Agriculture Reference
In-Depth Information
they are ownership of four selection houses that sell sugar beet seed in the Republic of
Croatia. Weather conditions during the research were significantly different. The first
was with increased, while the remaining two with small amounts of rainfall compared to
the long term average. In all three years monthly air temperatures during the growing
period were elevated, especially 2012th year. The obtained results show strong
dependence of yield and quality of the roots of through vegetation of conservation leaf,
hybrids and year. Because of damage to the leaves, on variants where no treatment was
carried out in relation to the well-preserved variant with three treatments, root yield was
reduced by an average of 15.92 t ha
-1
(20,64%), sugar content 1,61 (rel. 10,37%) and
sugar yield for 3,07 t ha
-1
(30,67%). Damages due to omitted fungicide application were
highly significant for all hybrids, and the repeated use of fungicides to combat
C. beticola
Sacc., it is still mandatory and highly cost-effective measures in sugar beet production.
On average of research by highest root yields hybrids were Boomerang, Colonia, KWS
and Sandor. The highest sugar content were found in Colonia KWS, Asketa and
Boomerang. Content of sugar in molasses best hybrid was Colonia KWS. By pure sugar
yield significantly better than the others were hybrids Colonia KWS and Boomerang.
Keywords
: sugar beets, hybrids
, Cercospora beticola
Sacc., yield, root quality
I
NTRODUCTION
Sugar beet is one of the most important industrial cultures in Croatia and the only raw
material for sugar production. Sugar beet is grown on about 25.000 ha annually. In the last
five years, the average root yield was about 52.0 t ha
-1
, while the sugar content was about
15.67%. Neither the producers nor the root processors are satisfied with such results. A large
number of factors have an impact on the achieved results in the sugar beet production,
whereby the most important one is the appearance and development of leaf disease caused by
C. beticola
Sacc. In the area where sugar beet is grown, the damage by this fungal plant
patogen is large. It depends on the cropping practices, abiotic factors, quality and quantity of
the composition of microorganisms in the soil and the disease control measures. Sugar beet
leaf spot is very harmful in all European countries with warm and humid summers (Ruppel,
1995). The most obvious damages are on the leaf surfaces. Generally, higher loss of leaf-mass
is registered in cases of early and strong infections. Leaf-mass reduction leads to lower
photosynthesis activity which results in lower yields and quality of sugar beet. Root yield
reduction might be about 15-30% (Hoffman and Schmulterer, 1999, Sharifi et al., 2007, Wolf
et al., 1998), but it might be also about 60% (Yoshimura et al., 1992). Kristek et al. (2006,
2008), testing a number of hybrids in conditions of natural infection with and without
fungicide treatment, recorded a root yield loss of about 13%. Sugar content decrease might be
about 2% (Wolf et al., 1998), or about 3-7% according to Yoshimura et al. (1992). Kristek et
al. (2006, 2008) reported about mean sugar content decrease of 1.35%. Rešić (2003) reported
that sugar content of the control plot was 0.40 - 1.35% lower in comparison with the once
treated plot and 0.74 - 1.83% lower in comparison with the twice treated plot. Root yield loss
and sugar content decrease in combination with increase of molasses elements at the same
time results in pure sugar yield loss of 40 - 50% (Wolf, 1998). Biancardi et al. (2001) tested
six hybrids with different levels of tolerance without fungicide application and with fungicide
applications every 10 and 20 days after the incidence of disease and registered that the impact
of genotype on pure sugar yield was always lower than the impact of fungicide applications
