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Inheritance of Resistance to Race 4 of Downy Mildew Derived from Interspecific Crosses in Sunflower
Author(s) -
Miller J. F.,
Gulya T. J.
Publication year - 1991
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1991.0011183x003100010009x
Subject(s) - downy mildew , biology , helianthus annuus , sunflower , hybrid , botany , interspecific competition , horticulture
Race 4 of downy mildew, incited by Plasmopara halstedii (Farl.) Berl. & de Toni, was first reported in sunflower ( Helianthus annuus L.) in the USA during 1985. Resistance to this race was found in lines derived from interspecific crosses of cultivated sunflower with three species of wild sunflower. The objectives of this investigation were to determine the genetic control of resistance found in the interspecific crosses and to determine if this resistance was conditioned by the same or different genes. Ratios tested utilizing a chisquare analysis for goodness of fit for F 2 and BC 1 F 1 generations indicated that resistance to Race 4 was conditioned by a single, dominant gene in all sources. Four lines (HA 335, HA 336, Charata R4, and Wild Ornamental) were determined to have the same resistance gene PI 6 . HA 335 and HA 336 were derived from wild H. annuus 423 and H. annuus 432, respectively. The resistance gene in HA 339, derived from H. praecox Engelm. & Gray ssp. runyonii , proved to be different and was designated PI 7 . The resistance gene in RHA 340, distinct from PI 6 and PI 7 and derived from H. argophyllus Torrey & Gray, was designated PI 8 . Using divergent resistance genes in sunflower commercial hybrids should decrease genetic vulnerability to changes in pathogenicity of downy mildew. However, additional wild species of sunflower should be collected and tested to identify new sources of resistance to downy mildew.