Effect of Storage Temperature and Postharvest Tuber Treatment with Chemical and Biorational Inhibitors on Suppression of Sprouts During Potato Storage

Consumption of ware potatoes in the tropics may be enhanced by storage under conditions that inhibit sprouting, most important of which is the temperature. The effects of storage temperatures (10 °C and 23 °C) and two alternatives to the chlorpropham (CIPC): 1,4-dimethylnaphthalene (DMN) and peppermint oil (PMO), a biorational inhibitor, were evaluated for tuber sprout suppression at postharvest. Tubers of three cultivars – ‘Asante’, ‘Kenya Mpya’, and ‘Shangi’ – with different dormancy lengths were assessed. Storage temperatures and suppressant effects on tuber sprouting, sprout length and sprout numbers per tuber were investigated in replicated storage experiments. Significant differences in sprout inhibition were observed between the two temperatures with suppressive effects higher at 10 °C than in 23 °C. CIPC had the greatest suppressive effect on tuber sprout inhibition at both temperatures. After 24 weeks of storage, the suppressive effects of CIPC at 10 °C was 100% on the three cultivars, whereas all the nontreated tubers sprouted after six (‘Shangi’), twelve (‘Asante’), fourteen (‘Kenya Mpya’) weeks of storage. At 23 °C, the effectiveness of CIPC followed the dormancy period of the cultivars, with ‘Shangi’ recording significantly more sprouted tubers followed by ‘Asante’ and ‘Kenya Mpya’. The inhibition of sprouting by DMN and PMO varied with storage temperatures and cultivars, but were significantly greater than the nontreated tubers. At 10 °C, the effectiveness of DMN treatment was equal to that of CIPC for ‘Kenya Mpya’ resulting in 100% inhibition. In the PMO treatments, complete inhibition of sprouting was observed for 18 weeks on cultivars ‘Asante’, ‘Kenya Mpya’ and 14 weeks on ‘Shangi’. At 23 °C, PMO suppressed sprouts for 14 weeks on ‘Asante’ and ‘Kenya Mpya’ and on ‘Shangi’ for 8 weeks. Storage temperature effects on sprout length and numbers varied with inhibitor type and cultivar. These findings showed that in potato tuber storage, inhibitors can replace low temperature but to an extent depending on the cultivar dormancy character and storage length, thus enabling greater consumption of potatoes in tropical regions.

Simulated Glyphosate Drift to Potato Mother Plants and Effect on Daughter Tubers Used for Seed Production

Field trials were conducted to evaluate the effect of simulated glyphosate drift rates applied to two non-irrigated potato cultivars in the late tuber bulking stage grown for potato seed production. Mother plants receiving a sublethal glyphosate application had similar yields regardless of the year or cultivar. ‘Red LaSoda' seed pieces visually evaluated the following spring had more sprout inhibition from glyphosate-treated plots. With ‘Russet Burbank', only seed pieces from mother plants that received more than 18 g ha−1 glyphosate showed sprout inhibition. Total yield reductions the year following glyphosate treatments were attributed to fewer and smaller tubers from plants that did not emerge or were delayed in emergence. Red LaSoda seed pieces from mother plants receiving ≥ 71 g ha−1 glyphosate yielded less than the nontreated. In 2005, Russet Burbank seed pieces from mother plants receiving ≥35 g ha−1 glyphosate had reduced yields, whereas in 2006, all glyphosate treatments reduced total yield compared with the nontreated.

Chemical Diversity in Mentha spicata: Antioxidant and Potato Sprout Inhibition Activity of its Essential Oils

The essential oils from fresh aerial parts of Mentha spicata L. collected from ten different natural habitats of Uttarakhand, India were analyzed by a combination of GC, GC/MS and NMR spectroscopy. The analysis revealed that monoterpenoids (46.1%-91.6%), mainly carvone (15.3%-68.5%), piperetenone oxide (24.0%-79.2%) and α-humulene (0.1%-29.9%), were the major constituents of the essential oils, but with significant qualitative and quantitative differences among the other constituents. Cluster analysis of the oil composition was carried out in order to discern the differences and similarities within different accessions collected from different natural habitats. The essential oils were also screened for their antioxidant activities by chelating properties of Fe2+, DPPH radical-scavenging activity, and their reducing power. The essential oils of two chemo variants (viz. carvone and piperetenone oxide types) were also tested for potato ( Solanum tuberosum L.) sprout suppressant activity. The results showed that these oils exhibit good sprout inhibition activity in comparison to CIPC and iodine, the standard sprout suppressant.