An Assessment of Different Techniques for Inoculating Phaseolus vulgaris with Rhizobium

Abstract

A technique to better ensure reliable nodulation of pot-grown, P. vulgaris plants with cultured strains of Rhizobium is described. Nodulation, dinitrogen fixation (acetylene reduction) activity and growth of 28-day-oId plants were all stimulated markedly when seeds had been inoculated with culturedRhizobium phaseoli suspended in alginate gel (Agrigel) rather than in sucrose solution. Nodulation attributes of plants inoculated with R. phaseoli strain RCR 3644 which had been sub-cultured repeatedly on yeast mannitol agar slopes were consistently inferior to those recorded for the same strain but recently cultured from a freeze-dried sample. Some of the potential problems with open pot culture of nodule-dependent legumes are discussed.The ability of strains of Rhizobium to survive on inoculated legume seeds is of paramount importance if nodulation is to be effective (Burton, 1976). Liquid inocula can be as effective as solid carriers (such as peat, charcoal or vermiculite) in stimulating nodulation of Phaseolus vulgaris in the field, providing that strains of Rhizobium are applied at larger (5.6 x 10 6 cells cm row" 1 ) rather than smaller (2.5 x 10 4 cells cm row" 1 ) densities (Sparrow and Ham, 1983). Although peat-based inocula have often proved superior to other solid or liquid carriers (by prolonging the viability of Rhizobium on seeds and increasing nodulation in the field; Burton, 1976;Burton and Curley, 1965), nodulation of field-grown P. vulgaris plants has also been successful and effective when seeds were sown in an alginate gel (Agrigel) suspension containing R. phaseoli strain RCR 3644 using a fluid drill technique for planting the crop (Hardaker and Hardwick, 1978).When grain legumes are grown in pots in artificial climates, as an adjunct to research in the field, it is imperative that plants closely resemble morphologically and phenologically those grown in the natural environment. Notwithstanding the plant husbandry and culture techniques which are now wellestablished for pot-grown legumes (Summerfield et al., 1977), the procedures used and the results obtained from many experiments suggest that the variable under investigation is not always the primary one which has influenced plant response (Summerfield, 1980). Such limitations seem particularly common with mineral nutrients and, especially, through unsuspected and unintended t Present address:

Evaluation of polymers for the liquid rhizobial formulation and their influence in the Rhizobium-Cowpea interaction

“…In contrast, the more rigid structure and the high viscosity of the sodium alginate 2 polymers may have influenced the response (Zimmermann et al 2007). Rawsthorne & Summerfield (1984) obtained similar results in studies that showed an increased nitrogen fixation and higher nodule dry weights using alginate gel compared to controls.…”

Bradyrhizobium japonicum Survival in and Soybean Inoculation with Fluid Gels

“…Gelatinous substances previously have been used as carriers for rhizobia (3,11,13,18). Advantages of gels include the protection of microorganisms from desiccation and good microorganism-seed contact (13,16).…”

“…The gels used in these previous studies, however, were not of a fluid consistency during seed inoculation and were not used in conjunction with fluid drilling. Pot-grown dwarf french (field) beans were successfully inoculated with R. phaseoli by using a wet alginate gel (18). Field beans inoculated with R. phaseoli in an alginate gel during fluid drilling had more nodules per plant 28 days after sowing than did beans inoculated with a peat carrier (11).…”