Submitted to: Journal of Nematology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/7/2004
Publication Date: 9/1/2005
Citation: Handoo, Z.A., Skantar, A.M., Carta, L.K., Schmitt, D.P. 2005. Morphological and molecular evaluation of a meloidogyne hapla population damaging coffee (coffea arabica l.) in maui, hawaii. Journal of Nematology. 37(2):136-145. Interpretive Summary: Nematodes are microscopic worms that cause ten billion dollars of crop losses in the United States each year. Root-knot nematodes are an important group of nematodes that damage many kinds of plants by invading the roots and interfering with nutrient uptake. Until now, coffee production in Hawaii was only known to be affected by the coffee root-knot nematode and the southern root-knot nematode. In the present study, ARS scientists used host range tests as well as anatomical and molecular data to positively identify an unusual variant of the northern root-knot nematode that was highly damaging to coffee plants grown in Maui, Hawaii. This is the first report of northern root-knot nematode occurrence and damage on coffee in the Pacific region. The results are significant because they provide the molecular and anatomical details necessary for scientists to identify this species variant wherever it may occur in the world. Scientists, action agencies, and extension agencies engaged in nematode research and control will use this research.
Technical Abstract: An unusual male /female population of Meloidogyne hapla, earlier thought to represent an undescribed species, was found to cause large galls without proliferating rootlets and significant damage to coffee on Maui in the Hawaiian islands for the first time in the Pacific region. Similar galls and damage to coffee by this species was reported before only from Brazil. The morphology of this population is described in detail, including SEM images. Identification was verified by morphology, esterase isozyme pattern, and 5 DNA sequences: ribosomal large subunit (28S), ITS and IGS rDNA, mitochondrial interval between cytochrome oxidase (CO) II-16S, and the nuclear gene HspP0. Sequences for ITS, IGS and mitochondrial genes were variably similar to other species in alignments, and LSU-D3 had a similar haplotype to a previously analyzed population with two minor haplotypes. Hsp90 exhibited some minor variations between Maryland and Hawaiian populations and were clearly distinct from other species. Twenty percent of perineal patterns had perpendicular lines atypical for the species. Female interphasmidial distance was relatively high, and anus to tail terminal distance was intermediate among 5 populations. The average length of juveniles from this Hawaiian population was considerably smaller than for most other populations of M. hapla. Populations sampled in summer and winter had significantly different juvenile body lengths. Tail lengths were different from type populations but similar to an atypical African population. Host range, cultivar, and biogeographical issues are discussed.