Grey Leaf Spot (GLS) of maize (Zea mays. L.), a fungal disease caused by Cercospora zeae-maydis, is becoming increasingly important in southern and eastern Africa. Inheritance of GLS resistance was studied for four experimental open-pollinated maize populations developed at CIMMYT-Zimbabwe: streak virus resistant versions of highland populations Kitale II and Ecuador 573, and populations ZM605 and ZM607. Individual F2 plants were scored for GLS using a scale of 1 (resistant) to 5 (susceptible) under heavy natural infestation during summer 1996-97. Kitale-SR and Ecuador-SR plants were selfed to make S1's, whereas reciprocal full-sib families were made randomly within both ZM605 and ZM607. The Sl lines and full-sib families were planted in replicated trials at Harare during summer 1997-98 and were artificially inoculated by placing GLS-infected ground leaves into the whorls of 4-week-old plants. GLS was evaluated 3, 5 and 7 weeks after flowering. Heritability of GLS resistance, estimated by parent-offspring regression, was 0.31 and 0.62 for Kitale-SR, 0.37 and 0.50 for Ecuador-SR, 0.27 and 0.26 for ZM607 , and 0.23 and 0.32 for ZM605 on first and last scoring dates, respectively. Phenotypic correlation coefficients for GLS score of offspring with mid-parent ranged from 0.40 to 0.65 for the four populations on the three evaluation dates. Frequency of obtaining highly resistant lines (GLS<2.0) from moderately resistant parents (GLS 2.5- 3.5) was virtually nil.

Genetic Resources Program

English

0103|AL Maize Program|R99-00CIMPU|AGRIS 0102|AJ|3

Jose Juan Caballero

INT1617

CIMMYT Staff Publications Collection