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Ying Gao, Hao Liu and Dong Pei

Monoclonal anti-indole acetic acid antibodies were used to monitor the temporal and spatial pattern of auxin during staminate flower differentiation in walnut (Juglans regia) cultivars Liaoning 1 and Liaoning 3. The relationship between morphological characteristics and histological structure was established. Seven stages of differentiation were recognized based on the visibility and color of the squama, bract, perianth, and rachis as follows: Stage 1, several bract primordia were present in the squama with catkins protruding from the squama as the only externally visible portion of the floret (Stage 1); the bract became externally visible, and the floret, perianth, and stamen primordia formed basipetally (Stage 2); the length of catkins were elongated, only bracts visible and getting brown (Stage 3); the bracts were brown and wrapped tightly, cellular specialization occurred to form a central core containing reproductive cells and tapetal cells that differentiated (Stage 4); the perianth became visible externally, reproductive cells and tapetal cells separated from the exterior layers of the anther wall (Stage 5); the anther walls were reduced to two cell layers (epidermis and endothecium) as the anthers became visible and matured (Stage 6); and the anther turned black, dehisced, and released its pollen grains (Stage 7). The histological differentiation of the flowers was related to auxin. The auxin signal was strongest in the shoot apical meristem (SAM) during bract primordia differentiation; thus, the SAM may be a site of auxin production. When the floral organs began centralized differentiation, auxin was distributed mainly in the differentiating tissues. Our findings indicate that a high level of auxin may strongly affect morphogenesis. Additionally, the tapetal and reproductive cells that arise during cellular specialization may be important for auxin production. The distribution of auxin was centralized in germ pores at the pollen grain surface, indicating that a high level of auxin induces pollen germination.

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Ying Liu, Huawei Song, Juming Zhang and Michael D. Richardson

Bahiagrass (Paspalum notatum) is widely used for slope protection and water and soil conservation in southern China. The plants develop an extensive root system that plays a crucial role in the protection of both soil and water. However, little is currently known about the factors that influence early root growth in bahiagrass. Here, the effects of boron (B), calcium (Ca), iron (Fe), lanthanum (La), cerium (Ce), salicylic acid (SA), and melatonin (MLT) on root growth characteristics were examined. Bahiagrass seedlings were grown in 1/25 strength modified Hoagland nutrient solution supplemented with boric acid, calcium chloride, ferric ethylenediaminetetraacetic acid (Fe-EDTA), lanthanum chloride, cerium chloride, SA, or MLT. Root lengths, root surface areas, and the number of root tips were analyzed using a root scanning system after 2, 4, and 6 days of treatment. We found significant effects on root growth after some treatments. Thus, 0.270 or 0.360 mm B for 2 days enhanced root tip number, whereas 0.15 mm Fe for 6 days increased root surface area. Although 3 or 5 mm Ca caused an increase in root tip numbers, the root length was reduced. The addition of La to the nutrient solution significantly increased root length and surface area, and addition of Ce increased root surface area and root tip numbers. Root growth characteristics were optimal after 0.3 μm La for 6 days or 1.0 μm La for 4 days. For Ce treatment, optimal root characteristics were observed at 0.5 μm Ce for 6 days. Root tip numbers increased after 0.1 or 1.0 μm MLT for 6 days, whereas SA treatment reduced the root length, surface area, and root tip numbers. Overall, the analyses indicate that treatment with B, Fe, La, Ce, and MLT benefited root growth in bahiagrass seedlings.

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Ying Gao, Hao Liu, Ningguang Dong and Dong Pei

We used anti-indole-3-acetic acid (IAA) monoclonal antibodies to monitor the temporal and spatial pattern of IAA during pistillate flower bud differentiation in the walnut (Juglans regia) cultivar Liaoning 1. Based on morphological changes, the process of pistillate flower bud differentiation was divided into five stages. The flower induction stage, which includes the early phase, midphase, and late phase, persisted from 25 Apr. to the end of May. The pedicel differentiation stage began on 5 June. The bract primordium stage began on 25 June and persisted through mid-March of the next year. Both the perianth and pistil differentiation stages persisted for nearly 2 weeks. During the floral induction period, little IAA was present in the shoot apical meristem (SAM); hence, the SAM may not always be a site of IAA production. IAA was obviously concentrated in cells of the first several layers of the SAM during pedicel primordium formation. High levels of IAA were also noted in the phyllome, young leaf tips, and vascular bundle of leaves and gemmae. This direct evidence indicates that no close relationship exists between IAA and physiological differentiation; instead, IAA may strongly affect morphogenesis. These findings comprise a first step toward elucidating the walnut flowering mechanism.

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Jie Fu, Qiaoyan Xiang, Xianbao Zeng, Mei Yang, Ying Wang and Yanling Liu

To assess the genetic diversity among lotus (Nelumbo) accessions and evaluate the correlation between genetic variation and morphological classification, we sampled 138 accessions: two of N. lutea, 112 of N. nucifera, 17 of hybrids between N. nucifera and N. lutea, and seven Japanese cultivars. The 11 selected combinations of amplified fragment length polymorphism (AFLP) primers produced 138 polymorphic loci, and the percentage of polymorphism was 28.7%. The unweighted pair group method with arithmetic mean (UPGMA) dendrogram clustered all the accessions into two groups: Group I comprised N. lutea and its hybrids with N. nucifera; Group II included N. nucifera and its hybrids with N. lutea and Japanese cultivars. Population structure analysis identified four main clusters: N. lutea clustered mainly in C1, whereas N. nucifera clustered in C2, C3, and C4, which was consistent with the UPGMA and principal coordinate analysis results. The Japanese cultivars were related more closely to N. nucifera (genetic similarity coefficient = 0.74) than to N. lutea (0.46); hence, the Japanese cultivars can be classified as N. nucifera. Moreover, rhizome lotuses formed a separate subclade, whereas seed lotuses were interspersed among flower lotuses, which demonstrated that rhizome lotuses were distinct from flower and seed lotuses. Plant size, flower color, and other morphological criteria used commonly to classify lotuses were correlated with genetic variation to a certain extent but not sufficiently for accurate classification. It appears that it is necessary to use both DNA markers and morphological characteristics to classify lotus species and cultivars.

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Jun Tang, Kang-Di Hu, Lan-Ying Hu, Yan-Hong Li, Yong-Sheng Liu and Hua Zhang

Hydrogen sulfide (H2S) has been shown to be a gaseous molecule in the regulation of many processes in plants such as abiotic stress tolerance, root organogenesis, stomatal movement, and postharvest fruit senescence. We studied the role of H2S in the regulation of senescence and fungal decay in fresh-cut sweetpotato (Ipomoea batatas L., cv. Xushu 18) roots. H2S donor sodium hydrosulfide (NaHS) alleviated senescence in fresh-cut sweetpotato root tissue in a dose-dependent manner with the optimal concentration of 2.0 mmol·L−1 NaHS solution. At the optimal concentration of 2.0 mmol·L−1 NaHS, H2S fumigation maintained higher levels of reducing sugar in sweetpotato fresh-cut root. H2S treatment also significantly increased the activities of guaiacol peroxidase (POD) and decreased those of polyphenol oxidase (PPO) in sweetpotato during storage. Further investigation showed that H2S treatment maintained a lower level of lipoxygenase (LOX) activity compared with water control. Consistently, the accumulation of malondialdehyde (MDA) was reduced in H2S-treated groups. Three fungal pathogens, Rhizopus nigricans, Mucor rouxianus, and Geotrichum candidum, were isolated from sweetpotato tissue infected with black rot or soft rot. H2S fumigation at 1 to 2.5 mmol·L−1 NaHS resulted in effective inhibition of the three fungi when grown on medium. When the three fungi were inoculated on the surface of sweetpotato slices, H2S fumigation greatly reduced the percentage of fungal infection. In conclusion, these data suggest that H2S effectively alleviated the senescence and decay in sweetpotato slices and might be developed into a novel fungicide for reduction of black rot or soft rot in sweetpotato.

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Beibei Li, Jianfu Jiang, Xiucai Fan, Ying Zhang, Haisheng Sun, Guohai Zhang and Chonghuai Liu

In this study, we present the molecular characterization of 61 Chinese grape landraces and 33 foreign cultivars by using nine microsatellite DNA markers. A total of 115 distinct alleles were amplified, and the average allele number was 12.78. The average observed and expected heterozygosity values were 0.797 and 0.839, respectively. The effective allele numbers ranged from 5.011 to 8.575. The average polymorphism information content (PIC) was 0.816. Eighty distinct genotypes were detected, and new synonyms and homonyms were found. The clustering dendrogram indicated that 94 Vitis materials could be divided into five major groups, and the cluster analysis showed that part of the Chinese grape landraces had a close relationship with the foreign cultivars. Assessment of the true cultivar identity, and the identification of synonyms and homonyms will be a contribution to improve the grape germplasm management and protect breeders’ intellectual rights.

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Xiu Cai Fan, Hai Sheng Sun, Ying Zhang, Jian Fu Jiang, Min Li and Chong Huai Liu

In this study, simple sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) markers were used to analyze the genetic diversity of 48 wild Vitis davidii accessions. A total of 78 distinct alleles were amplified by 11 SSR primers, and the average allele number was 8.8. The average observed heterozygosity (Ho) and expected heterozygosity (He) values were 0.785 and 0.814, respectively. The effective allele numbers ranged from 3.92 to 9.61. The average polymorphism information content (PIC) was 0.798. Twelve of 169 SRAP primer combinations were selected for SRAP analysis. A total of 188 bands were produced, and the average was 15.7 bands per primer combination; the average percentage of polymorphic bands was 84.0%. The average PIC was 0.76. The results of the clustering analysis based on SSR markers showed that the 48 wild V. davidii accessions could be classified into five main clusters and had a genetic similarity coefficient level of 0.68. The dendrogram obtained from the SRAP data showed that 48 wild V. davidii accessions could be classified into five main clusters and had a genetic similarity coefficient of 0.72. SSR and SRAP markers differentiated all accessions studied including those with a similar pedigree. We speculated on the origin of Ciputao 0941♀, Ciputao 0940♂, and Fu’an-ci-01 using SSR markers and used both SSR and SRAP markers to resolve homonymy. The result will be valuable for further management and protection of V. davidii germplasm resources.

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Zhuping Fan, Yike Gao, Ling Guo, Ying Cao, Rong Liu and Qixiang Zhang

Bearded iris (Iris ×hybrida Hort.) is a large horticultural hybrid complex in the Iris genus, and the lack of understanding about its inheritance laws has seriously hindered the breeding process. From parental bearded iris ‘Indian Chief’ and ‘Sugar Blues’, four hybrid populations—including F1, F2, BC1P1, and BC1P2—were generated through hybridization. Fifteen key phenotypic traits, including plant height (PH), scape height (SH), length of fall (LF), width of fall (WF), length of standard (LS), width of standard (WS), and so on, were measured, and several genetic parameters (e.g., trait variation, heritability, trait correlation, distribution of flower color) were analyzed. The variation of phenotypic traits indicated that the F1 generation could produce larger flowers and a greater number of blooming stems than other generations, whereas backcrossing was beneficial at producing more flowers on one scape in the offspring of ‘Indian Chief’ and ‘Sugar Blues’. WF had the greatest broad-sense heritability (73.91%) among the 15 phenotypic traits, whereas the broad-sense heritability of SH was the lowest (2.06%). The correlation between a vegetative trait (PH) and a reproductive trait (WS) provided a path to early selection of germplasm. Furthermore, four important floral traits (LF, WF, LS, and WS) also correlated significantly to each other, thus simplifying the selection of larger flowers. Genes regulating fuchsia flower color were dominant over those for bluish purple flowers. Genetic effects of flower color in recurrent parents could be reinforced by backcrossing, thereby providing a potential way to modify flower color through hybridization.

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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.

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Panpan Meng, Ying Ge, Qianjin Cao, Jie Chang, Peng Pan, Chi Liu, Yijun Lu and Scott X. Chang

Lycoris species have appealing characteristics for potting plants, cut flowers, and landscaping decorations, including attractive foliage, which is very similar to that of cymbidium. Lycoris species have been extensively propagated and marketed in Asia. Understanding the response of Lycoris spp. to irradiance intensity will help the horticultural industry improve the production of potting plants of those species. We studied the responses of photosynthesis, growth, and biomass allocation of potted Lycoris spp. (L. chinensis, L. longituba, and L. sprengeri) bulbs grown under three levels of irradiance, i.e., 100%, 70%, and 30% full sunlight. We found that in terms of biomass production L. chinensis can be cultivated under all levels of irradiance studied from full to 30% sunlight. For L. longituba, high irradiance levels increased the rate of net photosynthesis. For both L. chinensis and L. longituba, the full sunlight treatment produced the most attractive plants characterized by shorter, wider, and darker green leaves, features that appeal to consumers. However, none of the growth traits of L. sprengeri were affected by the irradiance treatment over the entire experimental period. It can be concluded that potting plants of L. chinensis and L. longituba are best produced under full sunlight, whereas L. sprengeri can be produced under irradiance levels from 30% to full sunlight.