Combining Fusarium head blight resistance and barley yellow dwarf virus tolerance in spring wheat (Triticum aestivum L.)
Pradhan, Manika Pakhrin
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Fusarium head blight (FHB), a fungal disease caused principally by Fusarium graminearum, and barley yellow dwarf (BYD) caused by BYD luteoviruses are two serious fungal and viral diseases of wheat resulting in high economic losses annually. Wuhan, a Chinese wheat cultivar resistant to FHB, and Maringa, a Brazilian cultivar tolerant to BYDV were inter-crossed and crossed with Roblin, a Canada western red spring wheat susceptible to both FHB and BYDV, to determine the genetic basis of resistance/tolerance and to combine the two traits. Four hundred ninety nine F1-derived doubled haploid (DH) lines were generated from reciprocal crosses using corn pollen-mediated DH technology. The DH lines and the parents were evaluated for disease symptoms, reduction in height and spike mass for BYD and for disease incidence, disease severity and Fusarium-damaged kernels for FHB in field and controlled environments. A subset (20/150) of the best performing DH lines from Wuhan/Maringa populations for both BYD and FHB were further evaluated. Plants were point inoculated with F. graminearum in greenhouse experiments, and macroconidial spray inoculations and spread of corn inoculum were used in field environments to evaluate FHB. BYDV inoculations were performed by placing ten to fifteen viruliferous aphids (Rhopalosiphum padi infected with BYDV-PAV isolate 9301PAV), at the one to two leaf stage for both greenhouse and field trials. The studies showed that both FHB and BYDV are quantitatively inherited. Transgressive segregants were observed and the broad sense heritability was high (0.90 to 0.97) for all traits evaluated. Results from independent testing of diseases on Wuhan/ Maringa populations showed fourteen DH lines were as, or more resistant than Wuhan for FHB and Maringa for BYDV tolerance and have combined both BYDV tolerance and FHB resistance. Identifying such lines facilitates the pyramiding of independent genes to obtain adequate levels of enduring resistance. A further experiment was conducted on the 14 lines by inoculating them with BYDV and F. graminearum successively on the same plant. Six out of 14 selected DH lines demonstrated high resistance to FHB and tolerance to BYDV. These six lines can be used in FHB/BYDV resistance/tolerance breeding programs.