Tesis doctoral de Laura Cortada González
The response of 10 mi-1 tomato rootstocks to a mi-avirulent population of m. Javanica was determined in pot tests conducted in a greenhouse in spring when temperatures remained below the mi-1 functionality resistance threshold (28 ºc), and in summer when daily temperatures exceeded the mi-1 expression threshold. Rootstocks were also evaluated in the field exposing them to high population densities of the nematode. Results on infectivity and reproduction below 28 ºc indicated a wide variability in the resistance response of the rootstocks ranging from highly or intermediate resistance (pg-76, gladiator, mkt-410; brigeor, 42851, 43965, big power and he-man) to fully susceptible (beaufort and maxifort). At high temperature conditions, only pg-76 and he-man inhibited the reproduction of m. Javanica. Rootstocks pg-76, brigeor, beaufort and maxifort were challenged to different populations of m. Arenaria, m. Incognita and m. Javanica. Rootstock pg-76 was highly resistant to all the populations tested, whereas the response of brigeor ranged from highly to moderate resistance; the resistance response of rootstocks beaufort and maxifort varied according to the population tested. Molecular characterization of the resistance phenotype was performed for all the tomato hybrid rootstocks and cultivars tested. The markers pm3, pmi, mi23, for the characterization of the mi-locus of hybrid tomato rootstocks (s. Lycopersicum í– s. Habrochaites and s. Lycopersicum í– s. Chilense) were used for pcr reactions. In silico analyses were done with specific markers for the mi-1.2 gene (mint-up/do, c1/2, c2s4, imo-f1/r1, and vigs). Markers pmi and mi23 were polymorphic for the mi-1 locus in wild solanum species (s. Chilense, s. Habrochaites, and s. Peruvianum) and for s. Lycopersicum (marker mi23). Marker pm3 detected the mi-1.2 gene in s. Lycopersicum í– s. Habrochaites hybrid rootstocks, but not in the s. Chilense hybrids. As marker pm3 is located outside the coding sequence of the mi-1.2 gene, expression of this homolog could not be determined in beaufort and maxifort. In silico results indicated that none of the available markers for the mi-1.2 gene could distinguish this homolog from the other mi-homologs from s. Lypcopersicum and s. Peruvianum species. A new marker pau-do, in combination with c2s4, was designed to amplify in cds of the mi-1.2 gene. Amplification with these primers of cdna from beaufort and maxifort indicated that the mi-1.2 gene was expressed in both rootstocks, despite their susceptible phenotypic response to some meloidogyne populations. The durability of the mi-1 gene after repeated cultivation of resistant tomato rootstocks (pg-76 and brigeor) was determined through field trials during three consecutive years. Rootstock pg-76 responded as highly resistant after the first cropping cycle, although it became fully susceptible after the second and the third cropping cycles. Rootstock brigeor and the resistant tomato cultivar monika (control), retained intermediate resistance levels at the end of the third year. Bioassays confirmed that selection of virulence occurred more rapidly in plots with rootstock pg-76 followed by brigeor and the resistant tomato cultivar monika. The virulent phenotype of the selected m. Javanica populations in the field experiments was determined with mvc molecular marker, designed to distinguish selected from naturally virulent populations of meloidogyne spp. The populations analyzed included two japanese selected virulent populations, and the three virulent populations selected in the field trials, and one naturally virulent population and one avirulent population from spanish. Dna samples were obtained from individual juveniles (j2) or adult females from all the selected virulent populations. Experiments included water samples free of nematodes (5-µm filtered), obtained from the draining-water of a plant infected by a japanese selected virulent population. Amplification of dna only occurred in samples of filtered water, but not in those containing only nematode genetic material. Sequencing and blast of the dna fragments amplified by the mvc molecular marker, established a strong correlation of the amplified bands with proteins from betaproteobacteria species overall, these results showed that the mvc marker is not related to a nematode virulence gene (avr) but to betaproteobacteria. New root-knot nematode resistant mi-homologs were searched in accessions of the wild solanum species. The s. Huaylasense accession la-1358 reduced reproduction of a population of m. Arenaria to similar levels than the resistant tomato cultivar anairis. Nevertheless, the resistance response of s. Huaylasense accession la-1358 was also nematode-species specific.
Datos académicos de la tesis doctoral «Tomato rootstocks for the control of meloidogyne spp.«
- Título de la tesis: Tomato rootstocks for the control of meloidogyne spp.
- Autor: Laura Cortada González
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 05/03/2010
Dirección y tribunal
- Director de la tesis
- Soledad Verdejo Lucas
- Tribunal
- Presidente del tribunal: nicola Greco
- pablo Castillo castillo (vocal)
- francesc Sepulcre sánchez (vocal)
- (vocal)