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Effects of southern root knot nematode population densities and plantage on growth and yield parameters of cucumber Muhammad Zameer Kayani a , * , Tariq Mukhtar b , Muhammad Arshad Hussain c a Green Belt Project, Department of Agriculture, Rawalpindi, Pakistan b Department of Plant Pathology, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan c Plant Pathology Section, Regional Agricultural Research Institute, Bahawalpur, Pakistan a r t i c l e i n f o Article history: Received 10 July 2016Received in revised form10 September 2016Accepted 10 September 2016Available online 13 October 2016 Keywords: Root-knot nematodesInoculum levels Cucumis sativus YieldGrowth Meloidogyne incognita a b s t r a c t Southern root-knot nematode ( Meloidogyne incognita ) is one of the major constraints to cucumberproduction throughout the world. The effects of M. incognita on growth and yield of cucumber have notbeen studied. In the present studies, the effects of ve initial population densities (500,1000, 2000, 4000and 8000 freshly hatched second stage juveniles) of M. incognita were investigated on growth and yieldparameters of cucumber. The relationships between inoculum levels and growth and yield parameters atthree plant ages were also determined. Cucumber plants of 2-, 3- and 4-week ages were inoculated withdifferent nematode densities and observations were recorded 9 weeks after inoculation. Reductions ingrowth and yield parameters by nematode densities were calculated over control. All inoculum densitiesand ages of plants at the time of inoculation in uenced growth and yield of cucumber. A positive cor-relation was found between inoculum levels and percent reductions in growth and yield parameters. Onthe other hand, ages of plants at inoculation had negative correlations with percent reductions in theseparameters at each inoculum level. It is concluded that M. incognita has the potential to severely impairthe growth of cucumber and delaying exposure of cucumber to nematodes can signi cantly abate yieldlosses. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction The southern root-knot nematode, Meloidogyne incognita , hasbeen found infecting a wide range of crops throughout the world(Khan et al., 2005; Anwar et al., 2007; Hussain et al., 2012, 2016;Kayani et al., 2013; Ntidi et al., 2016; Shigueoka et al., 2016). Veg-etables are among the most susceptible and severely affected bythese nematodes (Naz et al., 2016; Podest a et al., 2016; Zhou et al.,2016). These nematodes adversely affect uptake of nutrients andwater and translocation of photosynthates and minerals(Williamson and Hussey,1996) resulting in a change in root: shootratio (Anwar and Van Gundy, 1989) which has a negative dominoeffect on the yield (Orr and Robinson, 1984). In vegetables, yieldreductions with phytopathogenic nematodes have reached as highas 30% for susceptible genotypes in some production areas (Anwaret al., 2009; Mukhtar et al., 2013a, 2014; Hussain et al., 2014). Theroot systems of infected plants may be deformed and undergroundparts are damaged making them unmarketable (Roberts, 1987;Sikora and Fernandez, 2006). Root-knot nematodes have alsobeen found involved in many disease complexes. Damping off caused by Rhizoctonia solani and Pythium debaryanum and vascularwiltscausedby Fusariumoxysporum incotton,tobacco,banana,andinsome important solanaceous vegetables weremoreseverein thepresence of Meloidogyne spp. (Evans and Hydock,1993; Francl andWheeler, 1993). Similarly, incidence and severity of bacterial wiltcaused by Ralstonia solanacearum and crown gall incited by Agro-bacterium tumefaciens increased when root-knot nematodes werepresent (Shahbaz et al., 2015). In fungal and bacterial wilt resistantcultivars, resistance broke due to root-knotnematodes. In addition,these nematodes also cause reduction in plant tolerance to abioticstresses (Castillo et al., 2003; Fourie et al., 2016).In many parts of the world including Pakistan, the yields of vegetable crops are comparatively lower due to abiotic and bioticconstraints. Among biotic constraints, root-knot nematodes areconsidered as important production-limiting factors causing 22%yield losses annually in the tropical parts of the country (Sasser,1979; Hussain et al., 2011a, b). Pakistan has a subtropical climatewhich is conducive to root-knot nematode survival, infection, and * Corresponding author. E-mail address:
[email protected] (M.Z. Kayani). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro http://dx.doi.org/10.1016/j.cropro.2016.09.0070261-2194/ © 2016 Elsevier Ltd. All rights reserved. Crop Protection 92 (2017) 207 e 212 multiplicationallyearround.Likewise,thesoilsinthearidzonesof the country being warm and sandy are suitable for infestation anddevelopment of nematodes. Furthermore, the nematode multipli-cationisgreaterintheirrigatedareasduetomonocropping(Kayaniet al., 2012; Mukhtar et al., 2013b).So far over one hundred species of Meloidogyne have beendescribed from different areas of the world (Karssen and Moens,2006). Of all these root-knot nematode species only four( M. incognita , M. javanica , M. arenaria and M. hapla ) have beenfound to be of economic signi cance and cause about 95% in-festations in plantations. The worldwide distribution of thesespecies is as follows: M. incognita 47%, M. javanica 40%, M. arenaria 7% and M. hapla 6% (Sasser, 1980). In Pakistan the occurrence of these four major species is M. incognita 52%, M. javanica 31%, M. arenaria 8%, M. hapla 7% while the rest of the Meloidogyne spe-cies constitute about 2% (Maqbool, 1987). Root-knot nematodeshave become a serious threat to the pro table cultivation of cu-cumber in the country. About 33% yield losses due to root-knotnematodes have been estimated in cucumber (Sasser, 1979). InPakistanupto52%infestationofcucumberby Meloidogyne spp.hasbeen reported (Khan et al., 2005). Of all the root-knot nematodespecies associated with cucumber, M. incognita constituted 78.53%, M. javanica 19.03%, M. arenaria 1.82% and M. hapla 0.62% (Kayaniet al., 2013).Damage caused by the nematode is determined by relating pre-plant nematode densities to growth and yield of annual crops. Theminimal density that causes a measurable reduction in plantgrowth or yield varies with nematode species, host plant, cultivarand environment (Barker and Olthof, 1976). Infections of non-ef cient or ef cient hosts by low densities of Meloidogyne spp.may enhance growth and yield of the host (Madamba et al., 1965;Olthof and Potter, 1972) or have no effect (Madamba et al., 1965), or cause severe damage to the crop (Barker and Olthof, 1976). Theseverity of plant damage by Meloidogyne spp. in uenced by inoc-ulum densities has been published for a number of crops (Sasanelliet al., 2006; El-Sherif et al., 2009; Hussain et al., 2015) but there ispaucity of information on the relationships between initial den-sities of M. incognita and growth and yields of cucumber as in u-enced by plant ages at the time of exposure to nematodes.Therefore, in the present studies, the effects of ve initial popula-tion densities (500, 1000, 2000, 4000 and 8000 freshly hatchedsecondstagejuveniles)of M. incognita wereinvestigatedongrowthand yield parameters of cucumber. The relationships betweeninoculum levels and growth and yield parameters at three plantages were also determined. 2. Materials and methods 2.1. Nematode inoculum The root-knot nematode, M . incognita , used in the experimentwas isolated from infected cucumber roots. The nematode wasmultiplied from a single egg mass on tomato cv. “ Money maker ” and was con rmed by its perineal pattern (Taylor and Nestscher,1974). The nematode was further mass produced on tomato cv.Money maker in pots in the glasshouse at 25 C ± 2. The eggs of M. incognita were collected following the method described byHusseyandBarker(1973)andjuvenileswereextracted(Whiteheadand Hemming,1965), standardized and concentrated. 2.2. Effect of inoculum densities of M. incognita on cucumber The highly susceptible cultivar of cucumber (Royal Sluis)(Mukhtar et al., 2013c) was used in the experiment to ascertain theeffect of different inoculum levels of M. incognita . Three seeds of cucumbercv. ‘ Royal Sluis ’ weresown inplasticpotscontaining 3kgof sterilized soil (sand 70%, silt 21%, clay 8%, pH 7.5, organic matter,1%) at weekly intervals in the greenhouse. After emergence onehealthy seedling was maintained. When the plants attained ages of 2, 3 and 4 weeks, they were inoculated with 500,1000, 2000, 4000and 8000 freshly hatched juveniles (24 h old) of M. incognita con-tained in 1 mL of water by making four holes around the stem. Theun-inoculated plants served as a control. Each treatment wasreplicated ve times. The pots were arranged in the glasshouse at25 ± 2 C and watered when required. 2.3. Data collection Nine weeks after inoculation growth and yield data wererecorded. 2.3.1. Plant growth After nine weeks, the plants were uprooted and roots weregently washed with running tap water. The plants were cut at themargin of the root and shoot. The lengths of the root and the shootwere measured. 2.3.2. Fruit yield measurements Fruits were harvested three times per week from the 30 th dayafter inoculation till the termination of the experiment. At eachharvest,thetotalnumberoffruitsandtheirweightswererecorded.Mean fruit weight and total fruit yield were calculated. 2.4. Statistical analysis Theexperimentwasconductedtwice.Acompletelyrandomizedfactorial design was used with three plant ages, each of which had ve inoculum levels. Percent reductions in growth and yield pa-rameters were calculated over the control prior to statistical anal-ysis(Iqbaletal.,2014).Allthedatawerefoundnormallydistributedand did not require transformation. Firstly, the data of both theexperiments were analyzed to examine interaction between theexperiments. As no signi cant interaction was observed betweenthe data of both the experiments, the two sets of data were com-bined (making ten replications) for nal analysis. The combineddata were subjected to two-way Analysis of Variance (ANOVA)using GenStat package 2009, (12th edition) version 12.1.0.3278(www.vsni.co.uk). The differences among means were comparedby Fisher's protected least signi cant difference test at (P ¼ 0.05).Standard errors of means were calculated in Microsoft Excel 2003.Pearson correlation analysis (2-tailed) was performed to establishthe relationships between inoculum levels and plant ages andgrowth and yield parameters. Data were also subjected to regres-sion analysis. Plant growth and yield parameters were regressed asthe dependent variable with the initial inoculum density as theindependent variable at three inoculation ages. 3. Results 3.1. Effect of inoculum densities on growth parameters Inoculum densities of M . incognita and agesof plants at thetimeof inoculation signi cantly affected growth parameters of cucum-ber cv. Royal Sluis. The interactions between these two factors ongrowth parameters were also highly signi cant. Maximum re-ductions in shoot and root lengths and shoot weights were recor-ded when plants were inoculated with 8000 J2s at the age of 2weeks. On the other hand, minimum reductions in these parame-terswereobservedataninoculumlevelof500J2swheninoculatedafter 4 weeks. The individual reductions in these parameters at M.Z. Kayani et al. / Crop Protection 92 (2017) 207 e 212 208 each inoculum level are shown in Tables 2, 4 and 5.With an increase in inoculum level, signi cant reductions inthese parameters were noticed and were found to be positivelycorrelated with inoculum densities. On the other hand, age of plants at inoculation had negative correlations with shoot length,rootlength andshootweight(Table1) showingthat themagnitudeof damaging effects of nematode densities decreased as the age of plants increased at the time of inoculation. Likewise, all the inoc-ulumlevelsresultedinanincreaseintherootweights.Amaximumincrease in root weight was observed at an inoculum level of 8000 J2s when the plants were inoculated 2 weeks after emergencewhile the minimum increase was noticed in pots where 500 J2swere applied at an age of 4 weeks (Table 3). There was a positiveandsigni cantcorrelationbetweeninoculumlevelsandincreaseinroot weight and a negative and signi cant correlation betweenplant ages and increase in root weight (Table 1). Linear modelsprovidedagood ttotherelationshipsbetweeninoculumdensitiesand reductions in shoot weight, shoot length, and root length; aswell as between inoculum densities and increases in root weight(Tables 2 e 5). 3.2. Effect of inoculum densities on yield parameters of cucumber The fruit yield parameters (number of fruits, fruit weights andfruityieldsperplant)weresigni cantlyaffectedbyinoculumlevelsandplant agesat thetime of inoculation. The maximum reductionsinyield parameters were obtained at an inoculum level of 8000 J2swhereastheminimumvalueswererecordedatadensityof500J2s.Plant ages also had a signi cant effect on mean number of fruits,fruit weights and fruit yields per plant. Maximum reductions wereobserved when the plants were inoculated after two weeks of emergencecomparedtothreeandfourweeks(Tables6 e 8).Resultsof correlation analysis of the yield components with the inoculumlevels and plant ages are presented in Table 1. Inoculum levels signi cantly correlated positively with percent reductions innumber of fruits per plant, fruit weight and fruit yield per plantwhereas plant ages were negatively correlated with these param-eters. The linear regression equations regarding these parametersare given in Tables 6 e 8. 4. Discussion The effects of different inoculum densities of different Meloi-dogyne species have also been studied by different workers ondifferent hosts (Haider et al., 2003; Hussain et al., 2011a; Irshadet al., 2012; Mukhtar et al., 2013d). The ndings of these workerscon rm that the increase in nematode populationsand subsequentreductions in yields of crops or other manifestations of pathogeniceffects, physiological responses (total leaf chlorophyll content, CO 2 exchange rate) and concentration of sodium, potassium, iron,manganese, copper and zinc are directly in uenced by initialdensity of nematodes in soil (Wallace, 1973; Haseeb et al., 1990).Yellowing of leaves, reduction in plant heights and weights are theconspicuous manifestations of the infections of root-knot nema-todes and have been documented by many researchers (Haideret al., 2003; Bora and Neog, 2006; Vovlas et al., 2008; Azam et al.,2011). Reduction in root and shoot lengths was likely a result of nematode feeding on giant cells, causing root growth to stop andtips to swell(Manser,1968;Siddiqui etal., 2014).This shorteningof the roots affected the growth and development of the cucumberplants by limiting their ability to uptake nutrients, minerals andwater from the soil, eventually resulting in stunting and smallerplants. Stunting by Meloidogyne spp. has also been reported byOgbuji and Okarfor (1984) in pepper ( Capsicum annuum ), Enopkaet al. (1996) in tomato, Haider et al. (2003) in pulse crops, Bora and Neog (2006) in tea, Khan et al. (2006) in balsam, Mishra and Usha (2007) in okra and Vovlas et al. (2008) in sweet basil (cv. Genovese). Stunted plants have reduced leaf weight or top weightwhich was also observed in infected cucumbers in this experiment. Table 1 Pearson correlation analysis (2-tailed) between different growth and yield param-eters and inoculum densities and plant ages at the time of inoculation.Parameter Correlation withInoculum level Plant ageReduction in shoot weight 0.875** 0.351**Increase in root weight 0.853** 0.372**Reduction in shoot length 0.897** 0.365**Reduction in root length 0.879** 0.236*Reduction in number of fruits/plant 0.903** 0.213 ns Reduction in fruit weight 0.808** 0.246*Reduction in fruit yield 0.880** 0.224 ns ** Correlation is signi cant at P ¼ 0.01.* Correlation is signi cant at P ¼ 0.05.ns ¼ non-signi cant. Table 2 Effect of inoculum densities of Meloidogyne incognita on reduction in shoot weight (g).Plant ages %Reduction in shoot weight (g) at inoculum levels of M. incognita Regression equations R 2 500 J2s 1000 J2s 2000 J2s 4000 J2s 8000 J2s2 Week 10.56 ± 1.89 c 14.02 ± 1.95 e 24.3 ± 1.69 g 32.02 ± 1.96 i 33.2 ± 2.16 i y ¼ 6.328 þ 3.836 0.9483 Week 7.30 ± 1.83 b 10.96 ± 1.65 c 11.8 ± 1.95 cd 19.62 ± 2.30 f 28.5 ± 1.72 h y ¼ 5.106 þ 0.318 0.9074 Week 3.76 ± 1.48 a 5.72 ± 1.66 ab 7.4 ± 1.94 b 13.50 ± 1.75 de 14.9 ± 1.83 e y ¼ 3.006 þ 0.038 0.943Data are means of ten replicates.Means sharing common letters within columns do not differ signi cantly by Fisher's protected least signi cant difference test at P < 5%. Table 3 Effect of inoculum densities of Meloidogyne incognita on increase in root weight (g).Plant ages % Increase in root weight (g) at inoculum levels of M. incognita Regression equations R 2 500 J2s 1000 J2s 2000 J2s 4000 J2s 8000 J2s2 Week 6.04 ± 0.32 abc 9.08 ± 0.46 cd 17.12 ± 0.70 f 26.16 ± 1.15 hi 30.94 ± 1.50 j y ¼ 6.688 2.196 0.9783 Week 5.18 ± 0.34 ab 8.04 ± 0.73 bcd 13.06 ± 1.05 e 25.20 ± 1.93 gh 29.00 ± 1.52 ij y ¼ 6.48 3.344 0.9494 Week 4.02 ± 0.31 a 6.20 ± 0.31 abc 11.06 ± 0.83 de 18.40 ± 1.53 f 22.80 ± 1.05 g y ¼ 4.976 2.432 0.973Data are means of ten replicates.Means sharing common letters within columns do not differ signi cantly by Fisher's protected least signi cant difference test at P < 5%. M.Z. Kayani et al. / Crop Protection 92 (2017) 207 e 212 209 Root-knot nematodes have been shown to act as a metabolicsink, causing a redistribution of nutrients from the leaves to thenematodes developing inside the roots (Bergeson, 1966; McClure,1977). Ploeg and Phillips (2001) suggested that the reduction in the number of fruits produced by plants growing under high M. incognita populations is due to the metabolic sink activity of thenematodes which compete with plants and thereby inhibit fruitdevelopment.There are, however, contradictory reports as to the number of juveniles responsible for reduction in the growth of plants. In thepresentstudy500J2s,thelowestinoculumlevel,causedsigni cantreductions in growth parameters of cucumber plants. In anotherstudy, 1 juvenile per 5 g of soil caused signi cant reduction ingrowth of egg plant (Srivastava and Upadhyay, 1974). Sharma and Sethi (1975) found that 100 M. incognita juveniles were requiredto cause a reduction in cowpea shoot weight, while considerabledamage to shoot and root lengths and root weight was done atinoculum levels of 1000 and 10,000 juveniles respectively. Gergon Table 4 Effect of inoculum densities of Meloidogyne incognita on reduction in shoot length (cm).Plant ages %Reduction in shoot length (cm) at inoculum levels of M. incognita Regression equations R 2 500 J2s 1000 J2s 2000 J2s 4000 J2s 8000 J2s2 Week 14.26 ± 0.79 d 22.76 ± 0.98 f 36.72 ± 1.76 g 52.04 ± 1.61 i 68.06 ± 1.11 k y ¼ 13.688 2.296 0.9893 Week 8.98 ± 0.63 b 17.06 ± 0.65 e 22.92 ± 1.24 f 41.08 ± 0.98 h 54.12 ± 0.65 j y ¼ 11.43 5.458 0.9634 Week 6.96 ± 0.59 a 12.08 ± 1.09 c 16.78 ± 0.89 e 37.98 ± 1.39 g 41.90 ± 1.25 h y ¼ 9.578 5.594 0.920Data are means of ten replicates.Means sharing common letters within columns do not differ signi cantly by Fisher's protected least signi cant difference test at P < 5%. Table 5 Effect of inoculum densities of Meloidogyne incognita on reduction in root length (cm).Plant ages %Reduction in root length (cm) at inoculum levels of M. incognita Regression equations R 2 500 J2s 1000 J2s 2000 J2s 4000 J2s 8000 J2s2 Week 11.5 ± 0.99 bc 16.3 ± 0.60 d 28.06 ± 1.64 g 38.9 ± 2.21 i 50.9 ± 1.77 j y ¼ 10.14 1.288 0.9833 Week 9.96 ± 0.41 b 14.7 ± 0.75 cd 22.3 ± 1.31 f 33.4 ± 1.26 h 40.7 ± 1.38 i y ¼ 8.018 þ 0.158 0.9844 Week 4.2 ± 0.23 a 9.52 ± 0.87 b 18.2 ± 1.18 de 21.7 ± 1.24 ef 31.8 ± 1.66 h y ¼ 6.738 3.13 0.982Data are means of ten replicates.Means sharing common letters within columns do not differ signi cantly by Fisher's protected least signi cant difference test at P < 5%. Table 6 Effect of inoculum densities of Meloidogyne incognita on reduction in number of fruits.Plant ages %Reduction in number of fruits at inoculum levels of M. incognita Regression equations R 2 500 J2s 1000 J2s 2000 J2s 4000 J2s 8000 J2s2 Week 2.82 ± 0.96 ab 7.46 ± 0.29 bc 15.10 ± 1.15 de 27.43 ± 1.12 g 39.05 ± 1.73 i y ¼ 9.243 9.357 0.9693 Week 1.94 ± 0.47 a 3.84 ± 1.56 ab 11.54 ± 1.52 cd 23.16 ± 1.16 fg 34.05 ± 0.56 h y ¼ 8.354 10.156 0.9484 Week 1.46 ± 0.36 a 2.36 ± 0.26 a 10.48 ± 0.29 cd 18.88 ± 0.99 ef 26.09 ± 1.87 g y ¼ 6.578 7.88 0.957Data are means of ten replicates.Means sharing common letters within columns do not differ signi cantly by Fisher's protected least signi cant difference test at P < 5%. Table 7 Effect of inoculum densities of Meloidogyne incognita on reduction in fruit weight (g).Plant ages %Reduction in fruit weight (g) at inoculum levels of M. incognita Regression equations R 2 500 J2s 1000 J2s 2000 J2s 4000 J2s 8000 J2s2 Week 2.21 ± 1.18 a 7.51 ± 1.48 abcd 12.09 ± 1.05 cdef 16.11 ± 2.27 efg 26.85 ± 0.52 h y ¼ 5.788 4.41 0.9603 Week 1.67 ± 0.33 a 5.49 ± 1.27 abc 9.67 ± 0.39 cde 13.97 ± 1.93 def 22.24 ± 1.61 gh y ¼ 4.962 4.278 0.9714 Week 0.57 ± 0.50 a 2.46 ± 1.52 ab 6.91 ± 1.18 abcd 9.68 ± 1.52 bcde 18.54 ± 1.99 fg y ¼ 4.316 5.316 0.929Data are means of ten replicates.Means sharing common letters do not differ signi cantly by Fisher's protected least signi cant difference test at P < 5%. Table 8 Effect of inoculum densities of Meloidogyne incognita on reduction in fruit yield (kg).Plant ages %Reduction in fruit yield (kg) at inoculum levels of M. incognita Regression equations R 2 500 J2s 1000 J2s 2000 J2s 4000 J2s 8000 J2s2 Week 3.93 ± 1.43 a 14.13 ± 1.95 bc 25.18 ± 1.05 d 39.07 ± 1.20 f 55.11 ± 0.72 g y ¼ 12.73 10.706 0.9913 Week 3.47 ± 0.52 a 9.11 ± 1.43 ab 20.21 ± 0.20 cd 34.02 ± 0.96 ef 48.42 ± 1.19 g y ¼ 11.48 11.397 0.9774 Week 2.28 ± 0.99 a 4.49 ± 1.89 a 16.17 ± 5.53 bc 26.86 ± 0.48 de 39.32 ± 1.70 f y ¼ 9.65 11.111 0.963Data are means of ten replicates.Means sharing common letters within columns do not differ signi cantly by Fisher's protected least signi cant difference test at P < 5%. M.Z. Kayani et al. / Crop Protection 92 (2017) 207 e 212 210 et al. (2002) reported a decrease in leaf weight and root length of ‘ Yellow Granex 429 ’ onion seedlings with a minimum initial pop-ulation of 50 juveniles of M. graminicola and a mild stimulation inplant height at the vegetative growth stage. Mild stimulation of plantgrowthatlowinitialnematodedensitieshasbeenreportedinvarious vegetables in the case of M. hapla (Olthof and Potter,1972),in pepper in the case of M. javanica (Madamba et al., 1965) and inrice under upland conditions in the case of M. graminicola (Protet al., 1994). Growth improvement has been attributed to the pro-ductionof certainplantgrowth regulators inresponse tonematodeinvasion (Tandingan et al., 1996). These variations in populationdensities of nematodes affecting growth of plants might be due todifferencesinthebehaviorofnematodespeciesandcultivarsof theplants. In the present study root weight of cucumber plantsincreased at all inoculum levels, lower densities resulting intolesser increase. The increase in root weight was more at higherinoculum densities. The increase in root weight due to nematodeinfection has also been reported by Peters (1961) and was in u-enced by inoculum levels too. The increase in root weight is due toformation of galls stimulated by nematodes and is affected by thenumber and size of galls being proportionate to the amount of inoculum. At lower densities of nematodes, the galls producedwere smaller in size and fewer in number resulting in less increasein root weight while bigger and numerous galls developed as aresult of higher nematode inoculum densities and caused moreincreaseinrootweight.Anumberofresearchershavealsoreportedsimilar results (Parveen, 2006; Niyaz and Hisamuddin, 2008).However, our study contradicted the nding of Srivastava andUpadhyay (1974) who reported a signi cant decrease in rootweight of brinjal at an initial inoculum level of ten nematode ju-veniles per 500 g of soil.The damaging effects of M. incognita population levels weregreater on younger plants compared to older ones. This was due tothe tenderness and succulence of tissues of younger plants; beingmore attractive and susceptible to a large number of nematodes.The older plants being harder and stronger were less affected.Wong and Mai (1973) reported that high populations of M. hapla retarded the growth of young seedlings of lettuce more comparedto older plants. Choudhury (1985) reported that one week oldseedlings of tomato cv. ‘ Money maker ’ did nottolerate the attack of M. incognita larvae, while 3 and 5 week old seedlings did. Salaresand Gapasin (1988) found that percent yield reduction of ampa-laya ( Momordica charantia ) was lower on 8-week old plantscompared with 2-, 4- and 6-week old plants when inoculated withdifferent inoculum densities of M. incognita . 5. Conclusions The results from this study demonstrate that M. incognita hasthe potential to severely impair growth of cucumber and causesevere yield losses. 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