高产 IAA 哈茨木霉突变株 M95 的筛选 及其对黄瓜的促生作用.

[Objectives]The aim of this study was to screen M95 which was mutant strains of Trichoderma harzianum with high yield of 3-indoleacetic acid (IAA) by irradiation with high-energy rays, and evaluate its growth-promoting effect on plants. [Methods]The mutant library of Trichoderma harzianum was obtained by X-ray irradiation, and the mutant strain M95 with the highest yield of IAA was screened by Salkowski colorimetry and high performance liquid chromatography (HPLC). Then the carbon source utilization characteristics of high-yielding IAA mutants were studied by the Biolog FF MicroPlateTM. The expression levels of auxin biosynthesis-related genes in M95 were detected by quantitative real-time PCR. Finally, the growth-promoting effect of M95 on cucumber was investigated by hydroponics and pot experiments. [Results]Thirty-eight mutants were screened from the mutant library. The IAA production of M95 was 20.51% higher than that of the wild type. The results of the Biolog FF MicroPlateTM showed that M95 grew fastest and significantly faster than the wild strain NJAU 4742（WT）under the condition of D-fructose as the sole carbon source. Quantitative PCR results showed that the transcript levels of acetamide dehydrogenase gene iaaH2 and nitrilase gene nit2 increased by 32.68 and 14.58 times, respectively, compared with WT. The growth-promoting effect of M95 on cucumber seedlings was significantly better than that of WT. Relative to WT,cucumber plant height, leaf area, below ground fresh weight and dry weight in the M95 treatment increased by 14.79%,16.84%,31.41% and 47.96% in the hydroponic condition, 20.99%,13.92%,17.92% and 34.02% in the first season pot trial, respectively, and 12.23%,15.15%,23.29% and 30.02% in the second season pot trial. In addition, the number of inter-root bacteria, fungi and xylem increased by 1.91%,5.80% and 5.08%,respectively, in the M95 treatment compared to WT in the pot trial. [Conclusions]The IAA high-yielding strain T.harzianum M95 was obtained by screening, and it had a significant promoting effect on the growth of cucumber seedlings. The increase in the transcription levels of acetamide dehydrogenase and nitrilase in M95 was the main reason for the improvement of its IAA-producing ability. [ABSTRACT FROM AUTHOR]