9 kg for 1 F1 (Bun Long x PH21), and 1.1 kg for 1 F1 (Piko Eleele x PH15).

4 1999 Crosses: In 1999, 24 successful genetic crosses were made between selected F1 progeny from our 1998 crosses and commercial type taros generating over 800 progeny. A few of the crosses made are shown in Table 3. These modified backcrosses were initiated to restore commercial type characteristics. Maui Lehua, the major commercial taro variety grown in Hawaii for poi, was used in several crosses between selected 1998 F1s. Table 2. 1998 crosses between 3 TLB resistant accessions and 7 commercial taro varieties (recurrent parent) and the number of hybrid progeny generated for each cross. TLB resistant parent Recurrent parent No. Hybrids Selected Bangkok Niue Waula 30 12 Bangkok Eleele Naioea 15 2 Bangkok Moi 3 1 Bangkok Apowale 100 2 PH15 Piko Eleele 5 3 PH21 Bun Long 2 1 PH15 Red Moi 15 2

All BC1 progeny were transplanted in field plots, visually evaluated in April 2000 for desirable horticultural characteristics and 120 progeny were selected for further evaluation as possible food and 24 as possible ornamental types. Five to 10 suckers from each selected BC1s were removed and planted in field plots on April 10, 2000 and evaluated for commercial potential on March 27, 2001.

Thirty-four out of the 120 BC1s were selected in our evaluations, 30 for food and 4 for ornamental uses (Table 4). Fourteen out the 30 BC1s selected as potential food taros came from one cross between F1 (Bangkok x Niue Waula 21) and Maui Lehua. These BC1s varied from one another in their corm flesh color, average corm weights and in the number of suckers produced.

Table 3. 1999 modified backcrosses between selected F1 hybrid and recurrent commercial type taro varieties, number of BC1 progeny generated and number (percent) of BC1 individuals selected for further evaluation.

Selected F1 Recurrent No. Selected parent Hybrids No. Percent F1 (Red Moi x PH15) Maui Lehua 8 0 0 F1 (Bangkok x Niue Waula 21) Maui Lehua 67 22 32.8 F1 (Bangkok x Niue Waula 21) Niue 53 7 13.2 F1 (Bangkok x Niue Waula 21) T6 47 6 12.8 F1 (Bangkok x Niue Waula 21) Veo 12 2 16.7 F1 (Bangkok x Niue Waula 21) Fasa Fa Uli 5 1 20 F1 (Bangkok x Apowale 9) Maui Lehua 40 7 17.5 F1 (Bangkok x Apowale 9) Lauloa Keokeo 8 2 25 F1 (Moi x Bangkok 2) Lehua Maoli 10 2 20 F1 (Moi x Bangkok 3) Van 49 16 2 12.5 F1 (Bangkok x Eleele Naioea 9) Maui Lehua 12 0 0 F1 (Bangkok x Eleele Naioea 9) Lauloa Keokeo 27 0 0 F1 (Bangkok x Eleele Naioea 9) Van 26 63 13 20.6 F1 (Bangkok x Eleele Naioea 6) Veo 28 1 3.6 F1 (Bangkok x Eleele Naioea 6) Kai Ala 84 8 9.5

5 F1 (Bangkok x Eleele Naioea 6) T2 12 0 0 F1 (Bangkok x Eleele Naioea 6) Van 96 15 3 20 F1 (Bangkok x Eleele Naioea 6) Veo 45 1 2.2

Table 4. Attributes of thirty-four 1999 BC1 individuals selected for further evaluation for commercial food or ornamental uses. Corm Corm Selected Recurrent No. Selected F parent Color wt. Use BC 1 parent suckers 1 fresh (kg) BC99-2 F1 [Bangkok x Niue Waula 21] Maui Lehua Pink 2.1 17.5 food BC99-3 F1 [Bangkok x Niue Waula 21] Maui Lehua Purple 1.8 12.5 food BC99-4 F1 [Bangkok x Niue Waula 21] Maui Lehua Purple 2.6 9.7 food BC99-5 F1 [Bangkok x Niue Waula 21] Maui Lehua Purple 2.4 5.3 food BC99-6 F1 [Bangkok x Niue Waula 21] Maui Lehua Purple 4.4 7.3 food BC99-7 F1 [Bangkok x Niue Waula 21] Maui Lehua Pink 2.2 11 food BC99-8 F1 [Bangkok x Niue Waula 21] Maui Lehua Purple 1.4 16.7 food BC99-9 F1 [Bangkok x Niue Waula 21] Maui Lehua Purple 2.8 4.5 food BC99-11 F1 [Bangkok x Niue Waula 21] Maui Lehua Pink 2.6 24 food BC99-13 F1 [Bangkok x Niue Waula 21] Maui Lehua White 1.6 10 food BC99-24 F1 [Bangkok x Niue Waula 21] Maui Lehua White 3.2 12.5 food BC99-31 F1 [Bangkok x Niue Waula 21] Maui Lehua Pink 2.4 15.5 food BC99-32 F1 [Bangkok x Niue Waula 21] Maui Lehua White 2.1 12 food BC99-19 F1 [Bangkok x Niue Waula 21] Maui Lehua White 2.5 6.5 food BC99-1 F1 [Bangkok x Niue Waula 21] Niue White 2.6 17.5 food BC99-21 F1 [Bangkok x Niue Waula 21] WBL White 1.4 17 food BC99-25 F1 [Bangkok x Niue Waula 21] T6 White 3.0 10.5 food BC99-26 F1 [Bangkok x Niue Waula 21] T6 Pink 1.6 19 food BC99-34 F1 [Bangkok x Niue Waula 21] T6 Yellow 2.8 food BC99-22 F1 [Bangkok x Niue Waula 21] Van 110 Pink 1.5 14 food BC99-30 F1 [Bangkok x Niue Waula 21] Veo White 2.2 13 food BC99-10 F1 [Bangkok x Eleele Naioea 9] Van 26 Pink 0.8 13.3 ornamental BC99-15 F1 [Bangkok x Eleele Naioea 9] Van 26 White 1.5 21 ornamental BC99-16 F1 [Bangkok x Eleele Naioea 9] Van 26 White 2.5 6.5 ornamental BC99-17 F1 [Bangkok x Eleele Naioea 9] Kai Ala White 2.8 13 food BC99-20 F1 [Bangkok x Eleele Naioea 6] Kai Ala White 3.7 11 food BC99-12 F1 [Bangkok x Niue Waula 6] Fasa Fa Uli Pink 0.6 25 ornamental BC99-23 F1 [Bangkok x Niue Waula 6] Fasa Fa Uli Pink 2.9 17.5 food BC99-14 F1 [Bangkok x Apowale 9] Maui Lehua Pink 1.3 7.7 food BC99-18 F1 [Bangkok x Apowale 9] Maui Lehua Pink 1.4 8 food BC99-27 F1 [Moi x Bangkok 3] Van 49 Pink 2.3 14 food BC99-33 F1 [Moi x Bangkok 2] Lehua Maoli Yellow 2.2 food BC99-28 F1 [Red Moi x PH15] Van 4 White 2.8 14 food BC99-29 F1 [Red Moi x PH15] Maui Lehua White 2.0 13.5 food

Backcrosses between F1 (Bangkok x Niue Waula 21) and commercial type taros accounted for over 60 percent of the BC1 individuals that were selected for desirable horticultural characteristics. Five taste tests were conducted on the islands of Maui, Kauai, Hawaii, and

6 to evaluate the eating quality of the selected BC1s for poi and table taro uses. Kauai evaluators selected BC99-6, BC99-7, and BC99-9 as comparable in poi taste and color to the industry standard, Maui Lehua when grown under wetland conditions. All three came from the {[F1 (Bangkok x Niue Waula 21)] x Maui Lehua} cross. In two preliminary experiments, BC99- 6 and BC99-7 out yielded Maui Lehua. BC99-6 produced 5.9 kg and 5.8 kg per plant; BC99-7 produced 6.2 kg and 5.8 kg per plant; and Maui Lehua produced 2.6 kg and 4.1 kg per plant, respectively. Further evaluation of these hybrids is in progress. When grown under drip irrigation, evaluators on Maui, Hawaii, and Molokai selected BC99-11, BC99-5 and BC99-4 over others both as table and poi taros.

Seven BC1s were selected as potential ornamental taros. Four exhibited green, white and/or red striped petioles derived from (F1 [Bangkok x Eleele Naioea 9]) x Van 26 cross and (F1 [Bangkok x Niue Waula 6]) x Fasa Fa Uli cross. 2000 Crosses: In 2000 twenty-one genetic crosses were made between Hawaiian taro varieties (food type) and ten different TLB resistant taros from Micronesia (Pwetepwet, Olgang, Thailand, Gilin), Palau (Ngesuas-P1, Moalech-P8, Dirratengadik-P20), Indonesia (Ketan 36, Kuat, Java 74), and Papua New Guinea (PH21) that resulted in 432 first generation F1 hybrids. One hundred fourteen F1 hybrids were selected for further improvement. Seven F1 hybrids (F1 (Pwetepwet x Maui Lehua 3), F1 (Pwetepwet x Maui Lehua 9), F1 (Pwetepwet x Maui Lehua 13), F1 (Maui Lehua x Thailand 54), F1 (Maui Lehua x Thailand 56), F1 (Moi x P20-9), F1 (Maui Lehua x Sushi 7) produced large corms weighing between 2.2 to 3.8 kg per plant; these F1 hybrids are being evaluated in on farm trials for TLB resistance, yield, and taste characteristics.

Nine modified backcrosses were also made between selected 1998 F1 hybrids and commercial taros that resulted in 205 BC1 progeny. Twenty-two BC1s were selected for further backcrosses. Twenty crosses were made for the development of ornamental taros. Nine crosses used PH21 as one of the parental lines to develop F1 populations with purple and green striped petioles. Six crosses used a Hawaiian taro, Lauloa Palakea-papamu, for its dark purple petiole color. Genetic crosses between Indonesian taros (Ketan 36, Kuat, Java 74) and Maui Lehua, PH21, and Agaga resulted in F1 progeny that showed a wide variation in phenotype. Variation occurred in plant size from 0.3 m to over 2.5 m in height, leaf shape and size, and plant color. Six out of 29 F1s from a cross between Ketan 36 and PH21 were selected as possible ornamental taros. A commercial nurseryman is now evaluating these taros. This kind of segregation where individuals of the population fall beyond their parental phenotypes has been referred to as transgressive segregation. This type of segregation might have evolutionary implications, since it can affect characters of adaptive significance leading to new races or species (Schwarzbach et al. 2001). Transgressive segregation may allow individuals to occupy new ecological niches or to better compete in existing environments (Rieseberg et al. 1999). For breeding, it represents a potential source of novel variation. These transgressive segregants will be evaluated for possible sources of root knot nematode resistance, increased yields, and as potential ornamentals.

2002 Crosses: In 2002, four hundred modified backcrosses were made between F1 hybrid plants selected from our 1998 and 2000 crosses and commercial type Hawaiian taros for the development of food type taros. Again many crosses were made to generate more ornamental type taros. More than 5,000 seedlings have been transplanted in field plots for selection sometime this year.

7 Citations and Literature Cited Chang, T.K., 1958. Dispersal of taro in Asia. Ann Assoc Am Geo 48:255-256 Coates, D.J., D.E. Yen, & P.M. Gaffey, 1988. Chromosome variation in taro, Colocasia esculenta: implications for the origin in the Pacific. Cytologia 53:551-560 Deshmukh, M. J., and Chibber, K. N. 1960. Field resistance to blight (Phytophthora colocasiae Rac.) in Colocasia antiquorum, Schott. Curr. Sci. (Bangalore) 29:320-321. Greenough, D. R., E. E. Trujillo, & G. Wall. 1996. Effects of nitrogen, calcium, and or (sic) potassium nutrition on the resistance and/or susceptibility of Polynesian taros, Colocasia esculenta, to the taro leaf blight, caused by the fungus Phytophthora colocasiae. In ADAP Project Accomplishment Report, Year 7, pp. 19-25. Agricultural Development in the American Pacific Project, , Hawaii. Hamasaki, R., H. D. Sato, A. Arakaki, R. Shimabuku, S. Fukuda, D. Sato, , R. Yoshino, and N. Kanehiro. Leaf blight tolerant taro variety trial. http://www.extento.hawaii.edu/IPM/taro/default.htm Handy, E. S. C. 1940. The Hawaiian planter Volume 1 His plants, methods and areas of cultivation. Bernice P. Bishop Museum Bull. 161, Bishop Museum Press, Honolulu Handy, E. S. C., & E. G. Handy, 1972. Native planters in Hawaii: their life, lore, and environment. Bernice P. Bishop Museum Bull. 233, Bishop Museum Press, Honolulu. Irwin, S. V., P. Kaufusi, K. Banks, R. de la Pena & J. J. Cho. 1998. Molecular characterization of taro (Colocasia esculenta) using RAPD markers. Euphytica 99:183-189. Kirch, PV.1985. Feathered gods and fishhooks. Univ. Hawaii Press, Honolulu, Krauss, B.H., 1993. Plants in Hawaiian culture. Univ Hawaii Press, Honolulu. Kokoa, P. & A. Darie. 1992. Field screening of taro (Colocasia esculenta (L.) Schott) for resistance to taro leaf blight (Phytophthora colocasiae) in Papua New Guinea. (internal report). Krauss, B. H. 1993. Plants in Hawaiian culture. Honolulu, University of Hawaii Press. Lebot, V., & K.M. Aradhya, 1991. Isozyme variation in taro (Colocasia esculenta (L.) Schott) from Asia and Oceania. Euphytica 56: 55-66. Paharia, K. D., and Mathur, P. N. 1964. Screening of Colocasia varieties for resistance to Colocasia blight (Phytophthora colocasiae Racib.) Sci. Cult. 30:44-46. Patel, M. Z., and Liloqula, R. 1985. Progress on breeding disease resistant taro in Solomon Islands. In: Fifth Conference on the Australasian Plant Pathology Soc., Auckland, New Zealand, 20-24 May 1985. Rieseberg, L.H., M.A. Archer, and R.K. Wayne. 1999. Transgressive segregation, adaptation, and speciation. Heredity 83:363-372. Schwarzbach, A.E., L.A. Donovan, and L.H. Rieseberg. 2001. Transgressive character expression in a hybrid sunflower species. American Journal of Botany 88:270-277 Trujillo, E. E. 1996. Taro leaf blight research in the American Pacific. ADAP Bulletin No. 1: 1- 3.

8 Wall, G. C. & A. T. Wiecko. 1998. Screening of 29 taro cultivars (Colocasia esculenta), propagated in vitro, for resistance to taro leaf blight (Phytophthora colocasiae). J. South Pac. Agric. 5:9-12. Yen, D. E., & Wheeler, J. M., 1968. Introduction of taro into the Pacific: the indications of the chromosome numbers. Ethnology 7:259-267.

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