The inheritance of components resistance to bacterial leaf spot of pepper (Capsicum annuum L.)

The inheritance of components resistance to bacterial leaf spot of pepper (Capsicum annuum L.)

Gainesville University of Florida United States

1985

xvi, 218p. : tables

Ph.D.

SB348.P46H5

Inheritance of resistance to bacterial leaf spot of pepper (Capsicum annuum L.) incited by Xanthomonas campestris pv. vesicatoria Dye was evaluated in progenies of resistant germplasm crossed with susceptible bell pepper. The basis for designating pathogenic races was avirulence on plants with genes derived from PI 271322. Race 1 induced a hypersensitive response (HR) in plants with Bs3, race 2 induced HR in plants with Bs1, and race 3 did not induce HR. Race 3 occurred frequently in laboratory cultures of races 1 and 2. Resistance to race 1 and to race 2 was detected after injections of leaves of plants with Bs1 and Bs3 with high concentrations of inocula (>1.0E8 cells/ml). Collapse of tissues occurred within 24 hours with race 1 and 12 hours with race 2. Concomitantly, electrolyte losses occurred and bacterial multiplication was inhibited. Both genes were incompletely dominant in heterozygotes of PI 271322 crossed with susceptible pepper. The gene Bs2 in cv. Florida XVR 3-25 controlled HR to both races 1 and 3. Genes Bs1, Bs2 and Bs3 segregated independently in crosses. Resistance to race 3 and concomitantly to races 1 and 2 was identified after injections of leaves with low concentrations of inocula (2 x 1.0E3 cells/ml). In resistant plants, lesions were fewer and always smaller than in susceptible plants. Lesion diameter and field resistance to race 3 were correlated (r=0.99). Monogenic additive-gene action controlled resistances to race 3 in PI 163189, 246331, and 271322. Lesion diameters in heterozygotes varied around mid-parent values. Parental values varied according to the bacterial isolates used for inoculation. Lesion numbers heterozygotes were few with weak isolates, but equalled the susceptible parent with aggressive isolates. The proposed symbol for this gene in PI 271322 is Bs4. Gene Bs4 segregated independently of Bs1 and Bs3 in crosses. Bell pepper stocks with all four genes were produced. [AS]

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