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Epimedium species are traditional Chinese medicinal plants as well as potential groundcover and ornamental plants. In this study, genome size and genome structures of Epimedium species were investigated using flow cytometric and fluorescence in situ hybridization (FISH). The nuclear DNA content of Epimedium species ranged from 8.42 pg/2C (8230.7 Mbp) to 9.97 pg/2C (9752.8 Mbp). The pairwise nucleotide diversity (π) of the fragments of the genes for reverse transcriptase (rt) of Ty1-copia retrotransposon within a species of rt fragments ranged from 0.251 to 0.428 in 10 Epimedium species. Phylogenetic analysis of the sequences revealed four major clades with the largest subclade containing 72 sequences of relatively low nucleotide diversity. FISH indicated that Ty1-copia retrotransposons are distributed unevenly along the pachytene chromosomes of E. wushanense and E. sagittatum, mostly associated with the pericentromeric and terminal heterochromatin. The relatively low sequence heterogeneity of Ty1-copia rt sequences implies that the Epimedium genomes have experienced a few relatively large-scale proliferation events of copia elements, which could be one of the major forces resulting in the large genome size of Epimedium species.
Forty-eight kiwifruit cultivars and selections, representing more than 90% of total world kiwifruit production, were investigated using nine SSR markers to establish genetic identities, and evaluate genetic diversity and relatedness. These nine SSRs were polymorphic and a total of 213 alleles were detected, resulting in a mean number of 23.7 alleles per locus, ranging from nine to 38 alleles. One hundred and thirty-three alleles were found to be common to both A. chinensis and A. deliciosa, while 33 and 36 were specific to A. chinensis and A. deliciosa, respectively. In addition, 34 alleles were specific to one single genotype and provided a set of valuable alleles for cultivar identification. A single SSR locus UDK 96-414 could differentiate all 48 genotypes except two presumable clones. Mean number of alleles per locus (A), percentage of polymorphic loci (P), and direct count heterozygosity (Ho) assessed for each genotype over all loci revealed considerable differences among these 48 genotypes. On average, A = 2.6, P = 89.4% and Ho = 0.546 were found in A. chinensis cultivars, while A = 3.5, P = 97.0% and Ho = 0.671 in A. deliciosa cultivars. Consensus fingerprint profiling using SSR markers is a useful and reliable method for establishing genetic identities of kiwifruit cultivars and selections. It also improves evaluation effectiveness of genetic diversity and relatedness compared to RAPD markers.
Sedum rubrotinctum is widely grown as an ornamental because of its attractive leaf shape and color. Increasing the morphological diversity and color will greatly add to its ornamental value. Environmental conditions such as light and temperature can change the leaf color of succulent plants, but the mechanism is uncertain. To examine this mechanism, we tested the effects of two commercial chemical products Sowing Goodliness (Sg) and Aromatic Garden (Ag) on the morphology, pigment content, and growth performance of Sedum rubrotinctum seedlings. The Sg treatment did not change foliage color, but can accelerate plant growth and increase lateral bud number. The Ag treatment had marked changes on the relative proportions of pigments and leaf color, and plant growth was severely reduced with mortality observed in some plants. After Ag stress was discontinued, the surviving plants began to regrow and had good ornamental value but had the fewest number of lateral buds and leaves, and the smallest leaf length and thickness, canopy diameter, and plant height. Foliage color changes are caused directly by shifts in the relative proportions of pigments, particularly chlorophyll b and anthocyanin. In Ag-treated plants, chlorophyll b declined much faster than chlorophyll a, indicating that the transformation of chlorophyll b into chlorophyll a is an important step in the chlorophyll degradation pathway. Ag provides a way to learn more about the mechanism of chlorophyll degradation and should be investigated further. Ag enhanced anthocyanin production rapidly and improved the ornamental value of Sedum rubrotinctum. Different concentrations of Ag and Sg were not studied in this trial and might be tested to determine the ideal balance between leaf color and plant growth.
Kiwifruit (Actinidia deliciosa) is a typical climacteric fruit, and its ripening is closely associated with ethylene. In this study, we present evidence that H2S alleviated ethylene-induced ripening and senescence of kiwifruit. Kiwifruit were fumigated with ethylene released from 0.4 g·L−1 ethephon solution or H2S with 1 mm sodium hydrosulfide (NaHS) as the donor or in combination. Fumigation with ethylene was found to accelerate kiwifruit ripening and H2S treatment effectively alleviated ethylene-induced fruit softening in parallel with attenuated activity of polygalacturonase (PG) and amylase. Ethylene + H2S treatment also maintained higher levels of ascorbic acid, titratable acid, starch, soluble protein, and reducing sugar compared with ethylene group, whereas suppressed the increase in chlorophyll and carotenoid. Kiwifruit ripening and senescence under ethylene treatment was accompanied by elevation in reactive oxygen species (ROS) levels, including H2O2 and superoxide anion and malondialdehyde (MDA), but combined treatment of ethylene plus H2S alleviated oxidative stress in fruit. Furthermore, the activities of antioxidative enzymes catalase (CAT) and ascorbate peroxidase (APX) were increased by ethylene + H2S treatment in comparison with ethylene alone, whereas the activities of lipoxygenase (LOX) and polyphenol oxidase (PPO) were attenuated by H2S treatment. Further investigations showed that H2S repressed the expression of ethylene synthesis-related genes AdSAM, AdACS1, AdACS2, AdACO2, and AdACO3 and cysteine protease genes, such as AdCP1 and AdCP3. Taken together, our findings suggest that H2S alleviates kiwifruit ripening and senescence by antagonizing the effect of ethylene through reduction of oxidative stress and inhibition of ethylene synthesis pathway.
Half or whole root systems of micropropagated `Gala' apple (Malus ×domestica Borkh.) plants were subjected to drought stress by regulating the osmotic potential of the nutrient solution using polyethylene glycol (20% w/v) to investigate the effect of root drying on NO3- content and metabolism in roots and leaves and on leaf photosynthesis. No significant difference in predawn leaf water potential was found between half root stress (HRS) and control (CK), while predawn leaf water potential from both was significantly higher than for the whole root stress (WRS) treatment. However, diurnal leaf water potential of HRS was lower than CK and higher than WRS during most of the daytime. Neither HRS nor WRS influenced foliar NO3- concentration, but both significantly reduced NO3- concentration in drought-stressed roots as early as 4 hours after stress treatment started. This reduced NO3- concentration was maintained in HRS and WRS roots to the end of the experiment. However, there were no significant differences in NO3- concerntation between CK roots and unstressed roots of HRS. Similar to the effect on root NO3- concentration, both HRS and WRS reduced nitrate reductase activity in drought-stressed roots. Moreover, leaf net photosynthesis, stomatal conductance and transpiration rate of HRS plants were reduced significantly throughout the experiment when compared with CK plants, but the values were higher than those of WRS plants in the first 7 days of stress treatment though not at later times. Net photosynthesis, stomatal conductance and transpiration rate were correlated to root NO3- concentration. This correlation may simply reflect the fact that water stress affected both NO3- concentration in roots and leaf gas exchange in the same direction.
Apple blotch caused by Alternaria alternata apple pathotype is a severe disease of apple (Malus ×domestica Borkh) occurring throughout the world, especially in eastern Asia. Phenotypic and genetic information about resistance/susceptibility of apple germplasm to this disease will be extremely valuable for selecting and developing new disease resistant cultivars. In this study, 110 apple cultivars obtained from the USDA apple germplasm in Geneva, NY, were evaluated for their resistance/susceptibility to apple blotch by field surveys, and inoculation of detached leaves with a suspension of germinated conidia of A. alternata apple pathotype. Disease incidence were different among the cultivars and categorized into resistant (R), moderately resistant (MR), or susceptible (S). Two molecular markers, S428, a random amplified polymorphic DNA (RAPD) marker associated with disease resistance, and a simple sequence repeat (SSR or microsatellite) marker CH05g07, linked to susceptibility were used to correlate the phenotypes expressed in field surveys and laboratory inoculations. The detection using either the S428 marker or the CH05g07 marker in 50 common breeding cultivars was consistent with R or S traits except for ‘Bisbee’ and ‘Priscilla’. These two cultivars were MR to apple blotch through phenotyping. However, SSR markers were detected, but RAPD markers were not and therefore were considered susceptible. Combined with the record of resistance to fire blight from Germplasm Resources Information Network (GRIN), ‘Dayton’, ‘Mildew Immune Seedling’, ‘Puregold’, and ‘Pumpkin Sweet’ were highly resistant to both diseases and considered as the best choices of parents for stacking resistance to multiple diseases in breeding program.
The resurrection plant Selaginella pulvinata (Hook. & Grev.) Maxim is used as an ornamental and medicinal plant. It is also a good candidate for exploring the desiccation tolerance of resurrection plants. However, there is not an efficient propagation method for S. pulvinata. In the present study, we evaluated the establishment of in vitro propagation of S. pulvinata using frond tips as explants. The original shoot induction, adventitious shoot proliferation and plantlet growth media, and substrate type of plantlet acclimatization were investigated. The highest induction rate of original shoots (61.77 ± 5.17%) was obtained on half-strength (1/2) MS medium supplemented with 0.1 mg·L−1 N6-benzylaminopurine (BAP). The 1/2 MS with 1.0 mg·L−1 BAP was the most effective medium for the adventitious shoot proliferation. The quarter-strength (1/4) MS containing 0.1% (w/v) active charcoal (AC) was optimum for plantlets proliferated from adventitious shoots and plantlet growth. Approximately 98 plantlets could be obtained from one single original shoot via one-time shoot proliferation cultivation and plantlet cultivation. The acclimated plants on a 5:1 (v/v) mixture of peat and perlite had the highest survival rate (92.13 ± 1.67%). The acclimated plants maintained excellent resurrection ability.
The king oyster mushroom [Pleurotus eryngii (DC.:Fr.) Quél.] is gaining popularity across the world due to its excellent taste, high nutritional quality, medicinal value, and long shelf life. Conventional substrates for king oyster mushroom cultivation consist of sawdust derived from various tree species. Sawdust demand is increasing worldwide, creating a need for alternative materials that can at least partially replace sawdust as substrate for king oyster mushroom. In Taiwan, as in other countries that grow fruit trees, pruned fruit tree branches are an expensive agricultural waste, particularly if they are not recycled or reused. In the present study, we evaluated substrates containing sawdust and different proportions of material ground from pruned wax apple or Indian jujube branches for cultivation of king oyster mushroom. Our results suggested that among all five substrate mixes tested, the best substitute for conventional sawdust (100% sawdust) was a substrate that contained 75% sawdust mixed with 25% materials ground from trimmed wax apple branches (Wax apple 25%). Furthermore, determination of mineral element content, pH, and electrical conductivity (EC) levels of the substrates both before spawn inoculation and after harvesting revealed no significant changes in mineral content, a slight reduction in pH value, and a minor increase in EC levels after cultivation. Taken together, results from this study suggest that agricultural wastes from pruned fruit tree branches can partially replace sawdust as the cultivation substrate for king oyster mushroom.
Chinese wild Vitis is a useful gene source for resistance to biotic and abiotic stresses, although there is little research on its genetic diversity and structure. In this study, nine simple sequence repeat (SSR) markers were used to assess the genetic diversity and genetic structure among 100 Vitis materials. These materials included 77 indigenous accessions representing 23 of 38 wild Vitis species/cultivars in China, 18 V. vinifera cultivars, and the five North American species V. aestivalis, V. girdiana, V. monticola, V. acerifolia, and V. riparia. The SSR loci used in this study for establishing an international database (Vitis International Variety Catalogue) revealed a total of 186 alleles in 100 Vitis accessions. The mean values for the gene diversity (GD) and polymorphism information content (PIC) per locus were 0.91 and 0.90, respectively, which indicates that the discriminatory power of the markers is high. Based on the genetic distance data, the 100 Vitis accessions were divided into five primary clusters by cluster analysis, and five populations by structure analysis; these results indicate these Chinese wild grapes were more genetically close to European grapes than to North American species. In addition, the clustering patterns of most accessions correlated with the geographic distribution. An analysis of molecular variance (AMOVA) revealed that 3.28%, 3.27%, and 93.46% of the variance occurred between populations, between individuals within populations, and between individuals within the entire population, respectively. In addition, we identified three previously undescribed accessions (Wuzhi-1, MZL-5, and MZL-6) by cluster analysis. Our results reveal a high level of genetic diversity and variability in Vitis from China, which will be helpful in the use of genetic resources in future breeding programs. In addition, our study demonstrates that SSR markers are highly suitable for further genetic diversity analyses of Chinese wild grapes.
Alternaria alternata apple pathotype (previously A. mali) causes alternaria blotch disease of apple (Malus ×domestica), which may result in leaf spots and up to 70% premature leaf drop in serious cases. This disease is of worldwide importance but is most serious in eastern Asia (Japan, Korea, and China) and in parts of the United States. The excessive use of fungicides not only adds cost to apple growers, but also pollutes the environment. In this study, we characterized a 5-year F1 population from a cross of a resistant cultivar (Huacui) and a susceptible cultivar (Golden Delicious) consisting of 110 individuals along with 14-year-old parent trees (10 each). A field evaluation of disease severity was conducted in 2008 and 2009 under the natural conditions in Liaoning, China (lat. 40°37′ N, long. 120°44′ E). Based on the field data, 110 F1 plants were divided into five groups. Artificial inoculation was carried out both on the living trees and on the detached leaves in 2009 to ensure that A. alternata apple pathotype was the causative agent. Eighty primer pairs of simple sequence repeat (SSR) were screened against the four genomic DNA pools, respectively, from six highly susceptible F1 plants, six most resistant F1 plants, one tree of the seed parent, and the one tree of the pollen parent. One pair of primers (CH05g07) was shown to be linked to the DNA pools of susceptible F1 and the parent tree, but not to the DNA pools of resistant F1 and parent trees. This primer pair was then used to screen all individual 110 F1 progenies and two parent trees. The differentiation of 103 individuals (97.3%) with the marker matched the field disease resistance rating. This marker was further screened with 20 cultivars with known susceptibility or resistance to A. alternata apple pathotype and its linkage to susceptibility was validated. These results suggest that this marker can be used in marker-assisted selection for resistance/susceptibility to alternaria blotch disease in apple.