Table 1.

HR induction and virulence of E. amylovoraEa321 and mutant derivativesa

Strain of E. amylovoraGenotypeHR rating of tobacco leafb(A/B/C)Disease rating of immature pear fruit treated withc:No. of bacteriad (CFU/pear half)
5 × 107 CFU/ml (A/B/C)5 × 106 CFU/ml (A/B/C)5 × 105 CFU/ml (A/B/C)
Ea321Rp hrpN + hrpW + 0/0/6 a0/0/10 e0/0/10 i0/0/10 m1.4 × 1011 ± 9.2 × 1010
Ea321-K49 hrpL 6/0/0 b10/0/0 h10/0/0 lNT1.3 × 108 ± 4.2 × 107
Ea321-T5 hrpN 2/4/0 b4/6/0 g5/5/0 kl8/2/0 n9.9 × 108 ± 1.2 × 109
Ea321-T5(pCPP1084) hrpN(hrpN +)0/2/4 a0/7/3 f1/6/3 j4/6/0 n7.7 × 109 ± 6.2 × 109
Ea321-G204 hrpW 0/0/6 a0/0/10 e0/0/10 i0/0/10 m1.3 × 1011 ± 1.1 × 1011
Ea321-T5/G204 hrpNhrpW 5/1/0 b7/3/0 gh6/4/0 kl8/2/0 n1.4 × 108 ± 6.9 × 107
Ea321-T5/G204(pCPP1012) hrpNhrpW (hrpN +hrpW +)3/3/0 b3/7/0 g2/8/0 jk3/7/0 n4.6 × 108 ± 5.7 × 107
Ea321-T5/G204(pCPP1233) hrpNhrpW (hrpW +)5/1/0 b5/5/0 gh6/4/0 kl8/2/0 n2.4 × 108 ± 2.8 × 108
  • a Values in HR and disease columns indicate the number of leaf panels or pear fruits that were given the rating A, B, or C (defined below). Ratings followed by the same letter within columns do not differ significantly at P = 0.05.

  • b Approximately 100 μl of the bacterial suspensions (ca. 5 × 107 CFU/ml) was infiltrated into each panel of tobacco leaves, and the results were recorded after incubating 3 days at room temperature. A, no HR; B, spotty and sometimes coalescing HR; C, complete HR over the infiltrated area.

  • c Pear fruits were cut in half longitudinally, wells approx. 7 mm deep were made in the middle of each pear half using a cork borer (4-mm diameter), and 100 μl of the bacterial suspension (5 × 107, 5 × 106, or 5 × 105 CFU/ml) was put into each. Pear halves were incubated at 28°C for 10 days before the readings were made. A, no ooze, no necrosis; B, clear or cloudy ooze droplets and/or partial necrosis, especially around the well; C, copious ooze and necrosis of the whole pear half. NT, not tested.

  • d Bacterial populations were estimated 7 days after inoculation with ca. 5 × 107 CFU/well of each pear half. Two average-looking pear halves from each treatment were chosen for population assay. Each sample was counted twice by diluting with 5 mM KPO4 buffer and spotting 10-μl aliquots on duplicates of Luria agar plates with appropriate antibiotics.