Effect Of Time And Method Of Paclobutrazol Application On Growth, Quality And Yield Of Potato (Solanum Tuberosum L.)

ABSTRACT

Potato is one of the most widely grown tuber crop that contribute significantly to human

nutrition and food security. Potato is a cool season crop and high temperatures are inhibitory

to tuberization resulting in low yields. This is mainly due to production of high levels of

gibberellins at high temperatures that promote vegetative growth at the expense of

tuberization. The balance of hormones that control tuberization can be managed by using

anti-gibberellin synthesis such as paclobutrazol to overcome the inhibitory effect caused by

gibberellins. Two experiments were set up in a greenhouse with 60% relative humidity, 34

0C(±3) and 21 0C(±3) day and night temperature respectively at Harare Research Station to

investigate the effect of paclobutrazol on growth, yield and quality of potatoes. The first

experiment was set up as a 4 x 2 factorial design in a CRD with 3 replications to investigate

the effect of time of paclobutrazol application on the growth, yield and quality of potato. The

first factor was potato variety and the levels were BP1 and Diamond. The second factor was

paclobutrazol application time and the levels were 28 DAP, 35DAP, 42DAP and no

paclobutrazol applied (control). Early application of paclobutrazol at 28DAP increased yield

and starch content by 108% and 28% respectively compared to the no paclobutrazol

treatments. The second experiment was set up as a 4 x 2 factorial design in a CRD with 4

replications to evaluate the effect of method of paclobutrazol application and variety on

growth, yield and quality of potato. The first factor was potato variety and the levels were

BP1 and Diamond. The second factor was paclobutrazol application method and the levels

were drench, foliar and no paclobutrazol applied (control). Regardless of the method of

application, paclobutrazol increased yield, grades and tuber starch content of potato but the

effect was more in drench applied plots compared to foliar applied treatments. Drench

application increased stem diameter and yield by 85% and 120% respectively.