INTRODUCTION

In Egypt and other countries with a similar climate, potatoes are grown as both a spring crop and an autumn crop. The spring crop is usually planted in January with imported seed tubers, while the autumn crop is planted in September using local seed tubers taken from the preceding spring crop. Attempts to grow the spring crop using local seed taken from the preceding autumn crop are usually hampered by the dormancy of the freshly harvested tubers. Potato varieties grown in Egypt show wide variation in length of dormancy and in their reaction to the different chemical agents that break dormancy.

METHOD

In the present investigation, seed tubers of five potato cultivars Alpha, Berolina, Domina, Granola and Hilta were purchased from the local market and grown on Assiut University Experimental Farm during the autumn season of 1984. After harvest in January 1985, tubers were exposed to the following treatments to break dormancy:

1. 1. Cutting of tubers (cut, whole).

2. 2. Pretreatment temperature (ambient temp. 5–22°C, high temp. 25–30°C).

3. 3. Chemical treatment: a) soak treatment: thiourea, potassium thiocyanate.

b) gas treatment; carbon disulphide (CS2), ethylene chlorohydrin, rindite. The tubers were planted on 19 February 1985 in a factorial experiment and data were recorded on rate of emergence, final plant stand, shoot length, number of stems per plant and total yield.

RESULTS

Alpha was the slowest cultivar to emerge and had the lowest number of stems per plant. Results for final plant stand (56 days after planting) are presented in Table 1.