|HARVESON, ROBERT - University Of Nebraska
|HUANG, H.C. - Agriculture Canada
Submitted to: American Phytopathological Society Press
Publication Type: Book / Chapter
Publication Acceptance Date: 7/17/2020
Publication Date: 1/1/2021
Citation: Dugan, F.M., Harveson, R., Huang, H. 2021. Pink Seed. In: Harveson, R.M., Pasche, J.S., Porter, L.D., Chen, W., and Burrows, M., Editors. Compendium of Pea Diseases and Pests, Third Edition. St. Paul, Minnesota. American Phytopathological Society Press. p.12-13.
Interpretive Summary: The plant disease Pink Seed is caused by a bacterium that discolors the seed coat of various legumes, and is especially notable in peas, chickpeas, lentils and beans. It similarly discolors grains of wheat, and can cause rot in rhubarb, onions and other vegetables. Losses are generally minor, but there is the danger that the disease might be mistaken for pink-colored pesticide seed treatment, in which case an entire harvested lot of peas or other legumes might be declared unfit for consumption. Therefore, correct diagnosis is critical. Unlike pink-colored seed treatment, the pink coloration induced by the bacterium cannot be readily removed by scrubbing with water. Strains of the bacterium infecting legumes can also infect cereals and vegetables, and vice versa.
Technical Abstract: Pink seed disease of field pea (Pisum sativum) was first reported in North America from Canada, and subsequently from the United States. Pink seed disease is also known from chickpea (Cicer arietinum), lentil (Lens culinaris), bean (Phaseolus vulgaris) and in grains of cereals, especially bread and durum wheat (Triticum aestivum, and T. durum = T. turgidum ssp. durum). The bacterium causing pink seed can also cause crown rot in rhubarb (Rheum rhaponticum) and sugar beet (Beta vulgaris), soft rot in garlic and onion (Allium spp.), necrosis of hyacinth (Hyacinthus orientalis), and rots of various other fruits and vegetables. On pea seed, the name of the disease is descriptive. Variability of pigmentation and its permanence readily distinguish diseased seed from seed coated with pink-colored pesticide, easily removed by scrubbing in water. On pea pods, discoloration is less intense. The bacterium can also induce a crown and shoot rot of pea. Erwinia rhapontici is a gram negative bacterium producing pinkish colonies on artificial media such as sucrose-peptone agar, but less reliably pinkish on potato dextrose agar. Erwina rhapontici has demonstrated potential for seed-transmission. Strains originating from pulses can infect other pulses as well as cereals, and strains from cereals can infect pulses. Grain inspection authorities have noted that symptoms of pink seed are similar to pink-colored pesticide seed treatments, so correct diagnosis can be critical to avoid mistakenly labeling seed lots as pesticide-contaminated.