Study on plant regeneration of callus from the stem of wild loquat

Abstract：【Objective】The Eriobotrya Lindl. belongs to the genus Maloideae of the Rosaceae subfamily.The loquat originates in the south of China and some countries in Southeast Asia, which are adjacent tothe southwest of China and there are more than 30 species or varieties. Breeding of wild loquat and quanti-tative cultivation test work has just begun. The lack of a system of rapid propagation system, especially theexplant material used in tissue culture of wild loquat, is scarce. The stem, which is relative to the wild lo-quat whole plant, is at the most convenient and rich place. Therefore it is necessary to establish the in vitro culture system for the regeneration of the stem callus of wild loquat. The study on wild loquat stem cov-ers callus induction, bud induction and plantlet formation of adventitious bud growth and regeneration, inorder to find suitable methods for induction of stem segment buds, adventitious bud and seedling culturemedium combination formula and environmental growth conditions.【Methods】This work used the stem of2 wild species of Eriobotrya Lindl., and 1 interspecific hybrid as materials to study the callus inductionand plant regeneration of wild loquats in the different combinations of plant growth regulators and cultureconditions. The two wild species are E. prinoides Redh. & Wils and E. bengalensis f. angustifolia Vidal, which were taken from the Yunnan province of China's Shiping county and Kunming city. In addition, ahybrid between the two species of the genus Rhaphiolepis indica×E. deflexa Nakai is a new species of Loquat Germplasm Resources in the South China Agricultural University.【Results】The optimum medium for inducing plant regeneration from callus of the stem segment of the wild species of Eriobotrya plants is MS+ 6-BA 1.0 mg·L^-1+ KT 1.0 mg·L^-1+ NAA 0.1 mg·L^-1. For example, in the regeneration of callus from the stems of E. prinoides Redh. &Wils, the induction rate, sprouting rate and plantlet rate are all100%, the maximum number of adventitious buds is 38.75. The E. bengalensis f. angustifolia Vidal of callus and Plantlet rate reached 100%, sprouting rate reached 65.91% and the number of adventitious buds was 2.32. However, for the intergeneric hybrid of Photinia serrulata Lindl.×E. deflexa Nakai, the best medium component for the generation of the stem callus are MS+6-BA 1.0 mg·L^-1+ NAA 0.1 mg·L^-1and MS+ 6-BA 1.0 mg·L^-1+ TDZ 0.1 mg·L^-1+ NAA 0.1 mg·L^-1, the plantlet regeneration of formula MS+ 6-BA 1.0 mg·L^-1+ TDZ 0.1 mg·L^-1+ NAA 0.1 mg·L^-1to the stem callus of E. prinoides Redh. &Wils and E.bengalensis f. angustifolia Vidal of the most suitable formula screening results are basically the same, but the MS+ 6-BA 1.0 mg·L^-1+ NAA 0.1 mg·L^-1from the late train performance is better in the formula between the two, where the sprouting rate is 100% and the number of adventitious buds is 48 and the plantlet rate is 100%. Among the many growth regulators, TDZ is more sensitive to callus induction and differentiation of the wild loquat, in the high concentration of TDZ, although the differentiation of adventitious buds to induce callus is also not conducive to sprouting.【Conclusion】In different types of wild loquat experiments, the plant regeneration induced effect on both show some similarities, but also show some differences. This may be related to the relationship between the gene and species of wild loquat, and Liu Yicun (2014, 2016) in Eriobotrya species embryo, leaf and stem tip culture in vitro in a series of reports of interspecific similarities and differences appear to be similar. The test found that grouper Photinia serrulata Lindl. × E. deflexa Nakai crossbred loquat in vitro seedling and easy propagation coefficient, and in the preliminary test, the in vitro culture of grouper Photinia serrulata Lindl. is also relatively easy to induce and the seedling propagation coefficient is also large, but the wild species of E. deflexa Nakai is not. Thus, Photinia serrulata Lindl. may have some genetic improvement effects on the reproduction ability of wild loquat. The wild loquat germplasm resources are low, it is easy to brown, slow breeding, and the tissue culture is difficult; compared with other genera of Rosaceae plant the research is relatively backward. A lot of wild loquat germplasm resources are scarce, so they cannot be studied in depth, such as drug extraction, germplasm conservation, breeding and transgenic research. A relatively reliable in vitro regeneration system of the wild species of the genus loquat was established, which simplified the steps of plant regeneration induction and shortened the time of plant regeneration induction, during a short period of time to produce a certain number of tissue culture seedlings, in order to provide the basic material and technical basis for further research on germplasm conservation, breeding and transgenic research.