Meloidogyne aberrans sp. nov. (Nematoda: Meloidogynidae), a new root-knot nematode parasitizing kiwifruit in China.

High infection rates of roots of wild kiwifruit (Actinidia chinensis Planch) and soil infestation by a root-knot nematode were found in Anshun, GuiZhou Province, China. Morphology, esterase phenotype and molecular analyses confirmed that this nematode was different from previously described root-knot nematodes. In this report, the species is described, illustrated and named Meloidogyne aberrans sp. nov. The new species has a unique combination of characters. A prominent posterior protuberance, round and faint perineal pattern and a medium-length stylet (13.6-15.5 μm) characterized the females. Second-stage juveniles (J2) were characterized by a smooth lip region with distinctly protruded medial lips and a depression in outline at the oral aperture, a relatively long stylet (15.9-16.8 μm), four incisures in the lateral field and a very short, even poorly defined, hyaline tail terminus (2.2-5.5 μm). More incisures (11-15) existed in the lateral field of males, and the stylet and spicules of males were 18.2-19.6 μm and 22.7-36.8 μm long respectively. Egg masses were typically produced within the roots of kiwifruit. The new species had a rare Est phenotype, S2. Phylogenetic trees inferred from SSU, LSU D2D3, ITS, and partial coxII-16S rRNA revealed that M. aberrans sp. nov. was within the Meloidogyne clade and was distinguished from all described root-knot nematodes. Moreover, from histopathological observations, M. aberrans sp. nov. induced the formation of multinucleate giant cells

The small GTPase ROP6 interacts with NFR5 and is involved in nodule formation in Lotus japonicus

Nod Factor Receptor5 (NFR5) is an atypical receptor-like kinase, having no activation loop in the protein kinase domain. It forms a heterodimer with NFR1 and is required for the early plant responses to Rhizobium infection. A Rho-like small GTPase from Lotus japonicus was identified as an NFR5-interacting protein. The amino acid sequence of this Rho-like GTPase is closest to the Arabidopsis (Arabidopsis thaliana) ROP6 and Medicago truncatula ROP6 and was designated as LjROP6. The interaction between Rop6 and NFR5 occurred both in vitro and in planta. No interaction between Rop6 and NFR1 was observed. Green fluorescent protein-tagged ROP6 was localized at the plasma membrane and cytoplasm. The interaction between ROP6 and NFR5 appeared to take place at the plasma membrane. The expression of the ROP6 gene could be detected in vascular tissues of Lotus roots. After inoculation with Mesorhizobium loti, elevated levels of ROP6 expression were found in the root hairs, root tips, vascular bundles of roots, nodule primordia, and young nodules. In transgenic hairy roots expressing ROP6 RNA interference constructs, Rhizobium entry into the root hairs did not appear to be affected, but infection thread growth through the root cortex were severely inhibited, resulting in the development of fewer nodules per plant. These data demonstrate a role of ROP6 as a positive regulator of infection thread formation and nodulation in L. japonicus

Symptoms and histopathology of wild kiwifruit infected by <i>Meloidogyne aberrans</i> sp. nov.

<p>(A) Infested tree (arrow). (B) Fruits from healthy tree (upper) and infested tree (bottom). (C) Roots with severe root galling (arrows). (D) Transverse section of root infected with <i>M</i>. <i>aberrans</i> sp. nov. (E) Longitudinal section of root infected with <i>M</i>. <i>aberrans</i> sp. nov. (gc = giant cells; n = nematode).</p

Esterase and malate dehydrogenase phenotype electrophoresis patterns of protein homogenates from ten young, egg-laying females of <i>Meloidogyne aberrans</i> sp. nov. (lane 2) and from four young, egg-laying females of <i>M</i>. <i>javanica</i> as a reference population (lane 1).

<p>(A) Esterase patterns. (B) Relative mobility (Rm) of esterase bands. (C) Malate dehydrogenase patterns.</p

Bayesian consensus tree inferred from ITS of <i>Meloidogyne aberrans</i> sp. nov. under GTR+G+I (lnL = 10195.9648; AIC = 20411.9297; freqA = 0.2545; freqC = 0.1986; freqG = 0.2345; freqT = 0.3124; R(a) = 1.3819; R(b) = 2.3346; R(c) = 1.9930; R(d) = 0.6850; R(e) = 2.8412; R(f) = 1; Pinva = 0.0772; Shape = 1.1189).

<p>Posterior probability values exceeding 50% are given for appropriate clades.</p

Photomicrographs of <i>Meloidogyne aberrans</i> sp. nov. males and J2s.

<p>(A) Entire body of male. (B) Pharyngeal region of male. (C) Anterior region of male. (D) Tail of male. (E) Posterior region and testis of male. (F) Lateral field of male. (G) Entire body of J2. (H) and (I) Pharyngeal region of J2. (J) Anterior region of J2. (K) Stylet of J2. (L) Lateral field of J2. (M), (N) and (O) Tail of J2. (Scale bars: A, G = 200 μm; B-D, F, H-O = 10 μm; E = 100 μm).</p

Line drawings of <i>Meloidogyne aberrans</i> sp. nov.

<p>(A) Entire body of male. (B) Pharyngeal region of male. (C) Head of male. (D) Lateral field of male. (E) Tail of male. (F) Entire body of J2. (G) Pharyngeal region of J2. (H) Anterior region of J2. (I) Lateral field and tail of J2. (J) Tail of J2. (K) Entire body of female. (L) Anterior region of female. (M) Perineal pattern. (Scale bars: A = 100 μm; B, D, E, M, I and J = 20 μm; C, G and H = 10 μm; F = 50 μm; K = 200 μm; L = 30 μm).</p

Scanning electron microscope photographs of <i>Meloidogyne aberrans</i> sp. nov.

<p>(A) and (B) Lip region of female in <i>en face</i> view. (C) and (D) Perineal pattern. (E) and (F) Lip region of male in <i>en face</i> view. (G) and (H) Lateral field of male. (I) Tail of male. (J) and (K) Lip region of J2 in <i>en face</i> view. (L) Lateral field of J2. (M) Tail of J2. (Scale bars: A, B, E-M = 5 μm; C, D = 20 μm).</p

Bayesian consensus tree inferred from LSU D2D3 of <i>Meloidogyne aberrans</i> sp. nov. under GTR+G (lnL = 6787.5586; AIC = 13593.1172; freqA = 0.2278; freqC = 0.1940; freqG = 0.2868; freqT = 0.2915; R(a) = 0.8153; R(b) = 2.8655; R(c) = 1.5894; R(d) = 0.4230; R(e) = 3.6060; R(f) = 1; Pinva = 0; Shape = 0.3592).

<p>Posterior probability values exceeding 50% are given for appropriate clades.</p