Breeding of Early Maturity, High-Quality Auricularia heimuer Strains Using Protoplast Fusion

Auricularia heimuer is an important cultivated edible mushroom in China. This study used the early maturity, chrysanthemum-shaped, high yield strain "8808" and the late-maturity, single-shaped, high-quality strain "HW15" as parental strains. The objective was to develop a new strain of A. heimuer combining early maturity with excellent quality through protoplast fusion. Protoplasts from the parental strains were fused using a polyethylene glycol (PEG)-mediated method. The obtained hybrids were identified through clamp connection, antagonism tests, esterase isozyme analysis, and Inter-Simple Sequence Repeat (ISSR) molecular marker techniques, followed by ultimate selection through cultivation. Among the evaluated hybrids, strain R33 exhibited desirable agronomic traits: primordium formation occurred 4 days earlier than the parental strain HW15, harvest time was advanced by 6 days, yield increased by 14.7%, and the ratio of absorbed water improved by 29.8%. Transcriptomic analysis revealed that starch and sucrose metabolism as well as amino acid metabolism pathways were significantly upregulated in R33, which may be associated with its early maturity and high-yield phenotype. Overall, protoplast fusion technology can be used to create promising candidate strains that combine early maturity, high yield, and excellent quality.