Enhancing Tuber Calcium Concentration May Reduce Incidence of Blackspot Bruise Injury in Potatoes

Abstract

Our previous research has provided evidence that in-season calcium applications can increase tuber calcium and improve tuber quality with reduced internal defects.To determine if increasing the tuber calcium concentration also mitigates tuber bruise incidence, five commercially relevant potato (Solanum tuberosum L.) cultivars (ÔRusset BurbankÕ, ÔAtlanticÕ, ÔSnowdenÕ, ÔSuperiorÕ, and ÔDark Red NorlandÕ) were grown during three seasons, 1999-2001. Three split applications of a calcium/nitrogen water soluble blend totaling 168 kgÁha -1 calcium were made starting at hilling. All plots, including controls, received an equal amount of total nitrogen in a season. Tubers were allowed to be bruised during normal machine harvest standard to commercial production in Wisconsin. Over 100 tubers from each replication (5-10 replications/treatment) were cut and examined for the incidences of bruise and internal brown spot. Paired samples of medullary tissue were taken for measuring calcium concentration. As expected, tuber tissue calcium concentration increased significantly, in all cultivars and in all years, with in-season calcium application. Bruise incidence varied among cultivars and seasons. Although tuber calcium concentration varied among seasons, ÔAtlanticÕ and ÔSnowdenÕ consistently had the lowest calcium concentration, whereas ÔSuperiorÕ and ÔDark Red NorlandÕ consistently had the highest calcium concentration. Meta-analysis of pooled data for three years showed that blackspot bruise incidence was significantly reduced with calcium application in ÔAtlanticÕ, ÔBurbankÕ, and ÔSnowdenÕ. On the other hand, ÔDark Red NorlandÕ and ÔSuperiorÕ had low incidence of bruise and were unaffected by calcium applications. Regression analyses of pooled data from all cultivars for three years revealed a significant quadratic relationship between blackspot bruise and tuber tissue calcium as well as between blackspot bruise and internal brown spot. A linear to plateau plot of medullary calcium concentration versus blackspot bruise incidence revealed that bruise incidence is minimized between 200 and 250 mg/kg (dry wt) -1 tuber calcium concentration. To our knowledge, ours is the first study providing evidence for reducing bruise by improving tuber calcium. Variations in the bruise incidences among cultivars generally followed tuber calcium concentration suggesting a genetic control. Given the role of calcium in improved membrane health and enhanced wall structure, and as a modulator of physiological responses, it is not surprising that internal brown spot and bruise incidences are reduced by in-season application to calcium-deficient cultivars.

Exchangeable Soil Calcium May Not Reliably Predict In-season Calcium Requirements for Enhancing Potato Tuber Calcium Concentration

“…The results from these evaluations were reported by Ozgen et al (2006) and Karlsson et al (2006). With an increase in tuber calcium concentration, a reduction in the incidences of these tuber defects was found Ozgen et al 2006;Karlsson et al 2006). Pre-plant soil exchangeable Ca at Hancock varied between 285-563 mg kg −1 ( Table 2).…”

“…In addition to Ca concentration, tubers from these trials were evaluated for hollow heart, internal brown spot and black spot bruise. The results from these evaluations were reported by Ozgen et al (2006) and Karlsson et al (2006). With an increase in tuber calcium concentration, a reduction in the incidences of these tuber defects was found Ozgen et al 2006;Karlsson et al 2006).…”

“…As mentioned in the introduction, Ca application in potato production is recommended only when pre-plant exchangeable Ca is less than 300 mg kg −1 (Stark and Westermann 2003). Even though exchangeable soil Ca in a number of the trials at Hancock was over 300 mg kg −1 , tuber quality was improved with the addition of 168 kg ha −1 Ca at this location (Ozgen et al 2006;Karlsson et al 2006).…”

“…The soils in these two areas are loamy sand and silt loam, respectively, and the soil at our experimental sites tested at 285 to 563 and 530 to 1,340 mg kg −1 of exchangeable Ca, respectively. In spite of these high soil test values, we have been able to increase the tuber Ca concentration and reduce tuber internal defects as well as reduce black spot bruising by in-season application of 168 kg ha −1 Ca during the tuber bulking period (Kleinhenz et al 1999;Ozgen et al 2006;Karlsson et al 2006). The objective of the present study was to determine the relationship between exchangeable soil Ca and tuber Ca, with and without in-season Ca fertilization.…”

“…The control plots received split doses of nitrogen using the method described above. Both sources of Ca (calcium nitrate, and a mixture of calcium chloride and calcium nitrate) have been found to be effective in increasing tuber Ca concentration and improving tuber internal quality (Ozgen et al 2006;Kleinhenz et al 1999;Karlsson et al 2006).…”