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Inheritance of Resistance to Bacterial Spot (Xanthomonas Campestris Pv. Visicatoria (Doidge) Dye) in Peppers (Capsicum Spp.)
|Title:||Inheritance of Resistance to Bacterial Spot (Xanthomonas Campestris Pv. Visicatoria (Doidge) Dye) in Peppers (Capsicum Spp.)|
|Abstract:||From 201 lines of pepper tested for resistance to bacterial spot, 17 P.I. lines which were introduced from India and 3 which were introduced from Central or South America showed resistance.|
Seven isolates of Xanthomonas campestris pv. vesicatoria collected from various locations in Hawaii showed no differences in virulence. Pepper line 23-1-7 which has been reported by A. A. Cook to have resistance to race 2 of the pepper strain of X. campestris pv. Vesicatoria in Florida was susceptible to all the isolates, which indicates that the strain that occurs in Hawaii is pepper strain race 1 and not race 2.
The inoculation method generally used was infiltration with an inoculum level of 10 cells/ml. Infiltration was accomplished by forcing the inoculum into the underside of leaves of 1 month old seedlings with a DeVilbiss air brush connected to a compressor set at 20 psi until an area about 5 mm in diameter appeared water-soaked. Disease was graded 1 week after inoculation on a scale of 1 (low disease) to 4 (high disease). The results obtained from this inoculation method were highly correlated with the field performance of lines with varying degrees of resistance and of individual plants of an F2 population of the cross Keystone x line 112 (P.I. 308787).
Twelve resistant lines were crossed to the susceptible cultivar Keystone to study the inheritance of resistance. A hypersensitive reaction found in line 79 (P.I. 271322) was controlled by a single dominant gene. An "immune" response found in line 177 (P.I. 163192) was controlled by a single recessive gene. Both lines 79 and 177 also showed quantitatively inherited resistance as well. Lines 47 (P.I. 244670), 127 (P.I. 369994), 112 (P.I. 308787), 110 (P.I. 297495), 4 (P.I. 163192), 34 (P.I. 224451), 43 (P.I. 241670), 119 (P.I. 322719), 137 (P.I. 377688), and 131 (P.I. 369998) had only quantitatively inherited resistance. Lines 79, 177, 47, 127, and 112 were the most effective in transmitting resistance.
Crosses were made between line 79 (hypersensitivity), line 177 (immunity), and line 43 (quantitative factors). When line 79 and 177 were crossed, the hypersensitivity gene was masked by the immunity gene to give an F2 ratio of 9 hypersensitive ; 4 immune : 3 neither. The hypersensitive character segregated normally in the cross of lines 79 and 43, but the segregation of the immunity character was altered in the cross of lines 177 and 43.
The correlation coefficient between pungency and disease in the greenhouse of the F2 population of the cross of Keystone (low pungency) x line 112 (P.I. 308787) (high pungency) was not significant, but in the field it was significant (-0.216), suggesting that high pungency may contribute some field resistance to bacterial snot.
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Ph.D. - Horticulture|
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