e-ISSN 2477-9148

Identication of Mi-1 homologs in Solanum species

Carrera et al.

REVISTA ECUATORIANA DE MEDICINA Y CIENCIAS BIOLOGICAS

Volumen 39. No. 1, Mayo 2018

Identication of Mi-1 homologs in various Solanum species

Identicación de homólogos del gen Mi-1 en varias especias de Solanáceas

Saskya Estefany Carrera Pacheco

, María Gabriela Chacón Acosta

, María José Vallejo

López

, Francisco Javier Jarrín Cornejo

, Ricardo Francisco Oliva Pérez

y Karina Isabel

Proaño Tuma



The University of Queensland, Institute for Molecular Bioscience, 306 Carmody Road, St Lucia, Australia

Universidad de las Fuerzas Armadas ESPE, Departamento de Ciencias de la Vida, Laboratorio de Biotecnología

Vegetal, Av. General Rumiñahui s/n, Sangolquí, Ecuador, P.O.BOX 171-5-231B

Fundacion Vitroplant, Quintiliano Sánchez N15-113 y Solano, Quito, Ecuador

International Rice Research Institute (IRRI), Genetics and Biotechnology, Pili Drive, UPLB, Los Baños, 4031 La-

guna, Filipinas

*Corresponding author e-mail: kiproanio@espe.edu.ec

doi.org/10.26807/remcb.v39i1.566

Recibido 6-02-2018 ; Aceptado 21-05-2018

ABSTRACT.- In Ecuador, several solanaceous crops, including naranjilla (Solanum quitoense), are attacked by the

nematode Meloidogyne sp. Resistant cultivars are not available, and there is a need to identify potential sources of

resistance that can be incorporated into breeding programs. The Mi-1 gene from S. peruvianum is known to confer

resistance to Meloidogyne in tomato (S. lycopersicum). In this study, 42 plant accessions of wild and cultivated Sola-

num 

recombination. The Mi-1



tomato Mi-1 protein. The Mi-1 locus was highly polymorphic; most polymorphisms tend to accumulate in the NBS

rather than in the LRR region. Genetic recombination was detected among the tomato and potato related sequences,





KEYWORDS: homologs, Meloidogyne, Mi-1 gene, resistance, Solanum.

RESUMEN.- En el Ecuador, varios cultivos de solanáceas –incluyendo la naranjilla (Solanum quitoense)– son ata-

cados por nematodos del género Meloidogyne



El gen Mi-1 de S. peruvianum es conocido por la resistencia a MeloidogyneS. lycopersi-

cum). En este estudio, 42 accesiones de plantas silvestres y cultivadas de especies de Solanum, fueron analizadas para

Mi-1





proteína Mi-1 del tomate.

El locus de Mi-1

-





PALABRAS CLAVES:Meloidogyne, Mi-1 gen, resistencia, Solanum.

Artículo científico

REMCB 39 (1): 73-84, 2018

INTRODUCTION

In the highland region of Ecuador, large areas of land are

cultivated with local economically important Solanum

crops such as the potato (S. tuberosum and S. phureja),

tomato (S. lycopersicum), tree tomato (S. betaceum),

pear melon (S. muricatum), and naranjilla (S. quitoense).

In 2016, 3514 ha of tree tomato were planted which pro-

duced 28512 t (INEC, 2014). There is no current infor-

mation on naranjilla production, but the crop is cultivated

  

(INEC, 2000). In both crops, production has been cons-

trained, among other factors, by the attack of the root-

knot nematode (RKN) Meloidogyne sp. The nematode

restricts the plants’ absorption of nutrients and water up-

take from the soil, resulting in a reduction in yield and in

the useful life of crops (Trudgill, 1991). In naranjilla, for

instance, M. incognita is one the main diseases causing

  

nematode interacts with Fusarium oxisporum, and redu-





diseases was the principal cause ofornaranjilla produc-

tion collapse in Ecuador (Ochoa et al., 2008). In tree to-

mato plantations, M. incognita



life can be reduced by half (Revelo et al., 2003; Revelo

et al. ,2004). The nematode has traditionally been con-



the case of the naranjilla, by clearing primary forests to

introduce the crop in virgin soils (Vásquez et al., 2011).

Resistant cultivars, accepted by farmers, are not availa-

ble in both crops, and national breeding programs are

seeking new sources of resistance.

      

the ability of a plant to suppress its development or re-

production (Roberts, 2002), and is currently the most

      -

     -

tant cultivars have proven commercially successful in

the control of the most damaging Meloidogyne species

(Castagnone-Sereno 2002).

Plants have evolved several defense mechanisms against

a broad range of pathogens, including resistance genes

or R-genes. One of these genes is the tomato Mi-1 gene,

        

peruvianum, and then introduced into cultivated tomato

using embryo rescue (Smith, 1944). Mi-1 confers resis-

tance to three RKNs (M. arenaria, M. incognita and M.

javanica) (Dropkin, 1969a), to the potato aphid Macro-



Bemisia tabaci (Nombela et al., 2003). The use of resis-

tant tomato cultivars with this gene has proven highly

-

tant cultivars yield normally on infested land (Roberts

and May, 1986). Nowadays, all commercially available

tomato cultivars resistant to RKNs carry the Mi-1 gene

and it is the only commercially available source of resis-

tance to these nematodes in the crop. Mi-1-



tomato cultivar development (Jablonska et al., 2006), but

new sources of resistance against nematodes, which can

be incorporated in breeding programs, are required.

The Mi-1 gene encodes a 1257 amino acid protein and

         -

longs to a major class of plant R-genes (NBS-LRR) that

encode nucleotide binding sites and leucin-rich repeats

(Kaloshian et al., 1998; Milligan, 1998), and a putative

coiled-coil domain preceding the NBS. NBS-LRR pro-

teins mediate pathogen recognition and initiate defense

signaling that leads to host resistance (Belkhadir et al.,

2004). In plant R proteins, the NBS is part of a larger,

      

acids (Leipe et al., 2004), whereas the LRR domain is

generally the most variable region among closely related

R genes (Bergelson 2001).

Mi-1 is located in the short arm of chromosome 6 of the

tomato (Kaloshian et al., 1998). The short arm of chro-

mosome 6 in various Solanum species is an important

-

     

In the Mi locus, three genes, Mi-1.1, Mi-1.2, and Mi-1.3

Mi-1.2 gene is able to confer

resistance to RKNs (Milligan, 1998; Rossi et al., 1998).

This gene will henceforth be referred to as Mi-1 in the

        

the vicinity of the Mi-1 in S. lycopersicum and S. pe-

ruvianum

some Mi homologs considered pseudogenes, the identity

of the DNA sequences for all Mi-1 -

   

2007)

In tomato, the function of Mi-1 and of other RKN R-ge-

nes is lost at high temperature (Ammiraju et al., 2003).

For instance, Mi-1

below 28 °C (Holtzmann 1965; Dropkin 1969b). Howe-

ver, the Mi-9 gene from S. arcanum, a homolog of Mi-1

and localized in the same chromosomal interval as Mi-1,

confers heat-stable resistance to RKNs at 25 °C and 32

°C (Ammiraju et al., 2003; Jablonska et al., 2006). There

are also some Mi homologs discovered in chromosome

12 that inhibit reproduction of virulent nematode isola-

tes and maintain a phenotypic resistance response when

soil temperatures are above 28 °C (e.g. Mi-3 and Mi-5)

(Jablonska et al., 2006).v

Identication of Mi-1 homologs in Solanum species

Carrera et al.

REVISTA ECUATORIANA DE MEDICINA Y CIENCIAS BIOLOGICAS

In the potato, gene Rpi-blb2 of the wild potato

S. bulbocastanum, which confers broad resistance to

Phytophthora infestans, also maps to this region. This

gene is the nearest homolog to the gene Mi-1 known in

       

with the tomato gene Mi-1 (Vossen et al., 2005). Re-

sistance genes against M. incognita have not yet been

reported in tuber-bearing potatoes. However, 59 Mi-1

homologs were described and studied in the cultivated

potato species S. tuberosum ssp. tuberosum and S. phu-

reja (Sanchez-Puerta and Masuelli, 2011).

The principal aim of this study was to provide insight into

Mi-1 gene among di-

Solanum (Solanaceae)

in order to identify potential sources of resistance to Me-

loidogyne spp., particularly in naranjilla. To accomplish

this, 42 plant accessions of wild and cultivated Solanum

species were screened to determine its presence, diversi-



MATERIALS AND METHODS

Plant Material.-A total of 42 wild and cultivated

Solanum plant accessions, belonging to 25 species and

9 sections, were used in this study (Table 1). Solanum

seed were derived either from the Germplasm Bank of

the National Department of Phytogenetic Resources of

the National Autonomous Institute for Agricultural Re-

search (Departamento Nacional de Recursos Fitogenéti-



Agropecuarias - INIAP-DENAREF Quito) or the Inter-

national Potato Center - Quito (CIP-Quito). In the speci-



used. Seeds were germinated, and plants were grown in



of 10 cm.

Isolation of Nucleic Acids.- The genomic DNA of each

accession (Table 1) was obtained from 100 mg of fresh

leaves using the DNeasy Plant Mini Kit (Qiagen, Hilden,

Germany) protocol, diluted to 5 ng.µL



and stored at



leaves (13 plant accessions) and roots (only two acces-

sions) (Table 1) with the RNeasy Plant Mini Kit (Qiagen,

Hilden, Germany) and the TRIzol Reagent (Invitrogen,

Carlsbad, CA, USA) protocols, respectively. Quality and

quantity of DNA and RNA was checked using the Na-

noVue Spectrophotometer (General Electric Company,

  



PCR Analyses and Sequencing.- To search for Mi-1 ho-

molog sequences, primers corresponding to a conserved

       Mi-1 gene (Williamson

and Kumar, 2006) were designed. Primer sequences used

were 1F 5’-AACTCGAGAAAAGGAAGTGG-3’ and

1R 5’-CAAGATTGATCCTTTGTTAGACAC-3’. Reac-

-

ning 150 µM dNTPs, 1.5 mM MgCl

, 1 µM of each pri-

mer, 1 U Taq DNA polymerase and 1X DNA polymerase





and 72 °C, 10 min. Amplicons were analyzed by elec-



DNA Gel Stain (Invitrogen, Carlsbad, CA USA) in TBE



amplicons were recovered from gel using the QIAquick

-

ments obtained were then sequenced on both strands by

Macrogen S.A. (Seul, Corea).

Diversity Analysis.- Nucleotide sequences were

analyzed with the software BioEdit (Hall, 1999) and

translated into amino acid sequences. All sequences

were aligned using MUSCLE (Edgar, 2004). BlastN and

BlastP search strategies were conducted to identify DNA

and/or protein sequences homolog to Mi-1. Putative ho-

-





as true homologs. The same strategy was used to identi-

fy protein domains. The number of polymorphic amino

      

(Larkin et al., 2007).

Phylogenetic Analysis.- 



under the General Time Reversible model with parame-

ters for invariant sites and gamma-distributed rate hete-

rogeneity (Tamura et al., 2011). One hundred bootstrap

replicates were performed. The trees were visualized

using FigTree 1.4.3 (Rambaut, 2009). For these analyses,

11 Mi-1 gene homologs obtained from this study, plus 23

Mi-1 homologs belonging to S. tuberosum, S. lycopersi-

cum, S. peruvianum and S. phureja (Sanchez-Puerta and

Masuelli 2011) were used. Mi-1.2 from S. lycopersicum,

Rpi-blb2 from S. bulbocastanum (Vossen et al., 2005),

CaMi (Chen et al., 2007) and Me (Mao et al., 2008) from

Capsicum annuum were used for comparison.

Test of Gene Recombination.- Recombination events

of the Mi-1

using the Split Decomposition Method (Huson, 1998)

integrated in the Splits Tree4 program (Huson and Br-





Gene Expression analysis.-    

100mg of leaf (13 Solanum accessions) and leaf and root

REMCB 39 (1): 73-84, 2018

Table 1. Plant accessions belonging to different Solanum sections used for Mi-1 

analysis.

Code Species Section

Gene expression analysis

S45

S. mamosum

Acanthophora

S. brevifolium

Anarrichomenum

S. brevifolium

Anarrichomenum

S. sodiroi

Anarrichomenum

S12

Solanum spp./tomatillo

Anarrichomenum

S17

S. caripense

Basarthum



S. juglandifolium

Juglandifolia

S. juglandifolium

Juglandifolia

S. juglandifolium

Juglandifolia

S28

S. juglandifolium

Juglandifolia



S29

S. ochrantum

Juglandifolia

La15

S. gradiflorum

Lasiocarpa

La17

S. hirtum

Lasiocarpa

La16

S. hyporhodium

Lasiocarpa

S35

S. hyporhodium

Lasiocarpa



La21

S. pectinatum

Lasiocarpa

La22

S. pectinatum

Lasiocarpa

S37

S. pseudolulo

Lasiocarpa



S32

S. quitoense

Lasiocarpa

S33

S. quitoense

Lasiocarpa



S42

S. quitoense

Lasiocarpa



S34

S. sessiliflorum

Lasiocarpa



S38

S. vestisimum

Lasiocarpa



S36

Solanum sp.

Lasiocarpa

S19

Solanum spp. #61

Lasiocarpa

Ly23

S. habrochaites-like

Lycopersicon

Ly24

S. habrochaites

Lycopersicon

S57

S. lycopersicum (cv. Advantage)

Lycopersicon

S59

S. lycopersicum (cv. Flora Dade)

Lycopersicon



Ly10

S. peruvianum

Lycopersicon

S. melongena

Melongena



S. andreanum

Petota

S. andreanum

Petota

S18

S. andreanum

Petota



S16

S. colombianum

Petota



S. minutifoliolum

Petota

S. paucijugum

Petota

S15

S. paucijugum

Petota



S14

S. solisii

Petota

S. hispidum-like

Torva

S. hispidum-like

Torva

S. hispidum-like

Torva

root tissue

Identication of Mi-1 homologs in Solanum species

Carrera et al.

REVISTA ECUATORIANA DE MEDICINA Y CIENCIAS BIOLOGICAS

(2 accessions) tissue (Table 1) as stated above. RNA was

  -

-



The reaction was incubated for 15 min at room tempera-

ture and DNase I inactivation was performed using 1µL

of EDTA at 65 °C. Superscript III reverse transcriptase

Kit (Invitrogen, Carlsbad, CA USA) was used to perform



µL of oligo (dT)18 primer (0.5 µL.µL

-1

) and 1 µL dNTPs

(10 mM) were added and incubated for 5 minutes at 65

°C. It was immediately placed on ice for 1 minute and 4



µL of Superscript III reverse transcriptase (200 U.µL

-1

)





°C for 15 min. cDNA was stored at -20 °C until use. Qua-

   



and Mi-1 genes. GAPDH gene was used as a constitu-

     

were the same as cited above and amplicons were visua-



RESULTS AND DISCUSSION

Mi-1 Gene Homologs Are Present in Solanum Spe-

cies.-       

locus in the Solanum accessions was performed through



the Mi-1 tomato gene. This fragment spans amino acid

672-964 and includes the NBS (672 to 802) and the LRR

(803 to 964) regions. The 1 Kb amplicon was detected

          

was present in all the Anarrichomenum and wild potato

accessions (Petota) analysed, as well as in most acces-

sions of S. quitoense and its close relatives (Lasiocarpa

section). Four accessions showed an additional 0.9 Kb

fragment, and eight accessions did not show any ampli-



may correspond to uncharacterized paralogs or pseudo-

genes (Meyers, 1998; Noel, 1999), which seems to be

common among resistance genes. Pseudogenes may be

potential sources of variation (Meyers, 1998; Michelmo-

re and Meyers, 1998) and a rapid way to achieve new

        

evolve more quickly than the functional genes.

To verify if the amplicons obtained corresponded to Mi-1

homologs, the 1 Kb and 0.9 Kb fragments of 12 plant ac-

cessions were sequenced (Table 3); some of these acces-

sions were relevant for the national breeding programs.

   -

-

les or Mi-1 paralogs.

Table 2.- Description of the Mi-1       

Solanum analyzed in this study.

Section Plant accession

Presence of a

1 Kb

fragment

Presence of a

0.9 Kb fragment

None

Anarrichomenun

A1, A2, A4



S12



Basarthum

S17



Juglandifolia

J2, J3, S28, S29



Acanthophora

S45



Melongena



Petota

S1, S16, S18, P7, P8



S3, S15, S14



Torva



T1,T2



Lycopersicon

S57, S59, Ly10



Ly23, Ly24



Lasiocarpa

S19, S32, S33, S34,

S35, S36, S37, S38,

S42, La17, La21, La22



La15, La16



REMCB 39 (1): 73-84, 2018

Multiple alignment of the nucleotide sequences with

        

      

indicated that most accessions were homozygous,

whereas two accessions (S17 of S. caripense and S18 of

S. andreanum) were heterozygous (Table 3).

The 16 allele sequences were translated into amino

acids. MUSCLE alignment showed that they encoded



S59 were the same (Table 3). Sequences from A1, S12-1,

and S18 presented premature stop codons or frameshift





A BlastP search against non-redundant protein sequen-

ces showed that all resultant amino acid sequences enco-



with the tomato Mi-1 protein that confers resistance to

Meloidogyne. The sequences analyzed corresponded to



part of the LRR region of these proteins.

Multiple amino acid sequence alignments between the



revealed a total of 117 polymorphic amino acid sites (Fi-

gure 1a). Most polymorphisms tended to accumulate in

the NBS region (57/131) rather than in the LRR region

      -

tionally, 71 gaps were found in the NBS region and 80

in the LRR region. These results show that, compared

to the NBS portion, the LRR portion tended to be less

divergent among the Mi-1 

Solanum accessions analyzed.

To investigate the phylogenetic relationships among the

Mi-1 loci, a phylogenetic tree was constructed using

the nucleotide sequences from 11 Solanum accessions

(Table 3), 23 Mi-1 homologs from S. tuberosum, S.

lycopersicum, S. peruvianum and S. phureja (Sanchez-

Puerta and Masuelli, 2011) and the Mi-1.2, Rpi-blb2,

CaMi and Me genes. The resulting tree topology is

shown in Figure 1b. Mi-1 sequences obtained from

Solanum sections are distributed all across the

tree and were closely related to the Mi-1 homologs. The



main cluster, the tomato cluster (TC), included the CaMi

gene from C. annuum (which is similar to the gene Mi-1

from tomato), the Mi-1.2 gene from S. lycopersicum,

one accession from S. peruvianum, two accessions

from S. lycopersicum, and various tomato Mi-1 related

sequences; one sequence from S. paucijugum and one

Table 3. Polymorphisms identified in the Mi-1 locus in 12 Solanum accessions.

Nucleotide sequence

Amino acid sequence

Section Species Code Allele 1 Allele 2 Allele 1 Allele 2

Anarrichomenum

S. brevifolium

brf_na1

brf_pa1

S. spp/tomatillo

S12-1

tol1_na1

tol1_pa1

S. spp/tomatillo

S12-2

tol2_na1

tol2_pa1

Basarthum

S. caripense

S17

car_na1

car_na2

car_pa1

car_pa2

Lasiocarpa

S. sessiliflorum

S34

ses_na1

ses_pa1

S. hyporhodium

S35

hyp_na1

hyp_pa1

S. quitoense

S42

qui_na1

qui_pa1

Melongena

S. melongena

mel_na1

mel_pa1

Lycopersicon

S. lycopersicum

(Advantage)

S57 adv_na1

adv/fda_pa

S. lycopersicum

(Flora Dade)

S59 fda_na1

adv/fda_pa

S. peruvianum

Ly10

per_na1

per_pa1

Petota

S. paucijugum

S15-1

paj1_na1

paj1_pa1

S. paucijugum

S15-2

paj2_na1

paj2_pa1

S. andreanum

S18

and_na1

and_na2

and_pa1

and_pa2

Sequences classified as pseudogenes.

Amino acid sequences were the same.

Identication of Mi-1 homologs in Solanum species

Carrera et al.

REVISTA ECUATORIANA DE MEDICINA Y CIENCIAS BIOLOGICAS

Fig. 1. Multiple sequence alignment of the NBS and LRR regions of the predicted Mi-1 homologs, and nucleotide phylogenetic tree. (a) Multiple

alignments of the predicted Mi-1 homologs amino acid sequences revealed a highly polymorphic family. (b) Phylogenetic analysis of nucleotide

sequences from 11 Mi-1 homologs found in this study (in blue), 23 Mi-1 homolog sequences from Solanum tuberosum (StMi1h genes), S. lyco-

persicum (Mi genes), S. phureja (SpMi1h) (Sanchez-Puerta & Williams, 2011) and S. peruvianum, and four sequences of the genes Mi-1.2 from S.

lycopersicum, Rpi-blb2 from S. bulbocastanum (van der Vossen et al., 2005), CaMi (Chen et al., 2007) and Me (Mao et al., 2008) from Capsicum

annuum, which were used for comparison. The tree was rooted with gen Me  



Lasiocarpa cluster.

REMCB 39 (1): 73-84, 2018

from “tomatillo” were closely related. The second main

cluster, the potato cluster (PC), included the Rpi-blb2

gene, S. tuberosum and S. phureja related sequences,

but surprisingly, S. caripense members were very close

related. The third cluster, the Lasiocarpa cluster (LC),

was poorly resolved and grouped three sequences

coming from plant accessions of section Lasiocarpa; S.

paucijugum was strongly related to this cluster. Each



Additionally, phylogenetic trees were constructed using

only the sequences of NBS and LRR domains to deter-

mine if these would maintain the same functional dis-

   -

pology (data not shown). Phylogenetic reconstruction of

Mi-1

loci with several members distributed among Solanum

species.

Fig. 2. Recombination analysis with the Split Decomposition Method (Huson, 1998). Trees show an interconnected network between some acce-

(a) Tomato clade.

 (b) Potato clade. Fifthteen accessions show evidence of recombiantion with



Identication of Mi-1 homologs in Solanum species

Carrera et al.

REVISTA ECUATORIANA DE MEDICINA Y CIENCIAS BIOLOGICAS

Mi-1 locus



Solanum.-

cation of Mi-1 homologs in sections as distant as Petota

or Lasiocarpa (Bohs, 2005), suggests that this gene is

highly conserved in the genus Solanum and that it may

have originated from an ancestral common gene which

        -

thogen recognition. The presence of polymorphic and

conserved regions among the sequences analyzed also

suggests that all Mi-1-like sequences evolved from a

common ancestor (Michelmore and Meyers, 1998).

The tree Mi-1 homologs detected in Lasiocarpa are

potential sources of resistance to Meloidogyne in the

naranjilla crop. The three Mi-1  

in Petota in the wild potatoes S. paucijugum and S.

andreanum are also potential sources of resistance to

the nematode. Previously, Mi-1 homologs have been

S. bulbocastanum (Vossen et al., 2005),

and the cultivated potatoes S. phureja and S. tuberosum

ssp. tuberosum (Sanchez-Puerta and Masuelli, 2011).

Further cloning and functional analysis of these genes

will assess its role in plant defense.

Recombination Contribution to Sequence Diversity in

the Mi-1 loci.- Investigation of Mi-1 loci recombination



Split Decomposition Method (Huson 1998). This method

        

clades to a phylogenetic tree topology. The higher the





for genetic recombination was found only within the



evidence was observed in the Lasiocarpa

According to the network diagrams, a group of 11, 15,

and zero sequences showed evidence of recombination

in the tomato, potato, and Lasiocarpa clusters,

respectively (Figure 2; Lasiocarpa cluster not shown).

This means that most of the Mi-1  

in this study generated by interallelic recombination and

not by mutation, and that recombination appears to be

the predominant mechanism in the generation of allelic

variation. Recombination was absent in the Lasiocarpa

sequences analyzed, implying that the Mi-1 homologs



target for cloning; and hence, potential sources of

resistance to Meloidogyne in the naranjilla crop.

Fig. 3.Mi-1 and GAPDH genes in non-infected leaves and roots of some Solanum accessions. (a)Mi-1 gene in

non-infected leaves and roots of the tomato plant S. lycopersicum (S59, Flora Dade); GAPDH-

genous control. Low DNA mass ladder (Invitrogen, Carlsbad, CA USA) was used to determine the molecular weight of fragments. (b) Transcript

accumulation of Mi-1Solanum accessions (non-infected leaves).

REMCB 39 (1): 73-84, 2018

Mi-1 Gene Homologs Are Constitutively Expressed

in Some Solanum Accessions.-

Mi-1 gene was evaluated in some plant accessions. For



roots and cDNA was synthesized. The GAPDH gene was



-

fected leaves and roots of tomato (S59) and naranjilla

      

both genes in both roots and leaves, suggesting the cons-

 Mi-1 gene (Figure 3a; results of

naranjilla not shown).

In a second assay, non-infected leaves of 13 accessions

of 12 species were evaluated. The Mi-1-

sed in only seven samples (Figure 3b) even though the

Mi-1 gene was present in all samples tested at genomic

level.



suggests that pathogen infection is not required to induce

Mi-1  -

Mi-1 homologs at the plant level

makes them good candidates for cloning.

CONCLUSIONS

The Mi-1 gene was detected in 34 wild and cultivated

plant accessions of Solanum, distributed in seven sec-

tions of the genus.

      

-



 Mi-1 amino acid

sequence.

The Mi-1 

Most polymorphism tends to accumulate in the NBS ra-

ther than in the LRR region.

Evidence of genetic recombination was detected in the

tomato and potato clusters, but not in the Lasiocarpa

Lasiocar-

pa are good targets for gene cloning, and hence potential

sources of resistance to Meloidogyne in naranjilla.

Mi-1 homologs in non-infected



These genes may also be considered as potential sources

of resistance against the nematode.

ACKNOWLEDGEMENTS

The authors would like to thank the National Department

of Phytogenetic Resources of the National Autonomous

Institute for Agricultural Research (INIAP-DENAREF

Quito) and the International Potato Center - Quito (CIP-

Quito), for providing the seeds from their Germplasm

Bank. This project was funded by Universidad de las

Fuerzas Armadas - ESPE, Sangolqui, Ecuador.

Quito (CIP-Quito), for providing the seeds from

their Germplasm Bank. This project was funded by

Universidad de las Fuerzas Armadas - ESPE, Sangolqui,

Ecuador.

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