荔枝霜疫霉的生物学特性

Biological Characteristics of Peronophthora litchii

通过不同培养基和培养条件的筛选,研究荔枝霜疫霉的生物学特性及病菌侵染的超微形态特征。结果表明,该菌的孢囊梗属于多级有限生长,其孢子囊萌发后形成多种真菌形态,如游动孢子、芽管、孢囊梗及次生孢子囊;芽孔位于孢子囊一端、两端或四周,在1个芽孔处可萌发1根、2根或多根芽管,位于基部的芽孔萌发能力较强。该菌培养35d后可产生厚垣孢子,培养45d可产生大量的卵孢子,菌龄为10d时产生孢子囊的萌发率最高。温度为16～24℃时孢子囊萌发形成游动孢子,在26℃以上萌发形成芽管。该菌在PDA培养基上的产孢量最高,在燕麦培养基上的生长速度最快。生长的最适pH值为6～8。超微形态研究结果表明,该菌可通过孢子囊及游动孢子从荔枝果皮的嵴点裂缝处与皮孔处侵入,并在果皮内扩展,直到荔枝的内果皮。试验结果加深了对该病菌的了解,为进一步了解该病的发生危害提供了理论依据。

Peronophthora litchii Chen ex Ko was cultured on selected mediums under selected conditions and its biological characteristics and ultra-structures were observed. The results demonstrated that the growth of sporangiophore of this fungus was of muhi-determinative type. The sporangia were germinated to form various shapes, such as zoospores, tubes, sporangiophore, or secondary sporangia. The germinating holes were located at one end, both ends or the periphery of the sporangia. One, two or more radical buds were germinated from one germinating hole. The germinating holes from the base of the sporangia generally had higher germination capability. This fungus produced chlamydospores and oospores 35 days and 45 days respectively after cultured. The sporangia produced from the fungus cultured for 10 days had the highest germinating rate. The sporangia were germinated to form zoospores at 16-24℃ and tubes at 26℃. The fungus produced most spores on the PDA plate, and grew fastest on the oat plate. The most suitable pH for its growth was 6-8. Observation of the uhrastructures of this fungus showed that the fungus invaded lychee fruit through the lenticels and cracks of the rind by means of sporangia or zoospores, then germinated and dispersed within the pericarp and then into the endocarp. The results offer a deeper understanding of this pathogen and provide theoretical basis for understanding of the occurrence and damage of the Litchi downy blight.