Sources of Resistance to Sunflower Diseasesin a Global Collection of Domesticated USDA Plant Introductions

Abstract

ABSTRACTBasal stalk rot (BSR) and head rot (HR) caused by Sclerotinia sclerotiorum (Lib.) de Bary are traditionally major diseases of sunflower (Helianthus annuus L.) in the United States, while Phomopsis stem canker (PSC) caused by Phomopsis helianthi Munt.‐Cvet. et al. has become increasingly damaging in recent years. Host resistance is the most effective approach to managing these diseases. Here we report new sources of resistance to these diseases identified in the USDA sunflower Plant Introduction (PI) collection. A total of 260 PIs, including USDA‐ARS–developed inbred lines, were tested in multiple years and locations of North Dakota, South Dakota, and Minnesota. The effects of genotype (G), environment (E), and G × E interaction were significant. Broad sense heritability (H2) for BSR, HR, and PSC were estimated as 0.70, 0.79, and 0.83, respectively, reflecting a large genetic variation in the panel for these diseases. A total of 6.2, 29.6, and 36.9% of the genotypes showed significantly higher resistance than checks against BSR, HR, and PSC, respectively. Two PIs, 531389 and 531366, were significantly more resistant than checks against all three diseases. Head rot disease incidence was positively correlated with PSC (r = 0.52, p < 0.0001), while it was negatively correlated with BSR (r = −0.16, p < 0.05). A total of 13 PIs, mostly from Hungary, exhibited dual resistance against HR and PSC. Overall, sufficient variation exists among germplasm sources to facilitate further resistance breeding of sunflower against BSR, HR, and PSC diseases.