Field Performance of Twenty-One Strawberry Cultivars in a Black Root Rot-Infested Site

Abstract

Twenty-one commercial strawberry cultivars were planted into field soil naturally infested with the black root rot pathogens Rhizoctonia fragariae, Pratylenchus penetransand Pythiumspp. Plant growth and yield were evaluated for up to 3 years after planting. Root rot evaluations and pathogen isolations were also conducted. R. fragariae, P. penetransand Pythiumspp. were consistently isolated from all plots, and the gradual decline of cultivars in these soils over four years paralleled the development of disease typically observed in commercial strawberry production fields. Strawberry cultivars differed in root weight, shoot weight, and fruit yield over the length of the experiment. Plant shoot weights were highest in 2001 and 2003 and least in 2002 (P ≤ 0.0001) and ranged from an average weight of over 200 g per plant over 3 years for ‘Earliglow’, ‘Latestar’ and ‘Northeaster’ to only 29.2 g for ‘Tristar’. Root weights were higher in 2002 and 2003 than in 2001 ( P≤ 0.0001), but root systems consisted of an increasing proportion of perennial roots each year. Root weights ranged from over 30 g per plant for ‘Primetime’, ‘Latestar’, ‘Idea’ and ‘Earliglow’ to under 10 g per plant for ‘Tristar’ and ‘Marmolada’. There were no significant interactions among cultivars and years. Strawberry fruit yields ranged from over 800 g per plant (‘Earliglow’ and ‘Latestar’) to just over 100 g per plant for ‘Marmolada’ and ‘Tristar’. Yields declined by only about 12% from 2002 to 2003, but were not significantly different. However, the yield of some cultivars increased by as much as 35% (‘Latestar’) while yields decreased for 14 of the 21 cultivars (by as much as 86% for ‘Marmolada'). Our results indicate that selection for plant performance may best be conducted in infested soils over multiple years and that certain strawberry cultivars may be more tolerant of the black root rot complex under field conditions than others.