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Resistance

The Relationships Among Plant Stature, Maturity Class, and Susceptibility to Septoria Leaf Blotch of Wheat. Tamar Danon, Former graduate research assistant, Division of Mycology and Plant Pathology, Department of Botany, The George S. Wise Faculty of Sciences, Tel Aviv University; J. M. Sacks(2), and Z. Eyal(3). (2)Geneticist, Division of Statistics and Experimental Design, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel; (3)Associate professor, Division of Mycology and Plant Pathology, Department of Botany, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel. Phytopathology 72:1037-1042. Accepted for publication 4 December 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-1037.

The relationships between Septoria leaf blotch severity and plant stature, and maturity class were investigated in parental, F1, and F2 populations, and selected lines derived from crosses among 16 parents in an incomplete diallel crossing scheme. Resistant parents were selected among tall (120145 cm) late maturing wheats, semidwarf early and late maturing wheats, and winter wheat cultivars; susceptible parents included semidwarf (90110 cm) and dwarf (4585 cm) cultivars. Based on the analyses of F1 and F2 progeny, we concluded that resistance to the virulent Septoria tritici isolate IS 398A1 in the winter wheat cultivar Bezostaya 1, the tall late-maturing spring wheats (cultivars Colotana, Fortaleza-1, Polk/Waldron, Sheridan, and Titan), and in the winter wheat cultivar Oasis is controlled by relatively few genes. Cultivars Chris Mutant and Olaf have moderate resistance that appears to be simply inherited. Disease expression in F1 and F2 populations of certain crosses may be dictated in part by modifying genes. Small negative correlations were found between plant height and pycnidial coverage in F2 populations. The low correlations between plant height and severity of Septoria leaf blotch do not support the hypothesis for linkage or pleiotropy between short-stature and susceptibility. The moderate negative correlation (r = 0.30) between heading date and resistance in the F2 population might suggest linkage. Short-statured (5080 cm), early-maturing (heading <110 days from seedling emergence), resistant plants were recovered in F2 populations and continued to express resistance to a wide spectrum of virulence in succeeding generations. The implications of these studies on the incorporation of resistance conditioned by different genetic factors in agronomically suitable wheats is discussed.

Additional keywords: genetics, Triticum aestivum.