Abstract
The genotypic variability in molybdenum (Mo) accumulation in common bean seeds has been demonstrated in cases in which soil is the main Mo source, but this variability is yet unknown when Mo is foliar-applied. Therefore, seed Mo concentrations (SMoCc) and seed Mo contents (SMoCt) of 12 genotypes were determined in four experiments in the Zona da Mata, Minas Gerais, Brazil, in which plants were sprayed with 600 g ha-1 Mo. For comparison, two additional experiments without external Mo were conducted. Without Mo application, the average SMoCc was undetectable or 2.83 µg g-1, without significant differences among genotypes. On average, with Mo applications, SMoCc ranged from 14.7 to 25.0 µg g-1 and SMoCt, from 3.94 to 6.84 µg. 'Majestoso' was among the genotypes with the highest SMoCc in the four experiments. However, the large-seeded 'Jalo MG-65' and 'Carnaval' generally had higher SMoCt than the small-seeded 'Majestoso'. 'Ouro Negro' and especially 'Valente' were among the genotypes with the lowest SMoCc and SMoCt. The values of these variables were 61 and 90 %, respectively, higher for 'Majestoso' than those for 'Valente'. Our results suggest that common bean genotypes differ in their capacity to accumulate foliar-applied Mo in the seeds. Mo-rich seeds of large-seeded genotypes or of small-seeded of small-seeded genotypes with good capacity to accumulate Mo in seeds can be produced with relatively less Mo fertilizer.
Highlights
Molybdenum (Mo) is a constituent of three enzymes related to the nitrogen (N) nutrition of plants: nitrogenase, nitrate reductase and xanthine dehydrogenase
Four field experiments were conducted in which plants of 12 common bean genotypes were sprayed with 600 g ha-1 Mo
The average seed Mo concentrations (SMoCc) in Oratórios was 2.83 μg g-1, whereas seed Mo contents (SMoCt) varied from 0.61 to 1.32 μg, depending on the genotype. These results suggest that the soil in Coimbra is poorer in Mo than the soil in Oratórios, since SMoCc indicates the Mo availability in the soil (Brodrick et al, 1995)
Summary
Molybdenum (Mo) is a constituent of three enzymes related to the nitrogen (N) nutrition of plants: nitrogenase, nitrate reductase and xanthine dehydrogenase. These enzymes act, respectively, in the acquisition of N by means of biological N fixation, in N utilization absorbed as nitrate, and in the degradation of purine (Mendel, 2011). Two other plant enzymes contain Mo: sulfide oxidase and aldehyde oxidase The latter is involved in the synthesis of abscisic acid, which plays an important role in plant growth and development and in the adaptive response to various stress environments (Mendel, 2011). Sulfide oxidase is involved in cell detoxification of excess sulfide (Mendel, 2011) and in the degradation of sulfurcontaining amino acids (Kaiser et al, 2005)
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