Chrysanthemums (Chrysanthemum morifolium Ramat.) are famous ornamental crops with high medicinal and industrial values. The inflorescence and leaf traits are key factors that affect the yield and quality of chrysanthemum. However, the genetic improvement of those traits is slow within chrysanthemum because of its hexaploidy, high heterozygosity and enormous genome. To study the genetic control of the important traits and facilitate marker-assisted selection (MAS) in chrysanthemum, it is desirable to populate the genetic maps with an abundance of transferrable markers such as microsatellites (SSRs). A genetic map was constructed with expressed sequence tag–simple sequence repeat (EST-SSR) markers in an F₁ progeny of 192 offspring. A total of 1000 alleles were generated from 223 EST-SSR primer pairs. The preliminary maternal and paternal maps consisted of 265 marker alleles arranged into 49 and 53 linkage groups (LGs), respectively. The recombined parental maps covered 906.3 and 970.1 cM of the genome, respectively. Finally, 264 polymorphic loci were allocated to nine LGs. The integrated map spanned 954.5 cM in length with an average genetic distance of 3.6 cM between two neighbouring loci. Quantitative trait loci (QTLs) analysis was performed using the integrated map for inflorescence diameter (ID), central disc flower diameter (CDFD), number of whorls of ray florets (NWRF), number of ray florets (NRF), number of disc florets (NDF), number of florets (NF), ray floret length (RFL), ray floret width (RFW), ray floret length/width (RFL/W), leaf length (LL), leaf width (LW) and leaf length/width (LL/W). Overall, 36 (21 major) QTLs were identified. The successful mapping of inflorescence and leaf traits QTL demonstrated the utility of the new integrated linkage map. This study is the first report of a genetic map based on EST-SSR markers in chrysanthemum. The EST-SSR markers, genetic map and QTLs reported here could be valuable resources in implementing MAS for chrysanthemums in breeding programs.

Gene silencing is the epigenetic regulation of any gene in order to prevent gene expression at the transcription or translation levels. Among various gene silencing techniques, RNA silencing (RNAi) is notable gene regulation technique that involves sequence-specific targeting and RNA degradation. However, the effectiveness of transgene-induced RNAi in F₁ generation of chrysanthemum has not been studied yet. In the current study, we used RNAi-constructed CmTFL1 (white-flowered) and CmSVP overexpressed (yellow flowered) transgenic plants of previously conducted two studies for our experiment. Cross hybridization was performed between these intergeneric transgenic and non-transgenic plants of the winter-growing chrysanthemum selection “37” (light pink flowered). The transgene CmSVP was confirmed in F₁ hybrids by RT-PCR analysis, whereas hybrids of CmTFL1 parental plants were non-transgenic. Besides this, quantitative real-time PCR (qPCR) was used to explain the molecular mechanism of flower development using reference genes. Intergeneric and interspecific hybrids produced different colored flowers unlike their respective parents. These results suggest that generic traits of CmSVP overexpressed plants can be transferred into F₁ generations when crossed with mutant plants. This study will aid in understanding the breeding phenomenon among intergeneric hybrids of chrysanthemum plants at an in vivo level, and such transgenics will also be more suitable for sustainable flower yield under a low-light production system.

Daylily (Hemerocallis fulva) is an important ornamental and medicinal plant, possessing high economic and cultural significance. Flooding stress has emerged as a substantial limiting factor for the daylily plant cultivation. However, the molecular mechanisms underlying daylily responses to waterlogging are largely unclear. In this study, 23 daylily cultivars and species were collected, and their tolerance to submergence was assessed using an evaluation system. A high-depth transcriptome analysis was performed to investigate the mechanisms underlying daylily root responses to submergence in the highly tolerant 'Here Lies Butch' and the highly sensitive 'Bonibrae Sharky'. During a 24-h submergence period, analysis of differentially expressed genes revealed distinct waterlogging tolerance-associated pathways in daylily roots, including ethylene biosynthesis, reactive oxygen species production and scavenging, alcoholic fermentation, abscisic acid biosynthesis, gibberellin biosynthesis, and programmed cell death. These pathways are responsible for energy production, adventitious root growth, aerenchyma formation, and internode elongation, facilitating the plant adaptation to hypoxia under waterlogging. A number of differentially expressed transcription factors (TFs), belonging to ERF, ARF, bHLH, MADS, MYB, NAC, WRKY, and ZFP families, were identified in both highly tolerant and sensitive cultivars. The potential correlations between TFs and genes in waterlogging tolerance-related pathways were thus predicted through principal component and interaction network analysis. The data obtained here contribute to the understanding of molecular events underlying waterlogging responses in daylily.