Some nematode species first recorded in Lam Dong

Figure 1. Dr. Trinh Quang Phap working with members of the research team

Plant parasitic nematodes are known to be one of the objects of plant harm. Research on the diversity of plant-parasitic nematodes is still modest, focusing mainly on valuable crops such as coffee, pepper and vegetables and flowers. In recent years, Lam Dong has recorded 15 species and 2 new varieties, bringing the total number of recorded species of plant parasitic nematodes to 85 species, 17 varieties. However, there are many other groups of nematodes encountered quite a lot in Lam Dong, but which have not been studied.

Figure 2. Sample collection habitat in Lam Dong: A: pine+coffee+vegetables (Di Linh); B: pine+coffee+vegetables (Don Duong); C: vegetables (Duc Trong)

The ecological relocation from forest land to coffee or other crops has changed the composition of plant parasitic nematodes in the Central Highlands in general and Lam Dong in particular. It is a fact that species that have barely been encountered before occur with high frequency, such as Radopholus arabocoffeae, Apratylenchus vietnamensis and M. moensi.

The purpose of the research team is to analyze and forecast the group of nematodes posing risk of crop pest outbreak in Lam Dong. This is an important point to help managers make decisions on the orientation of agricultural production areas in the future.

Based on density, Bursaphelenchus nematodes have the greatest potential for harm at an average density of 1265 individuals per sample. In the world as well as in Vietnam, there have been many reports of particularly serious harm of Bursaphelenchus nematodes. Therefore, although this variety has only been found to parasitize pests on pine trees, the appearance of this group of nematodes should be of particular concern to conifers.

Based on the frequency of occurrence, nematodes of the genus Helicotylenchus, Pratylenchus and Meloidogyne are the groups presenting most risk of outbreaks into pests with a high frequency of occurrence and density. In particular, Pratylenchus and Meloidogyne-like nematodes are widely distributed and are considered the leading group of nematodes capable of causing serious harm on a variety of crops, from monocotyledons to dicotyledons.

Based on host plant habitat, Helicotylenchus and Meloidogyne nematodes are the groups with the widest host spectrum with 10/13 and 6/13 hosts, respectively. Besides, trees with high economic value such as coffee and pine are also parasitized and harmed by the most groups of nematodes with 17/26 and 12/26 groups of nematodes parasitizing plants, respectively.

Figure 3. Nematode sampling in Lam Dong

Of the total 107 species of plant nematodes recorded in Lam Dong, the team recorded 38 species and 23 species for the first time in Lam Dong. The team completed 100 samples of 38 species and registered 07 DNA sequences (D2D3, ITS and 18S) of 4 plant nematode species on GenBank.

Physicochemical factors affecting nematodes such as pH, OM index, and soil density are most strongly correlated with soil nematode density of migrating groups of root mammoths and endoparasitic nematodes. The nematode composition is quite similar, there is no discernible difference between the 3 districts of Don Duong, Di Linh and Duc Trong. The vegetable host plant factor is the most susceptible to root nematodes and endoparasitic nematodes migrating.

The results of the project are important data, serve as a basis for orientation for localities in crop development and economic zone development, identification of potentially harmful species to plants, serving the integrated control of nematodes parasitizing agricultural crops,  predict the likelihood of each species' outbreak. In addition, soil factors such as pH increase, organic content and soil content are also concerned in the process of cultivation and pest control, minimizing chemical drugs in agriculture.

The topic has published 04 articles, including 03 international articles on the list of SCI-E and 01 article in VAST02 journal.

Currently, in Lam Dong, other crop shifting patterns continue in some districts, while some other districts are having nematode disease outbreaks on many mulberry trees, medicinal plants. Therefore, the research team looks forward to continuing to determine the location and classification of nematode species, conduct research to complete and clarify the results of the project to orient agricultural development in Lam Dong in particular and the Central Highlands in general.

Translated by Phuong Ha
Link to Vietnamese version