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“Resistance-breaking” nematodes identified in California tomatoes

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Authors

Isgouhi Kaloshian , Department of Nematology, UC Davis
Valerie M. Williamson, Department of Nematology, UC Davis
Gene Miyao, Yolo/Solano Counties
Dennis A. Lawn, San Juan Bautista
Becky B. Westerdahl, Department of Nematology, UC Davis

Publication Information

California Agriculture 50(6):18-19. https://doi.org/10.3733/ca.v050n06p18

Published November 01, 1996

PDF  |  Citation  |  Permissions  |  Cited by 36 articles

Author Affiliations show

Abstract

Resistance to root-knot nematodes in tomato is conferred by the gene Mi. We have identified two field populations of Meloidogyne incognita that parasitize tomato plants containing the Mi gene. This necessitates the use of planned crop rotation practices and the incorporation of other resistance genes into cultivated tomato.

Full text

Root-knot nematodes are important agricultural pests that parasitize a large number of cultivated crops worldwide. They cause serious yield loss to tomato crops, especially in warm temperate areas where soil temperatures favorable for nematode development result in quick build up of nematode populations.

Resistance to these nematodes is available in many varieties of both processing and fresh-market tomatoes. The resistance is conferred by a single dominant gene Mi. To maximize the utility of Mi, it is important to assess the potential for the establishment of resistance-breaking nematodes that can infect Mi plants in tomato-growing areas. Previous studies have shown that resistance-breaking populations can develop after continuous exposure to resistant varieties. The increasing reliance on resistance due to restricted use of nematicide treatments enhances the potential for selection of resistance-breaking populations in tomato fields.

Root-knot nematodes

Root-knot nematodes (Meloidogyne spp) are microscopic roundworms; they are obligate parasites of plant roots that cause severe damage to tomato and many other crops. The infective stage of the nematode, the second-stage juvenile (J2), penetrates the roots behind the root tip and migrates between the cells until it reaches the vascular bundle. The nematode starts feeding on selected cells near the vascular bundle. These plant cells become transformed by the nematode into large multinucleate cells called “giant cells,” which serve as a feeding site to provide nutrition for nematode development. Cells in the cortical layer of the root near the feeding site divide and enlarge to form galls, the common symptom associated with root-knot nematode infections. Above-ground symptoms include poor growth and wilting due to limited water transport through the disrupted plant vascular element at the nematode feeding site and to alterations in nutrient partitioning.

Fig. 1. Polyacrylamide gel showing the malate dehydrogenase (Mdh) and esterase phenotypes of single root-knot nematode females. Isozyme patterns of A) known isolates of M. arenaria (a), M. incognita (i), M. hapla (h), and M. javanica (j); B) resistance-breaking nematodes from Woodland population (pop. 1), and M. javanica (j); C) resistance-breaking nematodes from Kettleman City population (pop. 2), and M. javanica (j).

All resistance to root-knot nematodes present in commercial varieties of tomato is conferred by the Mi gene. This gene confers resistance to three species of root-knot nematodes, M. arenaria, M. incognita and M. javanica, the most common root-knot species found in tomato-growing areas in the United States. The resistance was originally identified in Lycopersicon peruvianum, a wild relative of cultivated tomato, and was introduced into cultivated tomato using embryo rescue of a cross of the wild species and cultivated tomato, L. esculentum, about 50 years ago. Embryo rescue is a technique in which embryos are dissected from partially developed seeds within tomato fruits and cultured aseptically on an artificial medium to enhance their growth. A single hybrid plant was recovered. Progeny of this plant are the sole source of nematode resistance in currently available fresh-market and processing tomato cultivars. Another decade of breeding was required to develop the first releases of nematode-resistant tomato lines.

Although Mi confers resistance to the three economically important species of root-knot nematode listed earlier, it does not confer resistance to M. hapla, a species also present in some areas of California where tomatoes are grown. In addition, the resistance conferred by Mi is not effective in soils where temperatures rise above 28°C. Also, some isolates of M. incognita and M. javanica have been reported to cause galls and to reproduce on plants containing Mi.

Resistance-breaking nematodes

In the fall of 1995, two occurrences of root-knot nematodes growing on resistant tomato cultivars in California fields came to our attention. One field was located near Kettleman City in Kings County. The second field was located at Woodland in Yolo County. In both cases, galling of the roots was extensive and the infection was widespread in the fields. We initiated a series of experiments to identify the nature of this problem. Since the Mi gene does not confer resistance to M. hapla, our first step was to identify the species of the root-knot nematode to eliminate the possibility of M. hapla infection. Adult females were dissected from the field-infected tomato roots and isoenzyme electrophoresis was carried out with individual females. Gels stained for malate dehydrogenase and esterase gave diagnostic patterns of M. incognita for both isolates (fig. 1). In addition, the symptoms on the tomato roots were typical large galls caused by M. incognita or M. javanica. M. hapla usually produces smaller galls with a “hairy” appearance.

To confirm that the galled plants in the field carried the Mi gene, we performed a molecular test to identify the presence of the REX-1 marker, a DNA marker that correlates with Mi. This marker can be assayed on a small piece of leaf tissue using polymerase chain reaction and specific primers. Leaf tissue was available only from the tomato plants from the Woodland area. The analysis of the REX-1 marker showed that the plants were hybrids containing the Mi gene.

To confirm that these two root-knot nematode populations could reproduce on plants with Mi, root-knot nematode eggs isolated from the roots of field-infected tomato plants were used to infect tomato variety ‘VFNT,’ which is known to contain the Mi gene. ‘UC82-B,’ a tomato cultivar that does not have Mi, was included as a susceptible control. Tomato seeds were germinated in 1-liter cups in river sand and plants were grown in a greenhouse. For each nematode population, three seedlings of ‘VFNT’ and ‘UC82-B’ were infected with 10,000 eggs each and maintained in the greenhouse at 23° to 26°C. After 8 weeks, we washed the plant roots and estimated nematode reproduction by counting egg masses on the roots. Both field populations of root-knot nematodes were able to reproduce to high levels on ‘VFNT,’ as well as on control ‘UC82-B.’ We counted more than 100 egg masses per root system on both tomato varieties infected with the Woodland or the Kettleman City root-knot nematode populations. Standard nematode populations produce 0 to 5 egg masses on ‘VFNT’ in similar assays.

Although nematodes from both locations were able to reproduce on resistant tomato plants, the histories of the two fields were quite different. The field in Woodland had been planted with six crops of tomato within a 10-year period; all varieties were processing-type hybrids containing the Mi gene. The pressure exerted on the nematode population by the frequent cultivation of resistant tomato could explain the development of the resistance-breaking population. On the other hand, the field from Kettleman City had been planted with only two tomato crops immediately prior to the infected crop in 1995, and had been left fallow for the 8 previous years. Records are not available regarding the varieties of tomato planted. In addition, there were some nematode problems with the first tomato crop, but little importance was placed on it. This population of root-knot nematode may have had an inherent capability to grow on Mi-containing plants. Although such populations of M. incognita are not thought to be common in California, they have been reported in other parts of the world.

Dealing with the problem

Root-knot nematodes are serious pests of tomato worldwide. Restrictions on the use of most nematicides coupled with the availability of Mi-resistance in many preferred tomato varieties have led farmers to rely increasingly on resistant tomatoes for nematode management. Repeated plantings of resistant tomato may lead to the selection of resistance-breaking root-knot populations on some sites. Because all root-knot resistance in tomato is conferred by the same gene, the substitution of one cultivar for another will not be helpful. Increased awareness of proper rotation practices of resistant tomato with other crops will extend the durability of the Mi gene.

The recent emergence in California of root-knot nematode populations that can overcome the resistance conferred by Mi is a cause for concern. However, it is difficult to assess the magnitude of the threat from resistance-breaking nematodes based on these isolated finds with different cropping histories. Some populations have been shown to lack genetic potential for resistance breaking in controlled selection experiments. Furthermore, there is evidence that Mi-resistance-breaking populations are not able to break resistance in other crops. New sources of resistance to root-knot nematodes have been identified in wild tomato, but in will take many years of effort before they are in acceptable varieties. Development of novel resistance by using biotechnology to produce transgenic plants has promise for providing another source of resistance. Research to incorporate both natural and engineered resistance into cultivars as well as investigation of the biology of the nematode is needed in order to develop additional control strategies for root-knot nematode in the years to come.

Root-knot nematodes collected from resistant tomato plants at Woodland were able to produce galls on the roots of the resistant ‘VFNT’ tomato.

Return to top

Citations

Mapping of a Heat-Stable Gene for Resistance to Southern Root-Knot Nematode in Solanum lycopersicum
Yinlei Wang et al. 2013. Plant Molecular Biology Reporter 31(2):352
http://dx.doi.org/10.1007/s11105-012-0505-8

Managing for soil health can suppress pests
Amanda Hodson and Edwin Lewis 2016. California Agriculture 70(3):137
http://dx.doi.org/10.3733/ca.2016a0005

Fine mapping of the nematode resistance gene Mi-3 in Solanum peruvianum and construction of a S. lycopersicum DNA contig spanning the locus
J. Yaghoobi et al. 2005. Molecular Genetics and Genomics 274(1):60
http://dx.doi.org/10.1007/s00438-005-1149-2

Hemipteran and dipteran pests: Effectors and plant host immune regulators
Isgouhi Kaloshian and Linda L. Walling 2016. Journal of Integrative Plant Biology 58(4):350
http://dx.doi.org/10.1111/jipb.12438

Molecular Cloning of a cDNA Encoding an Amphid-Secreted Putative Avirulence Protein from the Root-Knot NematodeMeloidogyne incognita
Jean-Philippe Semblat et al. 2001. Molecular Plant-Microbe Interactions 14(1):72
http://dx.doi.org/10.1094/MPMI.2001.14.1.72

Root-knot nematodes on tomatoes in Kyenjojo and Masaka districts in Uganda
Mwesige Rose et al. 2016. African Journal of Agricultural Research 11(38):3598
http://dx.doi.org/10.5897/AJAR2016.11311

Nonchemical Management of Soilborne Pests in Fresh Market Vegetable Production Systems
D. O. Chellemi 2002. Phytopathology 92(12):1367
http://dx.doi.org/10.1094/PHYTO.2002.92.12.1367

Silencing a Candidate Nematode Effector Gene Corresponding to the Tomato Resistance Gene Mi-1 Leads to Acquisition of Virulence
Cynthia A. Gleason et al. 2008. Molecular Plant-Microbe Interactions 21(5):576
http://dx.doi.org/10.1094/MPMI-21-5-0576

MeloidogyneVirulence Locus Molecular Marker for Characterization of SelectedMi-Virulent Populations ofMeloidogynespp. Is Correlated with Several Genera of Betaproteobacteria
Laura Cortada et al. 2011. Phytopathology 101(4):410
http://dx.doi.org/10.1094/PHYTO-04-10-0123

Variation in resistance to the root-knot nematode Meloidogyne incognita in tomato genotypes bearing the Mi gene
M. Jacquet et al. 2005. Plant Pathology 54(2):93
http://dx.doi.org/10.1111/j.1365-3059.2005.01143.x

A Population ofMeloidogyne javanicain Spain Virulent to theMiResistance Gene in Tomato
C. Ornat et al. 2001. Plant Disease 85(3):271
http://dx.doi.org/10.1094/PDIS.2001.85.3.271

Virulence response to the Mi.1 gene of Meloidogyne populations from tomato in greenhouses
S. Verdejo-Lucas et al. 2012. Crop Protection 39:97
http://dx.doi.org/10.1016/j.cropro.2012.03.025

A Study of Gene Expression in the Nematode Resistant Wild Peanut Relative, Arachis stenosperma, in Response to Challenge with Meloidogyne arenaria
Patricia Messenberg Guimarães et al. 2010. Tropical Plant Biology 3(4):183
http://dx.doi.org/10.1007/s12042-010-9056-z

Management of Insect Pests to Agriculture
Isgouhi Kaloshian and Linda L. Walling 2016.
http://dx.doi.org/10.1007/978-3-319-24049-7_9

Plant nematode resistance genes
Valerie M Williamson 1999. Current Opinion in Plant Biology 2(4):327
http://dx.doi.org/10.1016/S1369-5266(99)80057-0

ROOT-KNOT NEMATODE RESISTANCE GENES IN TOMATO AND THEIR POTENTIAL FOR FUTURE USE
Valerie M. Williamson 1998. Annual Review of Phytopathology 36(1):277
http://dx.doi.org/10.1146/annurev.phyto.36.1.277

Aphid-Induced Defense Responses inMi-1-Mediated Compatible and Incompatible Tomato Interactions
Oscar Martinez de Ilarduya et al. 2003. Molecular Plant-Microbe Interactions 16(8):699
http://dx.doi.org/10.1094/MPMI.2003.16.8.699

Selection of virulent populations ofMeloidogyne javanicaby repeated cultivation ofMiresistance gene tomato rootstocks under field conditions
S. Verdejo-Lucas et al. 2009. Plant Pathology 58(5):990
http://dx.doi.org/10.1111/j.1365-3059.2009.02089.x

Responses of Tomato Genotypes to Avirulent andMi-VirulentMeloidogyne javanicaIsolates Occurring in Israel
Ionit Iberkleid et al. 2014. Phytopathology 104(5):484
http://dx.doi.org/10.1094/PHYTO-07-13-0181-R

The pepper resistance genes Me1 and Me3 induce differential penetration rates and temporal sequences of root cell ultrastructural changes upon nematode infection
Teresa Bleve-Zacheo et al. 1998. Plant Science 133(1):79
http://dx.doi.org/10.1016/S0168-9452(98)00021-1

Resistance-breaking population of Meloidogyne incognita utilizes plant peroxidase to scavenge reactive oxygen species, thereby promoting parasitism on tomato carrying Mi-1 gene
Tinglong Guan et al. 2017. Biochemical and Biophysical Research Communications 482(1):1
http://dx.doi.org/10.1016/j.bbrc.2016.11.040

Selection and parasite evolution: a reproductive fitness cost associated with virulence in the parthenogenetic nematode Meloidogyne incognita
Philippe Castagnone-Sereno et al. 2007. Evolutionary Ecology 21(2):259
http://dx.doi.org/10.1007/s10682-006-9003-5

Resistance in Peanut Cultivars and Breeding Lines to Three Root-Knot Nematode Species
W. B. Dong et al. 2008. Plant Disease 92(4):631
http://dx.doi.org/10.1094/PDIS-92-4-0631

Screening of Tagetes patula L. on different populations of Meloidogyne
Ana Piedra Buena et al. 2008. Crop Protection 27(1):96
http://dx.doi.org/10.1016/j.cropro.2007.04.011

Advances in Botanical Research
Pierre Abad and Valerie M. Williamson 2010.
http://dx.doi.org/10.1016/S0065-2296(10)53005-2

Natural genetic and induced plant resistance, as a control strategy to plant-parasitic nematodes alternative to pesticides
Sergio Molinari 2011. Plant Cell Reports 30(3):311
http://dx.doi.org/10.1007/s00299-010-0972-z

Evaluation of the ability of lectin from snowdrop (Galanthus nivalis) to protect plants against root-knot nematodes
Christophe Ripoll et al. 2003. Plant Science 164(4):517
http://dx.doi.org/10.1016/S0168-9452(02)00448-X

A Molecular Marker Correlated with Selected Virulence Against the Tomato Resistance Gene Mi in Meloidogyne incognita, M. javanica, and M. arenaria
Jianhua Xu et al. 2001. Phytopathology 91(4):377
http://dx.doi.org/10.1094/PHYTO.2001.91.4.377

Crop rotations with Mi gene resistant and susceptible tomato cultivars for management of root-knot nematodes in plastic houses
M. Talavera et al. 2009. Crop Protection 28(8):662
http://dx.doi.org/10.1016/j.cropro.2009.03.015

Analysis of tomato gene promoters activated in syncytia induced in tomato and potato hairy roots by Globodera rostochiensis
A. Wi?niewska et al. 2013. Transgenic Research 22(3):557
http://dx.doi.org/10.1007/s11248-012-9665-4

Rme1is Necessary forMi-1-Mediated Resistance and Acts Early in the Resistance Pathway
Oscar Martinez de Ilarduya et al. 2004. Molecular Plant-Microbe Interactions 17(1):55
http://dx.doi.org/10.1094/MPMI.2004.17.1.55

Virulence development and genetic polymorphism inMeloidogyne incognita(Kofoid & White) Chitwood after prolonged exposure to sublethal concentrations of nematicides and continuous growing of resistant tomato cultivars
Hari C Meher et al. 2009. Pest Management Science 65(11):1201
http://dx.doi.org/10.1002/ps.1810

Histological response of resistant tomato cultivars to infection of virulent Tunisian root-knot nematode (Meloidogyne incognita) populations
H. Regaieg and N. Horrigue-Raouani 2012. Archives Of Phytopathology And Plant Protection 45(17):2036
http://dx.doi.org/10.1080/03235408.2012.720470

Resistance to root-knot nematodesMeloidogynespp. in woody plants
Simon Bernard Saucet et al. 2016. New Phytologist 211(1):41
http://dx.doi.org/10.1111/nph.13933

Variability in the Response ofMacrosiphum euphorbiaeandMyzus persicae(Hemiptera: Aphididae) to the Tomato Resistance GeneMi
Fiona L. Goggin et al. 2001. Environmental Entomology 30(1):101
http://dx.doi.org/10.1603/0046-225X-30.1.101

Effect of manipueira on tomato plants infected by the nematode Meloidogyne incognita
Érica das Graças Carvalho Nasu et al. 2015. Crop Protection 78:193
http://dx.doi.org/10.1016/j.cropro.2015.08.005

“Resistance-breaking” nematodes identified in California tomatoes

Isgouhi Kaloshian, Valerie M. Williamson, Gene Miyao, Dennis A. Lawn, Becky B. Westerdahl
Webmaster Email: wsuckow@ucanr.edu

“Resistance-breaking” nematodes identified in California tomatoes

Share using any of the popular social networks Share by sending an email Print article
Share using any of the popular social networks Share by sending an email Print article

Authors

Isgouhi Kaloshian , Department of Nematology, UC Davis
Valerie M. Williamson, Department of Nematology, UC Davis
Gene Miyao, Yolo/Solano Counties
Dennis A. Lawn, San Juan Bautista
Becky B. Westerdahl, Department of Nematology, UC Davis

Publication Information

California Agriculture 50(6):18-19. https://doi.org/10.3733/ca.v050n06p18

Published November 01, 1996

PDF  |  Citation  |  Permissions  |  Cited by 36 articles

Author Affiliations show

Abstract

Resistance to root-knot nematodes in tomato is conferred by the gene Mi. We have identified two field populations of Meloidogyne incognita that parasitize tomato plants containing the Mi gene. This necessitates the use of planned crop rotation practices and the incorporation of other resistance genes into cultivated tomato.

Full text

Root-knot nematodes are important agricultural pests that parasitize a large number of cultivated crops worldwide. They cause serious yield loss to tomato crops, especially in warm temperate areas where soil temperatures favorable for nematode development result in quick build up of nematode populations.

Resistance to these nematodes is available in many varieties of both processing and fresh-market tomatoes. The resistance is conferred by a single dominant gene Mi. To maximize the utility of Mi, it is important to assess the potential for the establishment of resistance-breaking nematodes that can infect Mi plants in tomato-growing areas. Previous studies have shown that resistance-breaking populations can develop after continuous exposure to resistant varieties. The increasing reliance on resistance due to restricted use of nematicide treatments enhances the potential for selection of resistance-breaking populations in tomato fields.

Root-knot nematodes

Root-knot nematodes (Meloidogyne spp) are microscopic roundworms; they are obligate parasites of plant roots that cause severe damage to tomato and many other crops. The infective stage of the nematode, the second-stage juvenile (J2), penetrates the roots behind the root tip and migrates between the cells until it reaches the vascular bundle. The nematode starts feeding on selected cells near the vascular bundle. These plant cells become transformed by the nematode into large multinucleate cells called “giant cells,” which serve as a feeding site to provide nutrition for nematode development. Cells in the cortical layer of the root near the feeding site divide and enlarge to form galls, the common symptom associated with root-knot nematode infections. Above-ground symptoms include poor growth and wilting due to limited water transport through the disrupted plant vascular element at the nematode feeding site and to alterations in nutrient partitioning.

Fig. 1. Polyacrylamide gel showing the malate dehydrogenase (Mdh) and esterase phenotypes of single root-knot nematode females. Isozyme patterns of A) known isolates of M. arenaria (a), M. incognita (i), M. hapla (h), and M. javanica (j); B) resistance-breaking nematodes from Woodland population (pop. 1), and M. javanica (j); C) resistance-breaking nematodes from Kettleman City population (pop. 2), and M. javanica (j).

All resistance to root-knot nematodes present in commercial varieties of tomato is conferred by the Mi gene. This gene confers resistance to three species of root-knot nematodes, M. arenaria, M. incognita and M. javanica, the most common root-knot species found in tomato-growing areas in the United States. The resistance was originally identified in Lycopersicon peruvianum, a wild relative of cultivated tomato, and was introduced into cultivated tomato using embryo rescue of a cross of the wild species and cultivated tomato, L. esculentum, about 50 years ago. Embryo rescue is a technique in which embryos are dissected from partially developed seeds within tomato fruits and cultured aseptically on an artificial medium to enhance their growth. A single hybrid plant was recovered. Progeny of this plant are the sole source of nematode resistance in currently available fresh-market and processing tomato cultivars. Another decade of breeding was required to develop the first releases of nematode-resistant tomato lines.

Although Mi confers resistance to the three economically important species of root-knot nematode listed earlier, it does not confer resistance to M. hapla, a species also present in some areas of California where tomatoes are grown. In addition, the resistance conferred by Mi is not effective in soils where temperatures rise above 28°C. Also, some isolates of M. incognita and M. javanica have been reported to cause galls and to reproduce on plants containing Mi.

Resistance-breaking nematodes

In the fall of 1995, two occurrences of root-knot nematodes growing on resistant tomato cultivars in California fields came to our attention. One field was located near Kettleman City in Kings County. The second field was located at Woodland in Yolo County. In both cases, galling of the roots was extensive and the infection was widespread in the fields. We initiated a series of experiments to identify the nature of this problem. Since the Mi gene does not confer resistance to M. hapla, our first step was to identify the species of the root-knot nematode to eliminate the possibility of M. hapla infection. Adult females were dissected from the field-infected tomato roots and isoenzyme electrophoresis was carried out with individual females. Gels stained for malate dehydrogenase and esterase gave diagnostic patterns of M. incognita for both isolates (fig. 1). In addition, the symptoms on the tomato roots were typical large galls caused by M. incognita or M. javanica. M. hapla usually produces smaller galls with a “hairy” appearance.

To confirm that the galled plants in the field carried the Mi gene, we performed a molecular test to identify the presence of the REX-1 marker, a DNA marker that correlates with Mi. This marker can be assayed on a small piece of leaf tissue using polymerase chain reaction and specific primers. Leaf tissue was available only from the tomato plants from the Woodland area. The analysis of the REX-1 marker showed that the plants were hybrids containing the Mi gene.

To confirm that these two root-knot nematode populations could reproduce on plants with Mi, root-knot nematode eggs isolated from the roots of field-infected tomato plants were used to infect tomato variety ‘VFNT,’ which is known to contain the Mi gene. ‘UC82-B,’ a tomato cultivar that does not have Mi, was included as a susceptible control. Tomato seeds were germinated in 1-liter cups in river sand and plants were grown in a greenhouse. For each nematode population, three seedlings of ‘VFNT’ and ‘UC82-B’ were infected with 10,000 eggs each and maintained in the greenhouse at 23° to 26°C. After 8 weeks, we washed the plant roots and estimated nematode reproduction by counting egg masses on the roots. Both field populations of root-knot nematodes were able to reproduce to high levels on ‘VFNT,’ as well as on control ‘UC82-B.’ We counted more than 100 egg masses per root system on both tomato varieties infected with the Woodland or the Kettleman City root-knot nematode populations. Standard nematode populations produce 0 to 5 egg masses on ‘VFNT’ in similar assays.

Although nematodes from both locations were able to reproduce on resistant tomato plants, the histories of the two fields were quite different. The field in Woodland had been planted with six crops of tomato within a 10-year period; all varieties were processing-type hybrids containing the Mi gene. The pressure exerted on the nematode population by the frequent cultivation of resistant tomato could explain the development of the resistance-breaking population. On the other hand, the field from Kettleman City had been planted with only two tomato crops immediately prior to the infected crop in 1995, and had been left fallow for the 8 previous years. Records are not available regarding the varieties of tomato planted. In addition, there were some nematode problems with the first tomato crop, but little importance was placed on it. This population of root-knot nematode may have had an inherent capability to grow on Mi-containing plants. Although such populations of M. incognita are not thought to be common in California, they have been reported in other parts of the world.

Dealing with the problem

Root-knot nematodes are serious pests of tomato worldwide. Restrictions on the use of most nematicides coupled with the availability of Mi-resistance in many preferred tomato varieties have led farmers to rely increasingly on resistant tomatoes for nematode management. Repeated plantings of resistant tomato may lead to the selection of resistance-breaking root-knot populations on some sites. Because all root-knot resistance in tomato is conferred by the same gene, the substitution of one cultivar for another will not be helpful. Increased awareness of proper rotation practices of resistant tomato with other crops will extend the durability of the Mi gene.

The recent emergence in California of root-knot nematode populations that can overcome the resistance conferred by Mi is a cause for concern. However, it is difficult to assess the magnitude of the threat from resistance-breaking nematodes based on these isolated finds with different cropping histories. Some populations have been shown to lack genetic potential for resistance breaking in controlled selection experiments. Furthermore, there is evidence that Mi-resistance-breaking populations are not able to break resistance in other crops. New sources of resistance to root-knot nematodes have been identified in wild tomato, but in will take many years of effort before they are in acceptable varieties. Development of novel resistance by using biotechnology to produce transgenic plants has promise for providing another source of resistance. Research to incorporate both natural and engineered resistance into cultivars as well as investigation of the biology of the nematode is needed in order to develop additional control strategies for root-knot nematode in the years to come.

Root-knot nematodes collected from resistant tomato plants at Woodland were able to produce galls on the roots of the resistant ‘VFNT’ tomato.

Return to top

Citations

Mapping of a Heat-Stable Gene for Resistance to Southern Root-Knot Nematode in Solanum lycopersicum
Yinlei Wang et al. 2013. Plant Molecular Biology Reporter 31(2):352
http://dx.doi.org/10.1007/s11105-012-0505-8

Managing for soil health can suppress pests
Amanda Hodson and Edwin Lewis 2016. California Agriculture 70(3):137
http://dx.doi.org/10.3733/ca.2016a0005

Fine mapping of the nematode resistance gene Mi-3 in Solanum peruvianum and construction of a S. lycopersicum DNA contig spanning the locus
J. Yaghoobi et al. 2005. Molecular Genetics and Genomics 274(1):60
http://dx.doi.org/10.1007/s00438-005-1149-2

Hemipteran and dipteran pests: Effectors and plant host immune regulators
Isgouhi Kaloshian and Linda L. Walling 2016. Journal of Integrative Plant Biology 58(4):350
http://dx.doi.org/10.1111/jipb.12438

Molecular Cloning of a cDNA Encoding an Amphid-Secreted Putative Avirulence Protein from the Root-Knot NematodeMeloidogyne incognita
Jean-Philippe Semblat et al. 2001. Molecular Plant-Microbe Interactions 14(1):72
http://dx.doi.org/10.1094/MPMI.2001.14.1.72

Root-knot nematodes on tomatoes in Kyenjojo and Masaka districts in Uganda
Mwesige Rose et al. 2016. African Journal of Agricultural Research 11(38):3598
http://dx.doi.org/10.5897/AJAR2016.11311

Nonchemical Management of Soilborne Pests in Fresh Market Vegetable Production Systems
D. O. Chellemi 2002. Phytopathology 92(12):1367
http://dx.doi.org/10.1094/PHYTO.2002.92.12.1367

Silencing a Candidate Nematode Effector Gene Corresponding to the Tomato Resistance Gene Mi-1 Leads to Acquisition of Virulence
Cynthia A. Gleason et al. 2008. Molecular Plant-Microbe Interactions 21(5):576
http://dx.doi.org/10.1094/MPMI-21-5-0576

MeloidogyneVirulence Locus Molecular Marker for Characterization of SelectedMi-Virulent Populations ofMeloidogynespp. Is Correlated with Several Genera of Betaproteobacteria
Laura Cortada et al. 2011. Phytopathology 101(4):410
http://dx.doi.org/10.1094/PHYTO-04-10-0123

Variation in resistance to the root-knot nematode Meloidogyne incognita in tomato genotypes bearing the Mi gene
M. Jacquet et al. 2005. Plant Pathology 54(2):93
http://dx.doi.org/10.1111/j.1365-3059.2005.01143.x

A Population ofMeloidogyne javanicain Spain Virulent to theMiResistance Gene in Tomato
C. Ornat et al. 2001. Plant Disease 85(3):271
http://dx.doi.org/10.1094/PDIS.2001.85.3.271

Virulence response to the Mi.1 gene of Meloidogyne populations from tomato in greenhouses
S. Verdejo-Lucas et al. 2012. Crop Protection 39:97
http://dx.doi.org/10.1016/j.cropro.2012.03.025

A Study of Gene Expression in the Nematode Resistant Wild Peanut Relative, Arachis stenosperma, in Response to Challenge with Meloidogyne arenaria
Patricia Messenberg Guimarães et al. 2010. Tropical Plant Biology 3(4):183
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Screening of Tagetes patula L. on different populations of Meloidogyne
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Evaluation of the ability of lectin from snowdrop (Galanthus nivalis) to protect plants against root-knot nematodes
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Analysis of tomato gene promoters activated in syncytia induced in tomato and potato hairy roots by Globodera rostochiensis
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