Size, symbiotic effectiveness and genetic diversity of field pea rhizobia (Rhizobium leguminosarum bv. viciae) populations in South Australian soils
Introduction
Field pea (Pisum sativum L.) is the major pulse crop grown in South Australia (SA). There are 18 cultivars available, which are segregated into Dun, White and Blue seeded types. In 2000, 114,000 ha of field pea were grown in SA and produced 190,000 t of grain (O'Connell, 2001), an average yield of 1.7 t ha−1. Field pea is also valued because subsequent wheat crops are higher yielding and have higher N content than wheat on wheat rotations (Evans et al., 1991, Rowland et al., 1994). These benefits are partly attributable to changes in soil N balance after field pea, which has been estimated to add on average 44 kg N ha−1 (Evans et al., 2001b), with variation in N contributions strongly linked to biomass production of the legume crop (McCallum et al., 2000, Peoples et al., 2001).
Field pea is nodulated by strains of Rhizobium leguminosarum bv. viciae. The same rhizobia also form nodules with other legumes grown in SA, including faba bean (Vicia faba L.), vetch (Vicia sativa L.), lentil (Lens culinaris Medik.) and the infrequently grown grass pea (Lathyrus sativus L.). Numerous strains (SU302, SU331, SU364, SU390, TA101 and SU391) of R. l. bv. viciae have been used in commercial inoculants for field pea since the 1950s (Date, 1969). Strain SU303 (syn. NA533) replaced strain SU391 in 1990, when the poor symbiotic effectiveness of strain SU391 with faba bean was recognised (Silsbury, 1991). Subsequently, strain WSM1274 was introduced as a separate and more effective inoculant strain for faba bean from 1997 to 2000. While there is little doubt that commercial inoculants were used extensively and played a critical role in the early development of the pea industry, only about 30% of the SA pea crop is now inoculated with rhizobia (Gary Bullard, Bio-Care Technology). This is in part due to farmers' recognition that many of SA's alkaline soils now contain naturalised populations of pea rhizobia, and that the seed dressings which are required to control fungal disease can be detrimental to rhizobial survival (Stovold and Evans, 1980, Evans et al., 1989).
Yield trends point to a significant decline in grain yield of field pea (Peck and McDonald, 1998), especially in SA. While investigations have implicated disease build-up (Davidson and Ramsey, 2000) and sensitivity to herbicide residues (Gonzalez et al., 1996), there has been no consideration of the occurrence and efficacy of the soil rhizobia, which are relied onto nodulate many pea crops.
We describe the size and effectiveness of R. l. bv. viciae populations which have become naturalised in SA soils. We also examined the diversity of naturalised populations of rhizobia isolated from five soils, and determined their genetic relatedness to both former and current inoculant strains and to each other.
Section snippets
Collection and characterisation of soils
Thirty-three soils (32 from SA and one from Victoria) were used in the experiment (Fig. 1). Soils 1–26 were sub-sampled from bulk soil samples (about 2 kg) collected from April to May in 2000, from paddocks with a history of pea cropping during a study on soil borne-diseases of field pea. The remaining soils were collected directly from the paddock for use in rhizobial studies. Soil 30 was collected in 2001; soils 29, 31 and 32 were collected in 2000; soil 33 was collected in 1996; and soils 27
Most probable number of Rhizobium leguminosarum bv. viciae
The MPN of R. l. bv. viciae ranged from not detectable (six soils) to 32×103 g−1 soil (Table 1) with 24 of the 33 soils containing more than 1×102 rhizobia g−1 dry soil.
For soils which had grown a host legume and for which a reliable paddock history was available, there was no significant association (P=0.45, d.f.=25) between the time since the legume host was grown (either field pea, faba bean, vetch or lentil) and the MPN of pea rhizobia g−1 soil. For example, no pea rhizobia were detected in
Size of the rhizobial populations
In SA soils with a cropping history of field pea, faba bean, vetch or lentil, significant (detectable by MPN) residual populations of rhizobia were nearly always present. In some cases, substantial populations of pea rhizobia (>1×103 g−1 dry soil for soils 6 and 25) were measured five or more years after cropping with a host legume. Clearly, factors other than presence of the legume host influenced the size of these rhizobial populations. For example, a number of sites cropped to a legume host
Conclusions
Based on the generally good effectiveness of the pea rhizobia populations with the cultivar Parafield, we conclude that the N2 fixation capacity of the naturalised soil rhizobia is unlikely to be a major factor in declining field pea yields. However, not all soils contained populations of sufficient size needed for prompt nodulation. Hence, inoculation should still be recommended at least for pea crops sown on western Eyre Peninsula or where there is no history of a host legume having been
Acknowledgements
We would like to thank Mr Neil Schubert, Mrs Christine Schutz and Mrs Marzena Kaczmarek for excellent technical assistance. Financial assistance for this work was provided by the Grains Research and Development Corporation and the South Australian Grains Industry Trust. We also thank the staff of the Australian Legume Inoculants Research Unit for supplying cultures of strains that have been used in commercial pea inoculants.
References (32)
- et al.
Competitiveness and persistence of strains of rhizobia for faba bean in acid and alkaline soils
Soil Biology and Biochemistry
(1995) Rhizobial persistence and its role in the development of sustainable agricultural systems in mediterranean environments
Soil Biology and Biochemistry
(1995)- et al.
Differentiation of Rhizobium strains using the polymerase chain reaction with random and directed primers
Soil Biology and Biochemistry
(1995) - et al.
The number of Bradyrhizobium sp. (Lupinus) applied to seed and its effect on rhizosphere colonisation, nodulation and yield of lupin
Soil Biology and Biochemistry
(1993) PATN Pattern Analysis Package
(1995)Accuracy of a plant-infection technique for counting populations of Rhizobium trifolii
Applied Microbiology
(1963)- et al.
Evaluation of the symbiotic nitrogen-fixing potential of soils by direct microbiological means
Plant and Soil
(1988) A decade of legume quality control in Australia
The Journal of the Australian Institute of Agricultural Science
(1969)- et al.
Pea yield decline syndrome in South Australia: the role of diseases and impact of agronomic practices
Australian Journal of Agricultural Research
(2000) - et al.
Effect of nutrient medium pH on symbiotic nitrogen fixation by Rhizobium leguminosarum and Pisum sativum
Plant and Soil
(1980)
Rhizobial inoculant for iprodione-treated lupin seed: evaluation of an iprodione-resistant Rhizobium lupini
Australian Journal of Experimental Agriculture
Wheat response after temperate crop legumes in south-eastern Australia
Australian Journal of Agricultural Research
Requirement of field pea for inoculation with Rhizobium and lime pelleting in soils of Western Australia
Australian Journal of Experimental Agriculture
Pre-season soil establishment of legume inoculant rhizobia is not effective for the nodulation of lupin and faba bean crops in acidic soils
Australian Journal of Experimental Agriculture
Net nitrogen balances for cool-season grain legume crops and contributions to wheat nitrogen uptake: a review
Australian Journal of Experimental Agriculture
A simple chemical method of assessing potentially available inorganic nitrogen in soil
Communications in Soil Science and Plant Analysis
Cited by (26)
Rhizobium leguminosarum strain combination effects on nodulation and biological nitrogen fixation with Vicia villosa
2020, Applied Soil EcologyCitation Excerpt :Field studies have shown that rhizobia strains from inoculants can be predominant in nodules (Beyhaut et al., 2006; Denton et al., 2003) and also fail to occupy more nodules than resident rhizobia (Denton et al., 2002; Grossman et al., 2011; Malek et al., 1998). Although a specific strain can have measurable effects on BNF in legumes under controlled conditions (Ballard et al., 2004), when several strains are simultaneously present it is difficult to attribute changes in nodulation or BNF to the presence of a specific strain without knowing which strains are occupying root nodules. This limitation exists in part because tracking individual rhizobia strains has historically been difficult (Hirsch, 2005); however, the application of molecular biology techniques (e.g., DNA fingerprinting) to rhizobia studies facilitates tracking and identification of strains within nodules (Sarita et al., 2005; Thies et al., 2001; Wongphatcharachai et al., 2015).
Vicia faba L. in the Bejaia region of Algeria is nodulated by Rhizobium leguminosarum sv. viciae, Rhizobium laguerreae and two new genospecies
2018, Systematic and Applied MicrobiologyCitation Excerpt :This variation was significantly correlated with carbon (r = −0.614, P = 0.044) and nitrogen (r = 0.721, P = 0.012) concentrations. It is known that other factors such as soil type, degree of nodulation in the previous crop and historical soil nitrate concentrations may contribute to the numerical variation of rhizobial populations [4,46]. Edaphic and climatic conditions impact bacterial populations either directly or indirectly via the plant [17].
A ribosomal RNA gene intergenic spacer based PCR and DGGE fingerprinting method for the analysis of specific rhizobial communities in soil
2006, Journal of Microbiological MethodsThe abundance and efficacy of Rhizobium leguminosarum bv. viciae in cultivated soils of the eastern Canadian prairie
2006, Soil Biology and BiochemistryThe genetic diversity of Rhizobium leguminosarum bv. viciae in cultivated soils of the eastern Canadian prairie
2006, Soil Biology and Biochemistry