‘Chouya No. 37’, a Fusarium Root Rot (Race 2)-Resistant Lettuce

Abstract

Fusarium root rot of lettuce (RRL) caused by Fusarium oxysporum f. sp. lactucae (FOL) race 2 occurrs only in Nagano Prefecture, Japan. The area affected by the disease reached 17 ha in 2003. ‘Chouya No. 37’ crisphead-type lettuce (crisp lettuce), which is adaptable to summer cultivation, was bred with resistance to FOL race 2. As a maternal line to breed a resistant cultivar, the selection line of ‘Kikugawa No. 102’ was used as a genetic resource with resistance to FOL race 2. The resistant line was crossed with the selection line of crisp lettuce with slow bolting. The progeny had been selected by various methods until F₆, ‘Chouya No. 37’ was bred. ‘Chouya No. 37’ is as highly resistant to FOL race 2 as its maternal line. Its resistance is superior to that of other lettuce cultivars that are adaptable to mid-summer cultivation in Nagano. ‘Chouya No. 37’ is very vigorous, its leaf color is green to slightly dark green, and its leaf luster is relatively high. The leaf margins have relatively shallow incisions, indentations, and mild undulations. The quality of the head upon harvest is categorized as “relatively good” to “good”. It also has slow bolting in mid-summer.