Differential Host Test Research Articles

Detection of Root-Knot Nematode Species and Races in Kahramanmaraş Province, Türkiye

Root-knot nematodes (Meloidogyne spp.) are organisms that spread over large areas and cause economic damage to vegetables. In this study, root-knot nematode populations obtained from vegetable growing areas of Kahramanmaraş province were identified. Overall, 132 root samples were taken from the vegetable crop fields. Root-knot nematode was detected in 25 of the collected samples and their diagnosis was determined based on biochemical (esterase isoenzyme phenotype), perineal pattern, and molecular methods. The race determination of root-knot nematodes was made according to the North Carolina Differential Host Test. Results showed that while Meloidogyne incognita was detected in Andırın, Onikişubat, Dulkadiroğlu, Türkoğlu, and Ekinözü districts of Kahramanmaraş, both M. incognita and M. javanica were found in Beyoğlu of Türkoğlu. This is the first report of M. javanica infection in Kahramanmaraş. Races of root-knot nematodes were determined as M. incognita race 1, race 2 and M. javanica race 2.

Identification of the race of root knot nematode by differential host test method

Root knot nematode (Meloidogyne incognita) cause major damage to the fruit crops, vegetable crops and field crops. Infected plants showed declined symptoms and poor fruit yield also displayed stunting and yellowing symptoms. In order to choose appropriate management control techniques, nematode diagnosis and specimen identification must be accurate, quick and precise. The population of the nematode obtained from the experimental field of Post Graduate Institute, Mahatma Phule Krishi Vidyapeeth, Rahuri were assessed for their host-race status by the differential host test which relies on the combination of resistant and susceptible reactions of six differential hosts to the nematode population. Result revealed that the nematode population infected tobacco (NC 95), pepper (California Wonder), watermelon (Charleston grey), tomato (Rutgers) and unable to reproduce on cotton (Deltapine- 16) and peanut (Florunner) which indicated presence of race 2 of Meloidogyne incognita.

Pathogenic Variability of Meloidogyne incognita Populations Occurring in Pepper-Production Greenhouses in Israel Toward Me1, Me3 and N Pepper Resistance Genes.

Natural variation in the root-knot nematode Meloidogyne incognita is problematic for breeding programs: populations possessing similar morphological characteristics can produce different reactions on the same host. We collected 30 widely dispersed M. incognita populations from protected pepper production systems in major pepper-growing regions of Israel and accurately identified their virulence characteristics by modified differential host test in a growth chamber on tomato, tobacco, cotton, melon, pepper, and peanut. Galling indices and reproduction were determined on the different hosts. All populations fit the published scheme for M. incognita race 2, except for reproduction on cotton plants by five out of 25 tested M. incognita populations, indicating host-range variations. Reaction of three genes that confer resistance to M. incognita-Me1, Me3 and N-to the collected populations was evaluated. Several M. incognita populations induced galling and reproduced successfully on pepper genotypes carrying Me3 and N, whereas plant resistance conferred by Me1 was more robust for all examined populations. Moreover, the effect of genetic background on Me1 resistance demonstrated a relative advantage of several genotypes in nematode infestations. Efficiency of Me3 under local nematode infestation was further studied with a homozygous line carrying two Me3 alleles. Reproduction of virulent populations on the homozygotes (Me3/Me3) and heterozygotes (Me3/Me3+) was similar, suggesting a limited quantitative effect of Me3. These results present the first characterization of host range, reproduction, and molecular aspects of M. incognita from Israel and highlight the importance of taking a multidimensional approach in pepper-breeding programs for resistance to M. incognita.

Meloidogyne luci n. sp. (Nematoda: Meloidogynidae), a root-knot nematode parasitising different crops in Brazil, Chile and Iran

A new root-knot nematode parasitising vegetables, flowers and fruits in Brazil, Iran and Chile, is described as Meloidogyne luci n. sp. The female has an oval to squarish perineal pattern with a low to moderately high dorsal arc and without shoulders, similar to M. ethiopica. The female stylet is robust and 15-16 μm long; the distance from the dorsal pharyngeal gland orifice to the stylet base (DGO) is 3-4 μm. Males have a high, rounded head cap continuous with the body contour. The labial disc is fused with the medial lips to form an elongated lip structure. The head region is not marked by incomplete annulations. Male stylet robust, 20.8-23.0 μm long with rounded knobs; the DGO is 2.5-4.5 μm. The stylet of second-stage juveniles (J2) is 12.0-13.5 μm long and the DGO to the stylet base is 2.3-3.3 μm. The J2 tail is conoid with finely rounded terminus and is 40.0-48.5 μm long. Biochemically, the esterase phenotype L3 (: 1.05, 1.10, 1.25) is unique and is the most useful character to differentiate M. luci n. sp. from all other Meloidogyne species. Reproduction is by mitotic parthenogenesis (2n = 42-46 chromosomes). In a differential host test, the population from Lavandula spica, Caxias do Sul, RS State, Brazil, reproduced on tomato cv. Rutgers, tobacco cv. NC95 and pepper cv. California Wonder. No reproduction occurred on watermelon cv. Charleston Gray, cotton cv. Deltapine 61 or peanut cv. Florunner. In Neighbour-Joining analyses of ITS and D2-D3 rRNA sequences, populations of M. luci n. sp. from Brazil, Chile and Iran clustered together and were clearly separated from other Meloidogyne spp., thus confirming that all three populations are very similar and conspecific.

Host range study of Argentine Nacobbus aberrans sensu Sher populations and comments on the differential host test

The existence of races within the species Nacobbus aberrans sensu Sher has been confirmed; however, there is no consensus on a consistent system for race determination. Four plant species previously used as differential hosts in some N. aberrans race tests (tomato, pepper, sugarbeet and potato) were tested for susceptibility to seven nematode populations from Argentina. Plants were inoculated with second-stage juveniles and kept under glasshouse conditions at 21 °C for 90 days. The parameters evaluated (root gall index, egg mass index, and reproduction factor) in different nematode populations and plants showed significant differences. The reproductive fitness of the nematode populations differed among the plants that showed some degree of susceptibility. The results showed that N. aberrans comprises populations differing in host preference. Based on the nematode populations’ behaviour on these hosts, two groups were distinguished: i) populations that multiplied on all hosts, ii) populations that did not multiply on potato. The present work contributes to the analysis of criteria for developing a differential host test.

Host-pathogen interaction of root-knot nematode Meloidogyne incognita on pepper in the southeast of Spain

The feeder roots of pepper plants (cv. California Wonder) in Campo de Cartagena (southeast Spain) were found to be severely infected by Meloidogyne incognita. Morphometric traits, differential host test and DNA analysis based on PCR were used to characterize the nematode. Naturally and artificially infected pepper plants showed severe yellowing and stunting, with heavily deformed and damaged root systems. Root galls were spherical and commonly contained more than one female and egg masses with eggs. Typical giant cells with a granular cytoplasm and many hypertrophied nuclei were observed in histological preparations. The relationship between initial nematode population density (Pi) and pepper plant growth was tested in greenhouse experiments with inoculum levels that varied from 0 to 64 eggs and second-stage juveniles (J2) ml−1 soil. A Seinhorst model was fitted to plant height and top fresh weight data of inoculated and non-inoculated plants. The tolerance limit with respect to plant height and fresh top weight of pepper to M. incognita was estimated as 0.85 eggs and J2 ml−1 soil. The minimum relative values (m) for plant height and top fresh weight were 0.15 and 0.16, respectively, at Pi ≥ 64 eggs and J2 ml−1 soil. The maximum nematode reproduction rate (Pf/Pi) was 315.4 at an initial population density (Pi) of 4 eggs and J2 ml−1 soil. The obtained results could be used as a base to establish field experiments that allow strategies to prevent surpassing the threshold of nematodes in fields that are infested.

Characterization of Meloidogyne incognita populations from São Paulo and Minas Gerais state and their pathogenicity on coffee plants

Meloidogyne incognita is one of the most aggressive and harmful plant-parasitic nematodes attacking coffee plantations in Brazil. However, populations from Minas Gerais state (MG) do not incite disease on coffee plants as strongly as populations from Sao Paulo state (SP). This study aimed to compare the capacity to incite disease on coffee plants from SP and MG-populations based on penetration and post-infective development of second-stage juveniles (J2) stage. Both populations were confirmed as M. incognita by using esterase phenotype I1 and species-specific PCR. Physiologically they were classified as race 2 by differential host test. Susceptible (C. arabica 'Catuai Vermelho IAC 44') and resistant coffee seedlings (C. canephora 'Apoata IAC 2258') were inoculated with J2 and assessed for penetration and development from 2nd to 40th day after inoculation. Although the penetration rate of the J2 from both populations was higher in susceptible than in resistant seedlings, the SP-population showed a higher penetration than the MG-population for both variables. Post-infective development proceeded only in individuals of the SP-population in susceptible seedlings. The incompatibility between the MG-population and coffee seedlings was evident at the penetration phase, which was also followed by post-penetration resistance factors leading to significant J2 emigration, impeding nematode establishment.

Characterizing races of Meloidogyne incognita, M. javanica and M. arenaria in the West Mediterranean region of Turkey

A total of 95 samples of Meloidogyne incognita (60), Meloidogyne javanica (28) and Meloidogyne arenaria (7) collected from West Mediterranean region of Turkey were tested for identifying races of the nematodes using the North Carolina Differential Host Test. Races 2 and 6 of M. incognita were identified in 58 and 2 samples, respectively. Race 1 of M. javanica was identified from all 28 samples. Races 2 and 3 of M. arenaria were identified in 5 and 2 samples, respectively. The results also showed that two races of M. incognita and all races of M. javanica did not attack on pepper cv. California Wonder. These findings may contribute to improving resistant varieties and may also provide basis for developing a cropping system to control root-knot nematodes.

Occurrence of root-knot disease in green onion in Allahabad

Onion is an important indispensable item in every kitchen as condiment and vegetable, hence commands an extensive internal market. The green leaves and immature and mature bulbs are eaten raw or used in preparation of vegetables. Among the various pests and diseases associated with onion, the root knot nematode (Meloidogyne incognita) had proved itself as an important limiting factor for successful cultivation of this crop. Recently root-knot nematode was observed to cause serious losses to green onion crop grown mostly in the field located near the Jamuna & Ganga river belt of Allahabad and the surrounding area in U.P. Differential host test was done to confirm the root knot disease in onion. The specific identity of the nematode was determined by cutting perineal pattern of the females and was confirmed as Meloidogyne incognita.

Detection and identification of the blackeye cowpea mosaic strain of Bean common mosaic virus in seeds of cowpea from southern India

In different legume-growing regions of India, a total of 136 seed samples of cowpea (Vigna unguiculata (L.) Walp.) were collected and tested for the presence of the blackeye cowpea mosaic strain of Bean common mosaic virus, Cowpea aphid-borne mosaic virus, Cowpea mosaic virus, Cucumber mosaic virus and Bean yellow mosaic virus using growing-on test, enzyme linked immunosorbent assay, differential host test, electron microscopy and immuno-capture reverse transcription polymerase chain reaction. Among the 136 seedlots tested, 43 cowpea seedlots were found to be infected with BCMV-BlCM. The identity of three of these isolates as BCMV-BlCM was further supported by nucleotide sequencing in the 3′ region of the genome. The incidence of seeds carrying transmissible virus ranged from 0.67% to 13.49%. In most cases, only symptomatic seedlings in a growing-on test were found infected with the virus.

New Host Races of Meloidogyne arenaria, M. incognita, and M. javanica from Horticultural Regions of Spain

In total, 140 populations of the genus Meloidogyne collected from representative horticultural regions of Spain and maintained at the Department of Agroecology, Institute of Agrarian Sciences, Madrid were characterized using perineal morphology, sequenced characterized amplified region polymerase chain reaction with species-specific primers, and bioassay. Using a modified North Carolina differential host test as a basis, 13 Meloidogyne populations did not fit into the published race scheme. These populations had very limited host ranges, reproducing only on susceptible tomato cv. Marmande and sometimes also on tobacco cv. NC95 and the pepper cv. Sonar in the case of Meloidogyne arenaria. They did not reproduce on cotton or peanut. The species and new races were identified as M. incognita races 5 (6 populations) and 6 (2 populations) and M. javanica race 5 (2 populations), with new records of M. arenaria race 3 (2 populations) and M. javanica race 1 (23 populations) for Spain.

Evaluation of mistletoes (<i>Tapinanthus sp</i>) on the ornamental plants and trees in selected academic and research institutions in Zaria, Nigeria

The need for environmental protection of the natural and artificial vegetation as a means of biodiversity is of global interest. Therefore, a survey was conducted in some institutions in Zaria to identify common host species of mistletoes (Tapinanthus sp) and the level of damage induced by the parasite. Samples of the ornamental plants and trees were collected during the survey in 2001 and were identified in Ahmadu Bello University, Zaria herbarium. The severity and incidence of the parasite were determined by differential host test and the number of infected stands, were expressed in percentage of total stands sampled respectively. Results showed that the parasite is important in the Zaria as 100% incidence and severity of 50% and above (++) was observed on Dalbergia sissoo, Gmelina aborea, Khaya senegalensis, Thevetia nerrifoliea, and Azadirachta indica. Generally, the incidence of susceptible species ranged between 20%-100%. Dalbergia sissoo gave the highest severity as some stands were completely killed by the parasite particularly in the Federal College of Education, Zaria environment. Journal of Agriculture, Forestry and the Social Sciences Vol. 3 (2) 2005: pp.86-91

Virulence of root-knot nematodes, Meloidogyne spp., on tomato bearing the Mi gene for resistance.

Three species of root-knot nematodes, Meloidogyne javanica, M. incognita races 1 and 2, and M. arenaria race 2 occur in Jordan. These species and their races were identified using morphological characters, the North Carolina differential host test, and SCAR-PCR. The virulence of 83 isolates belonging to Meloidogyne species and races was assayed. The virulence assay was based on the isolate reproduction rate on a resistant tomato cultivar Betterboy bearing the Mi gene for resistance, and was compared with that on the susceptible tomato cultivar Rutgers. Three M. javanica isolates were highly virulent on the resistant cv. Betterboy as indicated by their high root gall index (4.73) and high reproduction factor (3.73). The horticultural parameters (shoot and root fresh weights and root dry weight) were negatively correlated with the reproduction factor.

First Report of the Root-Knot Nematode Meloidogyne arenaria Race 2 from Several Vegetable Crops in Jordan.

Meloidogyne arenaria (Neal) Chitwood (race 2) is reported for the first time in Jordan. The nematode populations were recovered from several vegetable crops, including tomato (Lycopersicon esulentum Mill), squash (Cucurbita pepo L.), cucumber (Cucumis sativus L.), and bean (Phaseolus vulgaris L.), at Dier Alla in the northern area of the Jordan Valley. Symptoms included root galling, leaf chlorosis, and stunting. Galled plant root samples were collected during a survey conducted from May 2002 to August 2003 covering most of the irrigated agricultural areas of Jordan. Eighty-three Meloidogyne spp. populations were collected from various vegetable crops and fruit trees. Identification to species and race levels of the nematode populations was based on combination of currently available methods including nematode morphology, host preference based on the North Carolina (NC) differential host test (1), and cytogenetics and DNA-fingerprinting. Seventy of the eighty-three collected populations were identified as M. javanica, five as M. incognita (race 1), three as M. incognita (race 2), and five as M. arenaria (race 2). The perineal patterns of M. arenaria were characterized by a low, round to indented dorsal arch near the lateral field with irregular forks in the lateral field, fine smooth striae, and a distinct whorl. Race 2 was identified with the NC differential host test. Cytogenetic studies indicated that M. arenaria populations were triploid with an average of 52.2 chromosomes, while the populations of M. incognita (race 1), M. incognita (race 2), and M. javanica were hypotriploid with an average of 45.2, 46.1, and 46.7 chromosomes, respectively. Two polymerase chain reaction (PCR)-based assays were used to confirm species identification and to study genetic variability of the Meloidogyne spp. populations including sequence characterized amplified regions (SCAR) and random amplified polymorphic DNA (RAPD). In the SCAR-PCR-based assay (2), typical DNA products of 420, 670, or 1,200 bp in size were amplified by using extracted DNA of M. arenaria (race 2), M. javanica, or M. incognita (race 1 or 2), respectively, as template DNA. The RAPD-PCR primer, OPA-01, produced DNA patterns with bands that clearly distinguished M. arenaria from the other two Meloidogyne spp. To our knowledge, this is the first report of the root-knot nematode, M. arenaria race 2, in Jordan.

Additional information on Meloidogyne ethiopica Whitehead, 1968 (Tylenchida: Meloidogynidae), a root-knot nematode parasitising kiwi fruit and grape-vine from Brazil and Chile

Abstract A root-knot nematode parasitising kiwi fruit (Actinidia deliciosa) in Rio Grande do Sul State, Brazil and grape-vine (Vitis vinifera) in Chile, is identified as Meloidogyne ethiopica Whitehead, 1968. The species is redescribed from this new material and compared with the type description of M. ethiopica and another population of the species from Kenya. The female has an oval to squarish perineal pattern with a moderately high to high dorsal arch, smooth, widely spaced striae, and no 'shoulders'. The head region is set off with an elevated squarish labial disc, usually marked by annulations, and the stylet is 12-15 μm long, the cone usually being slightly curved dorsally and the shaft gradually widening posteriorly to near the junction with the rounded stylet knobs. The DGO is 3.0-5.0 μm behind the knobs. The male has a high, rounded head cap which is continuous with the body contour and has a distinct labial disc, almost circular to hexagonal in shape, and distinctly separated from the medial lips. The stylet is robust, 23-27 μm long with a straight cone and a cylindrical shaft widening slightly near its junction with the basal knobs which are smooth, round to pear-shaped and backwardly sloping. The stylet length of the second-stage juvenile is 11-14 μm, the DGO is 2.0-3.0 μm behind the knobs and the tail length is 52-72 μm. Biochemically, the esterase phenotype E3 ( Ki3) is species-specific and is the most useful character for differentiating M. ethiopica from other species. Reproduction is by mitotic parthenogenesis, 2n 36-38. In a differential host test, populations of M. ethiopica reproduced on tomato, tobacco, pepper and watermelon. No reproduction occurred on cotton or peanut. Using the PCR-RAPD analysis to compare populations from Brazil, Chile and Kenya, a low proportion of polymorphic fragments (about 17.7%) was detected and the isolates clustered together with high bootstrap support (100%), thus confirming that all three populations are very similar and apparently conspecific.

Characterization of Root-Knot Nematode Populations Associated with Vegetables in New York State.

The northern root-knot nematode (Meloidogyne hapla) causes significant damage on vegetables in New York State. This study was conducted to determine if other species of Meloidogyne are also present in New York vegetable fields and to better characterize the root-knot populations in order to facilitate the development of effective rotations for nematode management. Populations of Meloidogyne were collected from 18 vegetable fields across New York and maintained in the greenhouse on tomato cv. Rutgers as both field populations and single-female populations. For the purposes of species identification, nematodes from each population were examined using perineal pattern analysis, scanning electron microscopy, and cytological analysis. All techniques identified the presence of only Meloidogyne hapla in the collected samples. The host range of the populations of Meloidogyne that were collected was investigated using a modified form of the North Carolina Differential Host Test. While host ranges were variable among the collected populations, the host range of all populations closely corresponded to that of M. hapla. The internal transcribed spacer region (ITS1) of the collected populations was amplified and sequenced. All sequences from the collected populations corresponded to the published sequence of M. hapla. Based on these results, it was concluded that M. hapla is the only root-knot nematode species present in New York vegetable fields. Crop rotational strategies for management of the root-knot nematode on vegetables in New York should be devised to reflect this fact.

Assessment of the North Carolina differential host test for identification of Australian populations of root-knot nematodes (Meloidogyne spp.)

Forty-one Australian populations of Meloidogyne were assessed for their host-race status by the North Carolina differential host test which relies on the combination of resistant and susceptible reactions of six differential hosts to the nematode population. Although in most cases the distinction between reactions of the NC differential hosts to nematode populations was clear, there was sufficient discrepancy to make the test unreliable for species and race identification in Australia when used alone. Five atypical combinations of reactions were found.

Reaction of Leucaena to Australian Populations of Root-Knot Nematode (Meloidogyne Spp.).

A nematode tentatively identified from its perineal pattern as Meloidogyne arenaria was found in a planting of Leucaena leucocephala at Crows Nest, Queensland. This is the first report of root-knot nematode on Leucaena in Australia. Further characterisation of the nematode using a standard differential host test confirmed its identity as M. arenaria race 2. Since most previous reports had suggested that Leucaena is resistant to Meloidogyne spp., L. diversifolia and L. leucocephala cw. Cunningham and Peru were tested in a glasshouse for their capacity to host Australian populations of M. javanica, M. incognita, and M. arenaria. L. diversifolia was susceptible to all species tested whereas L. leucocephala was resistant to M. javanica and M. incognita and susceptible to M. arenaria.