Abstract
Abstract Papaya seedlings being tested for resistance to Phytophthora palmivora root rot were inoculated with sporangial suspensions which varied from 0 to 18,000/plant. Mortality counts and disease ratings of seedlings taken 1 month after inoculation showed that: (a) developmental resistance increased as seedlings became older and appeared totally developed by the time seedlings were 2 months old; (b) comparisons among papaya lines inoculated with increasing concentrations of inoculum demonstrated a dosage response; (c) 1-month-old papaya lines inoculated with a uniform concentration of inoculum (5,250 sporangia/plant) could be separated into 3 distinct groups. Line 8, ‘Waimanalo’-23, ‘WaimanaIo’-24, and line 40 were resistant; 45-T22 and ‘Kapoho Solo’ were moderately resistant and ‘Higgins’ was susceptible. The correlation between greenhouse and field mortality was r = 0.955, which supports the reliability of the method.
Published Version
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