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Fenfen Yan, Zhiguo Liu, Mengjun Liu, Xingjuan Zheng, Zhi Luo, and Jiurui Wang

The establishment of large hybrid populations is the key basis to breeding new cultivars and genetic research, such as molecular mapping. However, it is extremely difficult to generate hybrid progeny using conventional artificial hybridization in Chinese jujube (Chinese date) (Ziziphus jujuba Mill.) because of its low fruit set of ≈0.01%. The objective of this study was to create large hybrid populations in Chinese jujube using bona fide male-sterile germplasm as the female parent. Two male-sterile varieties that lacked viable pollen (JMS1 and JMS2) previously discovered by our research group and three male-fertile genotypes (‘Xing16’, ‘Jiao5’, and ‘Wuhefeng’) were used as female and male parents, respectively. Bee-aided controlled hybridization of five combinations was conducted from 2014 to 2016. The results indicated that both JMS1 and JMS2 were stable male-sterile germplasm across the years examined. JMS2 showed more effective compatibility with the male parents tested than JMS1. A total of 7681 fruits were obtained from the five cross combinations, and 3120 of them contained seeds. The mean rate of the fruit with seed varied from 32.62% to 64.21%, and the highest rate (73.38%) was obtained from the cross of JMS2 × ‘Xing16’ in 2016. A total of 831 seedlings were obtained and consisted of 602 from JMS2 × ‘Xing16’, 221 from JMS2 × ‘Jiao5’, two from JMS1 × ‘Xing16’, five from JMS1 × ‘Wuhefeng’, and one from JMS2 × ‘Wuhefeng’. The 118 randomly selected progeny seedlings, including 96 from JMS2 × ‘Xing16’ and 22 from JMS2 × ‘Jiao5’, respectively, were identified to be authentic hybrids using SSR markers. Thus, JMS2 is a promising male-sterile female parent that possesses a good cross-compatibility and is free from the need for emasculation, embryo rescue, and hybrid identification. The largest hybrid population of 602 progeny was obtained in Chinese jujube using controlled hybridization. This study demonstrated the feasibility of a highly efficient crossbreeding approach using male-sterile germplasm as the female parent in Chinese jujube.

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Bo-Ling Liu, Zhi-Bin Fan, Ze-Qun Liu, Xun-Hong Qiu, and Yan-Hong Jiang

Salvia miltiorrhiza (commonly known in China as Danshen) is widely used in traditional Chinese medicine, and it is applied in the treatment of many diseases, particularly cardiovascular disease. Commercial propagation of Danshen is carried out either through seed germination or in vitro regeneration (micropropagation). However, it is not clear if the different propagation methods affect the chemical properties of the derived plants. In the present study, we first established a highly efficient tissue culture system for Danshen propagation. The addition of 1.0 mg·L−1 6-benzyladenine (BA) and 0.1 mg·L−1 α-naphthalene acetic acid (NAA) to Murashige and Skoog (MS) medium was optimal for inducing adventitious shoots; the highest rate of rooting was recorded on MS medium with 0.2 mg·L−1 NAA, on which the survival rate of transplanted plantlets was 95%. Next, we assessed antioxidant properties in the different tissues of plants of the same age, derived from micropropagation or seed germination, and measured tanshinone, total phenol, and total flavonoid contents. Our results showed that tissues of micropropagated plantlets had higher antioxidant activities than tissues of seed-derived plantlets; the micropropagated plantlets also had higher tanshinone contents in their roots. Thus, a rapid and efficient micropropagation system was established for Danshen, and it can be used for cultivating this plant to obtain therapeutic compounds.

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Li Huang, Wan-zhi Ye, Ting-ting Liu, and Jia-shu Cao

Cytological features of ‘Aijiaohuang’ chinese cabbage-pak-choi (Brassica campestris ssp. chinensis) Bcajh97-01A/B genic male-sterile AB line were examined to determine phenotypic reasons for male sterility. The sterile line Bcajh97-01A was found to undergo aberrant cytokinesis during male meiosis. Transcriptional profiling of the flower buds of both fertile and sterile plants was performed at the periods preceding meiosis, at the tetrad to uninucleate pollen period, and at the binucleate to mature pollen period. Transcript-derived fragments (TDFs) from corresponding genes that were expressed in flower buds at these three different stages could be divided into nine classes. We sequenced a total of 14 new TDFs that were differentially displayed at particular pollen developmental stages, including eight genes with unknown or hypothetical functions and six genes showing significant homology with known genes. This characterization of the Bcajh97-01A genic male-sterile line allowed the identification of candidate genes underlying genic male sterility.

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Xiao-min Liu, Xin-zhi Zhang, Yi-min Shi, and Dong-qin Tang

Genetic diversity of Narcissus was systematically studied on both morphological and molecular levels. Twenty-four characteristics of nine narcissi were observed and their differences evaluated by clustering method. The results showed that nine narcissi can be divided into two subclusters: one comprised by Narcissus pseudonarcissus, the other by Chinese Narcissus. The morphological diversity among five cultivars of N. pseudonarcissus is higher than that among four ecotypes of Chinese Narcissus (Narcissus tazetta var. chinensis). There are seven morphological characteristics in N. pseudonarcissus presenting obvious variations with coefficients from 33.33% to 91.67%. Only five morphological characteristics in Chinese Narcissus present certain variations with coefficients from 37.04% to 51.79%. On DNA level, two clusters are distantly related too. Based on the random amplified polymorphic DNA (RAPD) markers, 13 out of 40 random primers yielded scorable polymorphisms between samples. Wide variations in banding profiles between cultivars or between ecotypes were observed with nearly every primer tested. Among 95 band positions that were scored for all the 9 narcissi, 81 are polymorphic (85.26%). Cluster analysis of the calculated similarity matrix revealed that the genetic diversity between these individuals within the same section is low. However, the genetic diversity between two sections is obviously higher. Taken together, the methods combined morphological characteristics and RAPD technique allow a deep evaluation of the variation of Narcissus on both section level and cultivar/ecotype level.

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Yi Kai, Yang Bin, Zhang Min, Gao Ainong, Zhang Jinger, Liu Zhi, Sha Shoufeng, and Xie Chongxin

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Cai-Hong Jia, Ju-Hua Liu, Zhi-Qiang Jin, Qiu-Ju Deng, Jian-Bin Zhang, and Bi-Yu Xu

A full-length cDNA isolated from banana (Musa acuminata L. AAA group) fruit was named MaMDH, containing an open reading frame encoding 332 amino acids that represents the gene for cytoplasmic malic dehydrogenase (MDH). Sequence analysis showed that MaMDH shares high similarity with MDHs from castor bean (XP_002533463), tobacco (CAC12826), peach (AAL11502), and chickpeas (CAC10208). Real-time quantitative polymerase chain reaction (PCR) analysis of MaMDH spatial expression showed that it was expressed in all organs examined: roots, rhizomes, leaves, flowers, and fruits. The expression was the highest in flowers followed by the fruits and roots, whereas the rhizomes and leaves displayed the lowest expression levels. Real-time quantitative PCR revealed that MaMDH exhibited differential expression patterns in post-harvest banana fruits correlating with ethylene biosynthesis. In naturally ripened banana fruits, MaMDH expression was in accordance with ethylene biosynthesis. In accordance, for banana fruits treated with the ethylene analog 1-methylclopropene (1-MCP), MaMDH expression levels were inhibited and remained constant. After treatment with ethylene, MaMDH expression in banana fruits significantly increased with ethylene biosynthesis and peaked 3 days after harvest, which was 11 days earlier than that in naturally ripened banana fruits. These results suggest that MaMDH expression is induced by ethylene to regulate post-harvest banana fruits ripening.

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Wei Hu, Ju-Hua Liu, Xiao-Ying Yang, Jian-Bin Zhang, Cai-Hong Jia, Mei-Ying Li, Bi-Yu Xu, and Zhi-Qiang Jin

The banana, a typical climacteric fruit, undergoes a postharvest ripening process followed by a burst in ethylene production that signals the beginning of the climacteric period. Postharvest ripening plays an important role in improving the quality of the fruit as well as limiting its shelf life. To investigate the role of glutamate decarboxylase (GAD) in climacteric ethylene biosynthesis and fruit ripening in postharvest banana, a GAD gene was isolated from banana, designated MuGAD. Coincidently with climacteric ethylene production, MuGAD expression as well as the expression of the genes encoding the Musa 1-aminocyclopropane-1-carboxylate synthase (MaACS1) and Musa 1-aminocyclopropane-1-carboxylate oxidase (MaACO1) greatly increased during natural ripening and in ethylene-treated banana. Moreover, ethylene biosynthesis, ripening progress, and MuGAD, MaACS1, and MaACO1 expression were enhanced by exogenous ethylene application and inhibited by 1-methylcyclopropene (1-MCP). Taken together, our results suggested that MuGAD is involved in the fruit ripening process in postharvest banana.