Bicheng Dun

M. laxiflora is an endangered plant that grows in the Yangtze River floodplain of China and often suffers from flooding stress. Due to the lack of a reference genome for M. laxiflora, the molecular regulatory mechanism of waterlogging stress in this plant remains unclear. In this study, we report a high-quality reference genome of M. laxiflora with a size of 1.29 Gb. A total of 23,666 gene-encoding proteins and 5457 ncRNAs were predicted in this reference genome. A comparative genome analysis revealed that 902 and 4299 gene families significantly expanded and contracted, respectively, in M. laxiflora. The expansions of the 902 gene families were significantly related to the “response to stress”, “response to abiotic stimulus”, and “response to oxygen-containing compounds” pathways. In the M. laxiflora genome, 101 MylAP2/ERF genes were identified and divided into five subgroups. Several MeJA-, ABA-, and hypoxia-responsive elements were found in the promoter regions of these MylAP2/ERF genes. According to the transcriptome data analysis, 74 MylAP2/ERF genes responded to flooding stress. Moreover, three genes (MylAP2/ERF49/78/91) that belong to the same branch as the RAP2.2 gene exhibited different expression trends under flooding stress. Our results provide valuable information on the molecular regulatory mechanism of flooding stress in M. laxiflora.

Phalaenopsis aphrodite Rchb. F. is a plant of great ornamental and economic value, and its growth has strict requirements in terms of environment. In order to establish the rapid propagation of Phalaenopsis aphrodite Rchb. F., this study used the popular large-flowered variety ‘RED SUN’, which is found on the market, as the material, and studied the effects of pedicel taking time, site, plant growth regulators, and organic substances on the establishment of a regeneration system. The results indicated that the best combination of initiation culture was collecting peduncles in January + upper position of peduncles + 0.1% HgCl₂ sterilization for 8 min. The best recipe for inducing adventitious buds was MS + TDZ 0.4 mg/L + NAA 0.5 mg/L. The optimal combination for adventitious bud propagation was MS + TDZ 0.2 mg/L + NAA 0.4 mg/L. The best recipe for strong seedling from aseptic seedlings was MS + NAA 0.4 mg/L + banana powder 20 g/L + tryptone 2 g. The best recipe for rooting for aseptic seedlings was 1/2 MS + IBA 0.5 mg/L + charcoal 2 g/L. The best combination of acclimation and transplanting for Phalaenopsis was using sphagnum in the training seedling room, which produced a seedling survival rate of 97%. Our findings, therefore, demonstrate the methods of rapid breeding of the Phalaenopsis orchid, which provide a scientific basis for the conservation of this species.