Management Of Ware Potato Sprouting During Long Term Storage In The Tropical Conditions Of Kenya

Abstract

Potato is an important crop in Kenya. However, its long term storage is low owing to a number of constraints. Amongst these is inadequate post-harvest handling techniques and short dormancy of popular cultivars leading to premature sprouting. There is a window of six months between harvests and most of the cultivars have dormancy period of 1-3 months therefore, management of sprouting has to be an integral part of short-term storage as well. Use of sprout suppressants to control premature sprouting of ware potato is therefore an attractive proposition. Researchers around the world and especially in temperate countries have developed sprout suppressing compounds but their effects under tropical conditions is not well known. This study was designed to determine the effectiveness of five sprout suppressants on three potato cultivars adapted to the ecologies of Kenya. Four separate experiments were carried out with the following specific objectives; to determine the effect of: (i) post-harvest application of Isopropyl-N-phenylcarbamate (CIPC), peppermint oil and 1,4-Dimethylnaphthalene (DMN) on ware potato storability (ii) storage temperature on the efficiency of sprout suppressants (iii) pre-harvest foliar application of Paclobutrazol and Ethephon on sprouting of ware potato tubers in storage (iv) packaging materials on ware potato quality during short-term storage. The study was conducted on three potato cultivars with varying levels of dormancy; Shangi (30 days), Asante (60 days) and Kenya Mpya (60 days). Four experiments were conducted separately and the parameters recorded were dormancy length, weight loss, sprouting and sprout growth, tuber rotting and tuber greening. In experiment 1, the results showed that sprout suppressants minimized the detrimental effects of sprouting thereby improving storability of ware potatoes. CIPC recorded the best sprout suppression with over 75% sprout suppression in all cultivars. In experiment 2, storage temperature influenced the efficacy of sprout suppressants. Sprout suppressants were more effective in delaying sprout emergence and subsequent sprout growth under cold storage compared to ambient storage in all the cultivars with CIPC and DMN recording up to 100% sprouting suppression. In experiment 3, pre-harvest applied sprout suppressants were effective in delaying dormancy end when tubers were stored at ambient storage. However, at cold storage, the treatments did not have an effect on dormancy period in all the cultivars. Among cultivars, Kenya Mpya was more responsive to the treatments compared to Shangi and Asante. In experiment 4, packaging and the type of packaging material affected the shelf life of ware potatoes. Packaging reduced post-harvest losses due to weight loss and tuber greening but increased the rate of sprouting and decay xvi incidences. Low density black polyethylene bag emerged as the best method for ware potato packaging. CIPC, DMN, peppermint oil and Paclobutrazol are effective sprout suppressant whose application in potato warehousing will contribute to the economic well being of Kenyans. Key words: Potato, postharvest loss, tropical environment, sprout suppressant, sprout control