Influence of the D genome in conferring resistance to fusarium head blightin spring wheat

Reciprocal crosses were made between resistant hexaploid spring wheat culti vars/lines Sumai 3, Ning8331, and 93FHB21, and susceptible tetraploids Stew art 63 and DT486 to generate 35 chromosome pentaploids. Four heads from eac h of five F-1 pentaploid plants from each cross were screened with Fusarium graminearum for fusarium head blight (FHB) reaction. No pentaploid was as resistant to FHB as the resistant parents. Pentaploids derived from several crosses were more resistant than the susceptible parents, a few were more susceptible, and all plants from crosses with 93FHB21 failed to survive. Mo st viable seeds were obtained from the cross Sumai 3 x DT486. From this cro ss four of the five F-1 pentaploid parents were fertile and 354 F-2 seeds d erived from these four pentaploids were sown and evaluated for their FHB re action. The majority of F-2 plants from pentaploids 1 and 3 had the visual appearance and level of resistance of Sumai 3, whereas progeny from pentapl oids 4 and 5 were more varied morphologically and generally more susceptibl e. Forty-three of the screened F-2 plants were tested for the presence of s pecific D chromosomes by wheat microsatellite analysis. There was no relati onship between presence/absence of D chromosomes and FHB reaction. Twenty-f our lines had all D chromosomes present of which 10 were intermediate-susce ptible and 14 were resistant to FHB. Three lines, one resistant and two int ermediate, had no D chromosomes. The remainder had between 1 and 6 of the D chromosomes present and ranged from resistant to susceptible in FHB reacti on. It appears that FHB resistance is not conferred by the D genome of Suma i 3.