|Perkins Veazie, Penelope|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2007
Publication Date: 2/1/2008
Citation: Taber, H., Perkins Veazie, P.M., White, W., Li, S., Rodermel, S., Xu, Y. 2008. Enhancement of tomato fruit lycopene by potassium is cultivar dependent. HortScience. 43(1):159-165. Interpretive Summary: Tomatoes are a major plant source of dietary lycopene. The type of tomato greatly influences the ability of the fruit to make lycopene, and there is interest in manipulating lycopene content by production methods. Potassium was applied to field and greenhouse grown tomatoes of regular and high lycopene types in Iowa. The high lycopene type had a 20% increase in lycopene after high potassium application and decreased beta carotene by as much as 50%. These changes indicate that the enzymes that control carotenoid synthesis may be sensitive to production method in high lycopene tomato types.
Technical Abstract: The purpose of this experiment was to determine the response of tomato (Solanum lycopersicum L.) cultivars with fruit of average and high lycopene to increased K fertilization. The field experiment was designed as a factorial, split-plot, randomized complete block with 4 replications. The main plot consisted K rates (0 to 372 kg'ha**-1 K as KCl) and the subplot was cultivar (‘Mountain Spring’ or the high lycopene Florida hybrid, ‘Fla. 8153’). The soil type was a well drained, central Iowa loam with a soil test level considered low. The soil K application effect on total marketable fruit yield was linear (P<.001, Y = 53 Mg'ha**-1 + 0.084x, r**2 =.51) with both cultivars responding similarly. Fruit K analysis indicated a linear response to fertilization across four harvest dates, from 1236 to 1991 mg'kg**1, fresh weight basis. Harvest date had no effect on fruit lycopene concentration, but there was a significant (P=.006) interaction of K fertilization rate and cultivar. Overall, the ‘Fla. 8153’ cultivar contained 9.5 mg'kg**-1 more lycopene in fruit tissue than ‘Mountain Spring.’ ‘Mountain Spring’ lycopene concentration was not enhanced by higher K fertilization (44.2 mg'kg**-1 ). ‘Fla. 8153’ lycopene concentration increased 21.7% at the highest K rate compared with lower rates (62.9 vs. 51.7 mg'kg**-1, respectively). A controlled greenhouse study in the fall of 2005 with the same cultivars indicated similar results. Fruit K concentration for ‘Fla. 8153’ was significantly (P<0.01) correlated to fruit carotenoids, phytoene and phytofluene, indicating a possible role for K in one of the enzymes that synthesize phytoene. In field and greenhouse studies, increasing fruit K concentration in the high lycopene ‘Fla. 8153’ depressed fruit B-carotene by 53%. These results indicate that K fertilization can affect carotenoid biosynthesis, and response of tomato to high K rate is genotype dependent.