Response of Two Periwinkle (Catharanthus roseus G.) Varieties to Growth Regulators

Abstract

This study was conducted in the nursery of the Department of Horticulture, College of Agricultural Studies –Shambat, Sudan University of Science and Technology during March to November 2016 to evaluate the effect of the single and combined foliar treatments with BA and GA3 on growth, flowering and fruiting of the white and red varieties of periwinkle. The completely randomized design was used with 6 replications where each plant in a plastic bag was considered a replicate. Data were collected at the end of the experiment for the following parameters: Plant height; Numbers of leaves, branches, flowers and pods, beside fresh and dry weights of shoots and roots. Data were subjected to analysis of variance and means were separated by Duncan's multiple range tests. The results revealed significant increase in the number of leaves and branches of the two varieties in plants treated with BA only. The single GA3 treatment increased the number of flowers and fruits in the white variety while the two measures were negatively affected by all growth regulator treatments in the red variety. The combined treatment of BA and GA3increased the plant height in the two varieties significantly and this increase was similar to the effect of single BA application. Besides, it increased flower number in the white variety like the increase caused by single BA treatment while it increased fruit number in the white variety which was similar to single GA3 treatment. In addition, it increased the fresh weights in the two varieties and it is worthy to recognize that the increase in the white variety was similar to that induced by BA in the white variety. This effect matched that imposed on root fresh weight in the white variety while the combined treatment caused a significant increase in root dry weight of the red variety. In conclusion, the single BA treatment was effective in increasing the number of leaves and branches, while the variety was a limiting factor for flowering and fruit formation responses as treatments resulted in negative impact for these parameters in the red variety whereas the white variety responded positively to the PGR treatments. Therefore this might be attributed to differences in the endogenous hormonal contents in the two varieties.