Diversity of Rhizobium-Phaseolus vulgaris symbiosis: overview and perspectives. Plant Soil
Plant and Soil
(Impact Factor: 2.95).
04/2003; 252(1):11-23. DOI: 10.1023/A:1024199013926
Common bean (Phaseolus vulgaris) has become a cosmopolitan crop, but was originally domesticated in the Americas and has been grown in Latin America for several thousand years. Consequently an enormous diversity of bean nodulating bacteria have developed and in the centers of origin the predominant species in bean nodules is R. etli. In some areas of Latin America, inoculation, which normally promotes nodulation and nitrogen fixation is hampered by the prevalence of native strains. Many other species in addition to R. etli have been found in bean nodules in regions where bean has been introduced. Some of these species such as R. leguminosarum bv. phaseoli, R. gallicum bv. phaseoli and R. giardinii bv. phaseoli might have arisen by acquiring the phaseoli plasmid from R. etli. Others, like R. tropici, are well adapted to acid soils and high temperatures and are good inoculants for bean under these conditions. The large number of rhizobia species capable of nodulating bean supports that bean is a promiscuous host and a diversity of bean-rhizobia interactions exists. Large ranges of dinitrogen fixing capabilities have been documented among bean cultivars and commercial beans have the lowest values among legume crops. Knowledge on bean symbiosis is still incipient but could help to improve bean biological nitrogen fixation.
Available from: Azam Shakeel
- "Results indicate that in very young leaves, ethylene is not able to induce leaf senescence, but when the leaves reach a certain level of maturity, ethylene will induce senescence, and as senescence is progressing, the process will run independently of ethylene presence (Fan et al., 2000). Harvested leafy vegetables produce small amounts of ethylene; however, senescence is accelerated if they are stored together with ethylene producing products (Ludford, 2003; Martinez-Romero et al., 2007; Whitaker, 2003). Ethylene can also motivate and accelerate wounding of membranes, loss of chlorophyll and vitamin C, toughening, and undesirable flavor changes (Kader, 2005). "
- "Nodulation genes of B. paxllaeri and B. icense belong to clade IV, which is found in rhizobia isolated mostly in subtropical regions from a wide range of legume plants growing in the Mediterranean region, Australia and China (Cardinale et al., 2008; Durán et al., 2013; Ormeño-Orrillo et al., 2013; Stepkowski et al., 2012). It is now recognized that most species of Phaseolus associate preferentially with Bradyrhizobium and only a minority, like P. vulgaris and P. coccineus, prefer to enter in symbiosis with fast growing rhizobial genera like Rhizobium or Sinorhizobium (Martínez-Romero, 2003; Servín- Garcidueñas et al., 2014). Occasionally, fast-growing rhizobia have been isolated from Lima bean in Peru (Matos-Cuzcano et al., 1998; Ormeño et al., 2007; Zúñiga-Dávila, 2007). "
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ABSTRACT: Like other leguminous plants, the Lima bean (Phaseolus lunatus) establishes a mutualistic symbiosis with nitrogen-fixing bacteria commonly known as rhizobia. These bacteria elicit the formation of nodule structures on the roots where they become intracellular and fix atmospheric nitrogen for the plant. The Lima bean shows a preference to form nodules with slow-growing bacteria of the genus Bradyrhizobium unlike its congeneric species, the common bean (Phaseolus vulgaris), which prefer fast-growing rhizobial strains. P. lunatus was independently domesticated in the Andes and Mesoamerica by pre Columbian societies. Knowledge of the genetic biodiversity of Lima bean symbionts has increased in recent years with data obtained in its domestication areas. In Peru, Lima beans host Bradyrhizobium yuanmingense, Bradyrhizobium paxllaeri, Bradyrhizobium icense, and a yet unnamed genospecies. At least seven Bradyrhizobium genospecies have been found in P. lunatus nodules in Mexico. This rhizobial richness indicates a relative promiscuity of Lima bean in contrast to previous statements that this plant was a restricted host for nodulation. Interestingly, Mexican and Peruvian bradyrhizobia are distinct, perhaps in relation to the different plant gene pools from which domestication occurred in those geographic areas. Besides Bradyrhizobium, other rhizobial genera such as Rhizobium, Sinorhizobium and Mesorhizobium can be found in Lima bean nodules in its domestication centers and in other areas. Although effective nodulation with these genera has been reported, the ecological relevance of those associations is presently unknown.
Available from: Olubukola Oluranti Babalola
- "Also genotype-specific selection by legume depends on the diversity of the rhizobial population present in the soil (Amarger 2001). The large number of rhizobial population that nodulated cowpea in the three locations supports the fact that cowpea is a promiscuous host (Martínez-Romero 2003). Also,Nour et al. (1994)reported high specificity of rhizobial strains for TGx soybean genotype and that soybean genotypes are more specific in the type of rhizobia they nodulate with than cowpea. "
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ABSTRACT: Nodule formation in legumes is a process that starts with root infection by rhizobia. The present study assessed the population and infectivity of the indigenous rhizobial strains in rainforest soils of Nigeria. Soils were collected from three sites – Idi-Ayunre, Orile-Ilugun (OI) and the University of Ibadan Teaching and Research Farm (UITRF) – and analysed for physico-chemical properties and rhizobial population. Soybean varieties TGx1448-2E and TGx1456-2E and a cowpea variety IT89KD-288 were planted as trap crops on each of the soils, and rhizobia were isolated from their nodules. Infectivity assay was conducted using eight varieties of soybean and a cowpea variety. Most probable number estimate of the rhizobial population showed that the UITRF had significantly higher rhizobial population than the other two locations. OI and the UITRF soils planted with TGx1448-2E had significantly higher nodules and number of strains than other treatments. Among the 70 slow-grower strains isolated, only nine were infective. Three of the nine strains – IDC8, TRC2 and OISa-6e – nodulated at least seven of the eight soybean varieties used for infectivity test. Indigenous rhizobial infectivity of the studied locations was low, and cultivation of grain legume may require rhizobial inoculation for high productivity.
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