Nodulation ofRj-soybean varieties withRhizobium frediiUSDA 193 under limited supply of nutrients

Abstract

The compatibility between rhizobia and host plants for nodulation was determined based on the genetic and physiological properties of both symbionts. It has been observed that soybean varieties carrying the Rj-gene were not nodulated effectively by certain strains or groups of rhizobia. Soybeans carrying the Rj2-gene, Rj2-varieties, were found to nodule ineffectively by the rhizobial strains belonging to the 3-24-44 and 122 serogroups (Caldwell 1966). In the same way, Rj3-and Rj4-varieties were found to nodule ineffectively by strains USDA 33 (Vest 1970) and USDA 61 (Vest and Caldwell 1972), respectively. Keyser et al. (1982) reported that Rhizobium fredii (R. fredii) also effectively nodulated an unimproved Chinese soybean cultivar, Peking and wild soybean, Glycine soja, but that it was largely incompatible with common commercial cultivars of soybeans for nodulation. Thereafter, Devine (1985) demonstrated that the majority of soybean plants introduced from Southeast Asia nodulated effectively with R. fredii USDA 205. Therefore, it was assumed that the nodulation-conditioning genes which enable to nodulate effectively with R. fredii were involved in the nodulation of these soybeans. Although most of these plants carries the Rj4-gene (Devine and Breithaupt 1980), the relation between effective nodulation with R. fredii and the presence of Rj-genes in host plants had not been elucidated.In legumes, micro nutrients playa significant role in nodulation and nitrogen fixation. Iron deficiency depressed nodule initiation before host plant growth, resulting in a decrease in the nodule number and mass (Tang et al. 1990). Nodulation of soybeans and peas was considerably increased by the application of molybdenum (Hagstrom and Berger 1963). The high concentrations of iron, cobalt, and calcium in soybean root hairs which were target cells for infection were discussed in relation to the high requirement of B. japonicum for these elements (Werner and Kuhlmann 1985). Physiological role of micro nutrients in nodulation still remains to be elucidated.In this paper nodulation with R. fredii USDA 193 was examined in terms of the compatibility with various Rj-genotypes of soybeans and in relation to the effects of nutrient levels in culture media on the nodulation. Materials and methodsPlants and rhizobium. The soybean (Glycine max L. Merr.) varieties, Bragg (non-Rj), Akisirome (non-Rj), CNS (Rj2RjJ, IAC-2 (Rj2 Rj3) , Akisengoku (Rj4)' Hill (Rj4)' and B340 (Rj2Rj3Rj4) were used. The Rj-genotypes are indicated in parentheses (Ishizuka et al.

Incompatible Nodulation of <i>Bradyrhizobium elkanii</i> Strains BLY3-8 and BLY6-1 with <i>Rj</i>3 Gene-Harboring Soybean Cultivars

“…Seeds were surface sterilized in 1% sodium hypochlorite solution for 5 min, rinsed five times with 10 mL of 99.5% ethanol, and washed five times with sterilized half-strength modified nitrogen-free Hoagland Nutrient (MHN) solution [21]. Seven seeds were sown in prepared culture pots filled with 1 L of vermiculite and 0.6 L of MHN solution.…”

Positive correlation between the number of root nodule primordia and seed sugar secretion in soybean (Glycine maxL.) seedlings inoculated with a low density ofBradyrhizobium japonicum

“…This phenomcnon is related to the Rj-genes of soybean (Caldwell 1966;Vest 1970;Vest and Caldwell 1972;Ishizuka et al 1991;Nakano et al 1997). Rj type of soybean may be an important factor affecting the nodulation intensity with a high rhizobium popUlation around the roots.…”

Effects of symbiosis withRhizobium frediion transport of fixed nitrogen in the xylem of soybean plants

“…Nodule number per plant inoculated with R. fredii was significantly higher at the flowering stage than at the pod elongation stage (p = 0.05). That is, the nodule number induced by R. fredii decreased with the growth of the soybean plants, presumably due to the fact that soybean plants inoculated with rhizobium with a low compatibility formed a large number of ineffective nodules (Nakano et al 1997). These results indicate that R. fredii displayed a lower compatibility with soybean cultivars in this study than USDA11O.…”

“…These strains were stored at 4"C on yeast extract mannitol agar. USDAllO was cultured in yeast extract mannitol broth (Vincent 1970) on a rotary shaker (100 rpm) at 30"C for 7 d and R. fredii strains for 3 d. The culture of USD A 110 and the culture of R. fredii strains were diluted to one hundredth with one-fourth strength of modified Hoagland nutrient (MHN) solution (Nakano et al 1997). These cell suspensions (about 10 7 cells mL-l per each strain) were used as inoculums as described below.…”