Sclerotinia-resistant Brassica

Abstract

The invention provides Brassica plants and lines having an improved Sclerotinia sclerotiorum Disease Incidence (SSDI %) score and represented by, or descended from, ATCC accession number PTA-6776 or PTA-6780.

Description

REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of U.S. application Ser. No. 11 / 422,623 filed Jun. 7, 2006, which claims priority to U.S. provisional application 60 / 688,687 filed Jun. 9, 2005, both of which are hereby incorporated by reference.TECHNICAL FIELD[0002]The present invention relates to Sclerotinia resistant Brassica. BACKGROUND OF THE INVENTION[0003]Sclerotinia infects over 100 species of plants, including numerous economically important crops such as Brassica species, sunflowers, dry beans, soybeans, field peas, lentils, lettuce, and potatoes (Boland and Hall, 1994). Sclerotinia sclerotiorum is responsible for over 99% of Sclerotinia disease, while Sclerotinia minor produces less than 1% of the disease. Sclerotinia produces sclerotia, irregularly-shaped, dark overwintering bodies, which can endure in soil for four to five years. The sclerotia can germinate carpogenically or myceliogenically, depending on the environmental conditions and crop canop...

AI Technical Summary

Benefits of technology

The present invention provides a population of Brassica napus plants or groups of plants with improved resistance to Sclerotinia sclerotiorum, a disease caused by a fungus. The plants have a lower average Sclerotinia sclerotiorum Disease Incidence (SSDI) score compared to the variety Pioneer Hi-Bred variety 46A76 or Pioneer Hi-Bred variety 46A65, meaning they are less susceptible to the disease. The plants can also have other desirable traits such as a solid component of the seed, oil with low erucic acid content, a (50%) flowering time of between about -30 to -90 days, and an SSDI score of less than (50%) of the variety Pioneer Hi-Bred variety 46A76 or Pioneer Hi-Bred variety 46A65. The invention also provides a population of Brassica napus plants with these desirable traits.

Problems solved by technology

Sclerotia that germinate carpogenically produce apothecia and ascospores that infect above-ground tissues, resulting in stem blight, stalk rot, head rot, pod rot, white mold, and blossom blight of plants.

Further, Sclerotinia can cause heavy losses in wet swaths.

Plants with girdled stems wilt and ripen prematurely.

Severely infected crops frequently lodge, shatter at swathing, and make swathing more time consuming.

(Johnson, 2005) However, use of fungicide is expensive and can be harmful to the user and environment.

However, success in developing partial resistance has been very limited, probably because partial physiological resistance is a multigene trait as demonstrated in bean (Fuller, et al., 1984).

(c) Cultural practices such as using pathogen-free or fungicide-treated seed, increasing row spacing, decreasing seeding rate to reduce secondary spread of the disease, and burying sclerotia to prevent carpogenic germination may reduce Sclerotinia disease but not effectively control the disease.

However, these morphological traits alone do not confer resistance to Sclerotinia, and all canola products in Canada are considered susceptible to Sclerotinia.

In Germany, for example, no Sclerotinia-resistant varieties are available.

If infection is already evident, there is no use in applying fungicide as it is too late to have an effect.

Either method is cumbersome and prone to errors.

Asiatic material cannot finish its reproduction cycle if planted in late spring.

However, some of these varieties are not canola quality, and all of them require vernalization.

Despite improvements in partial resistance in Zhong you 821, its reaction to disease is less stable under environmental conditions favorable for development of Sclerotinia (Yunchang, et al., 1999).

However, these varieties are not canola quality and are semi-winter types (see, Table 1).

Breeding for Sclerotinia field resistance in canola has been very difficult due to the quantitative nature of this trait.

Further, the incorporation of physiological resistance with morphological traits that avoid or reduce infection multiplies the complexity of breeding for resistance.

In addition, it has been very difficult to screen for resistance because of the direct environment interaction (i.e., temperature and humidity requirements, as well as microenvironment requirements) with the plant population.

Despite 30 years of extensive breeding efforts, no canola varieties resistant to Sclerotinia have previously been developed.

Several spring canola varieties with moderate tolerance to Sclerotinia have been developed (Ahmadi, et al., 2000a; Ahmadi, et al., 2000b; BaoMing, et al., 1999; and Liu, et al., 1991), however the level of tolerance is low and the lines cannot withstand high disease pressure.

Recently, transgenic canola has been developed carrying an oxalic oxidase gene (U.S. Pat. No. 6,166,291 and divisional patents thereof); however there are regulatory and social issues associated with transgenic plants.

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