Gaining ground against Cercospora: A decade of breeding for Cercospora Leaf Spot tolerance.

Abstract

Cercospora leaf spot (CLS) of sugar beet, caused by Cercospora beticola, is one of the most devastating diseases of sugar beet worldwide.  This polycyclic fungal disease is controlled via a combination of cultural, chemical, and genetic means.  Typically, genetic tolerance, while a critical part of an overall disease control program, has been limited due to an association between high disease tolerance with low yield performance under non-disease conditions.  Progress has been made over time, and in recent years high performing hybrids with strong tolerance have been available that provided an increased level of CLS tolerance without sacrificing performance in the absence of CLS pressure.  Recently, the introduction of CR+^®TM hybrids has provided a new valuable tool against Cercospora infection, offering significantly enhanced levels of CLS tolerance combined with even higher performance regardless of disease pressure.   Hybrids grown commercially in Michigan over the last decade were compared head-to-head in yield and disease nursery trials illustrating the breeding gains over time and higher relative performance in strong CLS hybrids.  More recently, initial CR+^®TM hybrids were competitive with traditional strong CLS tolerant hybrids for sugar yield and slightly weaker in sugar content, with a significant reduction in relative CLS rating (in % of benchmarks).  Subsequent CR+^®TM OVT entries pending commercial approval have shown a statistically significantly higher sugar content (LSD 0.05%) compared to initial CR+^®TM offerings, and an increase of over 10% (relative to benchmarks) in sugar yield, while staying under 50% of the benchmark level for CLS rating.