Abstract only

Fusarium head blight (FHB) or scab is an important fungal disease that affects wheat by reducing germination rate, kernel weight, crop yield and flour extraction rates in many wheat growing areas. In Asia it is particularly affecting parts of China, Japan, Korea and Iran. Several Fusarium species associated with scab produce mycotoxins that contaminate the grain and are harmful to human and animal health. The most important and distributed one is F. graminearum. The mycotoxins of primary concern with respect to FHB are the trichothecenes. The most common and important trichothecene in grain affected by scab is the mycotoxin known as deoxynivalenol (DON) or vomitoxin produced by F. graminearum and F. culmorum. Breeding for better scab resistance is an important component of integrated approaches aimed to minimize DON contamination. It is difficult to achieve due to the quantitative nature of the trait. A range of QTLs have been reported to be associated with FHB resistance. Breeding strategies include the accumulation of these resistance genes in broadly adapted germplasm harboring resistance to other diseases such as the rusts. Research toward improved resistance against FHB conducted at CIMMYT (Mexico) for more than 20 years and collaboration with China, Japan and Brazil led to the incorporation of superior levels of scab resistance into high yielding genotypes. However, since resistance is limited, research is on-going to expand this resistance base through the identification and validation of QTLs associated with field resistance and low level of DON. Haplotyping is a new tool that allows identifying the presence of existing QTLs in parental materials and helps to better target crosses toward diversifying resistance. In practice, germplasm screening, phenotyping of mapping populations and detection of novel resistance sources is conducted under strictly standardized field conditions at El Batan, where CIMMYT is located near Mexico City, under artificial inoculation of F. graminearum isolates for which the DON chemotype has been previously confirmed by PCR. At harvest, due to the high cost of mycotoxin detection, only specific research materials and samples of elite wheat germplasm consistently showing a low visual Fusarium Head Blight Index are ground to determine the DON level in the whole grain flour. Analysis for DON content is carried out by means of a commercially available immunoassay tests. Applied research includes the validation of quantitative PCR methods aimed at quantifying DON based on the fungal biomass in the grain and the presence of Tri-5 gene responsible for DON production, analyzing the correlation with FHB field symptoms. Other attempts to speed up the detection of low DON content in advanced wheat lines included the evaluation of a lateral-flow colloidal gold-based immunoassay for the rapid detection of deoxynivalenol with two indicator ranges. One of the objectives of CIMMYT?s wheat breeding program is to distribute high-yielding wheat germplasm with acceptable end-use quality and with resistance to FHB which also harbors a low DON content. Thus, efforts are done to add the information on the DON content in each line when nurseries are distributed. Since the main obstacles to provide a reliable quantitative information on resistance to mycotoxins (i.e. DON) in wheat germplasm are the high field evaluation and assay costs, understanding the factors affecting the correlation between phenotypical data and mycotoxin content is paramount to improve data accuracy and information reliability.

Research and Partnership Program

Text in English

INT1237

CIMMYT Staff Publications Collection