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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #145084
Title: BREEDING FOR RESISTANCE TO NEW AND EMERGING LETTUCE DISEASES IN CALIFORNIA.

Author
item Grube, Rebecca
item Ryder, Edward
item KOIKE, STEVE - UC COOP. EXTENSION
item McCreight, James - Jim
item Wintermantel, William - Bill

Submitted to: Eucarpia Conference on Lettuce and Leafy Vegetables
Publication Type: Proceedings
Publication Acceptance Date: 9/20/2002
Publication Date: 3/19/2003
Citation: Grube, R.C., Ryder, E.J., Koike, S., McCreight, J.D., Wintermantel, W.M. 2003. Breeding for resistance to new and emerging lettuce diseases in California. Eucarpia Leafy Vegetables 2003. pp. 37-42.

Interpretive Summary: Preventing crop loss due to diseases has historically been the primary focus of public lettuce (Lactuca sativa) breeding efforts in the United States. Recent years have seen a shift in the industry, with increasing percentages of romaine and mixed lettuces being grown under intensive production systems. Possibly related to this change, several diseases have recently been reported for the first time or have increased in incidence. Two of these, lettuce dieback and crown rot, affect primarily romaine lettuce, whereas a third, Fusarium wilt, threatens all types. Lettuce dieback is caused by soilborne viruses of the family Tombusviridae. This disease may be identical to 'brown blight', which was widespread in the 1940s but vanished when resistant crisphead cultivars were developed. Fusarium wilt of lettuce was initially observed in California in 1990, and first caused significant crop losses in both California and Arizona in 2001. Crown rot of romaine, now known as Phoma basal rot, was first observed in the Salinas Valley of California in 2001. The cause of this disease was recently identified as Phoma exigua. Progress and results of breeding for genetic resistance to these diseases will be discussed.

Technical Abstract: Preventing crop loss due to diseases has historically been the primary focus of public lettuce (Lactuca sativa) breeding efforts in the United States. Recent years have seen a shift in the industry, with increasing percentages of romaine and mixed lettuces being grown under intensive production systems. Possibly related to this change, several diseases have recently been reported for the first time or have increased in incidence. Two of these, lettuce dieback and crown rot, affect primarily romaine lettuce, whereas a third, Fusarium wilt, threatens all types. Lettuce dieback is caused by soilborne viruses of the family Tombusviridae. This disease may be identical to 'brown blight', which was widespread in the 1940s but vanished when resistant crisphead cultivars were developed. Fusarium wilt of lettuce was initially observed in California in 1990, and first caused significant crop losses in both California and Arizona in 2001. Crown rot of romaine, now known as Phoma basal rot, was first observed in the Salinas Valley of California in 2001. The cause of this disease was recently identified as Phoma exigua. Progress and results of breeding for genetic resistance to these diseases will be discussed.