Effect of Wild-Type and Mutant Plant Growth-Promoting Rhizobacteria on the Rooting of Mung Bean Cuttings

Abstract

Mung bean cuttings were dipped in solutions of wild type and mutant forms of the plant growth-promoting rhizobacterium Pseudomonas putida GR12-2 and then incubated for several days until roots formed. The bacteria P. putida GR12-2 and P. putida GR12-2/aux1 mutant do not produce detectable levels of the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, whereas P. putida GR12-2/acd36 is an ACC deaminase minus mutant. All bacteria produce the phytohormone indole-3-acetic acid (IAA), and P. putida GR12-2/aux1 overproduces it. Treatment of cuttings with the above-mentioned bacteria affected the rates of ethylene production in the cuttings in a way that can be explained by the combined effects of the activity of ACC deaminase localized in the bacteria and bacterial produced IAA. P. putida GR12-2 and P. putida GR12-2/acd36-treated cuttings had a significantly higher number of roots compared with cuttings rooted in water. In addition, the wild type influenced the development of longer roots. P. putida GR12-2/aux1 stimulated the highest rates of ethylene production but did not influence the number of roots. These results are consistent with the notion that ethylene is involved in the initiation and elongation of adventitious roots in mung bean cuttings.

Indole-3-acetic acid (IAA) producing Pseudomonas isolates inhibit seed germination and α-amylase activity in durum wheat (Triticum turgidum L.)

“…Although IAA is known as a prominent plant growth promoter, it can also stimulate transcription of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase. The latter enzyme facilitates a key step in ACC oxidasemediated ethylene biosynthesis (Mayak et al, 1999). The IAA-derived ethylene is believed to participate in the disruption of the normal growth (i.e.…”

Alternative rooting induction of semi-hardwood olive cuttings by several auxin-producing bacteria for organic agriculture systems

“…Besides, they utilize a simple and idealised system where it is possible to check the biotechnological potential of the studied bacterium. The use of Vigna radiata and Brassica napus have been reported widely by others (Mayak et al, 1999;Penrose & Glick, 2003;Shaharoona et al, 2006;Rashid et al, 2012). They have been mostly used in studies on the involvement of phytohormones, more specif ically auxin and ethylene, in the initiation and development of roots (Mayak et al, 1999).…”

“…The effects of bacterial strains on the development of adventitious roots on mung bean cuttings (Vigna radiata) were assessed as described by Mayak et al (1999), with minor modifications. Mung bean seeds (Wilczek) provided by Penelas Legumes, S.A. (León, Spain) were disinfected by 30 s treatment with 96% ethanol, 6 min with 6% sodium hypochlorite and six washes with sterile distilled water.…”

Role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils

“…In some of the plants, ACC is exuded from roots or seeds and then taken up by the bacterium and cleaved by ACC deaminase to ammonia and α-ketobutyrate . The bacteria utilize the ammonia evolved from ACC as a nitrogen source and thereby decrease ACC within the plant (Penrose and Glick, 2001) with the concomitant reduction of plant ethylene and promoting root elongation (Burd et al, 1998;Mayak et al, 1999;Grichko and Glick, 2001;Belimov et al, 2002). To maintain the gradient between internal and external ACC levels, the plant must exude increasing amounts of ACC.…”