Measurements of genetic variability for symbiotic dinitrogen fixation in fieldgrwon fababean (Vicia faba L.) using a low level15N-tracer technique

Abstract

Before starting a breeding program aimed at improving the nitrogen nutrition of Viciafaba, the authors tried an alternative technique to the acetylene reduction assay, to measure some genetic variability in the plant material. The quantity of dinitrogen fixed by several cultivars of Viciafaba was estimated using a low enrichment ~SN tracer method and high precision 15N mass spectrometry. The fababeans were cultivated for two years in two different soils.The percentage of fixed dinitrogen in the seed varied between genotypes from 40 to 83% of the total nitrogen and was positively correlated with the total seed nitrogen (r = 0.64 to 0.86). A highly significant positive correlation was also found between the total seed nitrogen and the quantity of fixed dinitrogen in the seed (r = 0.95 to 0.99).The technique used to measure dinitrogen fixation proved to be useful and reliable enough to discriminate between various genotypes, grown over a period of two years in two different soils. However, several non-fixing control plants showed significant differences in their 15N enrichment and the problem of choosing a good reference plant was raised and discussed.

Enhancing legume N2 fixation through plant and soil management

“…CA low irrigation frequency represented an allowable depletion limit of 120 mm evaporation from a class A pan evaporimeter (8 irrigations over the 109d growing season), while the high irrigation frequency was based on an allowable depletion limit of 60 mm (15 irrigations over 109d). Hardarson et al (1984), Kumar Rao and Dart (1987) and Duc et al (1988).…”

Measurement of Nitrogen Fixation by Soybean in the Field Using the Ureide and Natural 15N Abundance Methods

“…Therefore, the overall estimate of P will tend to be related to crop yield (total dry matter, total N, seed yield), particularly in those situations of limited nitrate supply (e.g. 12,16 Estimates of P varied between 0 and 68% (61'5N) and between 6 and 56% (ureide). At P > 40%, the ureide method underestimated P compared with the 65'5N method (Fig.…”

Genetic Adjustment to Changing Climates: faba bean

“…Spontaneous or induced mutants were isolated with either defective or super nodulation and for defective mycorhizal symbiosis (Duc and Picard 1986;Duc 1995;Duc et al 1989). A strong genotypic correlation was identified between yield potential and the quantity of fixed nitrogen (Duc et al 1987). Even though genetic variability is known, breeders have not started breeding directly on root symbiotic traits because of the high cost of this type of work, but they should keep attention on the efficiency of these symbioses in changing climatic conditions.…”

“…In nonlimiting situations, grain yields frequently surpass 6 t/ha of dry seeds and 12 t/ha of total biomass dry matter (DM) (Dantuma and Klein Hulze 1979). The symbiotic N 2 fixation allows more than 70% of nitrogen stored by the crop to be derived from air (Duc et al 1987;Schmidtke 2008). The plants are large and robust, facilitating mechanical weeding, and since synthetic nitrogen fertilizer is not needed, fossil fuel consumption is low, the risk of N 2 O emission linked to N fertilizers application is absent, and consequently this crop offers valuable ecological services in sustainable agriculture and in organic farming strategies.…”