Centipedegrass [Eremochloa ophiuroides (Munro) Hack] is a native grass of China, and information on soil adaptation ranges, including acid soils, among centipedegrass cultivars is limited. Therefore, objectives of this study were 1) to conduct a preliminary evaluation of relative aluminum tolerance of 48 centipedegrass accessions plus a cultivar, TifBlair, and a common centipedegrass under aluminum (Al) stress (0 and 1500 μM Al) by using a solution culture method; and 2) to determine Al effects on nutrient uptake between resistant-group and sensitive-group accessions among the 50 accessions and cultivars. Differences were found among accessions and cultivars, and the CV of relative root weight, relative shoot weight, and relative total weight were 39.9%, 32.9%, and 33.6%, respectively. After growing 28 days in an acid subsoil, the resistant-group accessions showed much better growth than the sensitive-group accessions. The Al concentrations in roots and shoots of the two groups of accessions were increased under Al treatment, but most absorbed Al remained in roots with greater Al absorption among the sensitive group compared with the resistant group. The concentrations of phosphorus (P), magnesium (Mg), calcium (Ca), and potassium (K) in the two groups were reduced under Al stress with reductions of 59.3%, 54.8%, 47.9%, and 41.3% in shoots and reductions of 8.70%, 52.5%, 43.2%, and 34.4% in roots, respectively. Under Al stress, differences in P, Mg, and Ca concentrations were found between the two groups; however, differences were not found for K. The resistant-group accessions maintained higher concentrations of Mg and Ca than the sensitive group.
Nine microsatellite loci were isolated from Primula obconica using the FIASCO protocol. We used 30 individuals from three populations for the assessment of microsatellite variation. Seven loci were detected with microsatellite polymorphism. The number of alleles per locus ranged from three to seven. The average observed heterozygosity and expected heterozygosity ranged from 0.167 to 0.6 and from 0.409 to 0.653, respectively. These microsatellite markers will be useful to assess the genetic variation and genetic structure of P. obconica.
Petal anthocyanins were systematically identified and characterized by high-performance liquid chromatography (HPLC)–electrospray ionization–mass spectrometry (MS) coupled with diode array detection among nine wild herbaceous peony (Paeonia L.) species (15 accessions). Individual anthocyanins were identified according to the HPLC retention time, elution order, MS fragmentation patterns, and by comparison with authentic standards and published data. Six main anthocyanins, including peonidin-3,5-di-O-glucoside, peonidin-3-O-glucoside-5-O-arabinoside (Pn3G5Ara), peonidin-3-O-glucoside, pelargonidin-3,5-di-O-glucoside, cyanidin-3,5-di-O-glucoside, and cyanidin-3-O-glucoside (Cy3G), were detected. In addition to the well-known major anthocyanins, some minor anthocyanins were identified in herbaceous peony species for the first time. Detection of the unique anthocyanins cyanidin-3-O-glucoside-5-O-galactoside and pelargonidin-3-O-glucoside-5-O-galactoside in both Paeonia anomala L. and P. anomala ssp. veitchii (Lynch) D.Y. Hong & K.Y. Pan indicated these two species should belong to the same taxon. Pn3G5Ara was found only in European wild species and subspecies suggesting different metabolic pathways between European and Chinese accessions. Anthocyanins conjugated with galactose and arabinose were observed in the genus Paeonia for the first time. The North American species, Paeonia tenuifolia L., had high Cy3G content in flower petals. This anthocyanin composition is distinct from the anthocyanin composition in Asian and European species and possibly is responsible for the vivid red coloration in flowers.
Aspergillus niger is a common pathogenic fungus causing postharvest rot of fruit and vegetable, whereas the knowledge on virulence factors is very limited. Superoxide dismutase [SOD (EC 188.8.131.52)] is an important metal enzyme in fungal defense against oxidative damage. Thus, we try to study whether Cu/Zn-SOD is a virulence factor in A. niger. Cu/Zn-SOD encoding gene sodC was deleted in A. niger [MA70.15 (wild type)] by homologous recombination. The deletion of sodC led to decreased SOD activity in A. niger, suggesting that sodC did contribute to full enzyme activity. ΔsodC strain showed normal mycelia growth and sporulation compared with wild type. However, sodC deletion markedly increased the cell’s sensitivity to intracellular superoxide anion generator menadione. Besides, spore germination under menadione and H2O2 stresses were significantly retarded in ΔsodC mutant compared with wild type. Further results showed that sodC deletion induced higher superoxide anion production and higher content of H2O2 and malondialdehyde (MDA) compared with wild type, supporting the role of SOD in metabolism of reactive oxygen species (ROS). Furthermore, ΔsodC mutant had a reduced virulence on chinese white pear (Pyrus bretschneideri) as lesion development by ΔsodC was significantly less than wild type. The determination of superoxide anion, H2O2, and MDA in A. niger-infected pear showed that chinese white pear infected with ΔsodC accumulated less superoxide anion, H2O2, and MDA compared with that of wild type A. niger, implying that ΔsodC induced an attenuated response in chinese white pear during fruit–pathogen interaction. Our results indicate that sodC gene contributes to the full virulence of A. niger during infection on fruit. Aspergillus niger is one of the most common species found in fungal communities. It is an important fermentation industrial strain and is also known to cause the most severe symptoms in fruit during long-term storage (). Meanwhile, plants activate their signaling pathways to trigger defense responses to limit pathogen expansion. One of the earliest host responses after pathogen attack is oxidative burst, during which large quantities of ROS are generated by different host enzyme systems, such as glucose oxidase (). ROS such as singlet oxygen, superoxide anion, hydroxyl (OH−), and H2O2 are released to hinder the advance of pathogens (). ROS can react with and damage cellular molecules, such as DNA, protein, and lipids, which will limit fungal propagation in the host plant ().
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.