Sanda Rašić

The influence of mycorrhizae on pea yield and quality in drought caused stress conditions

Mycorrhizas are associates of fungi, representatives of Zygomyceta, Basidiomyceta and Ascomyceta living on the higher plant roots. Mycorrhizal fungi fossil residues were found on the roots of the first vascular plants derived from the Devon period approx. 400 mil. years B. C. Botanists think that this symbiotic association played an essential role in developing and spreading vascular plants on the earth. However, regardless of their effect on vascular plants development of mycorrhizal fungi affected soil development. They produce humous components and an organic sticky substance (extra-cellular polysaharides) that hold soil into aggregates resulting in a well structured soil of good porosity and a large mycorrhizas intake in the total microbial bio-mass. These fungi colonize roots in about 90% of the vascular plants. The symbiotic association between higher plants and mycorrhizal fungi is highly-interrelated whereby plants benefit from their symbiont whereas fungi gets photosynthesis-formed carbon compounds. Owing to a dense hyphas network that interweaves large soil volume, an effective root absorption zone increases via hyphas. However, the mycorrhizal fungi also extracts chemical agents, thereby, making available elements such as phosphorus, iron, zinc, copper, boron, otherwise presented in low concentrations in a soluble form. Mycorrhizas produce antibiotics protecting plants from parasitic fungi and nematodes whereas owing to hypha network around a root, a plant is protected against parasites. Mycorrhized plants are more resistant to a drought-caused stress, have better and more adequate root system and vascular tissue development. Due to the aforesaid, dry conditions are characterized by plants having higher survival percent and higher yield elements compared to non-mycorrhized ones. Thanks to the traits of this symbiosis and all benefits possessed by mycorrhized plants compared to non-mycorrhized, an agricultural production does not rely only on the indigenous strains of these fungi but inoculation of seedling seed and root is done by a compatible strain of mycorrhizal fungi. Inoculation is done by a dry treatment or wet one in a way that the inoculum suspended is water prior to inoculation (similar to legume seed inoculation with bio-preparations of the nodule bacteria). This procedure is capable for ensuring effective symbiosis and reducing mineral fertilizer and pesticide requirements being very important from economical and ecological aspect.