The coloration of the apple fruit (Malus × domestica Borkh.) depends on pigment content. Light stimulus activates a broad range of photosynthesis-related genes, including carotenoids. The effect of light on two red commercial apple cultivars, ‘Summer Prince’ and ‘Arisoo’ at the juvenile stage were examined. Apple fruits were either bagged to reduce light irradiation or were exposed to direct, enhanced sunlight (reflected). The pigment content and the expression of carotenoid metabolism genes in the peel and flesh of apple fruits were significantly different between the shaded and the reflected parts. These parameters were also different in the two cultivars, highlighting the contribution of the genetic background. Further, a combination of light and transient overexpression of carotenogenic genes increased fruit coloration and pigment content in the variety ‘RubyS’. Western blot analysis showed the expression of small heat shock proteins (smHSP) in lysates extracted from the reflected part of the fruits but not in the bagged fruits, indicating the activation of smHSP in response to heat generated by the reflected light. Therefore, the synergy between the genes and the environment dictates the color of apple fruits.

Anthocyanin accumulation is responsible for the red color of the skin of apple fruits (Malus × domestica Borkh.). Environmental stimuli, such as light, temperature, soil factors, tree factors, and the application of chemicals can alter the synthesis of anthocyanins. Herein, we examined the expression of genes related to anthocyanin biosynthesis in the fruit of apple cultivars, ‘Summer Prince’ and ‘Arisoo’ at the early stage of fruit development 60 DAFB (days after full bloom). The expression of genes, which included structural and regulatory genes involved in anthocyanin biosynthesis, and light-responsive genes was determined in fruits developed under the effect of sunlight exposure for seven days. Apple fruits were divided in to: ‘reflected sunlight’, ‘bagged’, and ‘control’ groups. The expression levels of the anthocyanin synthesis-related genes were significantly different among the groups and between the shaded and reflected sides. We also determined the difference in coloration patterns in the different groups using the colorimetric coordinates method. The shaded side of apple fruits quickly turned more redder after exposure to reflected sunlight and the coloration was almost similar to that on the exposed side after the treatment. Strong correlation coefficients between anthocyanin-related gene expression levels and coloration patterns were obtained. This study shows that sunlight plays an important role in stimulating the coloration of apple fruit by regulating the expression of genes involved in anthocyanin accumulation during the early stage of fruit development. The present study assumes importance because redder fruits, generated through a non-transgenic approach would be more acceptable to consumers.

Apples (Malus × domestica Borkh.) require up to several years for flowering and bearing fruits. The transition from vegetative to reproductive phase is controlled by floral regulators such as TERMINAL FLOWER 1 (TFL1) and FLOWERING LOCUS T (FT). TFL1 mediates the maintenance of vegetative phase, unlike the antagonistic function of FT to promote the transition into reproductive phase. In this study, we isolated apple TFL1-like gene (MdTFL1) to elucidate various phenotypic traits triggered by the antisense expression of MdTFL1 in tobacco apart from its floral induction function. Early flowering was observed in the tobacco line with MdTFL1 knockout, indicating the reduced time for transition to vegetative phases. Quantitative reverse-transcription PCR showed upregulation of genes involved in the regulation of floral induction, including NtAP1, NtSOC1, NFL1, and NtFTs, and downregulation of carotenoid cleavage dioxygenases (CCDs) and CEN-like genes in transgenic lines. Interestingly, transgenic tobacco expressing antisense MdTFL1 exhibited distinct morphological changes in lateral shoot outgrowth, internode length, and the development of leaves, flowers, and fruits. The results suggested that using the antisense expression of MdTFL1 gene is one of the approaches to shorten the vegetable phase and proposed improvement of plant architecture in horticultural crops.

The timing of fruit bag removal is important for achieving optimum fruit quality, coloration, and visual appearance. Therefore, this study investigated the effects of fruit bag removal timing on fruit quality and color and the occurrence of physiological disorders in ‘Arisoo’ apples. Fruits were bagged in two-layer paper bags, which were removed 30, 20, and 10 days before harvest (DBH). Unbagged fruits served as the control. The incidence of fruit cracking, sunburn, and pathogen infection was highest in the unbagged group, followed by the group with bag removal at 30 DBH, and lowest in those with bag removal at 20 and 10 DBH. However, bag removal at 10 DBH significantly reduced fruit weight and soluble solids content but increased firmness. Additionally, bag removal at 10 DBH resulted in poorly colored fruits with higher chlorophyll and lower anthocyanin and carotenoid pigments and lower expression levels of pigment-related genes, including anthocyanin-, carotenoid-, and chlorophyll degradation-associated genes, compared with those in the other treatment groups. Bag removal at 30 and 20 DBH did not significantly affect fruit quality or coloration, but it did affect fruit size. Overall, this study serves as a reference for determining the optimal timing of fruit bag removal to enhance the quality and coloration of ‘Arisoo’ apples.

Genetic transformation is a critical tool for gene manipulation and functional analyses in plants, enabling the exploration of key phenotypes and agronomic traits at the genetic level. While dicotyledonous plants offer various tissues for in vitro culture and transformation, monocotyledonous plants, such as rice, have limited options. This study presents an efficient method for genetically transforming rice (Oryza sativa L.) using seed-derived embryogenic calli as explants. Two target genes were utilized to assess regeneration efficiency: green fluorescent protein (eGFP) and the apple FLOWERING LOCUS T (FT)-like gene (MdFT1). Antisense MdFT1 was cloned into a vector controlled by the rice α-amylase 3D (Ramy3D) promoter, while eGFP was fused to Cas9 under the Ubi promoter. These vectors were introduced separately into rice embryogenic calli from two Korean cultivars using Agrobacterium-mediated transformation. Transgenic seedlings were successfully regenerated via hygromycin selection using an in vitro cultivation system. PCR confirmed stable transgene integration in the transgenic calli and their progeny. Fluorescence microscopy revealed eGFP expression, and antisense MdFT1-expressing lines exhibited notable phenotypic changes, including variations in plant height and grain quality. High transformation efficiency and regeneration frequency were achieved for both tested cultivars. This study demonstrated the effective use of seed-derived embryogenic calli for rice transformation, offering a promising approach for developing transgenic plants in monocot species.

Pruning is labor-intensive and increases production costs, while mechanical pruning offers a promising alternative. However, research on its effectiveness remains limited. To address this gap, we evaluated the effects of mechanical pruning over two consecutive years (2023 and 2024) on tree growth, yield, and fruit quality of ‘Arisoo’ apple trees. The treatment included hand (manual) pruning (HP), mechanical pruning (MP), and combined mechanical and hand pruning (MP + HP) applied during winter pruning in a super-spindle-slender-shaped apple orchard. MP significantly reduced pruning time; however, the amount of plant biomass removed was lower in the MP treatment than in the HP and MP + HP treatments. Canopy volume was higher in the HP treatment than in MP and MP + HP treatments; however, the pruning treatments did not affect trunk cross-sectional area or tree yield. Leaf chlorophyll and nitrogen contents were slightly lower in the MP treatment than in the HP treatment in 2023 but were not affected in 2024. The MP treatment also noticeably reduced light penetration within the canopy and produced smaller fruits with lower soluble solids content and poorer coloration at harvest compared to the HP and MP + HP treatments. In contrast, the HP and MP + HP treatments showed similar effects on light penetration, yield, fruit size, and fruit quality; however, the MP + HP treatment significantly reduced the pruning time compared with the HP treatment. Overall, this study found that MP reduced light penetration and produced smaller and poorly colored fruits, whereas a follow-up combination of HP after MP improved pruning efficiency, light penetration, fruit size, and fruit quality.