Effects of planting date, spacing, nitrogen source and irrigation rate on severity of soybean bacterial pustule
1995
Kullaya Tusanasarit
Xanthomonas campestris pv. glycines strains KUP34083 (evaluated from 88 strains) as antibiotic resistance marker (50 ml/L chloramphenical and 100 ml/L streptomycin) and leaf wash technique (compared with leaf swab technique) as a detection method of surface bacterial population, were investigated for soybean bacterial pustule endemicity initiated by inoculating of susceptible plants at the center of each experimented plot under different planting date, spacing, nitrogen source and irrigation rate at International Corn and Sorghum Research Center, Pakchong, Nakorn Rachasima during January, 1993-April, 1994. The spatial and temperal spread of the target epiphytes in all accessions tested was 1 meter far from each infection focus within 1 day after inoculation in with which the first symptom was observed at 6 days later. Colony forming unit (cfu) of such epiphytes was increased as the day after inoculation increased and the disease severity was also increased linearly with those cfu. Reversibly, the increased severity of disease resulted in decreased yield. Bacterial pustule spreading and severity of soybean planted at spacing of 20*50 cm; date of August; irrigation rate of triple qualitative evaporation; and KNO3 supplied were greater than 20*75 cm; September and July; double qualitative evaporation; and Rhizobium seed treatment plus with KNO3 or no N application or Rhizobium seed treatment alone, respectively. These data were used to study the relationship among cited accessions as well as to evaluate the equation of severity and/or spreading predictions. The severity (Y) correlated well with disease spreading (X1), planting date, plant spacing as the probability equation of Y=-114.2783+31.8979X1 having correlation of determination (r*[2)) of 0.7975 (P0.01) and with irrigation rate included nitrogen source as probability equation of Y
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