The effect of plant growth regulators on Verticillium wilt of potato

Abstract

Four classes of plant growth regulators were tested for their effects on Verticillium wilt (Verticillium dahliae) of potato (Solanum tuberosum L.). These substances had auxin, cytokinin, gibberellin, or growth retardant activity. Preliminary greenhouse experiments were conducted to screen materials for effectiveness and to determine suitable application rates. A series of field experiments was then conducted over a four year period. The auxin, napthalene acetic acid, consistently reduced wilt and stem colonization byV. dahliae both in the field and in the greenhouse. Indole acetic acid was only partially effective at reducing wilt and stem colonization, possibly due to its labile nature. Other growth regulators, benzyladenine, (a cytokinin), gibberellic acid — A₃ (a gibberellin), chlorflurenol and daminozide (growth retardants), either had no consistent effect or increased wilt and stem colonization. The effect of auxins on wilt reduction was observed in the highly susceptible cultivar Norgold Russet, the moderately susceptible Russet Burbank, and the highly resistant selection A66107-51. Although napthalene acetic acid significantly reduced wilt severity (up to 50%) in field grown Russet Burbank, the reductions in stem colonization byV. dahliae were not of the same magnitude as seen when comparing the highly resistant selection A66107-51 with a susceptible clone. Growth regulator treatments that suppressed wilt or stem colonization did not increase total yield and generally resulted in tuber malformations.