Effect of exogenous salicylic acid supply on nodule formation of hypernodulating mutant and wild type of soybean
2002
Sato, T. (Akita Prefectural Univ. (Japan)) | Fujikake, H. | Ohtake, N. | Sueyoshi, K. | Takahashi, T. | Sato, A. | Ohyama, T.
Soybean plant is characterized by a systemic autoregulatory control system of nodulation (autoregulation) by initial infection with rhizobia, and plants commonly display a systemic acquired resistance (SAR) to pathogenic microbe infection related to salicylic acid (SA) signal transmission. We investigated the effect of exogenous SA supply on soybean nodulation to determine whether SA affects the autoregulation of nodulation. Seedlings of the hypernodulating mutants NOD 1-3, NOD2-4 and their parent cv. Williams were treated or not treated (control) with a 100 microM-SA solution at 5 d before the inoculation of Bradyrhizo-biurn japonicum strain USDA110. The nodule dry weight and the number of nodules of the wild type soybean Williams exhibiting autoregulation drastically decreased by the addition of 100 microM SA. The decrease in the nodule number was not caused by the reduction of the rhizobium number in the medium. Salicylic acid inhibited only early nodule formation and did not affect the growth of formed nodules. The inhibitory effect of SA on the nodulation of NOD1-3 and NOD2-4 was significantly less pronounced than that in Williams. These results indicate that SA is directly involved in signal transmission in the autoregulation, and that SA or the SAR induced by SA stimulates the autoregulation of nodulation in soybean.
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