Background Cucurbita pepo L. cultivars display high morphological traits variation. In addition, C . pepo faces numerous threats, such as viral and fungal infections, which significantly influence crop cultivation. Recent genomic advancements improved the understanding of genetic diversity and stress responses in this crop. We investigated genetic variations related to plant morphology and quality traits. Additionally, the inclusion of both powdery mildew (PM) and Zucchini yellow mosaic virus (ZYMV) susceptible and tolerant varieties facilitated the examination of genetic diversity concerning biotic stress. Results The sequencing of eight Cucurbita pepo varieties produced an average of 40 million raw reads with a coverage of reference genome ranging from 22 to 40X. More than 4.7 million genomic variants were identified in all genomes. Based on admixture and PCA analysis, the eight C. pepo genotypes resulted organized in two clusters belonging to Cocozelle and Zucchini groups, with “Whitaker” separated from the rest of the accessions. Genes involved in pathways related to gibberellin regulation, leaf development, and pigment accumulation resulted highly affected by variation suggesting that the diversity observed among varieties in plant and fruit morphology could be related to variants identified in such genes. Each variety showed its own set of genetic differences. The genomic comparison of 381e, 968Rb and SPQ allowed the identification of variants in chromosome regions affecting response to Zucchini yellow mosaic virus (ZYMV) and powdery mildew (PM). Variants in key genes associated with resistant traits were identified, suggesting potential pathways and mechanisms involved in biotic stress response and plant immunity. Conclusions Genetic variations affecting morphology and fruit quality in C. pepo emphasize their significance for breeding efforts. Furthermore, the genomic comparison of 381e, 968Rb and SPQ highlighted variants in chromosomal regions influencing zucchini's response to PM and ZYMV. These findings could pave the way for more targeted and effective genetic improvement strategies, thereby potentially leading to increased agricultural productivity and quality.

Background: Cucurbita pepo is high susceptible to Zucchini yellow mosaic virus (ZYMV) and the resistance found in several wild species does not provide complete or broad-spectrum resistance. In this study, a source of tolerance introgressed in C. pepo (381e) from C. moschata, in True French (TF) background, was investigated 12 days post inoculation (DPI) at transcriptomic and genomic levels. Results: A comparative RNA-seq experiment on TF (susceptible to ZYMV) and 381e (tolerant to ZYMV), allowed to evaluate 33,000 expressed transcripts and to identify 146 differentially expressed genes (DEGs) in 381e, mainly involved in photosynthesis, transcription, cytoskeleton organization and callose synthesis. By contrast, the susceptible line True French triggered oxidative processes related to response to biotic stimulus, and key regulators of plant virus intercellular movement. Moreover, the genome mapping of transcripts allowed the identification of two chromosome regions rich in SNPs (Single Nucleotide Polymorphisms), putatively introgressed from C. moschata, containing genes exclusively expressed in 381e. Conclusion: The transcriptome reprogramming of 381e ZYMV challenged revealed a globally restoring of cellular activities and a reduced virus movement and replication. Furthermore, genes putatively involved in ZYMV tolerance were detected in C. moschata introgressed genomic regions. Our work provides new insight into the plant virus recovery process and a better understanding of the molecular basis of 381e tolerance.

Cucurbit crops are economically important worldwide. One of the most serious threats to cucurbit production is Zucchini yellow mosaic virus (ZYMV). Several resistant accessions were identified in Cucurbita moschata and their resistance was introgressed into Cucurbita pepo. However, the mode of inheritance of ZYMV resistance in C. pepo presents a great challenge to attempts at introgressing resistance into elite germplasm. The main goal of this work was to analyze the inheritance of ZYMV resistance and to identify markers associated with genes conferring resistance. An Illumina GoldenGate assay allowed us to assess polymorphism among nine squash genotypes and to discover six polymorphic single-nucleotide polymorphisms (SNPs) between two near-isogenic lines, "True French" (susceptible to ZYMV) and Accession 381e (resistant to ZYMV). Two F-2 and three BC1 populations obtained from crossing the ZYMV-resistant Accession 381e with two susceptible ones, the zucchini True French and the cocozelle "San Pasquale," were assayed for ZYMV resistance. Molecular analysis revealed an approximately 90% association between SNP1 and resistance, which was confirmed using High Resolution Melt (HRM) and a CAPS marker. Co-segregation up to 72% in populations segregating for resistance was observed for two other SNP markers that could be potentially linked to genes involved in resistance expression. A functional prediction of proteins involved in the resistance response was performed on genome scaffolds containing the three SNPs of interest. Indeed, 16 full-length pathogen recognition genes (PRGs) were identified around the three SNP markers. In particular, we discovered that two nucleotide-binding site leucine-rich repeat (NBS-LRR) protein-encoding genes were located near the SNP1 marker. The investigation of ZYMV resistance in squash populations and the genomic analysis performed in this work could be useful for better directing the introgression of disease resistance into elite C. pepo germplasm.

This paper presents the performance of an organic Rankine cycle (ORC) powered by medium-temperature heat sources. A simulation model, developed by the authors, has been improved to this scope. The model is based on zero-dimensional energy and mass balances for all the components of the system. It is also strictly related to the geometrical and design parameters of its components, especially in case of heat exchangers. The model evaluates the energetic and economic performance of the system, for different operating conditions and design criteria. In particular, the model allows one to set the geometrical parameters of heat exchanger and evaluate the off-design performance of the system. Hence, it could be an useful tool in the preliminary design of the plant. The n-butane has been used as working fluid according to results of the previous authors' work.Two types of simulations have been performed. The first simulation aims at selecting a design optimization criterion of some geometrical parameters of the shell and tube heat exchangers. The total cost of ORC plant has been selected as objective function. The parametrical analysis has been performed in steady-state regime.The second simulation evaluates the off-design performance of the ORC power plant. The thermal input of the cycle, i.e. diathermic oil coming from the heat source, has been varied in terms of mass flow rate and temperature to analyze the plant response to variations of boundary conditions starting from the design point.With respect to the total cost minimization, as objective function, the simulation results show that for all heat exchangers the higher the heat transfer area, the higher the net power generated and income. Instead, the evaporator shows different trends, hence it represents a key element in ORC design. The geometric optimization of heat exchangers allows the ORC to increase the economic benefit, the net power generated and the global efficiency of about 21.06%, 20.01% and 33.60% respectively.The results of the off-design analysis show that the heat source mass flow rate is a key parameter in net power generation. Fixed the heat source temperature on the upper bound of its variation range (185 degrees C), the net power generation shows both the maximum and minimum value, 335.4 kW and 269.3 kW, in correspondence of the lowest and the highest value of heat source mass flow rate respectively. Moreover, the results show that the plant efficiency decreases as both heat source mass flow rate and temperature increase. Its maximum value, 14.7%, is achieved for heat source temperature and mass flow rate equal to 155 degrees C and 18 kg/s, while its minimum value, 9.54%, is reached for heat source temperature and mass flow rate equal to 185 degrees C and 24 kg/s. (C) 2013 Elsevier Ltd. All rights reserved.