First report of Meloidogyne hapla on Paulownia tomentosa in Poland

Meloidogyne spp. are serious pests on many economically important plants, including food crops, vegetables, ornamental trees, and shrubs. Galled roots of Paulownia tomentosa Steud were collected from a plantation in the 2018 growing season in Poland. Morphological, morphometric, and molecular studies revealed the presence of Meloidogyne hapla in root systems and root zones of empress trees. To our knowledge, this is the first record of the occurrence of this nematode species on Paulownia tomentosa in Poland, as well as in Europe.


Introduction
The root-knot nematodes, Meloidogyne spp., includes worldwide distributed obligatory parasites of higher plants. Approximately 10 species of Meloidogyne are known to be serious pests of major food crops, vegetables, fruits, and ornamental plants in temperate, tropical, and subtropical regions [1][2][3][4].
One of the numerous host plants of root-knot nematodes is royal paulownia, Paulownia spp. This plant is native to East Asia and has been introduced to Europe and North and South America. The most common species within the genus are P. fortunei, P. kawakamii, P. taiwaniana, and P. tomentosa. Paulownia is a valued plant mainly for its high-quality wood, which is used for furniture, musical instruments, and dishes. Moreover, paulownia is known to be a good nectar producer and a fodder plant whose aboveground parts contain high levels of beneficial nutrients [5].
Out of a dozen root-knot nematode species that parasitize Paulownia spp., M. incognita, M. javanica, and M. arenaria [6][7][8][9][10] are most often mentioned as poor growth of paulownia plants has been observed in fields where these nemtadode species were identified.
The empress tree (Paulownia tomentosa Steud) has been cultivated for a long time in the southeastern region of Poland. In 2018, during a routine inspection of paulownia plantations, roots with outgrowths characteristic of the presence of Meloidogyne were observed. The population discovered was described using morphological, morphometric, and genetic methods. In this article, we provide the results of these investigations.

Material and methods
Soil samples with galled fragments of plant roots were collected from a 6-year-old plantation in Żołynia, Poland (50°09'52.0" N, 22°15'54.7" E). Females with egg masses were manually dissected out of tissues. Perineal patterns and hatched juveniles of the J2 stage were mounted on temporary microscope slides according to Hooper et al. [11]. Morphological observations and morphometric analysis of females, males, and J2 juveniles were performed using an Axioskop 2plus light microscope with the Nomarsky differentiated contrast.
The occurrence of single outgrowths on paulownia roots, as well as J2 specimens in the root zone indicate that this plant species supports the M. hapla population in the soil. Crops subsequent to paulownia may become infected by these nematodes and reduced yields or even wilting may occur as a consequence. This study should draw the