Abstract
As an endophytic fungus, Piriformospora indica has attracted great attention for its plant growth- and stress resistance-promoting effects on various host plants. However, up until now, there have been no reports on its application in asparagus. In this study, we report the colonization ability of P. indica in the roots of three asparagus varieties, 'Guanjun' (GJ), 'Fengdao No. 2' (FD), and 'Jin Lusun No. 1' (JL), with colonization ratios of 80.0%, 76.6%, and 73.3%, respectively. The influences of this fungal colonization on the growth of GJ, FD, and JL seedlings were further studied by determining the growth- and phytohormone-related parameters. The results showed that, at 2 months post inoculation (mpi), the P. indica-colonized seedlings exhibited improved total root length, peroxidase (POD) activity, and jasmonic acid (JA) accumulation in their roots and photosynthetic pigment accumulation in the leaves of all three varieties. At 8 mpi, most of the detected growth-related parameters, such as plant height, stem number and width, dry weight, photosynthetic pigment accumulation, and POD activity, were improved by the fungal colonization. However, the contents of 1-aminocyclopropane-1-carboxylic acid (ACC) in the P. indica-colonized roots were lower than that in the non-colonized ones. Moreover, the fungus's promoting effects on GJ were found to be the best of the three varieties. These results indicate that P. indica colonization can promote asparagus seedling growth and development by enhancing root development and by regulating phytohormone balance, with some variety-specific and temporal differences.