چكيده لاتين :
Introduction
In recent years, integrated farming systems have been developed based on reduced inputs of chemical fertilizers. Many researchers believe that using fungal bio-fertilizers is an environmentally-friendly approach, as it can help to enhance the crop growth and promote organic farming production (Bulluck et al., 2002; Chacon et al., 2007; Leck et al., 2008; Martinez-Medina et al., 2011). The network of arbuscular mycorrhizal fungi’s (AMF) mycelium connects to the roots and increases the soil volume, which can be more efficient in phosphate uptake than a non-mycorrhizal root (Yedidia et al., 2004; Meghvansi et al., 2008; Neumnn and George, 2009).
Fungal genus Trichoderma (T) is cosmopolitan in soils and the ecological adaptability of Trichoderma species is evident by its widespread distribution including under different environmental conditions and on various substrates (Zheng and Shetty., 2000; Harman, 2005; Yadav et al., 2009; Powlson et al., 2011; Medine et al., 2011). In addition, a synergistic effect of some saprophytic fungi on AMF colonization has been confirmed (Gosling et al., 2006; Meghvansi et al., 2008; Ene and Alexandru, 2008; Martinez and Johnson, 2010; Martinez-Medina et al., 2011; Hemashenpagam et al., 2011). Meghvansi et al. (2008) reported that some Trichoderma strains may influence AMF spore germination and activity.
In recent years, increase in soybean cultivation in Iran has improved the rural economy and socio-economic status of Iranian farmers. Therefore, this study was designed to evaluate the response of soybean seedling growth to inoculation of AMF (both G. intraradices and G. mosseae) and the beneficial fungus of Trichoderma harzianum under conventional and low input phosphate conditions.
Materials and methods
A field study was conducted at the research farm of the Genetics and Agricultural Biotechnology Institute of Tabarestan, the Sari Agricultural Sciences and Natural Resources University (SANRU) during the 2011-2012 growing season. This site is located at latitude 36?N, longitude 53?E and altitude of 25m below sea level (GARMIN ,GPSmap). A factorial experiment was used based on a randomized complete block design with three replicates. Treatments were two factors of fungi inoculation with six levels (T. harzianum and AMF genus Glumus: G. mosseae, G. intraradices, and co-inoculation of T. harzianum + G. mosseae, T. harzianum + G. intraradices and noninoculated control) and phosphorus amounts at three levels (conventional P: 140 k.ha-1 and reduced levels of P0%: 0 and P50%: 70 kg.ha-1). The data were analyzed by using GLM procedures included in the SAS statistical package version 9.1.
Results and discussion
Results of combined analysis showed that the inoculation of T. harzianum and G. mosseae increased SPAD value up to 17% and 16% at the reduced (70 kg.ha-1) and the conventional (140 kg.ha-1) phosphorus dosages as compared with the control, respectively. Using these inoculants plus either reduced or conventional phosphorous dosages had a more remarkable effect on chlorophyll a than those plots without phosphorous application. Co-inoculation of Trichoderma and mycorrhizae fungi in the reduced phosphorous dosage did not have a significant effect on the plant dry weight and chlorophyll a content than the conventional phosphorous dosage. In the present study, the effectiveness of these fungi on soybean growth was remarkable in the reduced phosphorous dosage (70 kg.ha-1) than the non-application of phosphorous. However, these fungi did not show any efficiency in the conventional phosphorous dosage.
Acknowledgements
This work was supported partly by the Genetics and Agricultural Biotechnology Institute of Tabarestan (GABIT) and the Sari Agricultural Sciences and Natural Resources University.
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