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Root-associated microbiota play a key role in plant growth, resilience, and health. In this study, the microbial community structure in the rhizosphere of 12 pumpkins accessions belonging to three Cucurbita species i.e. C. pepo, C. maxima, and C. moschata, was monitored using the soil dilution plating technique on specific media. All accessions tested were also screened for their production and yield parameters. Based on Principal Component Analysis (PCA), 4 accessions of C. maxima (namely C5, C23, C14.2 and C6.2) were characterized by the greatest average fruit weight and yield, the highest actinomycetes, bacterial, Trichoderma spp. and Aspergillus spp. communities, and the lowest total fungal population in their rhizosphere. Positive correlations were noted between fruit fresh weight, culturable bacteria and Trichoderma spp. populations in the rhizopshere of pumpkins accessions. Negative correlations were noted between fruit weight and yield parameters and the total culturable fungal populations. The current study clearly demonstrated that the rhizosphere soil microbial communities have been shaped by Cucurbita species and accessions. Based on the significant links observed between soil microbiota and yield parameters, future pumpkin breeding programs could be focused on the selection of accessions that are quite able to exploit these associated beneficial microbial communities.

Aphis gossypii (Glover) is one of the major pests of melon crops as well as an efficient vector of non-persistent virus such as Cucumber Mosaic Virus and Zucchini Yellow Mosaic Virus among others. Host-plant resistance is one of the best strategies that can be used to control this pest. In this study 14 Tunisian melon accessions were screened to identify new sources of resistance/tolerance to Aphis gossypii using phenotypic and molecular approaches. Antixenosis, antibiosis and tolerance tests were carried out to phenotype those accessions which were also analyzed by molecular markers linked to the Vat gene which confers resistance to both A. gossypii colonization and virus transmission. Results evidenced that only the accession TUN-7 showed antixenosis, antibiosis and tolerance (no leaf curling), at a similar level to that of the resistant control PI414723. Although plants of the accession TUN-13 did not show leaf curling either, the presence of the Vat gene was only detected in TUN-7; its fruit characteristics, of Ananas type, makes this accession as a valuable source of resistance to this aphid that can be used in breeding programs to develop new aphid resistant melon cultivars.

Melon Fusarium wilt (MFW), caused by Fusarium oxysporum f. sp. melonis ( Fom ), is one of the most destructive diseases of melon ( Cucumis melo L.). The development and deployment of resistant cultivars is generally considered to be the best approach to control MFW. Based on the host resistance genes associated with variants of this pathogen, Fom isolates were classified into four physiological races designated 0, 1, 2, and 1,2. Two dominant resistance genes, Fom - 1 and Fom - 2 , control resistance to races 0 and 2, and 0 and 1, respectively. Fom isolates classified as race 1,2 are able to induce disease in melon lines carrying the above resistance genes. Many sources of resistance to Fom races 0, 1, and 2 have been reported. Partial resistance to race 1,2 controlled by polygenic recessive genes was only detected in a few Far Eastern melon accessions, except for the breeding line BIZ where complete resistance was described. Identification of DNA markers tightly linked to genes conferring resistance to Fom has immediate application in MFW resistance breeding programs. The Fom - 2 gene has been cloned, and it encodes a protein with a nucleotide binding site (NBS) and leucine-rich repeats domain (LRR). Based on the sequence of this domain, some molecular markers linked to this gene were developed. Several DNA markers linked to Fom - 1 have also been described. However, the usefulness of these markers was variety-dependent. Therefore, their combined use would be very useful in marker assisted selection for introducing resistance to Fom races 0 and 2 in melon. Recently, these markers were used for the positional cloning of this gene, which encoded a protein with a NBS–LRR domains that shows similarity to the toll and interleukin-1 receptores (TIR). Regarding Fom race 1,2, nine QTL were detected on five linkage groups by composite interval mapping. In this paper we review the current knowledge of MFW disease, and focus on genetic resistance to Fom and marker-assisted selection for resistance.

The melon gene Fom-2, which confers resistance to Fusarium oxysporum f.sp. melonis (Fom) races 0 and 1, has been previously characterized by map-based cloning, and it encodes a protein with a nucleotide binding site (NBS) and leucine-rich repeats (LRRs). Here, we used the primer Fom2-LRR1639 to clone and sequence a partial LRR region of the Fom-2 gene in 11 melon accessions resistant to Fusarium wilt from various geographic regions. Our work revealed that the structure of the partial LRR domain is highly conserved between eight of these resistant accessions and is similar to the resistant allele in the previously characterized PI-161375 line. Conversely, PI-124111 is a unique line that presents the same resistant allele that was previously described in the MR-1 line. The accession Cum-355 presents a protein that differs from that encoded by both the resistant lines PI-161375 and MR-1. This result suggests that Cum-355 has a new resistant allele of Fom-2 that determines the same specificity. Importantly, based on the sequence of the Fom-2 LRR domain, two sequence characterized amplified region (SCAR) markers, Fom2-R408 and Fom2-S342, were developed for Fom-2 resistant and susceptible alleles, respectively. These allele-specific PCR markers could be used as co-dominant markers when their primer pairs were combined in a multiplex PCR reaction. The specificity of these functional markers (FM) was validated on a set of 27 genotypes representing several melon types. These FM markers are expected to enhance the reliability and cost-effectiveness of marker-assisted selection for the Fom-2 gene in melon.

In the present study, the potato cultivar 'Desirée' was transformed via Agrobacterium tumefaciens strain LBA4404 containing the plasmid pBIN19 which harbors the Ribosome Inactivating Protein (rip30). The potato leaf discs were used as an explant for transformation. The in vitro regeneration parameters (percentage of callus regenerated, number of shoots per callus, percentage of regenerated roots and percentage of the transgenic plants) were evaluated. The PCR technique was used for identification of transformed plants. Southern and Western blot analyses were applied for molecular characterization of the transgenic clones. A greenhouse assay was carried out to evaluate the resistance to Rhizoctonia solani pathogen of transgenic clones expressing the rip30 gene. The results revealed that not all the plants developed in selective medium were positive for the corresponding gene using the PCR technique. Southern blot analysis demonstrated that the tested transgenic plants integrated three copies of rip30 gene into their genome. The expression of the RIP30 protein was confirmed in the leaf extracts of the transgenic clones by Western blot analysis. Resistance evaluation of the transgenic plants in greenhouse conditions showed that disease incidence and severity were reduced for R. solani. [PUBLICATION ABSTRACT]

: This research was supported in part by Research laboratory LR21AGR03-Production and Protection for a Sustainable Horticulture, funded by the Ministry of Higher Education and Scientific Research of Tunisia and partially financed by the A11-20R project funded by the Aragon Government and by the AGROALNEXT program supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and PID2020-116055RB-C22 I+D+I project funded by MCIN/AEI/10.13039/501100011003.