Aims: Select melon genotypes with ideal traits and compare two selection indices. Study Design: 26 melon genotypes were evaluated using a randomized complete block design with three replications. Place and Duration of Study: In August 2023, the melon genotypes were transplanted inside greenhouse, located in Saltillo, Coahuila. Methodology: The inoculation with the fungus causing powdery mildew began in 15-day-old seedlings. Disease severity was visually assessed 28 days after transplant using a scale from 0 to 4, where 0 indicates high resistance and 4 indicates high susceptibility. In addition, the area under the disease progress curve was calculated. At 51 days after transplant, during flowering, the crop was subjected to severe heat stress for three days, and the variables relative chlorophyll content and leaf temperature were measured. When the fruit reached maturity, the following parameters were evaluated: days to first cut, fruit weight, total soluble solids, flavor, skin thickness, and pulp thickness. Results: The selection index highlighted genotypes 18, 27, 15, 20, 3, 12, 17, 29, and 13 as superior, while the MGIDI index selected genotypes 18, 27, 20, 12, 23, 29, 10, 5, and 15. The Harper-type melons (18, 27, and 15) stood out in both indices due to their combination of high yield, fruit quality, powdery mildew tolerance, chlorophyll content, and lower temperature under heat stress. Conclusion: The Harper-type melons were identified as the most promising. The discrepancy between the genotypes selected by the indices may be due to various factors related to the calculation methodology.

Powdery mildew outbreaks, caused by Podosphaera xanthii, cause reduced watermelon yields as the plants produce fewer and smaller fruits due to premature leaf senescence. The reduced leaf canopy can decrease fruit quality due to sun scalding. Sources of powdery mildew tolerance were previously identified by screening the USDA Citrullus germplasm collection with P. xanthii races 1 W and 2 W. However, not all gene loci associated with tolerance to race 2 W have been identified and markers tightly linked to such loci have not been developed. We employed a bulked segregant analysis approach using historical data from the USDA Germplasm Resource Information Network for an extreme-phenotype genome-wide association study (XP-GWAS) of tolerance to P. xanthii race 2 W in Citrullus accessions (N = 1,147). XP-GWAS identifies variants that segregate between pools of individuals chosen from the extremes of a phenotypic distribution from a diversity panel. Whole-genome resequencing of 45 individuals bulked from tolerant and susceptible extremes resulted in 301,059 high-quality biallelic SNPs. Two adjacent SNPs on chromosome 7 were significantly associated with P. xanthii race 2 W tolerance in the bulks and two additional SNPs had a strong signal in the XP-GWAS analysis. Kompetitive Allele-Specific PCR (KASP) markers were designed for sixteen SNPs across the three genomic regions. The KASP markers were validated by genotyping 186 accessions from the extremes of the disease response distribution of the Citrullus collection. Analysis of variance determined that thirteen of the markers were significantly associated, with the best marker in each region explaining 21–31% of the variation in powdery mildew tolerance.

Sainfoin (Onobrychis viciifolia Scop.) as an ancient forage crop has garnered interest due to its desirable characteristics and adaptability. This investigation was designed to study genetic variation and interrelationships of sainfoin via factor analysis and clustering methods. Thirty-two local native genotypes were collected from various geographical regions and assessed based on a randomized block scheme with four replicates. The first five factors explained 85% of the variance and were named yield performance, plant morphology, powdery mildew, forage quality and forage palatability. The first factor described 58% of the variability, encompassed forage yield and its related characteristics like stem number per plant, main stem's nodes, length of the longest stem, main stem's internodes, stem's leaves, stem fresh weight, leaf fresh weight, inflorescence fresh weight, stem dry weight, leaf dry weight, fresh weight and dry weight per unit area. The dendrogram of sainfoin genotypes is categorized genotypes into three groups, which is confirmed via the Wilks’ lambda of multivariate analysis of variance. Group-1 contains 10 genotypes with the highest forage yield performance, and high amounts for most of the other remained traits. Group-2 contains 9 genotypes with the lowest performance for most traits of powdery mildew, suggesting their good potential for powdery mildew tolerance, while Group-3 contains 13 genotypes and indicated moderate performance for measured traits of sainfoin. The ten desirable genotypes of Group-1 mostly from northwest Iran, were good candidates for commercial release in Iran because they performed well and had high values of most traits, so they can be advised for cultivation in cool upland rainfed conditions of semi-arid regions.

Powdery mildew (PM) is one of the most important diseases of greenhouse and field-grown tomatoes. Viruses can intervene beneficially on plant performance in coping with biotic and abiotic stresses. Tomato yellow leaf curl Sardinia virus (TYLCSV) has been reported recently to induce tolerance against drought stress in tomato, and its C4 protein acts as the main causal factor of tolerance. However, its role in response to biotic stresses is still unknown. In this study, transgenic tomato plants carrying the TYLCSV C4 protein were exposed to biotic stress following the inoculation with Oidium neolycopersici, the causal agent of tomato PM. Phytopathological, anatomic, molecular, and physiological parameters were evaluated in this plant pathosystem. Heterologous TYLCSV C4 expression increased the tolerance of transgenic tomato plants to PM, not only reducing symptom occurrence, but also counteracting conidia adhesion and secondary hyphae elongation. Pathogenesis-related gene expression and salicylic acid production were found to be higher in tomato transgenic plants able to cope with PM compared to infected wild-type tomato plants. Our study contributes to unraveling the mechanism leading to PM tolerance in TYLCSV C4-expressing tomato plants. In a larger context, the findings of TYLCSV C4 as a novel PM defense inducer could have important implications in deepening the mechanisms regulating the management of this kind of protein to both biotic and abiotic stresses.

Genome-wide characterization and expression analysis of the MLO gene family sheds light on powdery mildew resistance in Lagenaria siceraria

Powdery mildew is an economic threat for viticulture because it not only affects grape yield, but also causes a series of impacts on the qualities of fruit and wine, especially the flavors and various metabolites. Different grape varieties may have different levels of powdery mildew resistance/tolerance and their components of their metabolome are also various. In this study, two wine grape varieties, Guipu No.6 (GP6) and Marselan (Mar) with different levels of powdery mildew tolerance, were used to compare the quality differences in metabolism level by using the widely targeted metabolomics method. The results show that GP6 has a better powdery mildew leaf tolerance than Mar. A total of 774 metabolites were detected by using a UPLC-QQQ-MS-based metabolomics approach, and 57 differential metabolites were identified as key metabolites that were accumulated after infection with powdery mildew in GP6 and Mar, including phenolic acids, flavonoids, terpenoids, stilbenes, lipids, nucleotides and derivatives, lignans and coumarins, and quinones. This finding indicates that the defense mechanisms of grape fruit are mainly associated with phenylpropane-flavonoid metabolism. Specifically, stilbenes had greater variations after powdery mildew infection in GP6; while in Mar, the variations of flavonoids, especially kaempferol-3-O-glucuronide and luteolin-7-O-glucuronide, were more remarkable. The above results demonstrate that stilbenes may play a more important role than flavonoids in resisting powdery mildew infection in GP6’s fruits, and the drastic variations of these phenolic compounds in different wine grapes after powdery mildew infection might also lead to quality difference in the flavors. This study can provide new insights into the understanding of the cause of powdery mildew tolerance in different grape varieties and the effects on the quality of wine grapes infected with the disease exerted by metabolism level.

Genetic analysis of linseed plant genetic resources is very important to understand gene action and combining ability for crop improvement. Eight genetically diverse lines of linseed namely Surbhi, Bhagsu, Nagarkot, T-397, Himani, Baner, JRF-1 and JRF-4 were evaluated through half diallel cross analysis under sub temperate conditions of Western Himalayas. These eight parental lines identified for seed, fibre and dual purpose trait and 28 F1 progenieswere grown in CRBD to identify potential parents and their cross combinations for yield and associated traits under variable environments. Significant level of genetic variability was observed among studied genotypes for the yield, fibre and their contributing traits. Genotype×environment (G×E) interaction was also significant except for plant height and technical height indicating a definite role of environment in the performance of genotypes. Non-additive gene action was recorded for maximum traits. Based on GCA, three genotypes viz., Baner, Nagarkot and Surbhi were recorded to be good general combiner for seed yield whereas genotypes, JRF-1 and JRF-4 were good for early maturity and fibre yield. These promising genotype harbor the genes for various traits like high seed and fibre yield, early maturity, rust and powdery mildew tolerance. On the basis of high SCA effect, four cross combinations viz., Himani×JRF-4, T-397×JRF-4, Bhagsu×Nagarkot and Surbhi×Baner were found best for seed yield while four other viz., Surbhi×T-397, Nagarkot×Himani, Surbhi×Baner and Surbhi×Bhagsu were found best for fibre yield in pooled over environments. These genotypes and cross combinations can be used in further hybridization and selection can be done for early maturity, disease tolerance, seed, fibre and dual purpose trait as per the need of linseed breeding programmes in the country.

Mosaic (brand HBC 369) is a new flavor hop variety having unique and highly favored flavor characteristics. Mosaic was developed and released by the Hop Breeding Company LLC (HBC) and is protected by a U.S. plant patent (“Hop Plant Named ‘HBC 369’”). Mosaic's maternal parent, YCR 14 (Simcoe), is a commercial cultivar with a unique aroma but with relatively low yield and susceptibility to powdery mildew. YCR 14 was crossed to a male plant with powdery mildew resistance and high yield in its genetic background, with the ultimate goal of creating a commercial cultivar with unique aromatic/flavoring characteristics, resistance to powdery mildew, and good yield. HBC 369 (Mosaic) was selected from this cross on that basis. Mosaic has a unique aroma combined with high α-acid content, powdery mildew tolerance, and exceptional yield. To date, flavor testing of beer brewed with Mosaic, both at pilot and commercial scale, has brought about an enthusiastic response from brewers and tasters, and the future of this new hop variety looks promising. The aroma/flavor descriptors used commonly include fruity (blueberry), citrus (tangerine, grapefruit), tropical (mango, guava), floral, and earthy. The combination of these aroma/flavor descriptors with the relatively high α-acid levels allows this hop to serve a dual purpose, as both a bittering and flavor/aroma hop in the brewing process. Ultimately, Mosaic provides flavor and aroma profiles in beer that cannot be accomplished with other hop cultivars.

Association analysis is a useful method for evaluation of significant association between molecular marker and phenotype of trait. This study was performed to evaluate association between traits related with powdery mildew resistance and molecular markers. This investigation was performed using 77 barley genotypes and AFLP markers. In phenotypic evaluation, reaction of seedlings to powdery mildew was evaluated and the infection type and intensity were assessed based on 0-9 scale as the most important traits associated with resistance. Also in this study, the genetic diversity of genotypes was evaluated using seven combination primers<em> Eco</em>RI/<em>Mse</em>I. The average percentages of polymorphism and polymorphic information content were 92.37% and 0.43, respectively. General evaluation of the statistics of genetic diversity showed that among seven primer combinations, three combinations of E90-M160, E100-M160, and E100-M150 were higher value than others and had a more obvious effect in the detection and separation of barley genotypes. Association analysis was performed using four statistical models of GLM and MLM applying TASSEL software. In the complete MLM model, 33 markers showed significant association in the 5 percent probability level with traits and the highest coefficient of determination was related to marker E80-M150-3 that explained 14% of variations of infection intensity. E80-M510-3 and E80-M160-22 markers were showed significant association (pr<0.05) with both characteristic the severity and type of infection that can represent the effective role of this genomic region in resistance to powdery mildew. If the results are confirmed, it can be a suitable candidate for conversion to SCAR specific marker.

This study concerns the improvement of grape varieties for disease tolerance. Maternal varieties were from Vitis vinifera while disease tolerant varieties from the coastal area of the Black Sea Region were used as pollinators. Some genotypes were selected for detailed observations. Detection of powdery mildew tolerance of some varieties and selections under controlled conditions were also conducted. Some individuals in further stage were from backcrossing. Utilizing Gurcu, Ispir Uzumu, Yerli Isabella, Beyaz Kokulu, Kato Kara and Parlak Akuzum grape varieties that show resistance to powdery mildew under controlled conditions will be more effective in the breeding studies. Less powdery mildew was observed in the F 1 hybrids obtained from the combinations including Gurcu and Kokulu Siyah grape varieties. Italia x Favli-149 was selected as wine grape candidate with compact clusters. Chemical characteristics of the wine were in the standard limits and it was classified as good-medium wine.

Powdery mildew is a devastating disease in sesame during rabi season, causing considerable yield loss. Utilisation of host plant resistance mechanism is ideal disease management strategy and knowledge of inheritance of tolerance/resistance to powdery mildew will be quite helpful in formulating breeding program. In the present investigation, 30 genotypes were screened against powdery mildew, of which 18 showed susceptible and 12 tolerant reactions. None of the genotype recorded immune response. Study on inheritance of tolerance to powdery mildew revealed that susceptibility was dominant over tolerance and is controlled by two independent recessive genes with complementary epistasis.

Gummy stem blight incited by the fungus Didymella bryoniae is a major disease of melons worldwide. The objectives of the present study were to critically evaluate melon ( Cucumis melo L.) germplasm for resistance to D. bryoniae and to characterize the genetics of resistance in the resistant accessions. Two hundred sources of germplasm (plant introduction accessions, cultivars, breeding lines, landraces, and wild relatives) were screened against a single highly virulent isolate (IS25) of D. bryoniae in a plastic tunnel. The genetics of resistance to D. bryoniae was studied in three crosses between plant introductions 157076, 420145, and 323498, resistant parents that were fairly adapted (flowering, fruiting, powdery mildew tolerance) to Nanjing conditions, and plant introductions 268227, 136170, and NSL 30032 susceptible parents, respectively. Six populations of each cross (susceptible parent, resistant parent, F 1 , F 2 , the two reciprocal backcrosses) were analyzed for their responses to D. bryoniae . Seedlings in both studies were inoculated with a spore suspension (5 × 10 5 spores/mL −1 ) of D. bryoniae at the four to six true-leaf stages and assessed for leaf and stem damage at 7, 14, and 21 d postinoculation. Results of germplasm screening indicated most germplasms reported as resistant elsewhere were confirmed resistant under our conditions. However, some plant introductions identified as highly resistant elsewhere were susceptible under our conditions, the most interesting being plant introduction 482399. This plant introduction that was considered resistant was highly susceptible in our study. We also identified other sources of resistance not reported previously, for example, JF1; a wild Cucumis from the highlands of Kenya was rated highly resistant. Analysis of segregation of F 1 , F 2, and backcross generations of the three crosses indicated that each of the three plant introductions carry a single dominant gene for resistance to the D. bryoniae .

Premature harvest of acorn squash is a widespread problem because fruits reach maximum size and optimum color within 20 days after pollination (DAP), well before peak dry matter and sugar content occur. The present study was conducted to determine the relationship between harvest date and physiological factors affecting eating quality in Cucurbita pepo L. squash. In the summer of 2005, C. pepo squash cultivars were evaluated at three harvest dates, 25, 35, and 45 days after pollination (DAP), with or without a 10-day storage period at 21 °C. Four F1 hybrid cultivars carrying powdery mildew tolerance (PMT) were evaluated: a semi-bush, commercial acorn cultivar (`Tip Top'), a high quality experimental acorn, bush hybrid (NH1634), and two sweet dumpling-type, semi-bush hybrids (NH1635 and 1636). Data were collected on mesocarp DW, oBrix (soluble solids), and partitioning of biomass between mesocarp tissue and developing embryos during storage. Peak DWs of 20% to 21% occurred at 25 DAP in NH1634, 1635 and 1636, and at 35 DAP in Tip Top (19.5 %). At 25 DAP, Brix was low (means of 5.9 to 7.2) across all cultivars. With harvest at 25 DAP plus 10 days storage, oBrix was low in Tip Top (7.1), but was higher than 10 in NH1634 and NH1636. Brix reached near maximum (13 to 15) at 45 DAP in NH1634, 1635 and 1636, and at 55 DAP in Tip Top (12). Embryos were small (DW = 8 to 19 mg) at 25 DAP and grew fairly linearly to a maximum at 55 DAP. Mean embryo DW at 55 DAP was 87.5 mg for Tip Top, 76.9 mg for NH1636, 57.1 mg for NH1634, and 28.5 mg for NH1635. The proportion of total fruit biomass expressed as energy equivalents (kJoules) allocated to embryos in mature fruit (45 DAP + 10 days storage) was 11.8% in NH1635, 18.7% in NH1634, 27.4% in Tip Top, and 30.2% in NH1636. Reallocation of assimilates from mesocarp tissue to developing embryos was a major contributing factor, along with respiration, to a reduction in mesocarp dry matter during storage.

Acorn squash ( Cucurbita pepo L.) is one of the three major classes of squash consumed in North America. Breeding improvements over the past 30 years have focused on more compact cultivars, earlier maturity, darker rind color, and powdery mildew tolerance (PMT). Our observations from sampling acorn squash from local supermarkets at different times during the year show that eating quality is highly variable, and most often, not acceptable. Our taste tests indicate that for acceptable eating, quality acorn squash should have °Brix of 10 or higher, flesh %DW above 16, and a smooth, nonfibrous texture. Most commercial cultivars fail to meet the above minimum criteria for quality. Proper harvest time is a major determinant of squash eating quality. To obtain adequate °Brix levels, squash should not be harvested until at least 50 days after pollination (DAP). If squash are harvested between 25 to 40 DAP and then stored for two or more weeks, °Brix levels may increase to acceptable levels, but some mesocarp reserves will be remobilized to developing seeds, reducing mesocarp %DW and lowering eating quality. A major goal of the squash breeding efforts at the University of New Hampshire has been to increase mesocarp %DW for obtaining more consistent eating quality. We have evaluated several experimental PMT hybrids during the past 5 years, and in some of these, flesh DW has averaged 17% or higher, and eating quality has been rated consistently very good. The adoption of better quality acorn cultivars together with implementing proper harvest times and storage conditions could appreciably increase per capita consumption.