Key message

The response of potato microplants to Azospirillum inoculation is highly variable both in vitro and ex vitro.

Abstract

Plant inoculation with plant-growth-promoting rhizobacteria (PGPR) is widely used to increase the effectiveness of clonal micropropagation. Azospirillum rhizobacteria are model subjects to investigate associative plant–microbe interactions. Here we show that most Azospirillum strains cannot utilize sucrose as the sole carbon source and that their use to inoculate in vitro-grown plants does not lead to bacterial growth in the culture medium. Of the eleven surveyed strains, seven gave a significant increase in at least one growth variable of in vitro-grown potato (Solanum tuberosum L. cv. Nevsky) microplants. Inoculation with six strains led to better survival of the microplants in soil. Only with three strains (A. brasilense Sp245, SR80, and A. halopraeferens Au4^T) did inoculation in vitro significantly promote plant growth ex vitro. The inoculation results were correlated with the biochemical activity of the strains. Indole-3-acetic acid production ranged from 3.74 μg ml⁻¹ with A. brasilense S27 to 87.3 μg ml⁻¹ with A. brasilense Sp245. Active indole-3-acetic acid producers, but not nitrogen fixers, were better plant-growth-promoters. Inoculation in vitro with A. brasilense strains Sp245 and SR80 can be recommended for increasing the effectiveness of clonal micropropagation of potato.

中文翻译：

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固氮螺菌属根际细菌接种在马铃薯外植体中的功效

关键信息

在体外和离体中，马铃薯微型植物对拟螺旋体接种的反应都高度可变。

抽象

用促进植物生长的根际细菌（PGPR）进行植物接种可广泛用于提高克隆微繁殖的效果。根际固氮螺旋菌是研究相关的植物与微生物相互作用的模型对象。在这里，我们表明大多数固氮螺菌菌株不能利用蔗糖作为唯一的碳源，并且它们用于接种体外生长的植物不会导致细菌在培养基中生长。在所调查的11株菌株中，有7株显着增加了至少一种体外生长的马铃薯（Solanum tuberosum L. cv。Nevsky）微植物的生长变量。六株菌株的接种导致土壤中微植物的存活更好。只有三个品系（A. brasilenseSp245，SR80和A. halopraeferens Au4 ^T）确实在体外接种能显着促进离体植物的生长。接种结果与菌株的生化活性相关。吲哚-3-乙酸的生产从3.74微克毫升不等^-1与 A. brasilense S27至87.3微克毫升^-1与A. brasilense SP245。活性吲哚-3-乙酸生产者，而不是固氮剂，是更好的植物生长促进剂。可以建议使用巴西拟南芥菌株Sp245和SR80进行体外接种，以提高马铃薯克隆微繁殖的有效性。