ABSTRACT
Pinus yunnanensis is an important component of China's economic development and forest ecosystems. The growth of P. yunnanensis seedlings experienced a slow growth phase, which led to a long seedling cultivation period. However, asexual reproduction can ensure the stable inheritance of the superior traits of the mother tree and also shorten the breeding cycle. The quantity and quality of branching significantly impact the cutting reproduction of P. yunnanensis, and a shaded environment affects lateral branching growth, development, and photosynthesis. Nonetheless, the physiological characteristics and the level of the transcriptome that underlie the growth of lateral branches of P. yunnanensis under shade conditions are still unclear. In our experiment, we subjected annual P. yunnanensis seedlings to varying shade intensities (0%, 25%, 50%, 75%) and studied the effects of shading on growth, physiological and biochemical changes, and gene expression in branching. Results from this study show that shading reduces biomass production by inhibiting the branching ability of P. yunnanensis seedlings. Due to the regulatory and protective roles of osmotically active substances against environmental stress, the contents of soluble sugars, soluble proteins, photosynthetic pigments, and enzyme activities exhibit varying responses to different shading treatments. Under shading treatment, the contents of phytohormones were altered. Additionally, genes associated with phytohormone signaling and photosynthetic pathways exhibited differential expression. This study established a theoretical foundation for shading regulation of P. yunnanensis lateral branch growth and provides scientific evidence for the management of cutting orchards.
ABSTRACT
As one of the most influential environmental factors, drought stress greatly impacts the development and production of plants. Triploid-induced Passiflora edulis Sims 'Mantianxing' is an important new cultivar for multi-resistance variety selective breeding, which is one of the P. edulis breeding essential targets. However, the performance of triploid 'Mantianxing' under drought stress is unknown. In order to study the drought resistance of triploid 'Mantianxing', our study compared drought-related indicators in diploids and triploids under natural drought experiments, including morphological, physiological, and biochemical characteristics. Results showed that triploid P. edulis 'Mantianxing' showed variable responses to drought treatment. Compared with diploids, triploids showed higher photosynthesis and chlorophyll fluorescence, osmotic adjustment substances, and antioxidant enzyme activity under drought stress and faster chlorophyll biosynthesis and growth recovery after rewatering. Generally speaking, these results indicate that the drought resistance of triploid P. edulis is superior to diploid. This study provides scientific information for breeding stress tolerance variety of P. edulis 'Mantianxing' new cultivar.
ABSTRACT
The regeneration of shoots from endosperm tissue is a highly effective method to obtain triploid plants. In this study, we elucidated the establishment of an in vitro regeneration system from endosperm culture for the production of Passiflora edulis "Mantianxing." The highest callus induction rate (83.33%) was obtained on the media supplemented with 1.0 mg/L TDZ. Meanwhile, the MS medium containing 1.0 mg/L 6-BA and 0.4 mg/L IBA gave the optimum 75% shoot bud induction. Chromosome analysis revealed that the chromosomal count of P. edulis "Mantianxing" regenerated from endosperm tissues was 27 (2n = 3x = 27), which indicated that shoots regenerated from endosperm tissues were triploids. Triploid P. edulis had more drought resistance than diploid plants. Our study provided a method for breeding of passion fruit by means of a stable and reproducible regeneration system from endosperm culture, leading to the generation of triploid plants.