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BACKGROUND: Garlic is the second largest allium crop after onion and is grown all over the world. The onion maggot (Delia antiqua M.) is a pest that seriously affects the yield and quality of garlic. Cultural controls and insecticides have several potential problems, including pesticide residue and development of resistance. Screening resistant varieties is an ideal alternative method. RESULTS: The resistance of 213 accessions of garlic clones against onion maggot was identified. The results showed that the pest index was between 5.56% and 91.11%, with classification into six groups by cluster analysis: HR (highly resistant), R (resistant), MR (moderately resistant), MS (moderately susceptible), S (susceptible) and HS (highly susceptible). Among these accessions, 9 and 30 were HR and R to onion maggot, respectively. Comparing the resistances of seven pairs of accessions between the original accessions and their progenies showed that single bulb clonal selection could be an effective way to improve allicin content, onion maggot resistance and most morphological traits. The relationship between allicin content and resistance was investigated, and a significant positive relationship was found. Accessions with a high content of allicin have great potential as resistant accessions. CONCLUSION: This study showed significant differences among garlic germplasm in their response to Delia antiqua M. Some accessions were highly resistant and tolerant. Utilization of these accessions will help minimize environmental pollution, preserve agro‐ecosystems and biodiversity, and make management processes more economical. Furthermore, these accessions could be used in breeding programs to develop new maggot‐resistant onion cultivars. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Garlic ( Allium sativum L.), an asexually propagated crop, is an important vegetable and medicinal plant. China is the biggest garlic producer in the world; however, the genetic background of garlic from China is not well understood. In this study, population structure and clustering analysis of garlic germplasm was performed using amplified fragment length polymorphism ( AFLP), simple sequence repeat ( SSR) and insertion-deletion (InDel) markers. Among 212 accessions of garlic, genetic diversity analysis identified 546 alleles amplified by AFLP, SSR and InDel primers, and 492 of these were polymorphic. All accessions were divided into five groups by structure analysis and neighbor-joining clustering. Most traits, including allicin content, were only slightly affected by population structure, which indicated that this germplasm can be used as populations for association mapping. The results provide a molecular basis for understanding the genetic diversity of the garlic germplasm preserved in China. [ABSTRACT FROM AUTHOR]

China has a long history in garlic cultivation and is the biggest country of garlic production in the world. 375 accessions of garlic from 23 provinces and areas in China has been collected and preserved in national germplasm repository for vegetatively propagated vegetables in Beijing since 2002. However, the genetic background and diversity of garlic from China has not been well characterized. In this study, 212 of 375 accessions of garlic were evaluated based on 29 morphological traits and allicin content. Cluster, principal compound, principal ordinates, Shannon diversity index and Pearson correlation analysis were used. The results showed that the garlic clones from China had a widely diversity among all traits. Principal component analysis showed the cumulative proportion of the first eight components explained 71.35 % of total morphological variation in all accessions. Germplasm cluster analysis whether based on 29 morphological traits or bulb yield-related traits could distinguish all germplasm. All accessions were divided into two groups with bolting and non-bolting respectively, or into five subgroups with different traits based on 29 morphological traits. Principal coordinate analysis based on eight bulb related traits divided all accessions into 6 groups. Yield among the accessions ranged from 1.60 to 16.78 t/ha, and three accessions yielded above 15 t/ha. Pearson analysis suggested bulb yield was significantly positively correlated with bulb weight (r = 0.99), bulb diameter (r = 0.73), bulb height (r = 0.53), clove number (r = 0.52), leaf width (r = 0.52). Allicin content ranged from 0.81 to 3.01 %. Pseudostem diameter was found to be significantly positively correlated with allicin content but with the low correlation coefficient (r = 0.23). The result will obviously be helpful for breeder and researchers to comprehensively understand the genetic background of the collection and more easily select the target accessions, especially those with high yield and allicin content. [ABSTRACT FROM AUTHOR]

Genetic diversity of 56 radish accessions, representing nearly all the typical types and origins of cultivated radish germplasms conserved in the National Mid-term Genebank for Vegetables of China, was assessed with amplified fragment length polymorphism (AFLP) and random amplified polymorphic DNA (RAPD) markers. A total of 72 and 128 polymorphic bands were generated by the 12 selected RAPD primers and eight AFLP primer combinations respectively. A moderate correlation with the value of r = 0.66 was observed between AFLP and RAPD markers. The total 200 polymorphic bands were integrated to assess the genetic diversity of 56 radish accessions. The Jaccard similarity coefficients between the accessions varied from 0.30 to 0.83 with the mean of 0.54. Cluster analysis classified the germplasms into three groups of var. hortensis Becker, var. sativus, and var. niger Kerner. The three-dimensions scatter plot of principle coordinate analysis (PCA) further divided var. hortensis Becker germplasms into two separate groups. The results indicated that the genetic diversity harbored among var. hortensis Becker germplasms was very abundant, which could be further exploited for radish genetic improvement. [ABSTRACT FROM AUTHOR]

Background: Cucumbers (Cucumis sativus) are known for their plasticity in sex expression. DNA methylation status determines gene activity but is susceptible to environmental condition changes. Thus, DNA methylation-based epigenetic regulation may at least partially account for the instability of cucumber sex expression. Do temperature and photoperiod that are the two most important environmental factors have equal effect on cucumber sex expression by similar epigenetic regulation mechanism? To answer this question, we did a two-factor experiment of temperature and photoperiod and generated methylome and transcriptome data from cucumber shoot apices. Results: The seasonal change in the femaleness of a cucumber core germplasm collection was investigated over five consecutive years. As a result, 71.3% of the 359 cucumber accessions significantly decreased their femaleness in early autumn when compared with spring. High temperature and long-day photoperiod treatments, which mimic early autumn conditions, are both unfavorable for female flower formation, and temperature is the predominant factor. High temperatures and long-day treatments both predominantly resulted in hypermethylation compared to demethylation, and temperature effect was decisive. The targeted cytosines shared in high-temperature and long-day photoperiod treatment showed the same change in DNA methylation level. Moreover, differentially expressed TEs (DETs) and the predicted epiregulation sites were clustered across chromosomes, and importantly, these sites were reproducible among different treatments. Essentially, the photoperiod treatment preferentially and significantly influenced flower development processes, while temperature treatment produced stronger responses from phytohormone-pathway-related genes. Cucumber AGAMOUS was likely epicontrolled exclusively by photoperiod while CAULIFLOWER A and CsACO3 were likely epicontrolled by both photoperiod and temperature. Conclusions: Seasonal change of sex expression is a germplasm-wide phenomenon in cucumbers. High temperature and long-day photoperiod might have the same effect on the methylome via the same mechanism of gene-TE interaction but resulted in different epicontrol sites that account for different mechanisms between temperature- and photoperiod-dependent sex expression changes. [ABSTRACT FROM AUTHOR]

This study was conducted to explore the genetic variation of allicin content among Chinese and Egyptian garlic germplasm, the role of genetic improvement in allicin content enhancement and the combined influence of genetic and environmental factors on allicin contents in Egyptian garlic germplasm grown in Egypt and China respectively. Ultra performance liquid chromatography (UPLC) method was used for quantification of allicin in garlic bulbs. As the result of cluster analysis based on allicin content, all garlic germplasm (104 accessions) were divided into four groups. The germplasms with the highest allicin content presented in group A, comprising only two germplasm (one from Egypt and the other from China). The far distance among accessions in the cluster tree revealed the diversity in the garlic germplasm, which can selectively be used in garlic breeding programs for quality improvement. Clones selected were found to be different from their parents and had higher allicin content, which proves that clone selection is an effective way for garlic genetic improvement. Statistical analysis showed that the effects of germplasm, geographical location and interaction between germplasm and geographical location on the allicin content (P<0.001) in Egyptian garlic germplasm were highly significant. All Egyptian garlic germplasm grown in China had lower allicin content than those grown in Egypt. Allicin content reduction in same germplasms between two locations was 16~63.7%. It is clarified that production area selection for garlic allicin processing industry is important. [ABSTRACT FROM AUTHOR]