Characterization of resistance to Fusarium graminearum in a recombinant inbred line population of wheat: Resistance to fungal spread, mycotoxin accumulation, and grain yield loss, and trait relationships

Fusarium head blight (FHB or scab) caused by Fusarium species can lead to tremendous loss of grain yield and quality in wheat (Triticum aestivum L.) as well as severe mycotoxin contamination. Characterization of different types of resistance is of great significance for genetics and breeding studies. One hundred fifty-two F_6:7 recombinant inbred lines (RILs) derived from a cross CJ 9306/Veery were assessed in the greenhouse by single-floret inoculation to analyze three types of FHB resistance, i.e., resistance to fungal spread within spikes, deoxynivalenol (DON) accumulation, and grain yield loss. Each of the investigated resistance types exhibited a large and continuous variation in the RIL population, and thus was inherited quantitatively. Estimates of broad-sense heritability varied with resistance types, higher and less variable for spread resistance (0.85-0.93), but lower and more variable for resistance to DON accumulation (0.64-0.92) and/or resistance to grain yield loss (0.61-0.83). For spread resistance parameters (the number and percentage of scabby spikelets) and DON content, frequency distributions exhibited a few peaks and/or were skewed toward resistance, suggesting the existence of major resistance genes. Genetic correlation coefficients of spread resistance parameters with DON content and yield loss parameters were 0.85 to 0.92 and 0.78 to 0.94, respectively. The genetic correlations ranged from 0.63 to 0.77 between DON content and yield loss parameters. There were no noticeable genetic associations between FHB resistance and agronomic traits such as plant height, spike length, number of spikelets and grains per spike, grain weight, and heading date.