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Lily (Lilium L.) species produce among the most important cut flowers worldwide. China has ≈55 species of Lilium. Although many plants from this genus have been used in hybridization efforts, their cytology has remained unclear. The goal of the current study was to characterize the chromosomes of Lilium rosthornii Diels. Root tips were used to characterize Giemsa C-banding, propidium iodide (PI) banding, and 45S rDNA locations. The karyotype of L. rosthornii belongs to type 3B. C-banding revealed polymorphic banding patterns with the following formula: 2n = 24 = CI = 4C + 14CI₊ + 2I₊ +2I+ 2. Two of the four 45S rDNA hybridization sites were located at pericentromeric positions on the two short arms of the homologues of chromosome 1, and the other two were located on the long arms of one chromosome 6 homolog and one chromosome 11 homolog. Six of the eight PI bands were detected in the centromeres of the homologues of chromosomes 1, 5, and 8, and the other two PI bands were detected on the long arms of one chromosome 6 and one chromosome 11. Lilium rosthornii showed enriched banding in both Giemsa C-banding and PI painting. Interestingly, not all 45S rDNA was located in homologous chromosomal locations. These results may provide reference data for L. rosthornii for use in further Lilium breeding.

Karyotype comparison and fluorescence in situ hybridization (FISH) were conducted to analyze the wild Lilium species distributed in China. The karyotype results revealed that all species except Lilium lancifolium (2n = 3X = 36) were diploid and had two pairs of metacentric or submetacentric chromosomes. The karyotypes of all species are similar. FISH analysis revealed that there are 5–12 45S rRNA gene loci dispersed on the chromosomes of the 14 diploid species, and 15 45S rRNA gene loci were detected in the triploid species L. lancifolium. Most of the FISH signals were detected on the long arms and the centromeric regions. Three samples of L. brownii [Hubei, China (lat. 31°28′N, long. 110°23′E); Liaoning, China (lat. 40°07′N, long. 124°19′E); and Guangxi, China (lat. 25°06′N, long. 107°27′E)] showed very similar chromosome patterns in both the karyotype and the FISH analyses, further demonstrating that these samples belonged to the same species. L. brownii is widely distributed in China from latitude 25°06′N to 40°07′N, indicating that it is highly adaptable to the environment.

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 1.15.1.10)] 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 (Pel et al., 2007). 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 (Govrin and Levine, 2000). ROS such as singlet oxygen, superoxide anion, hydroxyl (OH⁻), and H₂O₂ are released to hinder the advance of pathogens (Gara et al., 2003). ROS can react with and damage cellular molecules, such as DNA, protein, and lipids, which will limit fungal propagation in the host plant (Apel and Hirt, 2004).