Fusarium scab screening program at CIMMYT - Mexico : CIMMYT, 1997. - Printed
Fusarium head blight (scab) is a common disease of cereals worldwide, causing severe yield losses and toxicological problems in humans and animals. CIMMYT began scab research in the early 1980s and has concentrated on two resistane types, type I (penetration) and type II (spread), at three hotspot locations in Mexico (Toluca, Patzcuaro, and sierra del tigre). The aim has been to develop high yielding germplasm with enough resistance to sustain good production levels in scab affected areas. Surveys carried out in Toluca and Patzcuaro during 1988-89 indicated that Fusarium graminearum was the most important scab producing pathogen in these localities. Although scab resistant germplasm is limited, resistance from genetic resources from Brazil, Japan, and China has been incorporated into high yielding genotypes. Despite the slow process, important results have been obtained and the first lines (Ningmai 7, Longmai 19, and Chuanmai 25) are being released in large areas of China. in the last five years, 583 synthetic bread wheats (Triticum turgidum / Aegilops squarrosa; 2n=6x=42, AABBDD) and derived lines have been developed by the Wheat Wide Crosses group at CIMMYT to increase the available genetic diversity. These materials have been tested under field conditions and diversity has been identified. A key synthetic cross is Gan/Ae. Squarrosa (427) with resistance types I and II. A new breeding scheme is being considered for incorporating combined resistances from numerous sources into well-adapted backgrounds. In the ICARDA/CIMMYT barley program based in Mexico, unique barley germplasm has been screened using Gobernadora (a widely grown variety in the lower Yangtze Valley, China) and Shyri/Copal//Shyri/Grit as parents. The lines were developed as a doubled haploid (DH) population by the Hordeum bulbosum method. DH lines that have better scab resistance than that of either parent have been identified. Durum wheat still remains the most scab susceptible crop, and no resistance sources have been identified in CIMMYT durum wheat germplasm. In the future, research at CIMMYT will focus on the mode of inheritance in the more resistant bread wheat lines and, in particular, on the identification of type III resistance.
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632.4 / DUB