草酸对重寄生真菌盾壳霉分生孢子萌发和菌丝生长的影响

 本文研究了草酸对核盘菌的重寄生真菌盾壳霉(Coniothyrium minitans)分生孢子萌发和菌丝生长的影响。结果表明:草酸对盾壳霉分生孢子萌发没有明显促进作用,在酸碱性非缓冲基质(水琼脂)和酸碱性缓冲基质中,抑制盾壳霉分生孢子萌发的最低浓度分别为150和700μg/mL。在马铃薯葡萄糖琼脂培养基中,当草酸浓度为100~2000μg/mL时,盾壳霉菌丝能够生长,且浓度为300~500μg/mL的草酸对盾壳霉的菌丝生长具有明显的促进作用。在以草酸为唯一碳源的合成培养基中,在酸碱性非缓冲的条件下,当草酸浓度为100~2000μg/mL时,盾壳霉菌丝能够生长,且草酸浓度为500μg/mL时对盾壳霉菌丝生长具有促进作用,而当草酸浓度为2500μg/mL时,盾壳霉菌丝则停止生长。在酸碱性缓冲的合成基质中,草酸浓度为100~4000μg/mL时,盾壳霉菌丝能够生长,且草酸浓度为1500~2500μg/mL时对盾壳霉菌丝生长具有促进作用。在含草酸钙的混浊培养基(以草酸为唯一碳源)上,盾壳霉菌落区域形成了透明圈。上述结果说明盾壳霉能忍耐一定浓度的草酸而进行分生孢子萌发及菌丝生长,且这种真菌可能对草酸分子具有分解作用。

Effect of oxalic acid on spore germination and mycelial growth of the mycoparasite Coniothyrium minitans

Oxalic acid (OA) is a phytotoxin produced by pathogenic fungi including Sclerotinia sclerotiorum. Effect of oxalic acid on spore germination and mycelial growth of C. minitans, the mycoparasite of S. sclerotiorum, was studied in media. The results indicated that OA could not stimulate the spore germination of C. minitans. On unbuffered and buffered media (water agar), the lowest OA concentration for inhibition of C. minitans germination was 150 and 700 μg/mL, respectively. On potato dextrose agar (PDA) amended with OA at 100-2 000 μg/mL, C. minitans could grow,and OA at 300-500 μg/mL in PDA could significantly stimulate the mycelial growth of C. minitans. On an unbuffered synthetic medium amended with OA ranging from 100 to 2 000 μg/mL as the carbon source, C. minitans could grow. The optimum OA concentration was 500 μg/mL and the maximum OA concentration was 2 500 μg/mL. On the buffered media, C. minitans grew at the OA concentration ranging from 100 to 4 000 μg/mL with the optimum OA concentration between 1 500 and 2 500 μg/mL. On opaque media containing calcium oxalate, a clear zone under each colony of C. minitans in each plate was observed. These results suggest that C. minitans could tolerate OA both for its spore germination and for its mycelial growth and C. minitans may degrade oxalic acid.