Link to home


Suppression of late blight by resistant tomato cultivars
M. T. MCGRATH (1). (1) Cornell Univ, Riverhead, NY, U.S.A.

Tomato cultivars bred to be resistant to late blight and tomatoes reported to be less susceptible to this disease were evaluated in two replicated experiments conducted outdoors on Long Island, NY. Seedlings were transplanted on 5 July 2012 and 17 June 2013. <i>Phytophthora infestans</i> genotype US-23 occurred naturally. Symptoms were first observed on 31 July 2012 and 16 Aug 2013. Degree of suppression achieved in 2013 based on AUDPC values relative to Mountain Fresh Plus (no known resistance) was 79% for Mountain Merit and 87% for Defiant PHR (both heterozygous for Ph2 and Ph3 resistance genes; red slicer fruit type), 88% for Iron Lady (homozygous Ph2 and Ph3; red slicer), 93% for Mountain Magic (heterozygous Ph2 and Ph3; campari), 81% for Mr Stripey (unknown resistance; slicer), 89% for Lemon Drop (unknown; cherry), 91% for Jasper (unknown; cherry), and 98% for Matt's Wild Cherry (unknown; cherry). New Yorker (Ph1), West Virginia 63 (Ph2), and Juliet (reported resistant) did not suppress late blight relative to Mountain Fresh Plus. Legend (Ph2) and Plum Regal (Ph3) provided limited suppression. Their foliage was significantly less severely affected than that of Mountain Fresh Plus only in 2012 when an organic fungicide program with Badge X2 copper fungicide, Actinovate, and Regalia was applied to all plots. Applications were started on 14 Aug when late blight was already severe on Mountain Fresh Plus (75% severity on 20 Aug), thus limiting achievable control.

View Presentation