Genetic Variability of the Tomato Leaf Miner (Tuta absoluta Meirick; Lepidoptera: Gelechiidae), in Tunisia, Inferred from RAPD-PCR

• Published in: Chilean journal of agricultural research Vol. 72; no. 2; pp. 212 - 216
• Main Authors: Bettaibi, Asma, Mezghani-Khemakhem, Maha, Bouktila, Dhia, Makni, Hanem, Makni, Mohamed
• Format: Journal Article
• Language: English; Portuguese
• Published: Chillán Chilean Journal of Agricultural Research 01.06.2012; Instituto de Investigaciones Agropecuarias, INIA
• Subjects: Agricultural production; AGRICULTURE, MULTIDISCIPLINARY; AGRONOMY; Genetic diversity; Nonnative species; Pest control; Polymerase chain reaction; Population; Studies; Tomatoes; Tunisia; insect populations; gene flow; Invasive species; flujo de genes; marcadores moleculares; especies invasivas; molecular markers; población de insectos
• ISSN: 0718-5839; 0718-5820; 0718-5839
• DOI: 10.4067/S0718-58392012000200008

The tomato leaf miner Tuta absoluta Meyrick has invaded tomato (Solanum lycopersicum L.) crop in Tunisia since 2008 and is representing today a major threat to the production of this crop. In this study, we used the Randomly Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) technology to assess the genetic variability within and among seven populations of T. absoluta, collected on tomato from different regions in Tunisia. Using five RAPD-PCR primers and 108 individuals, 140 polymorphic fragments were recorded. From 335 different RAPD phenotypes generated, 71 were redundant and 264 unique to a specific population. The genetic structure of T. absoluta was investigated using analysis of molecular variance (AMOVA), genetic distances (Fst) and multidimensional scaling (MDS). We detected a high genetic diversity within and among populations in conjunction with a significant differentiation between populations, suggesting that different founder genotypes would have been responsible of the introduction of T. absoluta in Tunisia. The presence of overlapping phenotypes probably indicates migration events between populations, mainly through infested plant material carried by humans. Variabilidad genética del minador de hojas de tomate (Tuta absoluta Meyrick; Lepidoptera: Gelechiidae) en Túnez desde RAPD-PCR. El minador de hojas de tomate Tuta absoluta Meyrick ha invadido el cultivo del tomate (Solanum lycopersicum L.) en Túnez desde 2008 y actualmente representa una importante amenaza para su producción. En este estudio usamos la tecnología de ADN polimórfico amplificado al azar-reacción de cadena polimerasa (RAPD-PCR) para evaluar la variabilidad genética dentro y entre siete poblaciones de T. absoluta, colectadas desde tomate en diferentes regiones de Túnez. Usando cinco primers RAPD-PCR y 108 individuos, se registraron 140 fragmentos polimórficos. Se generaron 335 fenotipos RAPD diferentes, entre los cuales 71 fueron redundantes y 264 únicos para una población específica. La estructura genética de T. absoluta se investigó usando análisis de varianza molecular (AMOVA), distancias genéticas (Fst) y escalamiento multidimensional (MDS). Detectamos una alta diversidad genética dentro y entre poblaciones en conjunto con una diferenciación significativa entre poblaciones, sugiriendo que los genotipos fundadores podrían haber sido responsables de la introducción de T. absoluta en Túnez. La presencia de fenotipos superpuestos probablemente indica eventos de migración entre poblaciones, principalmente a través de material vegetal infestado transportado por humanos. The level of genetic diversity in introduced populations of an invasive species is considered as a major factor influencing its survival and adaptation capacities (Sakai et al., 2001). The introduction processes can be explained by two hypotheses with respect to their expected consequences on genetic diversity. (i) A single introduction event from a single native population. Many biological invasions belong to this category (Lee, 2002); in this case, the introduced population is small and a strong loss of genetic variability can be detected in the invasive species, depending on the extent and duration of the bottleneck introduction process (Taylor et al., 2004). (ii) Several introduction events from several populations. Even if each introduced population contains only a part of the genetic diversity of the species in its area of origin, the mixture of those populations may result in a high level of diversity in the introduced population (Genton et al., 2005). Given this relationship between the genetic diversity and invasion process for a species, it is necessary not only to know its level of genetic variability in both native and invaded range, but also study its biology and the history of the invasion (Puillandre et al., 2008). The absence of a significant differentiation between TLM populations from the north, those from the centre and those from the south of Tunisia through MDS indicates substantial amounts of gene flow occurring between these populations. Specific RAPD phenotypes were identified for individuals from each collection site, but overlapping phenotypes were also found, indicating that the migration of genotypes over long distances exists and most likely occurs through infested plants carried, between sites, by humans. The significant differences among and within populations could be explained by Bohonak et al. (2001) hypothesis, which ascribed the high level of genetic variation in invasive species to the introduction of different founder genotypes into the receiving population, together with sexual recombination events. So, it is possible that the genetic differentiation detected here may have come from two or more TLM populations introduced into Tunisia, simultaneously or at different times. Consequently, the introduced genetic variation would have been packaged into diverse genotypes, which may then have been recombined by human-influenced dispersal.