First Report of Root-Knot Nematode, <i>Meloidogyne luci</i>, Parasitizing Chickpea (<i>Cicer arietinum</i>) in Ethiopia

Abstract

Chickpea (Cicer arietinum L.) is a significant legume crop, with Ethiopia being the largest producer in Africa and the fifth globally (FAO 2022). However, various factors, including plant-parasitic nematodes, reduce its yield. Among these, root-knot nematodes (RKN; Meloidogyne spp.) pose a severe threat by causing root galling and stunted growth (Castillo et al. 2008). Despite the impact, research on plant-parasitic nematodes, their diversity and effect on chickpea yield in Ethiopia is limited (Kefelegn et al. 2024). In 2021, a survey was conducted to assess diversity of nematodes associated with chickpea in Ethiopia. Root-knot nematodes collected from galled chickpea roots of the 'Arerti' cultivar in the Minjar district, Ethiopia (8°54'21.1"N, 39°24'46.5"E), were identified as M. luci using multiple approaches. Esterase isozyme patterns of egg-laying females (n=10) were consistent with those described for M. luci by Carneiro et al. (2014) and Gerič Stare et al. (2017). PCR amplification with M. luci-specific primers (Maleita et al. 2021) confirmed its identity . Additionally, various sequences obtained from second-stage juveniles (J2), following the method described in Janssen et al. (2016) and Kefelegn et al. (2024): COX1 (PQ448335), Nad5 (PQ462657), COX2 (PQ619863) of mtDNA, and the D2-D3 region of 28S rDNA (PQ454017), were found identical to the M. luci sequences KU372172, KU372417, KU372211, and KX130766, respectively. Populations of M. luci were established from single egg masses and maintained on tomato plants (cv. 'Marmande'). To evaluate the pathogenicity of M. luci on the 'Arerti' chickpea cultivar, seedlings were inoculated with initial population densities (Pi) of 1000, 4000 and 8000 J2 (pot)-1 (2-liter capacity, n= 8) in a temperature controlled growth chamber in the Flanders Research Institute for Agriculture, Fisheries, and Food (ILVO), Belgium. After eight weeks, all inoculated plants exhibited stunted growth and visible root galling, consistent with typical field symptoms. The nematode reproduction factor (RF = final population (Pf) /initial population (Pi)) was calculated from the whole root and soil samples. Rf values were 31, 11.5 and 9.5 for Pi 1000, 4000 and 8000 J2 (pot)-1, respectively, corresponding to Pf values of 32000, 46000 and 76000 J2 (pot)-1, respectively. This clear pattern of increasing Pf with higher Pi levels, coupled with the declining RF trend, reflects the expected dynamics of a pathogenicity test. Nematodes extracted from the roots were reisolated and identified as M. luci using PCR amplification with M. luci-specific primers and esterase isozyme patterns analysis of egg-laying females (n = 10), confirming the species identity. These results confirmed that the 'Arerti' cultivar is a suitable host for M. luci. Meloidogyne luci has previously been reported in chickpea fields in Türkiye (Şen & Aydinli 2021), in common bean and soybean in Brazil (Bellé et al. 2016), and various horticultural crops in Europe (Gerič Stare et al. 2017). This study marks the first report of M. luci parasitizing chickpea roots in Ethiopia and its first documented occurrence in Africa. Therefore, further investigations are essential to determine the distribution of M. luci and assess its damage potential on legumes and other crops in Ethiopia and across Africa.