The shortage of water resources is an unfavourable factor that restricts the production of flowers. The use of drought-resistant morphological markers is of great significance to distinguish the drought resistance of flower varieties. In this paper, we study the difference in drought tolerance of seven common lily varieties in the flower market by morphological and physiological markers. The results showed that there were differences in leaf morphological indices and anatomical structures among the seven varieties. Drought reduced the chlorophyll content, inhibited the photosynthetic rate, and increased catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), malondialdehyde (MDA), proline, soluble sugar, and soluble protein. After rewatering, the activities of CAT, POD, and SOD of ‘Lyon’, ‘Royal Sunset’, and ‘Robina’ varieties decreased, which was opposite to the varieties of ‘Immaculate’, ‘Elena’, ‘Siberia’, and ‘Gelria’. According to the membership function value of physiological indices, the drought resistance of seven lily varieties from weak to strong was ‘Immaculate’, ‘Elena’, ‘Siberia’, ‘Gelria’, ‘Robina’, ‘Royal Sunset’, and ‘Lyon’. Drought resistance is related to the thickness of leaves, palisade tissue, sponge tissue, and specific leaf area. Lily leaf structure can be used as one of the indices to judge drought resistance.

Lilies are well−known flowers with large anthers and a high quantity of pollen that easily contaminates clothing and tepals. The anthers need to be artificially removed, leading to production problems. Cultivating male−sterile or pollen−free lilies could solve these problems. The key period of male sterility in a specific male−sterile hybrid lily population was determined through cytological observation. The contents of hormones, soluble sugar, soluble protein, and proline were determined by high−performance liquid chromatography, tandem mass spectrometry and colorimetry. Transcriptome sequencing was used to identify the genes with altered expression. The key period of male sterility was determined to be the microspore mother and tetrad stages. The hormone contents were abnormal in the sterile line compared with the fertile line. The indole−3−acetic acid (IAA) content was higher in the sterile line than in the fertile line at all stages, while the gibberellic acid 4 (GA4) content showed the opposite result. Abscisic acid (ABA) accumulated in the sterile line in both the microspore mother and tetrad stages, and the zeatin riboside (ZR) content in the sterile line increased at the microspore mother stage but decreased at the tetrad stage. The contents of soluble sugar, soluble protein and proline were higher in the fertile line than in the sterile line. Genes involved in auxin and ABA synthesis and signalling pathways were highly expressed in the male−sterile line. Our data suggested that abnormal contents of hormones in the microspore mother and tetrad stages resulted in pollen abortion in a male−sterile hybrid lily population, which indicated that the hormone balance in specific stages plays critical functions in pollen development in lilies.

Flavonoid-3′,5′-hydroxylase (F3′5′H) is the key enzyme for the biosynthesis of delphinidin-based anthocyanins, which are generally required for purple or blue flowers. Previously, we isolated a full-length cDNA of PgF3′5′H from Platycodon grandiflorus, which shared the highest homology with Campanula medium F3′5′H. In this study, PgF3′5′H was subcloned into a plant over-expression vector and transformed into tobacco via Agrobacterium tumefaciens to investigate its catalytic function. Positive transgenic tobacco T₀ plants were obtained by hygromycin resistance screening and PCR detection. PgF3′5′H showed a higher expression level in all PgF3′5′H transgenic tobacco plants than in control plants. Under the drive of the cauliflower mosaic virus (CaMV) 35S promoter, the over-expressed PgF3′5′H produced dihydromyricetin (DHM) and some new anthocyanin pigments (including delphinidin, petunidin, peonidin, and malvidin derivatives), and increased dihydrokaempferol (DHK), taxifolin, tridactyl, cyanidin derivatives, and pelargonidin derivatives in PgF3′5′H transgenic tobacco plants by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) analysis, resulting in a dramatic color alteration from light pink to magenta. These results indicate that PgF3′5′H products have F3′5′H enzyme activity. In addition, PgF3′5′H transfer alters flavonoid pigment synthesis and accumulation in tobacco. Thus, PgF3′5′H may be considered a candidate gene for gene engineering to enhance anthocyanin accumulation and the molecular breeding project for blue flowers.

In order to evaluate the feasibility of using sugarcane bagasse (SCB) as a substitute for peat in lily cultivation, this study examines the effects of replacing different amounts of peat (0%, 25%, 50%, 75%, and 100%) with SCB on the physical and chemical properties of the substrate. The impact on the growth of cut flower and bulbs of the oriental lily variety ‘Siberia’ was investigated. The results show that the pH value, organic matter content, and reducing sugar content of the substrate were significantly increased (p < 0.05) when peat was replaced with SCB. Moreover, the bulk density, permeability porosity, water-holding porosity, and EC value, as well as the contents of hydrolyzed nitrogen, available phosphorus, available potassium, exchangeable calcium, and exchangeable magnesium were significantly decreased (p < 0.05). The bulk density (0.15–0.17 g·cm³), total porosity (64.2–69.6%), and water-holding porosity (41.0–48.4%) of the mixed media were in a suitable range. The addition of SCB led to shorter plant height, a thinner stalk, and a smaller leaf and flower diameter. The contents of total chlorophyll, chlorophyll a and b in leaves, as well as the activities of sucrose synthetase (SS) and sucrose phosphate synthetase (SPS) decreased with the increase in SCB in the substrates at different growth stages of lily cut flowers. The correlation analysis showed that, except for bulb height, other quality traits of cut flowers and bulbs were significantly negatively correlated with the pH, organic matter, and reducing sugar content of substrates. Plant height, stem diameter, leaf number, leaf length and width, flower diameter of cut flowers, as well as the fresh weight, starch content, the activities of SS and SPS of bulbs were significantly positively correlated with the bulk density, total porosity, water-holding porosity, and hydrolyzed N content of substrates (p < 0.05). The load factors of the principal components indicated that the diameter of stem and flower, leaf number, the content of chlorophyll a and b, and total chlorophyll of cut flowers and SPS activity in bulbs could be used as the core indicators for evaluating the suitability of lily cultivation substrate. In conclusion, when the proportion of peat replaced with SCB was lower than 50%, the quality of cut flowers and bulbs was the same as that found with whole peat. Thus, SCB has broad application prospects in the soilless cultivation of lily plants.

Fusarium wilt (caused by Fusarium oxysporum f. sp. Lilii) is one of the most damaging diseases in lily (Lilium sargentiae Wilson). Although some F. oxysporum-resistant lily varieties have been identified and are being utilized in resistant breeding, the regulation network of the resistance-associated mechanisms is yet to be studied due to the lack of reliable reference genes for qRT-PCR (quantitative reverse transcription PCR) normalization. The reliability of results by qRT-PCR relies mainly on the stability of the reference genes. This study investigated the reliability of nine candidate reference genes (CYP, EF1-α, GAPDH, TUB, UBQ, AQP, HIS, PGK, and RPL13) for qRT-PCR analysis of F. oxysporum-resistant genes. Expression stability analysis via common programs GeNorm, BestKeeper, and NormFinder, at different time points post-inoculation of F. oxysporum, revealed that all nine genes met the basic requirements of reference genes. Amongst them, HIS and GAPDH displayed the highest and the lowest expression stability, respectively. The reliability of HIS was further validated by analyzing the expression levels of four resistance-related candidate genes. The expression patterns of the four target genes were consistent with their responses to pathogenetic fungi in other plants. Our results show that HIS is the most suitable reference gene for accurately normalizing F. oxysporum-resistant genes’ expressions in L. sargentiae.