V.K. Murukesan and P.C. Josekutty
An overview of banana research and plant-
parasitic nematode studies in the Federated
States of Micronesia
V.K. Murukesan* and P.C. Josekutty
The Federated States of Micronesia (FSM) is located at the northwest
Pacific and is a relatively young independent nation. It was a part of
the United Nations Trust Territory of the Pacific Islands (TTPI)
administered by the United States of America until the two nations
signed a Compact of Free Association in 1986, leading to the
trusteeship termination by the United Nations in 1991. The Compact
treaty established a special relationship with America that provides
economic support to the FSM. The total landmass is 438 square miles
(702 km2 with a declared Exclusive Economic Zone (EEZ), covering
over one million square miles). The FSM is comprised of 607 islands
with land elevation ranging from sea level to the highest elevation of
about 2500 feet (760 m). The archipelago lies in the western Pacific
Ocean, north of the equator, between 1.0-9.9°N and 138.2-162.6°E.
Agriculture in the FSM
The rich and diverse agroforests and related traditional agricultural
systems of the FSM have attracted the interest of scientists from around
the world as possible models for sustainable agricultural development.
Agricultural production in the FSM is primarily for subsistence, with
some semi-commercial and commercial activities. The extensive man-
made agroforests are complex and environmental sustainable
agriculture systems are a result of thousands of years of development.
They mimic natural forest ecosystems and shelter extremely high
species/cultivar diversity. The cultivars of taro, yam, breadfruit, swamp
and fruit trees such as banana, orange, tangerine, mango, lime etc.
interspersed in an integrated system of shifting gardens and tree
garden/taro patch systems.
Banana, taro, breadfruit and yams are the major staple food crops in
the FSM, of which banana cultivation is significant for local
consumption and export. There are over 50 cultivars including Eumusa
and Fe’i bananas (Raynor and Fownes 1991). Similarly, the FSM is the
*Researcher, College of Micronesia-FSM Yap Campus.
An overview of banana research and plant-parasitic nematode studies...
world centre for swamp taro diversity (FSM 2002). Intercropping of
bananas, taro and other tuber crops with coconut is more common in
the island states of Kosrae, Pohnpei and Yap. While swamp taro and
yam cultivation is chiefly for domestic consumption, FSM produced
about 2300 metric tonnes of banana in 2000 (FAO 2001). The FSM
exported dessert banana for US$ 455 628 in 1994 but then declined to
US$ 154 317 in 1997 (FSM 1999). Production constraints (diseases
and pests) and marketing problems are the reasons for the decline in
Research on bananas
Research on banana in the FSM is progressing in the following five
1. tissue culture and genetic improvement
2. disease-resistance trials
3. introduction and performance evaluation of new cultivars
4. nutritional value of banana
5. germplasm conservation.
Following recommendations from the Asian Development Bank (ADB
Report 1997), Kosrae State has invested about US$ 500 000 to develop
an agribiotech laboratory, Micronesia Plant Propagation and Research
Center (MPPRC). MPPRC has developed tissue-culture procedures
for several locally grown cultivars of Eumusa and Australimusa. Results
of field trials confirmed better rate of field establishment, faster growth
and shorter pre-bearing period as advantages of tissue-culture bananas
(Josekutty et al. 2001, 2002, 2003a, b, c, 2004; Josekutty and Nena
2002). Research is also underway to develop variant bananas
resistant to fusarium wilt affecting cv. Saba. MPPRC also succeeded in
introducing disease-indexed tissue cultures of cv. Macao from Guam,
which is undergoing field trial in Kosrae. The College of Micronesia-
FSM Land Grant program in Pohnpei has gathered a few improved
and new banana varieties introduced by INIBAP which are now under
field trials. Early results indicate that some of these cultivars are
performing better in comparison with many local cultivars under
Pohnpei conditions. Englberger (2001) analyzed several cultivars of
banana for the nutritional value and some of them are reported to be
high in precursor of vitamin A. MPPRC has also embarked on a drive
for conserving banana germplasm in situ. Twenty-eight cultivars from
Kosrae State have been documented and established in a conservation
garden and the majority of them are also being multiplied in vitro.
V.K. Murukesan and P.C. Josekutty 15
Plant nematological studies
While surveying plant-parasitic nematode problems of several islands
in the region, Bridge (1988) reported that nematology is in its infancy
in the Pacific region. This is true for the FSM as well. Except for a
report of burrowing nematode in swamp taro, no effort has ever been
taken to survey or diagnose Micronesian soils. The small-scale farmers
of this region, being unaware of the nature and harmfulness of
nematode infestations in their fields, do not seriously consider the
destructive effect of these pests on their crops. Agricultural research in
the FSM is also in its infancy and has not focused on the
circumstances and needs of the majority of small-scale farmers,
particularly women farmers. With a notable exception of swamp taro,
symptoms of nematode damage are unknown for other crops to assess
the yield loss. Lack of trained work force is the reason behind the
situation. In the FSM, a comprehensive survey is necessary in order to
assess the damage caused by nematodes on economically
important crop species.
Dry corm rot of swamp taro in Yap: a novel candidate for
Giant swamp taro (Cyrtosperma merkusii (Hassk) Schott) is the most
popular root crop and had served the Micronesians for many centuries
as a cultivated plant of status and great economic significance (Figure.
1). Its starchy corm is the principal food source, especially of Yapese,
consumed several times a day all year long. Some of the yellow cultivars
are good sources of vitamin A, thus making it an ideal crop for vitamin
A-deficient island population.
The plants with corm rot show little or no above-ground symptoms.
However, lesions and extensive loss of feeder roots are very common
symptoms of pathogen attack.
Figure 1. Swamp taro patch.
Figure 2. Corm showing lesions.
16 An overview of banana research and plant-parasitic nematode studies...
Figure 3. Cross section of a corm
Figure 4. At an advanced stage,
showing symptoms of dry rot.
decay reaches center of the corm.
Lesions vary in size, from 1.0 to 3.0 cm in diameter and 0.5 to 3.0 cm
deep (Figure 2). Beneath these tissues, a brown-black rot is shown,
occasionally channeled deep into the corm (Figures. 3 and 4).
The first report of burrowing nematode, Radopholus similis, associated
with dry corm-rot of swamp came from Yap (Jackson 1986). Later,
Grandison (1990) studied the corm-rot disorder in samples collected
from Yap and Palau and confirmed the presence of this ubiquitous
pathogen. It is interesting, however, to note that a recent survey
conducted by Kagoshima University in Japan revealed the presence of
free-living Cephalobid nematodes, associated with infected corms of
swamp taro and not burrowing nematodes (Onjo et al. 2001). The
scientifically interesting aspect of this disorder is that we have a serious
nematode pest of many tropical crops that grow in normal drained
soils, but here it is infecting corms that grow in swampy areas.
Nevertheless, there is little doubt that nematodes, either on their own
or in combination with other pathogenic organisms, constitute an
important constraint to agriculture of the FSM.
The burrowing nematode has a wide host range in the Pacific and is a
major banana root pathogen. It was reported from Fiji, Guam, Niue,
Norflok, Papua New Guinea, Palau, Samoa, Solomon Islands and Tonga
(Bridge 1988; 1992; Bridge and Page 1984; Kirby et al. 1978). Although
extensive studies have been carried out in islands like Fiji and Papua
New Guinea (Bridge and Page 1984; Kirby et al. 1980; Orton Williams
1980), Micronesian islands remain unexplored by nematologists.
Susceptibility symptoms vary with cultivars. There are at least seven
cultivars of swamp taro in Yap with varying symptoms of susceptibility.
In Yap and many of its outer-lying islands, the extent of the problem is
not fully realized by the local farmers and they call the disease ‘ngal’,
or termite damage, though they know termites are not the causal
organism. During the survey, we found about 80–90% infestation,
depending on the cultivars. Being the staple food crop, such severe
infections may eventually affect food security of the island.
V.K. Murukesan and P.C. Josekutty
Plant-parasitic nematodes are a severe constraint for the swamp taro
cultivation in Micronesia. Although report of nematodes affecting
banana and other crops in the FSM are non-existent, considering the
traditional way of cultivation, it is reasonable to speculate that
nematodes are a matter of concern for these crops as well. Research
conducted so far revealed conflicting reports about the presence of
burrowing nematode and free-living nematodes. An extensive study is
therefore required to identify the host associations of plant-parasitic
nematodes from the FSM. Equally important is the cultivar screening
of major crops including banana and swamp taro to determine their
susceptibility to nematodes and associated yield loss. Information on
nematode diagnosis, biology, population dynamics and host-parasite
relationships are an essential prerequisite for the future establishment
of nematode control practices.
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