Understanding plant response to salinity, one of the major abiotic stresses, provides insights into the improvement of tomato salt tolerance. This work focuses on the responses of tomato cultivars to salt stress. Genotypes, representative of content and enzyme activities. QPCR analysis of WRKY, ERF, LeNHX and HKT genes was also performed. A high K+, Ca2+ and proline accumulation as well as a decrease in Na+ concentration mediated salt tolerance. Concomitant with a pattern of high antioxidant enzyme activities, tolerant genotypes also displayed differential patterns of gene expression.
A survey was conducted during 2009-2010 seasons to identify the distribution of Bemisia tabaci (Gennadius) biotypes in Tunisia. The genetic affiliation of collected populations was determined by polymerase chain reaction (PCR)-restriction fragment-length polymorphism (TaqI) of the mitochondrial cytochrom oxidase I (mtCOI) gene. Results, validated by sequencing and phylogenetic analysis, allowed the clustering of sampled sweetpotato whiteflies into B and Q biotypes. As B. tabaci harbors the obligatory bacterium Portiera aleyrodidarum, and a diverse array of secondary symbionts including Rickettsia, Hamiltonella, Wolbachia, Cardinium, Arsenophonus, and Fritschea, we report here the infectious status of Tunisian populations by secondary symbionts to find out a correlation between bacterial composition to biotype. The genetic variability and structure of B. tabaci populations in Tunisia was driven by analysis of molecular variance (AMOVA) and the hypothesis of isolation by distance was explored. Selective neutrality and genetic haplotype network tests suggested that Tunisian sweetpotato whiteflies have been undergoing a potential expansion followed by gene flow restriction.
Surveys were undertaken for tomato yellow leaf curl viruses in the main Tunisian tomato‐growing areas in fields and plastic houses. Symptoms included yellowing, leaf curling and stunting. Collected samples were submitted to molecular analysis using two approaches: (1) hybridization tests with two DNA probes corresponding to an intergenic region derived from a cloned dimer of an Egyptian full‐length TYLCV and to the coat region of a Tunisian TYLCV isolate; (2) PCR amplification coupled to RFLP allowing both identification and clustering of Tunisian isolates. Only Tomato yellow leaf curl Sardinia virus was detected in Tunisia.
Combining landscape ecology and genetics provides an excellent framework to appreciate pest population dynamics and dispersal. The genetic architectures of many species are always shaped by environmental constraints. Because little is known about the ecological and genetic traits of Tunisian whitefly populations, the main objective of this work is to highlight patterns of biodiversity, genetic structure and migration routes of this pest. We used nuclear microsatellite loci to analyze B. tabaci populations collected from various agricultural areas across the country and we determine their biotype status. Molecular data were subsequently interpreted in an ecological context supplied from a species distribution model to infer habitat suitability and hereafter the potential connection paths between sampling localities. An analysis of landscape resistance to B. tabaci genetic flow was thus applied to take into account habitat suitability, genetic relatedness and functional connectivity of habitats within a varied landscape matrix. We shed light on the occurrence of three geographically delineated genetic groups with high levels of genetic differentiation within each of them. Potential migration corridors of this pest were then established providing significant advances toward the understanding of genetic features and the dynamic dispersal of this pest. This study supports the hypothesis of a long-distance dispersal of B. tabaci followed by infrequent long-term isolations. The Inference of population sources and colonization routes is critical for the design and implementation of accurate management strategies against this pest.
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