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Anthracnose, caused by the fungal pathogen Colletotrichum orbiculare (Berk. & Mont.) Arx syn. lagenaria, is one of the most important diseases of watermelon in the United States and worldwide. The study was conducted to identify C. orbiculare race 1 resistance quantitative trait loci (QTL) in a ‘Charleston Gray’, resistant parent, and ‘New Hampshire Midget’, susceptible parent, biparental mapping population. The mapping population consisted of 228 F2 and the validation population consisted of 60 individuals each in BC1P1 and BC1P2. The disease severity was rated using a disease index comprising a rating scale of 0 to 100%. IciMapping was used to draw the linkage map and R/qtl non-parametric method (‘model = np’) was used to identity QTL. We identified a major disease resistance QTL, Qar1-8, on chromosome 8. The significant SNP marker S8_5149002, part of a putative coiled-coil (CC)–nucleotide-binding site (NBS)–leucine-rich repeat (LRR) (CC-NBS-LRR or CNL; ClCG08G002410), had a LOD of 14.06. The significant marker was validated on mapping populations using R package functions ‘chisq.test’, ‘wilcox.test’, ‘kruskal.test’, and ‘dunn.test’. The significant marker S8_5149002 was also tested for its ability to differentiate race 1 anthracnose resistance on 61 watermelon germplasm including 41 plant introduction (PI) lines. Hence, the diagnostic SNP marker S8_5149002 could be used for marker assisted selection (MAS) for race 1 anthracnose resistance in watermelon breeding programs.

Gummy stem blight (GSB), a major disease caused by Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), has caused significant losses of watermelon in the United States. The lack of progress in the development of resistant cultivars is the result of complex inheritance of resistance and breeding strategies that rely on single-plant selection. Because the sources of resistance are wild watermelon relatives, good fruit quality has been difficult to maintain during the selection process. Three hundred recombinant inbred line (RILs) in a population that carries resistance genes to GSB as well as good fruit quality were produced. This was accomplished by crossing and intercrossing resistant plant introductions, crossing the resulting progenies with elite cultivars, intercrossing those progenies, and, finally, self-pollinating to the S3 generation. The 300 RILs were evaluated for disease severity and fruit morphological and quality traits under greenhouse and field conditions in a randomized complete block design with 10 replications and 3 years. The means and correlations for disease severity ratings and fruit quality traits were estimated. Approximately 186 RILs had disease severity ratings below the mean value of the disease assessment scale (4.5), indicating that they possibly carry one or more genes for resistance to GSB. All disease severity ratings were correlated to each other (r = 0.67–0.98; P < 0.001), but they were not correlated with fruit quality traits. Most importantly, several resistant RILs showed good to excellent fruit quality. Our results provide evidence of improved germplasm with high resistance and good fruit quality.

Background. With coronavirus disease-19 (COVID-19), patients with diabetes mellitus are dealing with two pandemics and are at a higher risk of mortality. The present study was undertaken to evaluate interactions between hyperglycemia and clotting factors in COVID-19 patients. Methods. In this retrospective observational study, 53 real-time RT-PCR SARS-CoV-2 positive cases in 40 to 70 years of age, representing both sexes, were enrolled in the study from SMS Medical College, Jaipur (Rajasthan, India). Based on their history of diabetes mellitus and exclusion criterion, patients were divided into diabetics (N = 11) and non-diabetics (N = 17) groups. The data on clinical profile and coagulation profile was recorded along with the markers of inflammation and infection. The two groups were compared using the Mann-Whitney test and the Fisher’s exact test. Correlation coefficients between clotting factors were compared between two groups using Student t test. Results. There was no significant difference in age (p = 0.25) or gender (p = 0.12) between the two groups. The coagulation indicators FDP (p = 0.79), D-dimer (p = 0.30), APPT (p = 0.96), PT (p = 0.79), INR (p = 1.00) PLT (p = 0.17) and the markers of inflammation and infection did not differ significantly between the two groups. There was no significant difference in correlation coefficients among coagulation indicators between the two groups (p > 0.05). Conclusion. The study concludes that pathogenesis in clotting system is not significantly different in stud-ied groups. Further research is needed to explain the higher mortality in diabetic patients suffering from COVID-19.

Bottle gourd [Lagenaria siceraria (Molina) Standl.] is widely produced in some Asian and African countries as a fresh vegetable as well as for seed consumption. A major use of bottle gourd is for rootstocks in grafted watermelon production. There are several centers where bottle gourd genetic resources are maintained, with the U.S. Department of Agriculture (USDA) germplasm collection being one of the most important. There is little published information on the relationship between seed morphology and the early establishment of seedlings in bottle gourd. The objective of this study was to determine seed characterization, morphology, and cotyledon shape in 163 Lagenaria spp. accessions and measure any relationship between seed and cotyledon characteristics. In USDA Lagenaria germplasm, it has been determined that the common character in seeds was medium in terms of seed size (53% of accessions), intermediate in seed surface lustre (39% of accessions), brown in seedcoat color (89% of accessions), thin and uniform in seed margin (35% of accessions), and tan in seed margin color (64% of accessions). According to the research results, seed weight ranged from 0.11 g (PI 500820) to 0.36 g (PI 675112), seed length from 13.17 mm (PI 500820) to 23.68 mm (PI 675112), and seed width from 5.86 (PI 500808) to 11.21 mm (PI 491274). Cotyledon length ranged from 5.46 cm (PI 368640) to 2.47 cm (PI 381850). The widest cotyledon was 3.00 cm (PI 534552), and the narrowest was 1.50 cm (PI 381831). Interesting correlations were observed for seed weight with seed length (R2 = 0.259), and cotyledon length with cotyledon width (R2 = 0.547).

Cucurbit plants usually are sensitive to chilling and easily damaged. Although bottle gourds, which are members of the Cucurbitaceae family, are considered as fresh vegetables in some Asian countries, their main use in recent years is to be used as rootstocks in grafted watermelon cultivation. We tested 163 bottle gourd accessions of the U.S. Department of Agriculture (USDA) genebank for cold tolerance in the early seedling stage. The experiment was conducted using controlled environment chambers with 3 chilling durations (36, 48, and 60 hours) at 4 °C. Chilling damage was rated 0 to 9 (0 = no damage, 1 to 2 = trace of damage, 3 to 4 = slight damage, 5 to 6 = moderate damage, 7 to 8 = advanced damage, 9 = plant totally dead). We rated damage separately for the cotyledons, true leaf, and growing point. Cold damage was higher at a chilling duration of 60 hours, and decreased at 48 and 36 hours. Most tolerant cultigens were PI 491272, PI 491280, PI 491281, PI 491286, and PI 491326. Most susceptible were PI 381845, PI 381846, PI 534556, PI 636137, and PI 668365.

The Florida strain of Zucchini yellow mosaic virus (ZYMV-FL) is one of the major viral diseases of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. Although some screening has been performed for ZYMV resistance in watermelon, the germplasm collection has not been screened extensively for resistance. The objectives of this study were to screen the U.S. Department of Agriculture (USDA) watermelon germplasm collection for ZYMV resistance and to verify the disease rating for the most resistant and most susceptible accessions. We used a randomized complete block with four replications, 1613 PI accessions, and 41 cultivars. ‘Charleston Gray’ and ‘Crimson Sweet’ susceptible controls were used to verify that the ZYMV inoculum was virulent. After the last rating, an enzyme-linked immunosorbent assay (ELISA) was performed to determine the presence of a virus in the plant tissue. The PI accessions with high resistance to ZYMV-FL that also exhibited resistance to other watermelon viruses were PI 595203, PI 386015, PI 386016, PI 386024, PI 386025, PI 386026, PI 244018, PI 244019, PI 485583, PI 494528, and PI 494529. The ZYMV-FL retest of the most resistant 46 PI accessions showed that there were some escapes. Sixteen resistant PI accessions had a rating of 3.0 or less for the average and maximum ratings: PI 595203, PI 537277, PI 560016, PI 386016, PI 386019, PI 485580, PI 494529, PI 595200, PI 494528, PI 595201, PI 386025, PI 494530, PI 386015, PI 386021, PI 386026, and PI 596662. Overall, PI 595203 had the highest resistance according to both the germplasm screening and the retest studies.

Background: Since the outbreak of coronavirus disease-19 research has been continued to explore multiple facets of the disease. The objective of the present study is to evaluate the relationship between blood group phenotypes and COVID-19 susceptibility.Methods: In this hospital based, retrospective observational study 132 COVID-19 patients were enrolled from SMS Medical Hospital in Jaipur, India after receiving approval from the institutional ethics committee. The ABO, Rh and Kell blood group phenotypes along with demographic data of the patients were recorded. The observed proportions of ‘A’ , ‘B’, ‘AB’, ‘O’, ‘Rh’, and ‘Kell’ blood groups in COVID-19 patients were compared against the expected proportions (the null hypothesis) of the general population using Pearson’s chi-squared test and partition analysis.Results: There were significant differences between observed and expected frequency for the ABO and Kell blood phenotypes. Further partition analysis of ABO phenotypes showed that the group ‘A’ phenotypes were more susceptible to COVID-19. The Kell negatives were also more susceptible. The blood groups ‘AB’, ‘B’, ‘O’, and ‘Rh’ showed no significant difference for susceptibility to COVID-19.Conclusion: The study shows a relationship between ABO, Rh, and Kell blood groups and COVID-19 susceptibility. The application of these relationships in clinics should be explored in future studies.

[EN] The sexual expression of watermelon plants is the result of the distribution and occurrence of male, female, bisexual and hermaphrodite flowers on the main and secondary stems. Plants can be monoecious (producing male and female flowers), andromonoecious (producing male and hermaphrodite flowers), or partially andromonoecious (producing male, female, bisexual, and hermaphrodite flowers) within the same plant. Sex determination of individual floral buds and the distribution of the different flower types on the plant, are both controlled by ethylene. A single missense mutation in the ethylene biosynthesis geneCitACS4, is able to promote the conversion of female into hermaphrodite flowers, and therefore of monoecy (genotypeMM) into partial andromonoecy (genotypeMm) or andromonoecy (genotypemm). We phenotyped and genotyped, for theM/mlocus, a panel of 207 C. lanatusaccessions, including five inbreds and hybrids, and found several accessions that were repeatedly phenotyped as PA (partially andromonoecious) in several locations and different years, despite beingMM. A cosegregation analysis between a SNV inCitACS4and the PA phenotype, demonstrated that the occurrence of bisexual and hermaphrodite flowers in a PA line is not dependent onCitACS4, but conferred by an unlinked recessive gene which we calledpa. Two different approaches were performed to map thepagene in the genome ofC. lanatus: bulk segregant analysis sequencing (BSA-seq) and genome wide association analysis studies (GWAS). The BSA-seq study was performed using two contrasting bulks, the monoecious M-bulk and the partially andromonoecious PA-bulk, each one generated by pooling DNA from 20 F2 plants. For GWAS, 122 accessions from USDA gene bank, already re-sequenced by genotyping by sequencing (GBS), were used. The combination of the two approaches indicates thatpamaps onto a genomic region expanding across 32.24-36.44 Mb in chromosome 1 of watermelon. Fine mapping narrowed down thepalocus to a 867 Kb genomic region containing 101 genes. A number of candidate genes were selected, not only for their function in ethylene biosynthesis and signalling as well as their role in flower development and sex determination, but also by the impact of the SNPs and indels differentially detected in the two sequenced bulks., This work has been funded by grant UAL18-BIO-B017-B, awarded by the call "Proyectos UAL-FEDER " within the framework of the 2014-2020 FEDER-Andalusia Operational Program, as well as by the research group BIO293 of the University of Almeria.

Since the outbreak of coronavirus disease-19 research has been continued to explore multiple facets of the disease. The objective of the present study is to evaluate the relationship between blood group phenotypes and COVID-19 susceptibility. In this hospital based, retrospective observational study 132 COVID-19 patients were enrolled from SMS Medical College and attached Hospitals, Jaipur, India after the proper approval from the institutional ethics committee. The ABO, Rh and Kell blood group phenotypes and demographic data of the patients were recorded. The observed proportions of ‘A’ , ‘B’, ‘AB’, ‘O’, ‘Rh’, and ‘Kell’ blood groups phenotypes in COVID-19 patients were compared against the expected proportions (our null hypothesis) of the general population using multinomial tests and partition analysis. There were significant differences between observed and expected frequency in ABO and Kell blood group phenotypes. Further partition analysis of ABO blood phenotypes showed that the group ‘A’ phenotypes were more susceptible for COVID-19. The Kell negatives were also more susceptible. The blood groups ‘AB’, ‘B’, ‘O’, and ‘Rh’ phenotypes showed no significantly different susceptibility for COVID-19. The study shows relationship between ABO, Rh, and Kell blood group phenotypes and COVID-19 susceptibility. The application of these relationship in clinical practice requires more exploratory studies. The following core competencies are addressed in this article: Screening Tool, Epidemiology, Patient Management, Medical Research.

The forecasting of Coronavirus Disease-19 (COVID-19) dynamics is a centerpiece in evidence based disease management. Numerous approaches that use mathematical modeling have been used to predict the outcome of the pandemic, including data driven models, empirical and hybrid models. This study was aimed at prediction COVID-19 evolution in India using a model based on autoregressive integrated moving average (ARIMA). Retrieving real time data from the Johns Hopkins dashboard from 11 Mar 2020 to 25 Jun 2020 (N = 107 time points) to fit the model. The ARIMA (1,3,2) and ARIMA (3,3,1) model fit best for cumulative cases and deaths respectively with minimum Akaike Informaton Criteria. The prediction of cumulative cases and deaths for next 10 days from 26 Jun 2020 to 05 Jul 2020 showed a trend toward continuous increment. The predicted root mean square error (PredRMSE) and base root mean square error (BaseRMSE) of ARIMA(1,3,2) model was 21137 and 166330 respectively. Similarly, PredRMSE and BaseRMSE of ARIMA(3,3,1) model was 668.7 and 5431 respectively. We propose that data on COVID-19 be collected continuously, and that forecasting continue in real time. The COVID-19 forecast assist government in resource optimization and evidence based decision making for a subsequent state of affairs.

The sexual expression of watermelon plants is the result of the distribution and occurrence of male, female, bisexual and hermaphrodite flowers on the main and secondary stems. Plants can be monoecious (producing male and female flowers), andromonoecious (producing male and hermaphrodite flowers), or partially andromonoecious (producing male, female, bisexual, and hermaphrodite flowers) within the same plant. Sex determination of individual floral buds and the distribution of the different flower types on the plant, are both controlled by ethylene. A single missense mutation in the ethylene biosynthesis gene CitACS4, is able to promote the conversion of female into hermaphrodite flowers, and therefore of monoecy (genotype MM) into partial andromonoecy (genotype Mm) or andromonoecy (genotype mm). We phenotyped and genotyped, for the M/m locus, a panel of 207 C. lanatus accessions, including five inbreds and hybrids, and found several accessions that were repeatedly phenotyped as PA (partially andromonoecious) in several locations and different years, despite being MM. A cosegregation analysis between a SNV in CitACS4 and the PA phenotype, demonstrated that the occurrence of bisexual and hermaphrodite flowers in a PA line is not dependent on CitACS4, but conferred by an unlinked recessive gene which we called pa. Two different approaches were performed to map the pa gene in the genome of C. lanatus: bulk segregant analysis sequencing (BSA-seq) and genome wide association analysis studies (GWAS). The BSA-seq study was performed using two contrasting bulks, the monoecious M-bulk and the partially andromonoecious PA-bulk, each one generated by pooling DNA from 20 F2 plants. For GWAS, 122 accessions from USDA gene bank, already re-sequenced by genotyping by sequencing (GBS), were used. The combination of the two approaches indicates that pa maps onto a genomic region expanding across 32.24–36.44 Mb in chromosome 1 of watermelon. Fine mapping narrowed down the pa locus to a 867 Kb genomic region containing 101 genes. A number of candidate genes were selected, not only for their function in ethylene biosynthesis and signalling as well as their role in flower development and sex determination, but also by the impact of the SNPs and indels differentially detected in the two sequenced bulks.

Cucurbits suffer from many diseases that are caused by bacteria, fungi (and oomycetes), nematodes, viruses and phytoplasmas. Disease pathogens attack cucurbits at every stage of development, from damping off at the beginning of germination to postharvest fruit rots. Reliable fruit yield and quality of cucurbits is dependent on adequate pathogen control. This chapter describes bacterial and phytoplasma, fungal and oomycete, and viral diseases, as well as nematode pests, of cucurbits. Some measures to control them, including cultural, chemical and host resistance, are also discussed.

Insects are often a major obstacle to the successful production of cucurbits. They can severely reduce yield, injure or kill plants, spread disease and adversely affect fruit quality. Spider mites can also be a problem, particularly with glasshouse cucumbers. Integrated pest management requires an understanding of the biology and life history of the living organisms that interact with cucurbits. Management begins with cultural control methods, such as crop rotation, deep ploughing of crop residues, control of alternative hosts (i.e. weeds) and the use of trap crops. Cultural and physical controls alone are rarely sufficient for cucurbit pest management. Foliar application of chemicals is the most common means of controlling insects and mites in the field and aerial fumigation is also used in the glasshouse. Soil fumigation, although expensive, can eradicate soilborne pests. Beneficial insects are also employed for biological management. Breeding cucurbits for insect and mite resistance has great potential, but has not progressed nearly as far as breeding for disease resistance. This chapter describes insect and mite pests of cucurbits, and their control.

Much progress has been attempted in classical genetics and traditional breeding of bitter gourd which are mainly related to qualitative traits but significant advancement in several quantitative traits is difficult to achieve. The main purpose of this chapter is to highlight some of the key concepts that lay the genetical foundations for bitter gourd breeding. The study on classical genetics of bitter gourd has added an advantage to the breeders in the development of new varieties and F1 hybrids for earliness and higher productivity due to the involvement of gynoecious lines as one of the parents in breeding of these varieties. The selection based on morphological traits for high and stable yield requires the evaluation of germplasm in multiple environments over several seasons; which is very expensive and time-consuming process. Molecular markers technology have great potential to overcome many of the obstacles presented by traditional breeding techniques, but it is imperative that the development and utilization of these markers works in conjunction with traditional breeders who have necessary skill to evaluate the germplasm lines of economic value. Marker-assisted selection (MAS) certainly accelerates the breeding process and is a powerful tool for selecting for desirable traits. The construction of a genetic map is a common approach to detect quantitative trait loci (QTLs) for genetic improvement of bitter gourd.

Cucurbit fruits are comparable in nutrient content to other fruits and vegetables and are exceptional for high pro-vitamin A content of some cultivars of squash and melon, and the abundant oil and protein in seeds of Telfairia, Cucurbita and other cucurbits. Cucurbits are a good source of carbohydrates and play a significant role in human nutrition, especially in tropical countries where their consumption is high. This chapter describes the contents of moisture, solids, carbohydrates, proteins, oils, vitamins, minerals and secondary compounds (such as carotenoids, citrulline, flavonoids and phenolic acids), as well as toxic and potentially therapeutic compounds, of cucurbit fruits. Tabulated data are provided on nutritional composition of raw and processed cucurbits, and of cucurbit seeds, flowers and leaves. Each table is divided into: (a) major components (moisture, calories, protein, lipids, fatty acids and minerals); and (b) vitamins and carotenoids.

This chapter focuses on the cultivation and uses of minor crops such as Benincasa hispida, Coccinia grandis, Cucumis anguria, C. metuliferus, C. setosus, Cucurbita foetidissima, Cyclanthera pedata var. edulis, Lagenaria siceraria, Luffa spp., Momordica angustisepala and M. cymbalaria, M. balsamina, M. charantia, M. cochinchinensis, M. dioica, Praecitrullus fistulosus, Sechium edule, Sicana odorifera, Telfairia spp. and Trichosanthes spp. These cucurbits are primarily cultivated by smallholder farmers in Asia and are often part of home, school and community gardens.

This chapter focuses on distribution and ecology, nomenclature, taxonomy, morphology and anatomy, and growth and development of cucurbits.

This chapter focuses on the evolutionary history, commercial production, and cucurbits as weeds. The uses of cucurbits as food and drink, medicinal properties, and as ornamental plants are also discussed.

This chapter focuses on seed germination, land preparation, planting, thinning, spacing, mulches and plant covers, glasshouse culture, grafting, temperature, daylength and light intensity, soil, fertilizers, irrigation, support, training, pruning, and weed control in cucurbits.

Numerous abiotic stresses impact yield, quality and adaptation of cucurbit crops under the diverse cultivation systems across the globe. Irrigation systems, elevation, soil type, solar radiation, wind, pathogens, fertility and genotype all interact to determine the degree to which abiotic stress may impact the crop. This chapters describes some abiotic stresses affecting cucurbit cultivation, such as cold, heat, drought, flooding, nutrient deficiencies and excesses, and salinity. Tolerance or resistance to abiotic stress factors has been documented in the germplasm of multiple cucurbit crops. Utilizing wild accessions, landraces and known resistance sources, genes for abiotic stress resistance are being identified and introgressed into cultivars with desirable fruit quality. With the new gene editing technology, it may be possible to modify these endogenous stress resistance genes to enhance their effects in the near future.

Sources of resistance to the Zucchini yellow mosaic virus-Florida strain (ZYMV-FL) have been identified within the Citrullus genus. Inheritance of resistance to ZYMV-FL was studied in PI 595203 (Citrullus mucosospermus), a resistant watermelon accession. The F1, F2, and BC1 progenies derived from the cross ‘Calhoun Gray’ (CHG) × PI 595203 and ‘New Hampshire Midget’ (NHM) × PI 595203 were used to study the inheritance of resistance to ZYMV-FL. Seedlings were inoculated with a severe isolate of ZYMV-FL at the first true leaf stage and rated weekly for at least 6 weeks on a scale of 1 to 9 on the basis of severity of viral symptoms. A single recessive gene (zym-FL) was found to control the high level of resistance to ZYMV-FL in PI 595203.

The Gy14 cucumber (Cucumis sativus) is resistant to oomyceteous downy mildew (DM), bacterial angular leaf spot (ALS) and fungal anthracnose (AR) pathogens, but the underlying molecular mechanisms are unknown. Quantitative trait locus (QTL) mapping for the disease resistances in Gy14 and further map-based cloning identified a candidate gene for the resistant loci, which was validated and functionally characterized by spatial-temporal gene expression profiling, allelic diversity and phylogenetic analysis, as well as local association studies. We showed that the triple-disease resistances in Gy14 were controlled by the cucumber STAYGREEN (CsSGR) gene. A single nucleotide polymorphism (SNP) in the coding region resulted in a nonsynonymous amino acid substitution in the CsSGR protein, and thus disease resistance. Genes in the chlorophyll degradation pathway showed differential expression between resistant and susceptible lines in response to pathogen inoculation. The causal SNP was significantly associated with disease resistances in natural and breeding populations. The resistance allele has undergone selection in cucumber breeding. The durable, broad-spectrum disease resistance is caused by a loss-of-susceptibility mutation of CsSGR. Probably, this is achieved through the inhibition of reactive oxygen species over-accumulation and phytotoxic catabolite over-buildup in the chlorophyll degradation pathway. The CsSGR-mediated host resistance represents a novel function of this highly conserved gene in plants.

Sources of resistance to the watermelon strain of papaya ringspot virus-watermelon strain (PRSV-W) have been identified within the watermelon (Citrullus lanatus) germplasm collection. Inheritance of the resistance to PRSV-W was studied in three Citrullus amarus (formerly C. lanatus var. citroides) PI accessions: PI 244017, PI 244019, and PI 485583. Three susceptible parent lines, ‘Allsweet’, ‘Calhoun Gray’, and ‘New Hampshire Midget’, were crossed with resistant PI accessions to develop F1, F2, and BC1 progenies in six families. A single recessive gene was found to control the resistance to PRSV-W in all three resistant PI accessions. Allelism tests indicated that the three PI accessions carry the same resistance allele to PRSV-W. The gene symbol ‘prv’ is proposed for PRSV-W resistance in PI 244017, PI 244019, and PI 485583 in watermelon.

Reliable yield performance is important in cucumber because seed companies prefer to market cultivars adapted to multiple rather than single regions of the U.S. Also, growers benefit by using a cultivar that performs well in many environments. Future performance of cultivars is also important. The objectives of the study were to (i) evaluate the yield of cucumber genotypes over successive years and in different locations, and (ii) identify cucumber genotypes with high stability for yield. A diverse set of 22 pickling genotypes was evaluated over 3 years (1986, 1987 and 1988) and in 7 locations across the United States. Yield traits were evaluated using once-over harvest and counting the number of fruit that were marketable, culled or oversize. Total yield, marketable yield (total minus culled fruit), early yield (number of oversize fruit), percent culls and fruit per plant were calculated. Data were analyzed with SASGxE and RGxE programs using SAS and R programming languages, respectively. There were strong effects of environment(E) as well as genotype(G) xE interaction for all traits. Genotypes ‘Regal F1’, ‘Calypso F1’, ‘Carolina F1’, ‘Gy 3’, ‘Gy 14’ and ‘Fremont F1’ had high marketable yield and medium to high stability for all traits. There was an advantage of hybrids over inbreds for trait performance. Hybrids fell into a single cluster with large prediction intervals. Based on the stability statistics and divisive clusters, it appears possible to breed stable cucumber genotypes with high yield. The genotype with highest performance for marketable yield, greatest stability for yield, lowest 1-R2 ratio value (diverse and representative) were ‘Marbel F1’ and Gy 14.

Cucumber (Cucumis sativus L.) is one of the most popular vegetable crops grown in U.S. home and urban gardens. The objectives of this study were to identify cultivars and planting densities for high yield of container-grown cucumbers. Additional objectives were to determine the value of field trials for predicting cucumber performance in containers and to evaluate different plant types (dwarf-determinate vs. tall-indeterminate, gynoecious vs. monoecious, pickling vs. slicing) for container use and disease severity across cultivars. Fourteen cultivars and breeding lines were tested at three planting densities in two seasons for yield, quality, and disease resistance in field and patio trials. Significant differences were detected for seasons, cultivars, and densities. Yields were highest in the spring season compared with the summer season, and the best performance was obtained using three plants per 12 L container. There was a high correlation between patio and field trials, allowing extension specialists to recommend cucumber cultivars with high yield, high quality, and disease resistance based on field trial data. Home gardeners who want space-saving, high-yielding cucumbers with tender skin should consider a dwarf-determinate, pickling type that is monoecious. With monoecious type, no pollenizer is needed, and the harvest will be spread over more weeks than would be for gynoecious types.

Host resistances in PI 197088 cucumber to downy and powdery mildew pathogens are conferred by 11 (3 with major effect) and 4 (1 major effect) QTL, respectively, and three of which are co-localized. The downy mildew (DM) and powdery mildew (PM) are the two most important foliar diseases of cucurbit crops worldwide. The cucumber accession PI 197088 exhibits high-level resistances to both pathogens. Here, we reported QTL mapping results for DM and PM resistances with 148 recombinant inbred lines from a cross between PI 197088 and the susceptible line 'Coolgreen'. Phenotypic data on responses to natural DM and PM infection were collected in multi-year and multi-location replicated field trials. A high-density genetic map with 2780 single nucleotide polymorphisms (SNPs) from genotyping-by-sequencing and 55 microsatellite markers was developed, which revealed genomic regions with segregation distortion and mis-assemblies in the '9930' cucumber draft genome. QTL analysis identified 11 and 4 QTL for DM and PM resistances accounting for more than 73.5 and 63.0% total phenotypic variance, respectively. Among the 11 DM resistance QTL, dm5.1, dm5.2, and dm5.3 were major-effect contributing QTL, whereas dm1.1, dm2.1, and dm6.2 conferred susceptibility. Of the 4 QTL for PM resistance, pm5.1 was the major-effect QTL explaining 32.4% phenotypic variance and the minor-effect QTL pm6.1 contributed to disease susceptibility. Three PM QTL, pm2.1, pm5.1, and pm6.1, were co-localized with DM QTL dm2.1, dm5.2, and dm6.1, respectively, which was consistent with the observed linkage of PM and DM resistances in PI 197088. The genetic architecture of DM resistance in PI 197088 and another resistant line WI7120 (PI 330628) was compared, and the potential of using PI 197088 in cucumber breeding for downy and powdery mildew resistances is discussed.

Gummy stem blight (GSB), caused by three related species of Stagonosporopsis [Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), Stagonosporopsis citrulli, and Stagonosporopsis caricae], is a major disease of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] in most production areas of the United States. We studied the inheritance of resistance to GSB using three PI accessions of watermelon. Four families of six progenies (Pr, Ps, F1, F2, BC1Pr, and BC1Ps) were developed from four crosses of resistant PI accessions by susceptible cultivars. Each family was tested in 2002 and 2003 in North Carolina under field and greenhouse conditions for resistance to GSB. Artificial inoculation was used to induce uniform and strong epidemics. The effect of the Mendelian gene for resistance, db, was tested. Partial failure of the data to fit the single-gene inheritance suggested that resistance to GSB of PI 482283 and PI 526233 may be under the control of a more complex genetic system.

Firmness of skin is an important quality of processing cucumbers, which is a feature of the palisade epidermis in these types compared to flat epidermis in fresh cucumbers. This study was conducted to map the Pe (palisade epidermis) and analyse the candidate gene. Populations derived from the cross of two inbred lines, NCG122 with fruit flat epidermis and NCG121 with fruit palisade epidermis, were used to identify the inheritance of palisade epidermis and to map the gene involved in its development. The results showed that the palisade epidermis trait is controlled by a single gene, Pe, that is dominant over flat epidermis. Seven simple sequence repeat (SSR) and five insertion deletion (Indel) markers were identified to be linked to the Pe gene. It was mapped to cucumber chromosome 5 (Chr.5) between SSR14611 and Indelpe12 with genetic distances of 0.3 cM and 0.2 cM, respectively. The physical distance of the genomic region harbouring the gene was 227.5 kb with 26 predicted candidate genes. The accuracy of marker-assisted selection using the molecular markers, Indelpe12 and SSR14611, was 68% and 88%, respectively.

Genotype x environmental interaction (GxE) can lead to differences in performance of genotypes over environments. GxE analysis can be used to analyze the stability of genotypes and the value of test locations. We developed an Rlanguage program (RGxE) that computes univariate stability statistics, descriptive statistics, pooled ANOVA, genotype F ratio across location and environment, cluster analysis for location, and location correlation with average location performance. Univariate stability statistics calculated are regression slope (bi), deviation from regression (S2d), Shukla’s variance (σi2), S square Wricke’s ecovalence (Wi), and Kang’s yield stability (YSi). RGxE is free and intended for use by scientists studying performance of polygenic or quantitative traits over multiple environments. In the present paper we provide the RGxE program and its components along with an example input data and outputs. Additionally, the RGxE program along with associated files is also available on GitHub at https://github.com/mahendra1/RGxE, http://cucurbitbreeding.com/todd-wehner/publications/software-sas-r-project/ and http://cuke.hort.ncsu.edu/cucurbit/wehner/software.html.

Summary Years of selection for desirable fruit quality traits in dessert watermelon (Citrullus lanatus) has resulted in a narrow genetic base in modern cultivars. Development of novel genomic and genetic resources offers great potential to expand genetic diversity and improve important traits in watermelon. Here, we report a high‐quality genome sequence of watermelon cultivar ‘Charleston Gray’, a principal American dessert watermelon, to complement the existing reference genome from ‘97103’, an East Asian cultivar. Comparative analyses between genomes of ‘Charleston Gray’ and ‘97103’ revealed genomic variants that may underlie phenotypic differences between the two cultivars. We then genotyped 1365 watermelon plant introduction (PI) lines maintained at the U.S. National Plant Germplasm System using genotyping‐by‐sequencing (GBS). These PI lines were collected throughout the world and belong to three Citrullus species, C. lanatus, C. mucosospermus and C. amarus. Approximately 25 000 high‐quality single nucleotide polymorphisms (SNPs) were derived from the GBS data using the ‘Charleston Gray’ genome as the reference. Population genomic analyses using these SNPs discovered a close relationship between C. lanatus and C. mucosospermus and identified four major groups in these two species correlated to their geographic locations. Citrullus amarus was found to have a distinct genetic makeup compared to C. lanatus and C. mucosospermus. The SNPs also enabled identification of genomic regions associated with important fruit quality and disease resistance traits through genome‐wide association studies. The high‐quality ‘Charleston Gray’ genome and the genotyping data of this large collection of watermelon accessions provide valuable resources for facilitating watermelon research, breeding and improvement.

Downy mildew, caused by the oomycete pathogen Pseudoperonospora cubensis (Berkeley & Curtis) Rostov, is a major foliar disease of cucumber. Ten years after the reemergence of P. cubensis, downy mildew continues to be a major threat to cucumber production in the United States. Cucumber accessions with high levels of resistance have been identified. Development of cultivars with high levels of resistance remains an important objective of cucumber breeding programs. We tested a set of cucumber cultigens, including highly resistant PI accessions and susceptible control lines, to observe the effect of plant age on resistance. Cultigens responded differently to disease across plant developmental stages. In general, older plants had more disease symptoms, even those classified as resistant, such as PI 197088. However, PI 330628 and PI 605996 held their resistance even at late developmental stages. It is possible that these lines were resistant at late stages due to other factors, such as their rapid, indeterminate growth, that allows them to outgrow the disease. However, although PI 197088 appears to have a rapid, indeterminate growth habit, it did not have more resistance at later stages of plant maturity. Regardless of the mechanism involved, plant breeders should use the genetic resistance in PI 330628 and PI 605996 over PI 197088.