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Peng Shi

Seedling selections in pomegranates began in 1986. `Giant Green Sweet' (GGS) was used as the female parent. GGS was characterized by fruit size from 340 to 500 g, a green color with slight blush, thin fruit coat, hexalobate calyx, and semi-open ovary with 8 to 12 loculi. The seeds are red, abundant, juicy, and sweet. The seeds contain 15% to 16% soluble solids. The male, pollinating cultivars in the same garden were `Giant Red Sweet', `Giant Horse Teeth', `White Sweet', `Red Sour', `Bing Tang Zi', and `Qing Gang Liu'. Seeds were harvested from fruit that were open-pollinated and weighed 500 g. Seeds were germinated and planted at the end of March. One-year-old seedlings grew to 30 to 50 cm. Two-year-old seedlings grew to 1 to 1.5 m tall with many branches. Seedlings passed the juvenile period after 3 years of growth. Some seedlings blossomed, and a few blossoms developed into fruit. Seedlings were adult by the fourth year, and all of them blossomed and developed fruit. This is a shorter interval to maturation than the parent cultivars. Fruits were located from the lower middle of the tree crown to the top. Adult seedlings produced fruit of ≈400 g with a few seedlings producing fruits of 500 to 600 g. There were 400 to 500 seeds per fruit averaging 40 g per 100 seeds. Seeds from the offspring were bright red and larger than those of the female parent. Fruit flavor was similar to the female parent. Offspring were more cold hardy than the parent cultivars. There were no signs of cold injury in hybrid seedlings to –19°C. This study indicates that seedling selection in pomegranates has a high potential to create higher yield and quality pomegranates. Continuing experiments will reselect the best offspring to develop higher quality cultivars.

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Nan Wang, Shi Liu, Peng Gao, Feishi Luan and Angela R. Davis

Citrullus lanatus (watermelon) is an excellent daily source of dietary lycopene and β-carotene. To investigate the transcriptional regulation of carotenoid biosynthesis genes relative to lycopene and β-carotene accumulation in watermelon fruit, six watermelon accessions with different flesh colors were examined in this study: white-fleshed PI 459074, pale-yellow-fleshed ‘Cream of Saskatchewan’, light-pink-fleshed PI 482255, orange-yellow-fleshed ‘WM-Clr-1’, and red-fleshed ‘LSW177’ and ‘MSW28’. The expression patterns of eight genes (PSY1, PSY2, PDS, ZDS, CRTISO, LCYB, NCED1, and NCED7) involved in lycopene and β-carotene biosynthesis and biodegradation were analyzed. The results confirmed the accumulation of large quantities of lycopene in red-fleshed ‘LSW177’ and ‘MSW28’, reflecting the elevated expression of PSY1 and the low transcriptional expression of NCED1. The relative expression levels of NCED1 likely play an important role in the color development of the light-pink-fleshed PI 482255, whereas the reduced transcriptional expression of PSY1 and the increased expression of NCED1 appear to be the main factors contributing to the formation of white flesh in the fruit of PI 459074. Low transcriptional expression of PSY1 results in the pale-yellow flesh of the ‘Cream of Saskatchewan’ fruit.

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Peng Shi, Yong Wang, Dapeng Zhang, Yin Min Htwe and Leonard Osayande Ihase

Fruit oil content (FOC) is one of the most important commercial traits in oil palm; however, extensive study on related traits is still limited. The present study was conducted to analyze the relationship between FOC and fruit-related traits, as well as to predict the oil palm germplasm for potential improvement. In this study, a total of 11 traits, including fruit bunch number (FBN), average fruit weight (AFW), mesocarp-to-fruit ratio (M/F), kernel-to-fruit ratio (K/F), shell-to-fruit ratio (S/F), average fruit length (AFL), average fruit width (AFWD), average shell thickness (AST), mesocarp oil content (MOC), kernel oil content (KOC), and FOC were analyzed in 39 germplasms collected from seven different countries in Asia and Africa. Different statistical analyses were conducted to evaluate the relationship between FOC and fruit-related traits. Correlation analysis showed that FOC was positively and significantly correlated with M/F, MOC, and KOC, whereas negatively and significantly correlated with S/F and AST. Likewise, path analysis indicated that M/F and MOC have high positive direct effect on FOC, whereas S/F and AST have high negative direct and indirect effects on FOC. Furthermore, regression analysis showed significant correlation between predicted and observed FOC. In conclusion, FOC was mainly determined by M/F, MOC, S/F, and AST, and the FOC prediction in this study was reliable for germplasm evaluation. In addition, G39 (Tenera) and G2 (Parthenocarpy) have the highest FOC with 58.62% and 57.68%, respectively, indicating that they might be potential candidates for FOC improvement. These results could be applicable to oil palm breeding programs.

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Taifeng Zhang, Jiajun Liu, Shi Liu, Zhuo Ding, Feishi Luan and Peng Gao

Short internode length (SIL) is one of the most commercially and important traits in melon varieties (Cucumis melo L.). SIL can result in a compact vining type that promotes concentrated fruit in high-density crops, leading to greater use of light resources for photosynthesis and greater yield per unit area. In our study, two parental melon lines ‘M1-32’ (P1, standard vine) and ‘X090’ (P2, short internodes), and their F1, F2, BC1P1, and BC1P2 progenies were evaluated after being grown in plastic greenhouse conditions in 2017 and 2018. Main stem length (MSL) and internode length (IL) of six melon generations indicated that a single recessive gene (MD7) controlled dwarfism in the ‘X090’ melon line. Whole-genome analysis revealed a genomic region harboring the candidate dwarfism gene on chromosome 7. Six polymorphic cleaved amplified polymorphic sequence (CAPS) markers from chromosome 7 were used to construct a genetic linkage that spanned 30.28 cM. The melon dwarfing locus MD7 responsible for SIL was positioned between markers M7-4 and M7-5, with 3.16 cM of flanking distance. The CAPS markers M7-4 and M7-5 developed have the potential to accelerate the development of dwarf melon varieties, especially in situations when dwarf genotypes are an important breeding goal using marker-assisted selection.