Abstract
Sugi (Japanese cedar, Cryptomeria japonica) is the most important forestry tree species in Japan, covering 44% of the total artificial forest area. Large amounts of pollen released from these forests each spring cause allergic reactions in approximately 40% of the population, which are a serious social and public health problem in Japan. As a countermeasure, there is an urgent need to reforest using male-sterile plants (MSPs; pollen-free plants); however, the production of MSPs via conventional methods is inefficient, time consuming, and requires considerable resources in terms of labor and space. In the present paper, we described an improved and simplified methodology for the efficient propagation of pollen-free Japanese cedar, combining the use of genetic markers (marker-assisted selection or marker-aided selection) for the early selection of male-sterile genotypes and the use of somatic embryogenesis (SE) for the clonal mass propagation of seedlings. We describe all the stages involved in the production process of somatic seedlings. Our results demonstrated that this methodology easily and efficiently produces MSPs with a discrimination rate of 100% in a short period of time. Production of 243.6 ± 163.6 cotyledonary embryos per plate, somatic embryo germination, and plantlet conversion frequencies of 87.1 ± 11.9% and 84.8 ± 12.6%, respectively, and a 77.6 ± 12.1% survival rate after ex vitro acclimatization was achieved. Moreover, we also describe an easy method for the collection of somatic embryos prior to germination, as well as an efficient and practical method for their storage at 5°C. Finally, a representative schedule for the propagation of pollen-free sugi somatic seedlings is presented as a reference for practical uses. This methodology will definitively help to accelerate the production of C. japonica MSPs across Japan.
Highlights
Sugi (Japanese cedar, Cryptomeria japonica (Thunb. ex L.f.) D.Don, Cupressaceae) forests have been greatly exploited over the past 1,000 years; the artificial planting of sugi is estimated to have begun more than 500 years ago (Ohba, 1993), including clonal forestry via cuttings, which began in the beginning of the 15th century (Toda, 1974)
Since the MALE STERILITY 1 (MS1) gene itself was used as a DNA marker, based on the genotyping results, pollenfree ECLs could be selected with 100% accuracy
somatic embryogenesis (SE) from the vegetative material of selected adult trees is the ideal method for clonal propagation in all practical situations, like in other conifers, the initiation of SE in sugi remains limited to the use of seeds
Summary
Sugi (Japanese cedar, Cryptomeria japonica (Thunb. ex L.f.) D.Don, Cupressaceae) forests have been greatly exploited over the past 1,000 years; the artificial planting of sugi is estimated to have begun more than 500 years ago (Ohba, 1993), including clonal forestry via cuttings, which began in the beginning of the 15th century (Toda, 1974). In contrast to its commercial importance, the large amounts of pollen released from sugi forests each spring cause allergic reactions, which are a serious social and public health problem in Japan; an estimated 40% of people living in Japan suffer from allergic rhinitis caused by sugi pollen (Matsubara et al, 2020), resulting in significant economic losses each year. In this context, the use of malesterile plants (MSPs; pollen-free plants) in reforestation is one of the most effective countermeasures against pollinosis. Seeds for the propagation of C. japonica MSPs are produced by artificial crossing between a male-sterile tree (ms1/ms1), as a seed parent, and a pollen donor (an elite tree selected based on growth performance and morphological traits) with heterozygous sterile allele (Ms1/ms; Maruyama et al, 2020; Tsuruta et al, 2021a)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
