Submitted to: Northeastern and Southern Corn Improvement Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: February 22, 2001
Publication Date: N/A
Technical Abstract: Since first reporting on the occurrence of Phaeosphaeria leaf spot (PLS) in winter nurseries in South Florida in 1990, several studies were conducted to determine the potential to cause damage to U.S. maize production. PLS is widespread throughout the tropics and subtropics, having been reported from Central and South America, India, Central and southern Africa, and Hawaii. The disease is of particular concern in Brazil and South Africa where the incidence and severity of PLS has increased. An evaluation of the reaction of numerous public and proprietary foundation inbred lines supported earlier observations that inbred lines derived from B73 are particularly susceptible to PLS. However, when a large array of Pioneer and Dekalb hybrids were evaluated only (non Stiff Stalk) parent is probably providing adequate levels of resistance to most hybrids grown in the U.S. If the disease were ever to spread from Florida to the Corn Belt, U.S. maize production would probably not be threatened; however, seed production coul be affected, given the susceptibility of many commonly used female inbred lines. Resistance to PLS in the cross B73 x Mo17 has been studied. Both QTL markers and generation mean analysis indicate that resistance is controlled by a small (3-4?) number of genes acting in a strictly additive manner, with high heritabilities. Preliminary estimates of potential yield losses due to PLS indicate damage would be slight even in the most susceptible hybrid die to the late development of the disease. However, winter nurseries in South Florida are not the ideal environment for conducting yield loss studies. Future work will focus on overwintering, possible alternative hosts, and the infection process of this interesting pathogen.