Patterns for Pea-Rhizobium symbiosis efficiency response to pedological and varietal variations in Tunisia

Abstract

Pedological constrains and varietal recommendations are serious causes of Pea-Rhizobium symbiosis efficiency deviations in Tunisia limiting pea crop adaptation to varying environments. In order to explore variation patterns of this symbiosis in contrasting soils and varieties and appreciate its contribution to plant adaptation, nine locations with potential pea crop vocation are prospected for collection of soils. Two pea varieties with different cycle length are randomly sown on triplicate irrigated containers and placed on natural condition during two seasons. The results have shown that soil fertility is mostly low and highly variable. It is mainly affected by high active limestone content and pH or by salinity. The studied factors (Soil type, Variety) have presented highly significant effect on native rhizobia efficiency, pea root nodulation, shoot and root biomass production, and shoot nitrogen accumulation (p < 0.0001). The long cycle variety gave the highest nodulation and adaptability to pedological variations. The multivariate data analysis indicates that Pea-Rhizobium symbiosis efficiency variability is mainly due to soil microbial biomass, phosphorus, organic matter, and electrical conductivity differences between soils. However, Principal Coordinate Analysis has confirmed the determining effect of these variables on rhizobia effectiveness, pea nodulation, growth and nitrogen accumulation. These results confirm that nitrogen-fixing symbiosis does not contribute in adaptation of pea crop to pedological constrains in Tunisia. Rhizobial inoculation and sepecific fertilization managment have become an urgent need to improve the production of this crop.