Abstract:
The action of the holoparasite Orobanche cumana Wallr. on sunflower may be very different, from the non-visible
damage of plant tissues and the stagnation of host plant development until its death. Depending on the aggressiveness of
the broomrape and the climatic conditions, the yield losses vary within 5-90%, affecting the quantity and quality
(protein and lipids content) of the seeds. The aim of present investigation was to study some productivity indices, such
as hectolitre weight and 1000-seed weight, plant height, head diameter, number of seeds per head in a series of
experimental and commercial hybrids from the Republic Moldova and Romania in the conditions of infestation. The
analyses were performed during 2012 and 2013 years in the field with natural infection. As a control serves the
productivity indices of hybrids in the field without infection.
It was established that Orobanche cumana affects significantly the productivity indexes of sunflower hybrids. The
degree of infestation correlates, in particular, with the head diameter and seeds yield per head, and lesser with the plant's
height. Thus, in the case of a strong attack, the productivity losses in most cases exceed 20%, with maximum values
(30-40%) in susceptible hybrids Doina and Performer characterized by the highest attack degree (60-70%).
The values of the analyzed productivity indices vary a lot depending on the genotypes. So some hybrids (e.g. the
Milenium hybrid) are tolerant to broomrape and endure pathogen attack with low losses.
The data obtained are of major interest in the development and proposal of key intervention and control measurements
in integrated pest management programs.
