Rose (Rosa hybrida) is one of the most economically important ornamentals worldwide. Powdery mildew (Podosphaera pannosa) is a major disease in cut and potted roses. In dicots such as arabidopsis (Arabidopsis thaliana), pea (Pisum sativum), and tomato (Solanum lycopersicum), loss-of-function mutations in mildew resistance locus o (Mlo) genes confer high levels of broad-spectrum resistance to powdery mildew. Here, we present spatiotemporal expression patterns of four Mlo genes from R. hybrida based on real-time fluorescence quantitative polymerase chain reaction (qPCR). Phylogenetically closely related R. hybrida mildew resistance locus o (RhMLO) genes showed similar or overlapping tissue specificity and analogous responsiveness to external stimuli. RhMLO1 and RhMLO2 transcriptional levels were upregulated more than 2-fold by external stimuli, especially by inoculation with powdery mildew fungus P. pannosa at early time points. This phenomenon was not found for RhMLO3 or RhMLO4. The results indicated that RhMLO1 and RhMLO2 might play important roles in rose–powdery mildew pathogen interactions. Our findings may provide useful information for the study of mechanisms of powdery mildew susceptibility in rose.
Xianqin Qiu, Hongying Jian, Qigang Wang, Kaixue Tang, and Manzhu Bao
Xianqin Qiu, Hao Zhang, Hongying Jian, Qigang Wang, Ningning Zhou, Huijun Yan, Ting Zhang, and Kaixue Tang
Roses are one of the economically most important groups of ornamental plants. The internal transcribed spacers (ITS) of the nuclear ribosomal DNA and the chloroplast gene matK were used to investigate the genetic diversity and genetic relationships among Rosa germplasm including 39 wild species, 21 old garden roses, and 29 modern cultivars. Three dendrograms based on ITS and matK clustering data indicated that 1) 39 wild genotypes were consistent with their classification into botanical sections with only a few exceptions; 2) most of the wild genotypes were separated from rose cultivars. However, three sections, Synstylae, Chinenses, and Rosa, that contributed to the modern roses generally gathered together with almost all old garden and modern roses on the molecular level; and 3) the relationships between cultivated roses as inferred by ITS and matK sequences do not correlate with horticultural groups. Results demonstrated that both sequence techniques can contribute to clarifying the genetic relationships of rose accessions and germplasm conservation to enhance the ornamental and economic value of rose.
He Li, Cheng-Jiang Ruan, Li Wang, Jian Ding, and Xing-Jun Tian
Sea buckthorn (Hippophae rhamnoides) is an ecologically and economically valuable species that has been widely cultivated as a new berry crop rich in nutritional and medicinal compounds. RNA Sequencing (RNA-Seq) simple sequence repeat (SSR) markers were developed to evaluate the genetic relationships among 91 plants of 31 cultivars from two subspecies, mongolica and sinensis, as well as intraspecific hybrids between them. A total of 7540 RNA-Seq SSRs were identified as potential molecular markers, in which AG/CT (27.57%) was the most abundant unit type. AT/AT (9.93%), and AAG/CTT (11.95%) are the other main repeat motifs. A total of 110 primer pairs were randomly selected for validation of amplification. Seventeen SSR loci, located in genes encoding metabolic processes and cellulose synthases, were identified to be polymorphic among different sea buckthorn cultivars. These SSR loci generated 48 alleles, ranging from 2 to 5 per locus. Cluster analysis based on the proportion of shared alleles and unweighted pair group method with arithmetic average (UPGMA) algorithm divided all the genotypes into two main groups, with all of the ssp. sinensis cultivars (native to China) and hybrids in one group and ssp. mongolica cultivars (introduced from Russia) in the other group, which was in good agreement with their taxonomic classification. The RNA-Seq SSRs developed in this study have a potential use in the conservation of sea buckthorn germplasm and marker-assisted breeding (MAB).
Yansheng Li, Ming Du, Qiuying Zhang, Guanghua Wang, Jian Jin, Stephen Herbert, and Xiaobing Liu
Planting date influences grain soybean yield and quality, but no information is available regarding the responses of seed chemical compositions to delayed planting date in vegetable soybean [Glycine max (L.) Merr.]. Three vegetable soybean cultivars, CAS No.1, Tai 292, and 121, were planted on 3 May, 15 May, 27 May, and 8 June in the field during the 2010 and 2011 growing seasons. The experiment was a randomized complete block design with three replications on a typical Mollisol (black soil). We found that late planting reduced fresh pod yield in all cultivars and years. The reduction in fresh pod yield to delayed planting was significantly correlated with the reduction in the number of two-seed pods per plant. Cultivars with strong capacity in retaining more two-seed pods may possess an advantage if planting is delayed. Planting after 15 May increased seed protein content by 4.1% to 7.5% and reduced oil content by 2.4% to 26.3% for different cultivars. The contents of free amino acid, sum of fructose and glucose, raffinose, and stachyose in seed were also increased by late planting. By contrast, late planting reduced the seed sucrose content ranging from 7.6% to 45.5% for the different cultivars. Planting on 3 May usually produced the greatest fresh pod yield and highest seed sucrose content. These results demonstrated that late planting after early May might have a negative impact on the eating quality of vegetable soybean.
Xiuli Lv, Yuan Guan, Jian Wang, Yanwei Zhou, Qunlu Liu, and Zequn Yu
To reveal the genetic diversity and genetic relationships of China’s Bergenia germplasm, 28 Bergenia accessions from different regions in China were analyzed by 24 intersimple sequence repeat (ISSR) markers. The results showed that 318 sites were amplified in all germplasm, including 307 polymorphic sites, and the percentage of polymorphic sites was 96.54%. Cluster analysis showed that the 28 accessions were divided into three categories, with a similarity coefficient of 0.5475. Bergenia purpurascens was clustered into one category; B. scopulosa was clustered into one category; and B. tianquaninsis, B. emeiensis, B. stracheyi, and B. crassifolia were clustered into one category. The results of the cluster analysis indicated that the 28 accessions were not completely classified by origin. Using the ISSR marker technique to analyze the phylogenetic relationship of Bergenia germplasm is helpful for identifying valuable resources and providing a theoretical basis for the selection of breeding parents.
Jia-yi Wang, Jian-shuang Shen, Mengmeng Gu, Jia Wang, Tang-ren Cheng, Hui-tang Pan, and Qi-xiang Zhang
Yellow-leafed cultivars usually do not grow as vigorous as their green-leafed counterparts, which affect their use in landscapes. To breed Forsythia cultivars with both yellow leaves and vigorous growth, crosses between F. ‘Courtaneur’ (♀) and Forsythia koreana ‘Suwon Gold’ (♂) were conducted, and 52 F1 hybrid progenies with different leaf colors (green, chartreuse, and yellow) were obtained. The progenies were categorized into three groups [Yellow Group (YG), Chartreuse Group (CG), and Green Group (GG)] based on leaf colors. The growth index (GI) and the number of branches and leaves of YG progenies were significantly lower at 2%, 35%, and 34% of GG progenies. As the leaves changed from green to chartreuse and to yellow, chlorophyll content, leaf thickness, and chlorophyll fluorescence parameters decreased and the chloroplast structures were disintegrated gradually, which influenced the leaf photosynthetic activity and led to weak growth. Compared with yellow-leafed progenies, the leaf chlorophyll content and leaf thickness of chartreuse-leafed progenies were significantly higher at 71% and 9%. The chloroplast structure of stroma lamella of chartreuse-leafed progenies was relatively intact. Carboxylation efficiency (CE), photochemical efficiency of PS II (F v/F m), and the number of branches and leaves of GG progenies were significantly higher than YG progenies; however, they have no significant difference with CG progenies. The results were promising for breeding new forsythia cultivars from moderate growth and chartreuse leaves.
Yu-Xiong Zhong, Jian-Ye Chen, Hai-Ling Feng, Jian-Fei Kuang, Ruo Xiao, Min Ou, Hui Xie, Wang-Jin Lu, Yue-Ming Jiang, and He-Tong Lin
Fresh fruit of longan (Dimocarpus longan Lour.) are susceptible to pericarp browning and aril breakdown. Aril breakdown in longan fruit is regarded as one of the most important factors reducing quality and shortening storage life of the fruit. To better understand the molecular mechanism of aril breakdown, the expression patterns of three expansin (EXP) and three xyloglucan endotransglucosylase (XET) genes in relation to the aril breakdown of longan fruit stored at room temperature (25 °C) or low temperature (4 °C) were investigated. The results showed that aril breakdown index increased progressively during storage at 25 and at 4 °C. Northern blotting analysis revealed that the accumulations of three EXP and three XET genes exhibited differential characteristics with the occurrence of aril breakdown. During storage at 25 °C, the accumulations of Dl-XET3 increased after 1 day, suggesting that Dl-XET3 correlated well with the early aril breakdown, while Dl-EXP3 together with Dl-XET1 and Dl-XET2 was involved in later aril breakdown. However, expression of Dl-XET1 and Dl-XET2 could be mainly involved in aril breakdown of longan fruit stored at 4 °C. In addition, Dl-EXP2, whose accumulation increased sharply when longan fruit were transferred from low temperature to room temperature within 12 hours, was related to the aril breakdown in this storage period. These data indicated that Dl-EXPs and Dl-XETs were closely related to aril breakdown in longan fruit.
Zhi Quan, Bin Huang, Caiyan Lu, Yi Shi, Yanhong Cao, Yongzhuang Wang, Chuanrui He, Guangyu Chi, Jian Ma, and Xin Chen
Much nitrogen (N) is lost in high-input protected cropping systems mainly via leaching of not only nitrate-N but also extractable organic N (EON), but the role of EON in this process is poorly appreciated. A consecutive 3-year plot experiment was conducted to investigate the impact of co-application of manures with chemical N fertilizer on N accumulation and loss in a greenhouse soil rotationally planted with cucumber or tomato and lettuce. Application of manures significantly enhanced the average contents and stocks of NO3 −-N, EON, and total N (TN) in 0- to 60-cm soil layer, although EON accumulated within growing season, while NO3 −-N accumulated with fluctuation, and TN accumulated gradually throughout the 3-year experiment. With application rate at 120 or 180 t dry manures per hectare per 3 years, the corresponding apparent N surplus was 2710 or 3924 kg⋅ha−1 per 3 years. Due to little increase of biomass N uptakes during vegetable seasons, the accumulated N in soil profile would be a potential loss source, largely via leaching of both nitrate and EON. Application of manures slowed soil acidification but intensified secondary salinization of the greenhouse soil. Considering the manures-induced high soil N accumulation and loss, well-balanced evaluation of the role of manures in high-input agricultural ecosystems is needed.
Young-Hwan Shin, Rui Yang, Yun-Long Shi, Xu-Min Li, Qiu-Yue Fu, Jian-Liang Lu, Jian-Hui Ye, Kai-Rong Wang, Shi-Cheng Ma, Xin-Qiang Zheng, and Yue-Rong Liang
Albino tea plants are mutants that grow albino young leaves owing to lack of chlorophylls under certain environmental conditions. There are two types of albino tea plants grown in production, i.e., light- and temperature-sensitive albino tea cultivars. The former grows albino leaves in yellow color under intensive sunlight conditions and the later grows albino leaves with white mesophyll and greenish vein as the environmental temperature is below 20 °C. Both albino teas attract great attention because of their high levels of amino acids and the “umami” taste. There have been many studies focusing on the temperature-sensitive albino tea plants, whereas little attention has been given to the light-sensitive albino tea cultivars. The characteristics of the albino tea cultivars and the mechanism underlying them were reviewed in the present article based on the published literatures, including chemical compositions, morphological characteristics, and molecular genetic mechanism.