Characterization  of old wheat varieties for their capacity to form mycorrhiza and mycorrhization impact on the seed quality

Wheat (kind Tritucum aestivum, Poaceae family) is a very important cereal of agronomic interest. Some very ancient varieties are set aside for recent varieties often selected to meet a consumer intensive cultivation of pesticides. Organic farming production system assuming a reduction of synthetic chemical inputs in order to preserve the ecosystem can be defined as a practice where the use of synthetic fertilizers, chemical pesticides and genetically modified organisms is prohibited.

This practice is gaining more and more popularity and the amount of land cultivated in this way has increased by 60% between 2000 and 2004. Constraints associated with the production of organic grains include lower yields due to nutrient deficiencies in the soil and weed competition. During the past 90 years, the international efforts in wheat breeding have focused on increasing yield and quality parameters.

The establishment of a wheat database based on morphological, taxonomic and ecological criteria and the introduction of arbuscular mycorrhizal (AM), known to help in the selection and induce an increase in yield and quality of production with a perspective to increase production in an agriculture that respects the environment, could be an integral part of an appropriate strategy. However, mycorrhizal effects on yield and quality of production are not always predictable and the mechanisms that regulate these qualitative parameters are largely unknown.

Field screening of 53 ancient wheat varieties showed differences in their ability to interact with endogenous mycorrhizal fungi. Among the analysed plants, only five varieties were mycorrhized for all samples at tillering. All samples were mycorrhized at the heading stage for all varieties. Nineteen showed a decrease in the number of mycorrhized samples at the ears maturity.

Inoculation with a laboratory inoculum during a greenhouse experiments in pots, containing either the wheat field soil or “ Epoisses” soil, showed that all wheat varieties form mycorrhizal symbiosis. Between varieties tested, recent wheat varieties used in organic farming were better in forming symbiosis than the old, but the mycorrhizal effect on plant yield is seen only for old varieties. Demonstrating a variety effect on the development and 6 expression of symbiosis. The benefits of mycorrhizal symbiosis are more pronounced for the qualitative phenomena as the seed viability.

The addition of a commercial inoculum in a similar greenhouse experiment modified these observations. This inoculum helped to improve wheat development but also the seed quality of some varieties, demonstrating both the importance of the plant genome in the beneficial expression of the symbiosis and the impossibility of indigenous mycorrhizal fungi to ensure optimal development of symbiosis. The previously observed field varietal effect was confirmed even after adding an exogenous inoculum as, excepted for one variety, inoculation has improved yield. This was especially noticeable in the variety that was most productive, stressing the importance to develop crossing strategies to increase the wheat response to mycorrhiza.