Wheat production covers about 14,000 ha in Oaxaca State, Mexico, of which 95% is located in the Mixteca Alta (2,200 masl, 17º30'N and 97º20'W), where soils are characterized by low organic matter and high pH levels. Wheat is mainly grown under rainfed conditions and irrigation is limited. Since erosion is a concern for smallholder producers, reduced tillage cropping practices have increased in recent years. As a result of a lack of adequate rotation, and limited access to fertilizers and technological support, tan spot caused by Pyrenophora tritici- repentis has become a major concern. Although improved varieties are commonly used (Temporalera M-87, Arandas F-90, and Pavon F-76), they are highly susceptible to foliar diseases, particularly tan spot. In fungicide tests, manzate reduced disease severity by 25%, on average, compared with the control. There were no significant differences between two treatments of cyproconazole or propiconazole and one spray of tebuconazole; however, these five treatments reduced the average disease severity on combined flag leaf (F) and F-1 leaves by more than 75%. Only two sprays of tebuconazole (Folicur) caused a significantly larger reduction in disease severity (86%). Yield obtained after fungicide treatment correlated well with disease severity. At two sites (Yanhuitlan and Nochixtlan), 224 genotypes were screened under zero tillage and natural rainfed conditions, and disease pressure was high as a result of the wheat monoculture. Fifteen entries with higher yield and better disease resistance than the local check were identified.

Research and Partnership Program

English

9806|AGRIS 9802|anterior|R97-98PROCE|FINAL9798

Jose Juan Caballero

INT1237

CIMMYT Publications Collection