Rhizobium strains selected from the Amazon region increase the yield of snap bean genotypes in protected cultivation

Abstract

Although the use of inoculants containing rhizobia is encouraged, there are no official recommendations for inoculation of snap bean. In this respect, the aim of this study was to evaluate the agronomic performance of Rhizobium strains in symbiosis with snap bean cultivars with different growth habits and crop cycles. The experiment was carried out in pots with soil in a greenhouse in the spring-summer season in Lavras, state of Minas Gerais, Brazil. A completely randomized experimental design was used, with 4 replications, in a 4 × 7 factorial arrangement involving four snap bean cultivars and seven treatments -five strains of Rhizobium (UFLA 02-100, UFLA 02-127, UFLA 04-173, CIAT 899, and PRF 81), plus two controls without inoculation (with and without 500 mg N-NH 4 NO 3 ·dm -3 ). We conclude that: i) while genetic differences were observed among cultivars with respect to nodulating capacity, in all cases significant benefits were observed from BNF inoculation and ii) inoculation with selected strains of Rhizobium, as well as fertilization with mineral N, favors plant growth, snap bean yields, and accumulation of N in the pods and, therefore, can fully substitute nitrogen fertilization in snap bean grown under protected cultivation.

Selection of elite Rhizobium strains by biometric techniques for inoculation in common bean

“…Even numerous and competitive native soil bacterial populations are not always able to establish efficient symbiosis that significantly contributes to common bean growth. Thus, it may be necessary to employ inoculants containing strains that are more efficient in N 2 fixation (Ferreira et., 2009;Moreira, Siqueira & Brussaard, 2006;Oliveira et al, 2019;Oliveira, Ferreira, et al, 2018;Pádua Oliveira et al, 2017;Soares et al, 2006), such as those found in the present study (Tables 2 and 4; Figures 2, 3, and 4). The contribution of these populations rises, in turn, when complemented with 80 kg N-urea ha −1 (C7), that is, the increase in yield was due to the nitrogen fertilizer; however, C7 showed less stability than C6.…”

“…It is not by chance that the good performance of the UFLA02‐127 (S5) strain occurred in so many situations in this study, or that it often appears in Brazilian studies. Its efficiency in snap bean, also P. vulgaris , was greater than that of the native population and equivalent to that of the native control with mineral N in an experiment in pots with soil at pH 5.8 (Oliveira, Ferreira, et al., 2018). With common bean in the field, the strain led to a mean of 1,700 kg ha −1 in four rainy season crops in acid or moderately acid soils without soil amendment and with low use of inputs such as micronutrients or agricultural chemicals (Ferreira et al., 2009; Nogueira et al., 2017; Pádua Oliveira et al., 2017; Soares et al., 2006), reaching levels near 3.0 t ha −1 in one of them (Nogueira et al., 2017).…”

“…The strain UFLA02-127 (S5), just as the others of the UFLA code studied here, was isolated from acid soils of the Brazilian Amazon and also belongs to the Rhizobium genus. It is tolerant to acidity, has high ability in competition with already established strains, and has high N 2 fixation capacity (Nogueira et al, 2017;Oliveira, Ferreira, et al, 2018;Pádua Oliveira et al, 2017;Soares et al, 2006). Furthermore, It has performance comparable to that of CIAT899 in peat (Nogueira et al, 2017;Pádua Oliveira et al, 2017) and liquid (Oliveira, Ferreira, et al, 2018) vehicles, which increases its chance of being adopted by farmers.…”

“…The growth capacity of the UFLA02-100 (S2) strain under high (pH 4.9-5.0: Soares et al, 2006;Rufini et al, 2011), moderate (pH 5.6-6.0: Rufini et al, 2011;Nogueira et al, 2017;Oliveira, Ferreira, et al, 2018;Pádua Oliveira et al, 2017), and low (pH 6.4: Pádua Oliveira et al, 2017) active acidity provides conditions for adaptation to different environments, even though conditions for its development appear to be optimal since it had variable performance in this study, above all in E2 and E7, which affected the GE interaction. Even so, its yield remained at around 1,200 kg grain ha −1 in the varied environments (Table 1).…”

“…Studies in the Amazon have indicated a wide diversity of rhizobia with the ability to tolerate stresses predominant in tropical soils (Ferreira et al, 2012;Guimarães et al, 2012;Oliveira-Longatti et al, 2013Soares et al, 2014). Furthermore, Rhizobium strains isolated from the Brazilian Amazon region have shown the capacity for biological N 2 fixation with leguminous species (Costa et al, 2019;Ferreira et al, 2019;Guimarães et al, 2015;Nogueira et al, 2017;Oliveira et al, 2017Oliveira et al, , 2020Oliveira, Ferreira, et al, 2018;Oliveira-Longatti et al, 2013;Pádua Oliveira et al, 2017;Soares et al, 2006;Zilli et, al.,2009) and, for that reason, have received special attention in studies directed to the production of inoculants. In addition, attention to inoculant production has increased due to the possible adverse effect of chemical fertilizers on the environment and their production costs.…”