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Conventional crossbreeding remains an effective technique for chrysanthemum (Chrysanthemum ×morifolium Ramat.) breeding. However, there are always many problems when breeding chrysanthemum because of its complex genetic background, such as difficulty matching parents, selecting superior hybrid progenies, quantitatively describing certain target traits, and evaluating breeding results. A recent mathematical analysis method is an effective method for evaluating plant breeding progress. In this study, we used 505 multiflora chrysanthemum germplasm resources as test materials; we divided the flowering time into five groups using a grading analysis method, including extremely early group (genotypes that flowered when daylength was longer than 13.5 hours), early group (genotypes that flowered when daylength was 13.5–12.0 hours), medium group (genotypes that flowered when daylength was 12.0–11.0 hours), late group (genotypes that flowered when daylength was 11.0–10.0 hours), and extremely late group (genotypes that flowered when daylength was shorter than 10.0 hours). Moreover, the breeding objective was to breed early-flowering genotypes. Using 15 phenotypic characters as evaluation factors, 37 excellent genotypes, including four early-flowering genotypes, were screened out from the aforementioned resources according to an analytic hierarchy process (AHP) and weighting of the gray relational grade. We selected one early-flowering genotype and eight medium-flowering genotypes from these 37 genotypes and matched six hybridized combinations based on the genetic distance between genotypes calculated by the Q cluster analysis method. We used a comprehensive evaluation method combining AHP and the gray relational analysis (GRA) method for the evaluation of 367 progenies. Moreover, we screened out 52 superior hybrids, including 36 early-flowering hybrids. The results of this study demonstrate that the mathematical analysis method is an immensely effective method to breed new cultivars of early-flowering multiflora chrysanthemum. This study also provides an effective method to define and improve the flowering time of other cultivated plants.
Blueberries are now the hot point of fruit development in China. Researches conducted in the past since 1980s include mainly introduction and propagation. More than 30 cultivars of rabbiteye blueberries and southern highbush blueberries were introduced successfully in the Nanjing Botanical garden in late 1980s. For dormant cuttings of 4 rabbiteye blueberry cultivars Gardenblue, Tifblue, Climax, and Premier the rooting percentage could reach 84%, 52%, 62%, and 79% respectively under interrupted misting. Lignification of the cuttings seemed the key point for rooting. For soft cuttings the rooting percentage can reach 90% to 95% with chemical treatments. Seedling selection has been conducted and some promising individuals are under observation. So far, there were little experiments on cultural practice under taken. But looking at the difference of soils between the blueberry growing areas in the US and China it seems that there are a series of aspects should be researched in the future.
The native species of Vaccinium are distributed in both northeast and south of China but more species are in the South. Ecologically, there is a vast territory in the South with acidic soils and plenty of precipitation and warm weather. On the other hand in the northeast regions temperature in winter is usually a problem for cultivated blueberries and protection from freezing is necessary for young plantations. Based on the result of introduction of cultivars, including rabbiteye, southern highbush and lowbush blueberries, in both northern and southern parts in China during the last 2 decades authors suggested that the most prospective regions for blueberry growing could be mostly in south of China. In the between of the two regions the natural ecological conditions are not appropriate for blueberry growing but plantations under plastic film appeared relatively vigorous. 12 rabbiteye blueberry cultivars have been tested in the south and the performance of growth and fruiting are good. It is expected that the average of yield could reach about 15 t·ha–1. The quality of fruits is similar to that of the natives in North America. Up to now there are less insects and diseases damages. It seems that the regions in the south of Changjiang (Yangtze) River provide good conditions for blueberry commercial growing.
Garden impatiens (Impatiens walleriana), a very important floricultural crop in the United States, has been devastated by impatiens downy mildew (IDM) in recent years. This study was conducted to determine if induced tetraploidy could improve impatiens resistance to downy mildew. Tetraploids were induced by colchicine and confirmed by chromosome counting. Compared with diploids, induced tetraploids showed significant morphological changes, including larger and thicker leaves with larger and fewer stomata; thicker and fewer stems; larger and fewer flowers; and larger pollen grains with higher stainability. In detached leaf and in vivo inoculation assays, tetraploids exhibited improved downy mildew resistance, with lower disease severity, disease incidences, and sporangia densities. Plasmopara obducens, the causal agent of IDM, underwent a similar development process in the leaf tissue of diploids and tetraploids. These results suggest that induced tetraploidy can result in significant changes in impatiens leaf and plant morphology and can increase impatiens resistance to downy mildew to a certain extent.
Wild jujube (Ziziphus acidojujuba) and cultivated jujube (Ziziphus jujuba) belong to the family Rhamnaceae. Jujubes have marked drought- and salt-tolerant properties. After salt stress, wild jujube seedling growth was inhibited and photosynthetic efficiency was reduced. A bioinformatics approach was used to analyze the transcriptomics data from wild jujube seedlings grown under salt stress, and the genes differentially expressed under the salt stress were identified to provide a theoretical basis for the development and use of wild jujube plantations in salinized soil. The transcriptome sequencing from leaves of wild jujube seedlings was carried out using second-generation sequencing technology. The effects of salt stress on the differential expression of photosynthesis-related genes in wild jujube seedlings were analyzed. Transcriptome sequencing revealed a total of 5269 differentially expressed genes (DEGs), of which 2729 were up-regulated and 2540 were down-regulated. DEGs were mainly enriched with respect to photosynthesis, photosynthetic antenna proteins, glyoxylic acid and dicarboxylic acid metabolism, linolenic acid metabolism, cysteine and methionine metabolism, and porphyrin and chlorophyll metabolism. Among them, the photosynthesis pathway-related DEGs were most highly enriched. Further analysis of porphyrin and chlorophyll synthesis and photosynthesis-related pathways revealed that they were significantly enriched by 97 photosynthesis-related DEGs. The DEGs in the photosynthesis and photosynthetic antenna protein pathways were down-regulated, whereas the DEGs glutamyl-tRNA reductase (HEMA), ferrochelatase (HEMH), and pheophorbide a oxygenase (PAO) in the porphyrin and chlorophyll synthesis pathways were up-regulated, with the remainder being down-regulated. The nuclear gene encoding Rubisco, the key enzyme in the photosynthetic carbon fixation pathway, was also down-regulated. The results showed that the photosynthetic rate of wild jujube seedlings decreased following exposure to salinity stress, an effect that was related to the increased synthesis of 5-aminolevulinic acid and heme, and the up-regulation of expression of a gene encoding a chlorophyll-degrading enzyme, and was related to the down-regulation of gene expression in photosynthesis-related pathways such as light energy capture and carbon fixation. Selection of nine DEGs related to photosynthesis and chlorophyll biosynthesis by quantitative real-time-PCR confirmed that expression changes of these nine DEGs were consistent with the transcriptome sequencing results.
The addition of pulverized grape pruning wood to grape soils has a positive effect on fruit quality. However, its effects on the soil microecology of the root zone and the growth of the grape plants are not fully understood. To address this, ‘Shine Muscat’ grapes were cultivated in media consisting of garden soil and crushed grape pruning material at different mass ratios [100:1 (T1), 50:1 (T2), 30:1 (T3), 20:1 (T4), and 10:1 (T5)] and in garden soil without the pruning material, as a control. The changes in the plant fresh weight, leaf area, soil and plant analyzer development (SPAD) value, root development, soil organic carbon, microbial biomass carbon, and soil enzyme activity were determined over time. High-throughput sequencing technology was used to determine the soil bacterial community structures. The pruning supplementation increased the grape plants fresh weight, leaf area, and SPAD values. The T2 and T3 treatments increased the grape root length, surface area, and the projected area and number of the root tips; the soil organic carbon content, microbial biomass carbon content, soil invertase activity, amylase activity, and β-glucosidase activity were also significantly increased. The addition of the grape pruning material was found to increase the bacterial diversity and richness 60 and 150 days after treatment. At the phylum level, Proteobacteria, Acidobacteria, and Actinobacteria were the dominant groups, and the grape pruning material increased the relative abundance of the Acidobacteria and Actinobacteria after 60 and 150 days. The relative abundance of the Actinobacteria in the T2 treatment was 1.7, 1.3, 1.5, and 1.3 times that of the control, after 60, 90, 120, and 150 days, respectively. The T2 treatment was identified as the optimal treatment for grapes in the field because it improved the soil microecology and promoted root and tree development the most compared with the other treatments tested.
Resistance to grape anthracnose [Elsinoë ampelina (de Bary) Shear] was evaluated in 13 known Vitis species and five taxonomically undescribed grapes native to China. One hundred and eight clones of Chinese Vitis species were tested under field conditions between 1990 and 1992. Berry infection did not occur in these species. Leaves displayed strong resistance to anthracnose, although intraspecific variations were observed. There was no relationship between anthracnose resistance and geographical origin of the species. Results from this study indicate that oriental grape species are useful for disease-resistance breeding.
Pecan [Carya illinoinensis (Wangenh.) C. Koch], a world-famous nut tree native to North America, was introduced to China in the early 1900s. However, little success had been recorded in terms of its nut production. Based on comparative studies of the geoclimate, soil conditions, and growth and performance of the pecan crop between southeastern U.S. and China, as well as in 12 other countries with successful pecan cultivation, it is feasible to grow pecan in China within the latitudes 25–35°N. In these areas, the summer temperatures range from 25–35°C with lower DIF. The annual precipitation is 500–1500 mm. Further studies using the Dendroclimate Predicative Analysis of water and heat conditions in the U.S. Pecan Belt, which is composed of seven factors, including the annual mean and extreme low temperatures, annual frost-free days, and annual precipitation, concluded that four pecan cultivation regions should be designated in China. These regions were the Favorable Region (I), the Northern and Southern Suitable Regions (IIa, IIb), the Northern and Southern Marginal Regions (IIIa, IIIb), and the Northern and Southern Undesirable Regions (IVa, IVb). The Favorable Region is along both sides of the Yangtze River in-between latitudes 25–35 °N and longitudes 100–122 °E. Some areas with microclimates, such as western Yunnan, nourish several pecan cultivars and have demonstrated a promise of pecan production. The demand for pecan is high in China, and this regionalization of pecan cultivation will ultimately enhance further collaboration on pecan production between horticulturists in China, United States, and other countries. Future research will result in the introduction of much better pecan cultivars to the different cultivated regions in China.