Effect of Mycorrhizal (Glomus mosseae) and Mycorrhizal- like (Piriformospora indica) Fungi on Seedling Growth of Wheat and Some Weed Species

Arbuscular mycorrhizal fungi are one of the most important fungi in the soil, which coexist with the roots of many plants almost from 400 million years ago. These fungi play an important role in the sustainable functioning of agricultural ecosystems. Mycorrhizal fungi are not only beneficial and can increase the growth of plants, in some cases, some mycorrhizal species also cause growth reduction in certain species of plants. Investigating the effect of mycorrhizal fungus on growth of nine important weed species in the fields showed that the growth of weeds in the presence of fungi decreases. The Piriformospora indica is a root-endophytic fungus that was isolated from the rhizosphere soil in the Thar Desert of India. This fungus same as typical AMF greatly improves the grown and overall biomass production of a broad spectrum of hosts. This fungus coexists on the root of a number of crops and weeds of monocotyledons, dicotyledons, Chenopodiaceae and Brassicaceae that do not inoculated by mycorrhizal fungi. This research was conducted to evaluate and compare the growth response of wheat and some important weeds of this crop, to Glomus mosseae and P. indica in controlled conditions, for ecological management of weeds.

In order to investigate fungal root colonization of wheat and some weed species, nine separated trails were carried out as completely randomized design with five replications in 2016. Treatments were inoculation with  Glomus mosseae, Piriformospora indica and non-inoculated control on nine plant species of wheat (Tritium asativum L.) wild rye (Secale cereal L.), wild barley (Hordeum spontaneum Koch), barley (Hordeum morinum L.), wild oats (Avena ludoviciana Durieu), flixweed (Descurainia Sophia L.), drooping brome )Bromus tectorum L.), chickweed (Stellaria media L.) and grass pea (Lathyrus sativus L.). The soil used was (1:1) soil and fine sand. After passing through a sieve of two mesh, for three consecutive days and for four hours per day was sterilized in oven at 120 °C. After filling pots out with one kg of autoclaved soil, spores of G. mosseae and mycelia pieces of P. indica, were added to the pots. Ten seedlings were transferred in to each pot and were thinned to three seedlings per pot at 2-4 leaves stage. Plants were harvested 8 weeks after transplanting, the plants were removed from the crown and transferred to the laboratory. The roots of the plants were washed with distilled water to be thoroughly cleaned, and then the root of a plant from each pot was randomly cut into pieces of one centimeter and prepared to determine the percentage of colonization. Shoot and root dry matter and mycorrhizal growth responses were determined as well.

The results indicated the different effects of fungi on wheat and weed species. Roots of wheat were colonized by G. mosseae and P. indica fungi by 87.9 and 90%, respectively. The lowest amount of root colonization by P. indica and G. mossea was observed in the chickweed by 10 and 7.5%, respectively. As a result of coexistence of both species of fungi with barley, wild barley, flixweed, drooping brome and grass pea, root and shoot dry weight were increased, and in some other plants, in the presence of either G. mosseae or P. indica, the root and shoot dry weight decreased, compared to the control. The dry weight of wild rye and chickweed in coexistence with P. indica was 0.13 and 0.35 g plant-1, respectively, and in coexistence with G. mosseae was 0.14 and 0.33 g plant-1, respectively. Compared to the control, the use of P. indica reduced shoot dry weight of wild rye and chickweed by 31.58% and 14.63%, respectively, and the use of G. mosseae in wild rye reduced 26.36% of shoot dry weight. Dry weight of Elusine coracana in presence of Phizophagus intraradices mycorrhizal fungus increased by 40% and in the presence of P. indica increased by 81% compared with control. Biomass reduction in lambsquarters in the presence of mycorrhizal fungi was 26% compared with the un-inoculated plants. The weeds and wheat in the presence of P. indica and G. mosseae varied in terms of mycorrhizal growth response. Mycorrhizal growth response of weeds was varied from -32.26 to +48.78 percentages. Among the monocotyledon weeds, the highest growth response was observed in the presence of P. indica in the weed of barley (47.78%) and wild barley (44.14%). Both P. indica and G. mosseae caused a negative growth response in wild rye, so that the growth response in the presence of P. indica was -0.66% and in the presence of G. mosseae -23.22%, indicates that the growth reduction of wild rye was higher in the presence of P. indica. The difference in mycorrhizal growth response in weeds, in addition to plant species, depends on the type of soil and environmental conditions.

In general, due to the different reactions of wheat and some studied weed species to P. indica and G. mosseae inoculation, it seems that the application of these fungi in wheat fields could cause reduction in grass weed damages.