Abstract

Potassium (K) is an important nutrient for plant growth. However, less than 2% of K in the soil exists in plant-available forms. Further, fungi inhabiting saxicolous habitats are infrequently examined for their plant growth-promoting ability. Therefore, in this study, we isolated K solubilizing fungi (KSF) from saxicolous habitats and screened them for their ability to produce plant growth hormones, organic acids, and siderophore that may facilitate plant growth. Seventy-two saxicolous fungal isolates were screened for their K solubilization in Aleksandrow medium amended with mica. Of these, eight potential KSF isolates resembling Aspergillus species based on 18S rRNA gene sequencing were selected for further screening. Three of these KSF isolates KSF-07 (Aspergillus terreus), KSF-55 (Aspergillus niger), and KSF-69 (Aspergillus violaceofuscus) produced different organic acids (ascorbic, acetic, benzoic, citric, malic, and oxalic acid), indole acetic acid (0.678–46.326 µg L⁻¹), and siderophore (46.66–65.26 PSU) under in vitro conditions. The three Aspergillus species solubilized 56.56−59.80 mg L⁻¹ of K from mica and 33.97–39.19 mg L⁻¹ from potassium aluminum silicate. Inoculation of KSF and mica amendment significantly improved plant growth and K uptake by maize and also enhanced the KSF populations in post-harvest soil. Pearson’s correlation analysis revealed the existence of a significant negative correlation between soil pH and available K. Among the KSF isolates screened, A. violaceofuscus (KSF-69) presents an excellent prospect as a bio-inoculant for improving crop growth in different soil types.

摘要

钾（K）是植物生长的重要营养元素。然而，土壤中不到 2% 的钾以植物可利用的形式存在。此外，很少有人检查栖息在石竹属栖息地的真菌促进植物生长的能力。因此，在这项研究中，我们从鱼鲛栖息地中分离了钾增溶真菌 (KSF)，并筛选了它们产生可能促进植物生长的植物生长激素、有机酸和铁载体的能力。筛选了 72 株石竹属真菌分离株在用云母修正的 Aleksandrow 培养基中的 K 溶解度。其中，根据 18S rRNA 基因测序，选择了八种类似于曲霉属的潜在 KSF 分离株进行进一步筛选。其中三个 KSF 分离株 KSF-07 ( Aspergillus terreus)、KSF-55 ( Aspergillus niger ) 和 KSF-69 ( Aspergillus violaceofuscus)产生不同的有机酸（抗坏血酸、乙酸、苯甲酸、柠檬酸、苹果酸和草酸）、吲哚乙酸（0.678–46.326 µg L ^-1）和铁载体 (46.66–65.26 PSU)在体外条件下。三个曲霉物种溶解56.56-59.80毫克的L ^-1从云母和33.97-39.19毫克的L的K ^-1来自硅酸铝钾。接种 KSF 和云母改良剂显着改善了玉米的植物生长和钾吸收，并增强了收获后土壤中的 KSF 种群。Pearson 的相关分析表明土壤 pH 值和有效钾之间存在显着的负相关。在筛选的 KSF 分离株中，A. violaceofuscus (KSF-69) 作为生物接种剂在不同土壤类型中改善作物生长具有极好的前景。