黄骅盐碱地玉米根系内生真菌分离及耐盐促生功能

Isolation of endophytic fungi from the roots of maize in the saline-alkaline land in Huanghua and screening of strains improving salt tolerance and growth of maize

摘要:

【背景】 土壤盐渍化是影响玉米产量的主要因素之一，植物内生真菌可显著提高植物抗逆性，促进生长发育，玉米内生真菌的研究对玉米增产具有重要意义。【目的】 探究从黄骅盐碱地玉米根系分离的内生真菌的促生特性及对玉米植株的促生效果，为盐碱地玉米增产提供理论依据与材料支持。【方法】 采用组织块法从玉米根系中分离内生真菌并通过浸种实验筛选在NaCl胁迫下对玉米种子萌发具有促进效果的内生真菌；利用形态学和分子生物学相结合的方法对筛选到的内生真菌进行鉴定并测定其解磷解钾、分泌吲哚乙酸(indole-3-acetic acid, IAA)及产铁载体能力等促生特性；采用盆栽试验探究筛选的内生真菌在NaCl胁迫下对玉米生物量、株高、根长、SPAD值及抗氧化酶和丙二醛(malondialdehyde, MDA)等的影响，评价内生真菌对提高玉米促生耐盐效果的影响。【结果】 从玉米根系中共分离得到25株内生真菌，其中内生真菌DYM7和DYM11在0.15 mol/L NaCl胁迫下对玉米种子萌发具有显著促进效果，萌发率达90%；通过形态学与分子生物学鉴定，菌株DYM7为土栖棘壳孢(Setophoma terrestris)，菌株DYM11为嘴突凸脐蠕孢(Exserohilum rostratum)，其均具有解钾、产铁载体、分泌IAA的能力；在NaCl胁迫下，经菌株DYM7和DYM11处理提高了玉米的株高和根长，同时提高了超氧化物歧化酶(superoxide oxidase, SOD)和过氧化物酶(peroxidase, POD)活性，降低了MDA含量。经菌株DYM11处理的玉米的地上干重和地下干重较对照显著提高了16.43%和22.17%。【结论】 筛选的内生真菌通过提高玉米抗氧化酶活性、增加根长及株高、降低MDA含量，从而提高玉米对盐胁迫的耐受能力并促进玉米生长，为滨海盐碱区有益微生物增强农作物盐耐受性并提高其产量提供理论依据和材料支持。

Abstract:

[Background] Soil salinity is one of the main factors affecting maize yield, and endophytic fungi can significantly improve the resistance and growth of plants. Studying the endophytic fungi of maize is of great significance to increase maize yield. [Objective] To study the growth-promoting effects of endophytic fungi isolated from the roots of maize growing in the saline-alkaline land in Huanghua and the growth-promoting effects of the fungi on maize plants, so as to provide a theoretical basis and material support for increasing the maize yield in saline-alkaline land. [Methods] The tissue culture method was used to isolate endophytic fungi from the roots of maize. The seed soaking experiments were carried out to screen out the strains capable of promoting the germination of maize seeds under NaCl stress. The strains screened out were identified by morphological observation and molecular biological methods and characterized for the growth-promoting properties such as phosphorus- and potassium-solubilizing, indole-3-acetic acid (IAA)-secreting, and siderophore-producing abilities. Pot experiments were conducted to evaluate the effects of the strains on the biomass, plant height, root length, SPAD value, superoxide oxidase (SOD) activity, peroxidase (POD) activity, and malondialdehyde (MDA) content of maize plants under NaCl stress. [Results] A total of 25 strains of endophytic fungi were isolated from the roots of maize, among which the strains DYM7 and DYM11 significantly promoted the germination of maize seeds exposed to 0.15 mol/L NaCl, with the germination rate reaching 90%. DYM7 was identified as Setophoma terrestris and DYM11 as Exserohilum rostratum, both of which had the abilities of solubilizing potassium, producing siderophores, and secreting IAA. Under NaCl stress, strains DYM7 and DYM11 increased the plant height, root length, and SOD and POD activities and reduced the MDA content of maize. Moreover, strain DYM11 increased the aboveground dry weight and underground dry weight of maize plants by 16.43% and 22.17%, respectively, compared with the control. [Conclusion] The endophytic fungal strains capable of improving the salt tolerance and growth of maize by increasing the antioxidant enzyme activities, root length, and plant height, and decreasing the MDA content were screened out in this study. This study provides a theoretical basis and material support for the application of beneficial microbial in coastal saline-alkaline areas in improving the salt tolerance and yields of crops.