Moisture Stress in the Screening of Maize Cultivars for Stalk Rot Resistance and Yield. Maria Melis, Plant Pathologist, Summer Grain Sub-Centre, Cedara, Private Bag X9059, Pietermaritzburg, Republic of South Africa. F. H. J. Rijkenberg, Professor, Department of Plant Pathology, University of Natal, P.O. Box 375, Pietermaritzburg 3200, Republic of South Africa. Plant Dis. 72:1061-1064. Accepted for publication 6 June 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-1061.

A technique is described to screen cultivars under field conditions for stalk rot resistance and yield under a continuous range of rooting depths. The technique was tested from 1981 to 1983 using six hybrids. During the 1981–1982 season, stalk rot increased from 12.8 to 46.3% with decreasing rooting depth, while yield decreased by 23.4%. During the 1982–1983 season, rainfall was much lower from 1 wk before tasseling to harvest than during 1981–1982, and yield decreased by 97.7% with decreasing root depth, while stalk rot decreased from 40.8 to 17.9%. It was concluded that soil moisture stress increased stalk rot during 1981–1982, and that pretassel moisture stress during 1982–1983 reduced stalk rot during the latter season by reducing the photosynthetic sink, because plants subjected to the highest moisture stress did not produce grain. The technique permits the screening of hybrids for resistance to stress, taking both stalk rot and yield into account, and may have wider applicability.