REVISIÓN

Current knowledge and future prospects of lima bean (Phaseolus lunatus)-rhizobia symbiosis

Conocimiento actual y perspectivas de futuro de la simbiosis frijol de lima (Phaseolus lunatus)-rizobia

Marineide Rodrigues do Amorim ¹, Jadson Emanuel Lopes Antunes ¹, Louise Melo de Souza Oliveira ¹, Sandra Mara Barbosa Rocha ¹, Joao Pedro Alves Aquino ¹, Marcia do Vale Barreto Figueiredo ², Ademir Sérgio Ferreira de Araújo ¹

1 Agricultural Science Center, Federal University of Piauí. Teresina. Piauí. Brazil. asfaruaj@yahoo.com.br

2 Soil Biology Laboratory. Agronomical Institute of Pernambuco. Recife. Pernambuco. Brazil

Originales: Recepción: 20/02/2019 - Aceptación: 05/07/2019

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ABSTRACT

Lima bean (Phaseolus lunatus) is an important species of the genus Phaseolus for human consumption in tropical regions. The seeds are important source of protein for people from South America, Africa and Mexico. In addition, as a legume plant, lima bean presents the ability to perform the biological nitrogen fixation (BNF) through the symbiosis with nitrogen-fixing bacteria. The studies about diversity and efficiency of lima bean-rhizobia symbiosis have increased worldwide, mainly in Latin America. These studies have shown Bradyrhizobium and Rhizobium as the main symbionts, although Sinorhizobium, Mesorhizobium and Allorhizobium have been found associated with lima bean. Also, there is a large variation in the efficiency of N fixation by the current isolates of rhizobia and some rhizobia have presented high capability for fixing N. This review aims to explore the studies about diversity and efficiency of rhizobia in symbiosis with lima bean.

Keywords: BNF-efficiency; Phaseolus; Rhizobia diversity

RESUMEN

El frijol de lima (Phaseolus lunatus) es una especie importante del género Phaseolus para consumo humano en regiones tropicales. Las semillas son una fuente importante de proteínas para las personas de América del Sur, África y México. Además, como leguminosas, el frijol de lima presenta la capacidad de realizar la fijación biológica de nitrógeno (BNF) a través de la simbiosis con bacterias fijadoras de nitrógeno. Los estudios sobre la diversidad y la eficiencia de la simbiosis de frijol de lima-rizobio han aumentado en todo el mundo, principalmente en América Latina. Estos estudios han demostrado que Bradyrhizobium y Rhizobium son los principales simbiontes, aunque Sinorhizobium, Mesorhizobium y Allorhizobium se han asociado al frijol de lima. Además, existe una gran variación en la eficacia de la fijación de N por los aislamientos actuales de rizobios y algunos rizobios han presentado una alta capacidad para reparar N. Esta revisión tiene como objetivo explorar los estudios sobre la diversidad y la eficacia de rizobios en simbiosis con frijol lima.

Palabras clave: BNF-eficiencia; Phaseolus; Diversidad de rizobios

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INTRODUCTION

Legume plants belonging to the genus Phaseolus present economic importance worldwide. This genus comprises five species: P. vulgaris L., P. lunatus L., P. coccineus L., P. acutifolius A. Gray and P. polyanthus Greeman (14). Lima bean (P. lunatus L.) is considered the second most cultivated species from the genus Phaseolus, being an important species of plant for humans in tropical regions (11, 17, 23).

This legume is originated from Perú and was domesticated in the Andean Mountains, specifically in southern Ecuador-northwestern Perú, and centralwestern Mexico (25). The study of Mota-Aldana et al. (2010) also identified three main varieties: "Big Lima" (big seeds) domesticated in the Andean Mountains; "Sieva" and "Potato" (small seeds) originated in central-western Mexico. Lima bean is predominantly autogamous, although it has outcrossing rates up to 48% (6). It has been characterized by an indeterminate growth habit, a prolonged flowering period, and production of a large number of pods (37).

Lima bean is considered an important source of protein for people from South America, Africa, and Mexico. Interestingly, this crop is economically important in some regions of United States. For example, California has about 24,000 acres of lima bean with a value of about $32 million in 2017 (35). The seeds present high content of protein (210-260 g·kg^-1) and carbohydrate (550-640 g·kg^-1), low fat (10-23 g·kg^-1) levels and high fiber levels (32-68 g·kg^-1), high levels of the minerals K, Zn, Ca, and Fe, and low levels of Na and P (7).

It is also a relevant plant for Brazil, mainly in the Northeast region, where it is used as an alternative food source. Currently, Brazil produces approximately 14,951 t of lima bean from an area of about 37,521 ha. Since the Northeast region presents high annual temperature and drought periods, lima bean is adapted to these conditions and presents rusticity and tolerance to long and dry periods (5).

On the other hand, lima bean also presents the ability to associate symbiotically with nitrogen-fixing bacteria, commonly known as rhizobia, and therefore can perform the process of biological nitrogen fixation (BNF) (33). Since this plant needs about 100 kg N to produce 1.5 t of seeds (18), the BNF could be an ecological and economical alternative for supplying N to the plant.

Biological nitrogen fixation in lima bean

BNF is an important source of nitrogen (N) to the plants, which is important for plant growth. It has suggested that after photosynthesis, the process performed by plants to produce the energy necessary for their survival, BNF is regarded as the second most important biological process on the earth (http://cnx.org/content/ m47338/latest/). This process occurs through of a symbiotic system between legumes and rhizobia (36), and the fixed N 2 represents a renewable source of N within agriculture. The amount of N fixed by plants is ranged from 100 to 900 kg ha^-1 year^-1. For example, in soybean, an important crop worldwide, the contribution of N derived from the atmosphere via BNF represents 0 to 337 kg N ha^-1 (9).

The symbiosis rhizobia-legume occurs in root nodules that are established by legume in response to appropriate rhizobia (2, 33). Thus, the nodulation is usually a host-specific interaction where some specific bacteria infect a limited range of legumes and the N-fixing nodules are formed as a consequence of this interaction (30). Rhizobia able to nodulate d fix N ₂ in legumes comprise bacteria distributed among the genera Agrobacterium, Allorhizobium, Azorhizobium, Bradyrhizobium, Burkholderia, Cupriavidus, Devosia, Herbaspirrilum, Mesorhizobium, Methylobacterium, Ochrobactrum, Phyllobacterium, Rhizobium, Shinella and Sinorhizobium (8).

The success of symbiosis depends on the availability of compatible rhizobia to the specific legumes. Considering the genus Phaseolus, the studies have presented information about nodulation and BNF in common bean (P. vulgaris), which form symbiotic associations with several species from the genus Rhizobium (20, 21). There are variations among the efficiency of BNF in common bean. Recently, Moreira et al. (2017) evaluated the contribution of rhizobia isolates on N derived from the atmosphere, via BNF, to P. vulgaris and found a range of 509 to 1037 mg plant^-1 which represented 46% to 75% of the total N found in the plants. For lima bean, the studies about symbiosis with rhizobia have shown a miscellaneous of genera able to nodulate this legume with different efficiencies. In this way, studies about the diversity of rhizobia which present ability for associating with lima bean are increasing in the last years. Thus, this review aims to explore the studies about diversity and efficiency of rhizobia in symbiosis with lima bean.

Diversity of lima bean-nodulating rhizobia

Rhizobia are common inhabitants of diverse soil types and the number of cells can substantially differ from a few cells to 10⁵ bacteria per gram of soil (13). The wide geographical distribution of rhizobia may be related to the large genetic diversity among these bacteria (22). The knowledge about diversity of rhizobia provides information on host preferences, predominance of isolates, genetic structure and also source of efficient strains for using as inoculant (21).

The majority of legume-nodulating rhizobia belong to α-proteobacteria group that include Rhizobium, Sinorhizobium, Azorhizobium, Bradyrhizobium, Allorhizobium, Mesorhizobium, Bradyrhizobium and Methylobacterium (16). Usually, each genus is associated and nodulates with specific legumes. For example, Rhizobium is associated with common bean (Phaseolus vulgaris L.), while Bradyrhizobium nodulates soybean (Glycine max L. Merrill) and cowpea (Vigna unguiculata L.) (15).

Previous old host-based classification scheme included symbionts of lima bean in the same group of rhizobia associated with slow-growing cowpea (Vigna unguiculata) (29). This group was a diverse assemblage of strains that were later included in the genus Bradyrhizobium (1, 34). In these studies, the rhizobial isolates associated with lima bean were obtained from areas where this plant species is not native and the studies have only focused on morphological, physiological and symbiotic characteristics. Thus, the limitation of these methods did not address properly the existing diversity.

Currently, studies have been conducted with molecular tools that provide the possibility to identify taxonomic groups of rhizobia in soils and have shown several genera with ability to associate with lima bean (table 1, page 284).

Table 1. Rhizobia genera isolated from lima bean nodules.

Tabla 1. Géneros de Rhizobia aislados de nódulos de frijol de lima.

Indeed, molecular tools have identified a diverse group of rhizobia-nodulating lima bean comprising bacteria belonging to Bradyrhizobium, Rhizobium, Sinorhizobium, Mesorhizobium and Allorhizobium (4, 14, 26, 28, 32).

The majority of studies about the diversity of rhizobia in lima bean have assessed a relative wide collection from geographic locations including Perú, Mexico and Brazil (4, 14, 19, 23, 26, 32). Perú is considered the center of diversity of this plant species and the first study on the diversity of rhizobia, by using molecular tools, has characterized some symbionts of lima bean (26). Thus, Ormeño-Orrillo et al. (2017) evaluated the molecular diversity of rhizobial isolates associated with lima bean and found divergent bradyrhizobial lineages (B. yuanmingense and Bradyrhizobium sp.) according to Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) of the rpoB, dnaK, nifH and nodB genes and sequencing of the 16S rDNA. This finding could confirm that Bradyrhizobium is the main genus effectively associated lima bean. Indeed, the study conducted later by Duran et al. (13), by using a polyphasic approach, confirmed Bradyrhizobium-nodulating lima bean in Perú. However, the authors found two different lineages (B. paxllaeri sp. and B. icense) those described by OrmenoOrrillo et al. (2006). The hypothesis that Bradyrhizobium is the most important genus found in Perú was addressed by Matsubara and Zuñiga-Dávila (2015) who evaluated rhizobia associated with lima bean in Perú and found species belonging to Bradyrhizobium genus (B. yuanyrense, B. liaoningense, B. paxllaeri, and B. icense). However, this study also reported the genus Rhizobium (R. mesosinicum and R. alamii). Thus, these studies showed that there is a high diversity of rhizobia associated with lima bean in Perú and it indicates a relative promiscuity of lima bean in contrast to previous statements that this plant species has a restricted symbiont (28).

As an important center of domestication (25), Mexico also has a high diversity of rhizobia able to nodulate lima bean. The first study about diversity of rhizobianodulating lima bean in Mexico was conducted by Lopez-Lopez et al. (2013) who sequenced rpoB, recA, nodZ, and nifH genes of the rhizobia and found isolates described as Bradyrhizobium. It was the first report of nodule bacteria from lima bean in Mesoamerican region (center of origin and domestication) and it confirms Bradyrhizobium as the main bacteria associated with lima bean. Therefore, Bradyrhizobium seems to be the most abundant genus nodulating lima bean in Perú and Mexico.

Brazil is an important region of dispersion of lima bean and the studies have shown a high diversity of rhizobia associated with this plant species. Thus, a study about genetic diversity of native rhizobia associated with lima bean in Brazil was conducted by Santos et al. (2011) and shows a broad spectrum of rhizobial groups. In this study, rhizobia isolates were obtained and placed into groups based on divergence in their morphological, physiological and genetic traits. The restriction patterns obtained with endonucleases MboI, HaeIII, and NheI showed sufficient variability and identified isolates belonging to the genera Bradyrhizobium, Mesorhizobium and Rhizobium. Later, Araujo et al. 2015, sequenced the 16S rDNA of these isolates and found species belonged to the genus Bradyrhizobium, Sinorhizobium and Rhizobium. These results confirm that lima bean may be associated by diverse rhizobia species and also showed different groups than those reported in Perú and Mexico. Indeed, Araújo et al. (2015) found 14 isolates of rhizobia genetically different that those observed in Perú by Ormeño-Orillo et al. (2006). The isolates found by Araujo et al. (2016) were classified as Rhizobium, Bradyrhizobium and Allorhizobium.

Efficiency of rhizobia on BNF in lima bean

Studies about nodulation and efficiency of BNF have increased in the last ten years and the main objective is to evaluate suitable strains for recommendation of inoculation. These studies have focused on the evaluation of rhizobia in different genotypes of lima bean (3, 10, 11). Indeed, the first study about nodulation in lima bean evaluated different genotypes (12). The main question was to determine if the nodule formation coincides with plant development and they found a close relationship between plant and nodule growth. Later, Santos et al. (2009) evaluated the ontogeny of nodulation in lima bean and found that the highest nodule number and biomass occurred between 45 and 60 days after plant emergence, which correspond to the flowering period of the plant. Additionally, Santos et al. (2009) found red colored nodules as an indication of leghemoglobin (photo 1, page 286).

Photo 1. Nodules in lima bean roots at 45 days after plant emergence.

Foto 1. Nódulos en raíces de frijol de lima a los 45 días de la emergencia de la planta.

However, the confirmation that the rhizobia had high efficiency in fixing N in lima bean was reported by Antunes et al. (2004) who evaluated the symbiotic effectiveness of 17 rhizobial isolates associated with lima bean and compared with two strains of reference CIAT 899 and NGR 234. They found eight isolates with higher N accumulation and N₂-fixation efficiency compared with the strains CIAT 899 and NGR 234. Rhizobia isolated from different legume species seem to present ability for nodulating and fixing N in lima bean. Thus, Costa et al. (2017) evaluated rhizobia isolates from nodules of Vigna unguiculata, Campsiandra surinamensis, Inga sp. and Swartzia sp. on lima bean and found isolates with high efficiency in N fixation. Therefore, the prospection of rhizobia able to nodulate lima bean should be also done in different legume species.

As reported above, the main genus found in association with lima bean is Bradyrhizobium, although Rhizobium and other genera are able to associated with this plant species. Thus, in order to evaluate the efficiency of Bradyrhizobium and Rhizobium on nodulation and efficiency of BNF in lima bean, Costa Neto et al. (2017) found Bradyrhizobium more efficient than Rhizobium in establishing the symbiotic association with lima bean varieties. These authors also found isolates with high efficiency as compared with the other symbiotic pairs. Thus, the studies are in advance to find suitable and potential strains for inoculation in lima bean.

Future prospects

Lima bean is an important legume in tropical regions and the studies have shown a great diversity of rhizobia associated with this plant species. Also, there is a large variation in BNF efficiency observed in the current isolates of rhizobia. Therefore, further studies have to focus on: a) classification of rhizobia associated with lima bean in different regions; b) selection of specific and efficient strains for using as inoculant; c) improvement of N fixation ability by native rhizobia and adapted to different regions; d) selection of lima bean genotypes combined with high efficient strains; e) implementation of programs of lima bean breeding and management in Perú, Mexico and Brazil; f) analysis of the advantages of an adequate symbiosis for improving the content of protein and better quality of the nutritional offer for human nutrition.

REFERENCES

1. Allen, O. N.; Allen, E. K. 1939. Root nodule bacteria of some leguminous plants. II. Cross-inoculation tests within the cowpea group. Soil Science. 47: 63-67.         [ Links ]

2. Alonso, J. M.; Alvarez, J. A.; Vega Riveros, C.; Villagra, P. E. 2019. Finite (Hausdorff) dimension of plants and roots as indicator of ontogeny. Revista de la Facultad de Ciencias Agrarias. Universidad Nacional de Cuyo. Mendoza. Argentina.         [ Links ]

3. Antunes, J. E. L.; Gomes, R. L. F.; Lopes, A. C. A.; Araújo, A. S. F.; Lyra, M. C. C. P.; Figueiredo, M. V. B. 2011. Eficiência simbiótica de isolados de rizóbio noduladores de feijão-fava (Phaseolus luntaus L.). Revista Brasileira Ciencia Solo. 35: 751-757.         [ Links ]

4. Araujo, A. S. F.; Lopes, Â. C. A.; Gomes, R. L. F.; Junior, J. E. A. B.; Antunes, J. E. L.; Figueiredo, M. D. V. B. 2015. Diversity of native rhizobia-nodulating Phaseolus lunatus in Brazil. Legume Research-An International Journal. 38(5): 653-657.         [ Links ]

5. Azevedo, J. N.; Franco, J. D.; Araújo, R. O. C. 2003. Composição química de sete variedades de feijão-fava. Teresina. Embrapa Meio-Norte. 4 p.         [ Links ]

6. Baudoin, J. P.; Degreef, J.; Hardy, O.; Janart, F.; Zoro, B. I. 1998. Development ofan in situ conservation strategy for wild lima bean (Phaseolus lunatus L.) populations in the central valley of Costa Rica. In: Owens, S. J.; Rudall, P. J. (Eds) Reproduction Biology, Royal Botanic Garden Press. England. 417-426 p.         [ Links ]

7. Chel-Guerrero, L.; Domínguez-Magaña, M.; Martínez-Ayala, A.; Dávila-Ortiz, G.; Betancur-Ancona, D. 2012. Lima Bean (Phaseolus lunatus) Protein Hydrolysates with ACE-I Inhibitory Activity. Food Nutriton Sciences. 3: 511-521.         [ Links ]

8. Chidebe, I. N.; Jaiswal, S. K.; Dakora, F. D. 2017. Distribution and phylogeny of microsymbionts associated with cowpea (Vigna unguiculata) nodules across different agro-ecological regions of Mozambique. Applied Environment Microbiology. 84(2): 1-25.         [ Links ]

9. Ciampitti, I. A.; Salvagiotti F. 2018. New insights into soybean biological nitrogen fixation. Agronomy Journal. 110: 1185-1196.         [ Links ]

10 Costa Neto, V. P.; Mendes, J. B. S.; Araújo, A. S. F.; Alcântara Neto, F.; Bonifacio, A.; Rodrigues, A. C. 2017. Symbiotic performance, nitrogen flux and growth of lima bean (Phaseolus lunatus L.) varieties inoculated with different indigenous strains of rhizobia. Symbiosis. 73(2): 117-124.         [ Links ]

11. Costa, E. M.; Ribeiro, P. R. A.; Lima, W.; Farias, T. P.; Moreira, F. M. S. 2017. Lima bean nodulates efficiently with Bradyrhizobium strains isolated from diverse legume species. Symbiosis. 73(2): 125-133.         [ Links ]

12. Dobert, R. C.; Blevins, D. G. 1993. Effect of seed size and plant growth on nodulation and nodule development in lima bean (Phaseolus lunatus L.). Plant Soil. 148: 11-19.         [ Links ]

13. Drew, E. A.; Ballard, R. A. 2010. Improving N₂ fixation from the plant down: compatibility of Trifolium subterraneum L. cultivars with soil rhizobia can influence symbiotic performance. Plant and Soil. 327: 261-277.         [ Links ]

14. Durán, D.; Rey, L.; Mayo, J.; Zúñiga-Dávila, D.; Imperial, J.; Ruiz-Argüeso, T.; Martinez-Romero, E.; Ormeño-Orrillo, E. 2014. Bradyrhizobium paxllaeri sp. nov. and Bradyrhizobium icense sp. nov., nitrogen-fixing rhizobial symbionts of lima bean (Phaseolus lunatus L.) in Perú. International journal of systematic and evolutionary microbiology. 64(6): 2072-2078.         [ Links ]

15. Koskey, G.; Mburu, S. W.; Kimiti, J. M.; Ombori, O.; Maingi, J. M.; Njeru, E. M. 2018. Genetic characterization and diversity of rhizobium isolated from root nodules of mid-altitude climbing bean (Phaseolus vulgaris L.) varieties. Frontiers in Microbiology. 9: 968.         [ Links ]

16. Lemaire, B.; Dlodlo, O.; Chimphango, S.; Stirton, C.; Schrire, B.; Boatwright, J. S. 2015. Symbiotic diversity, specificity and distribution of rhizobia in native legumes of the Core Cape Sub-region (South Africa). FEMS Microbiology Ecology. 91: 1-17.         [ Links ]

17. Li, F.; Cao, D.; Liu, Y.; Yang, T.; Wang, G. 2015. Transcriptome sequencing of lima bean (Phaseolus lunatus) to identify putative positive selection in Phaseolus and legumes. International journal of molecular sciences. 16(7): 15172-15187.         [ Links ]

18. Lopes, Â. C. A.; Gomes, R. L. F.; Araújo, A. S. F. 2015. Phaseolus lunatus: Diversity, Growth and Production. New York: Nova Science Inc.         [ Links ]

19. López-López, A.; Negrete-Yankelevich, S.; Rogel. M. A.; Ormeño-Orrillo. E.; Martínez Esperanza, J.; Martínez-Romero, E. 2013. Native bradyrhizobia from Los Tuxtlas in Mexico are symbionts of Phaseolus lunatus (Lima bean). Systematic and Applied Microbiology. 36: 33-38.         [ Links ]

20. Martinez, E.; Segovia, L.; Mercante, F. M.; Franco, A. A.; Graham, P. H.; Pardo, M. A. 1991. Rhizobium tropici: a novel species nodulating Phaseolus vulgaris beans and Leucaena sp. trees. International Journal of Systematic and Evolutionary Microbiology. 41: 417-426.         [ Links ]

21. Martínez-Romero, E. 2003. Diversity of Rhizobium-Phaseolus vulgaris symbiosis: overview and perspectives. Plant and Soil. 252: 11-23.         [ Links ]

22. Martinez-Romero, E.; Caballero-Mellado, J. 1996. Rhizobium phylogenies and bacterial genetic diversity. Critical Reviews in Plant Sciences. 15: 130-140.         [ Links ]

23. Matsubara, M; Zúñiga-Dávila, D. 2015. Phenotypic and molecular differences among rhizobia that nodulate Phaseolus lunatus in the Supe valley in Perú. Annals of microbiology. 65(3): 1803-1808.         [ Links ]

24. Moreira, L. P.; Oliveira, A. P. S.; Ferreira, E. P. B. 2017. Nodulation, contribution of biological N₂ fixation, and productivity of the common bean (Phaseolus vulgaris L.) inoculated with rhizobia isolates. Australian Journal Crop Science. 11:644-651.         [ Links ]

25. Motta-Aldana, J. R.; Serrano-Serrano, M.; Hernández-Torres, J. H.; Castillo-Villamizar, G.; Debouck, D. G.; Chacóns, M. I. 2010. Multiple origins of lima bean landraces in the Américas: Evidence from chloroplast and nuclear DNA polymorphisms. Crop Science. 50(5): 1773-1787.         [ Links ]

26. Ormeño, E.; Torres, R.; Mayo, J.; Rivas, R.; Peix, A.; Velázquez, E.; Zúniga, D. 2007. Phaseolus lunatus is nodulated by a phosphate solubilizing strain of Sinorhizobium meliloti in a Peruvian soil. In: Velázquez, E. Rodríguez-Barrueco, C. (Eds). Developments in Plant and Soil Sciences. Springer-Verlag. The Netherlands. 243-247 p.         [ Links ]

27. Ormeño-Orrillo, E.; Vinuesa, P.; Zuñiga-Dávila, D.; Martínez-Romero, E. 2006. Molecular diversity of native bradyrhizobia isolated from lima bean (Phaseolus lunatus L.) in Perú. Systematic and Applied Microbiology. 29: 253-262.         [ Links ]

28. Ormeño-Orillo, E.; Zuniga, D.; Martinez-Romero, E. 2015. Biodiversity of nitrogen-fixing nodule bacteria associated with lima bean (Phaseolus lunatus L.) in its domestication centers. In: Lopes, Â. C. A., Gomes, R. L. F. Araújo, A. S. F. (Eds). Phaseolus lunatus: Diversity, Growth and Production, Publisher: Nova Science Publishers.         [ Links ]

29. Quirós, A.; Chichón, R.; Recio, I.; López-Fandiño, R. 2006. The use of high hydrostatic pressure to promote the proteolysis and release of bioactive peptides from ovalbumin. Food Chemistry. 54: 19-27.         [ Links ]

30. Santos, J. O. ; Araújo, A. S. F.; Gomes, R. L. F.; Lopes, Â. C. A.; Figueiredo, M. V. B. 2008. Rhizobia - Phaseolus lunatus symbiosis: Importance and diversity in tropical soils - A review. Dynamic Soil, Dynamic Plant. 2: 56-60.         [ Links ]

31. Santos, J. O.; Araújo, A. S. F.; Gomes, R. L. F.; Lopes, A. C. A.; Figueiredo, M. V. B. 2009. Ontogeny of nodulation in lima bean (Phaseolus lunatus). Brazilian Journal of Agricultural Research. 4: 426-429.         [ Links ]

32. Santos, J. O.; Antunes, J. E. L.; Lyra, M. C. C. P.; Araujo, A. S. F.; Gomes, R. L. F.; Lopes, A. C. A.; Figueiredo, M. V. B. 2011. Genetic diversity among isolates of Rhizobia from Phaseolus lunatus. Annals Microbiology. 61: 437-444.         [ Links ]

33. Schultze, M.; Kondorosi, A. 1998. Regulation of symbiotic root nodule development. Annual Review of Genetics. 32: 33-57.         [ Links ]

34. Thies, J. E.; Singleton, P. W.; Bohlool, B. B. 1991. Influence of the size of indi-genous rhizobial population on establishment and symbiotic performance of introduced rhizobia on field-grown legumes. Applied and Environmental Microbiology. 57: 19-28.         [ Links ]

35. USDA. 2019. Crop Production 2018 Summary. National Agricultural Statistics Service. 129 p.         [ Links ]

36. Zahran, H. H. 2001. Rhizobia from wild legumes: diversity, taxonomy, ecology, nitrogen fixation and biotechnology, Journal of Biotechnology. 91(23): 143-153.         [ Links ]

37. Zoro, B. I.; Maquet, A.; Baudoin, J. P. 2003. Population genetic structure of wild Phaseolus lunatus (Fabaceae), with special reference to population sizes. American Journal of Botany. 90: 897-904.         [ Links ]

ACKNOWLEDGEMENTS

The authors are grateful to 'Conselho Nacional de Desenvolvimento Científico e Tecnológico' (CNPq-Brazil) for financial support of research with lima bean. All authors are supported by Research fellowships from CNPq-Brazil (Research Productivity).