A novel bud mutant of navel orange (Citrus sinensis) shows tolerance to chlorosis in acidic and magnesium-deficient soils

Development of Yein-Early, a Unique Fruit-Color and Leaf-Shape Mutant of Citrus unshiu, and Its Specific Selection Marker

Citrus unshiu Marc. cv. Miyagawa-wase is one of the most widely cultivated citrus varieties on Jeju Island in Republic of Korea. Mutation breeding is a useful tool for inducing genetic diversity by causing genomic mutations in a short period of time. We previously conducted mutation breeding using gamma irradiation to develop new varieties of C. unshiu. Here, we describe one of these varieties, Yein-early, which has a redder peel, greater hardness, and higher sugar content compared with the wild type (WT). Yein-early leaves also showed a unique phenotype compared with the WT, characterized by longer longitudinal length, shorter transverse length, stronger curling, and longer petiole length. Genome resequencing of Yein-early and the WT uncovered significant single-nucleotide polymorphisms (SNPs) and insertions/deletions (InDels). These variations were crucial in identifying molecular markers unique to Yein-early. In addition, we developed an allele-specific PCR marker specifically targeting a homozygous SNP in Yein-early that distinguishes it from the WT and other citrus varieties. This study contributes to the understanding of pigment synthesis in fruits and provides a valuable tool for selection of the novel Yein-early variety in citrus breeding programs.

Investigating the Discoloration of Leaves of Dioscorea polystachya Using Developed Atomic Absorption Spectrometry Methods for Manganese and Molybdenum

The Chinese yam (Dioscorea polystachya, DP) is promising for the food and pharmaceutical industries due to its nutritional value and pharmaceutical potential. Its proper cultivation is therefore of interest. An insufficient supply of minerals necessary for plant growth can be manifested by discoloration of the leaves. In our earlier study, magnesium deficiency was excluded as a cause. As a follow-up, this work focused on manganese and molybdenum. To quantify both minerals in leaf extracts of DP, analytical methods based on atomic absorption spectrometry (AAS) using the graphite furnace sub-technique were devised. The development revealed that the quantification of manganese works best without using any of the investigated modifiers. The optimized pyrolysis and atomization temperatures were 1300 °C and 1800 °C, respectively. For the analysis of molybdenum, calcium proved to be advantageous as a modifier. The optimum temperatures were 1900 °C and 2800 °C, respectively. Both methods showed satisfactory linearity for analysis. Thus, they were applied to quantify extracts from normal and discolored leaves of DP concerning the two minerals. It was found that discolored leaves had higher manganese levels and a lower molybdenum content. With these results, a potential explanation for the discoloration could be found.

Physiological and transcriptional analyses reveal the resistance mechanisms of kiwifruit (Actinidia chinensis) mutant with enhanced heat tolerance

High temperature is an environmental stressor that severely threatens plant growth, development, and yield. In this study, we obtained a kiwifruit mutant (MT) of 'Hongyang' (WT) through 60Co-γ irradiation. The MT possessed different leaf morphology and displayed prominently elevated heat tolerance compared to the WT genotype. When exposure to heat stress, the MT plants exhibited stabler photosynthetic capacity and accumulated less reactive oxygen species, along with enhanced antioxidant capacity and higher expression levels of related genes in comparison with the WT plants. Moreover, global transcriptome profiling indicated that an induction in genes related to stress-responsive, phytohormone signaling, and transcriptional regulatory pathways, which might contribute to the upgrade of thermotolerance in the MT genotype. Collectively, the significantly enhanced thermotolerance of MT might be mainly attributed to profitable leaf structure variations, improved photosynthetic and antioxidant capacities, as well as extensive transcriptome reprogram. These findings would be insightful in elucidating the sophisticated mechanisms of kiwifruit response to heat stress, and suggest the MT holds great potential for future kiwifruit improvement with enhanced heat tolerance.