What is it about?

This is a study of Lotus Root Nematode Hirschmanniella diversa (Nematode; Pratylenchidae) that negatively impacts the commercial value of lotus tubers, which have long been utilized as medicinal and a food source in the East Asia, especially Japan, Korea and China. Lotus tubers were sampled from various lotus cultivation areas in Japan, and identified through morphological features, and analyzed their phylogenetic relationships using rRNA and mitochondrial COI genes. 305 specimens sampled from 16 lotus fields in 10 Japanese Prefectures were morphologically deduced to be belonging to the genus Hirschmanniella, in precise, H. diversa. 56 specimens revealed little variation in their rRNA sequences, therefore, no inference in their phylogenetic relationship. However, mitochondrial COI gene analysis showed that H. diversa in Japan had five haplotypes, indicating that H. diversa is more diverse than H. oryzae, both of which, belongs to the same genus Hrischmannilella.

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Why is it important?

It’s been speculated that there are two species of genus Hirschmanniella nematode that parasites on lotus root in Japan, H. diversa and H. imamuri, however, there are still loopholes as to how these two species are distributed and how they have come to inhabit the lotus fields. Determining the distribution therefore, can identify the species responsible for reducing lotus quality, and hence, designation of control measures. This study revealed that H. diversa is dominant in all Japanese lotus cultivation areas. In addition, because of the rapid increase in damages caused by the Hirschmanniella nematodes in recent years, it has been suggested that H. diversa may be an invasive species. But the high phylogenic diversity of the H. diversa in Japan suggested otherwise, that this species is native to Japan. The results may be useful in clarifying the spread and ecology of the lotus root nematode, H. diversa. While H. diversa control is heavily relied upon commercial pesticides and sporadic use of traditional methods, clarifying the distribution of this agriculturally essential nematode should pave the way towards designing of effective control strategies.


I collected Lotus root nematodes H. diversa from various lotus fields around Japan and employed significant amount of time and effort to analyze their genetic sequences. It took me seven years to sample, isolate, screen, analyze, write and publish this work. This would have not been possible without the guidance of my ever supportive co-authors. Addressing the elephant in the room, management of H. diversa in lotus production is a thousand miles ahead. As the saying goes, “...the journey to a thousand miles begins with a single step”...I believe this work is the “single step” needed in the development of innovative methods and strategies for the management of nematodes that affects lotus production.

Takagi Motonori

Read the Original

This page is a summary of: Geographical distribution and phylogenic relationships of Hirschmanniella diversa Sher (Nematoda: Pratylenchidae) in Japan, Nematology, December 2022, Brill,
DOI: 10.1163/15685411-bja10202.
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