Influence of Harvest Dates on Sugar Beet Quantitative Traits

Results of the investigation regarding influence of harvest dates on quantitative traits of sugar beet are presented in this paper. The three-year trial was conducted on five varieties developed by Institute of Field and Vegetable Crops, Novi Sad. Analysis of variance showed significant differences between harvest dates in 2008 and 2010 for all analyzed traits, but in 2009, due to severe drought differences were not found. With the delay of harvest date, root and raw sugar yield increased, while sugar content was dependent on climatic conditions (precipitation) between two harvest dates. There were no differences among the analyzed genotypes for measured traits in 2010. Interaction between genotype and harvest date has not been confirmed. Variety Drena had the highest root and raw sugar yields in 2008 and 2010. : genotypes, roots, harvesting dates, sugar beet, sugar content, sugar yield

into three types: E -high yield type, Z -sugar type and the transition between these two types N -normal type.In addition to the increased sugar content, Z -type varieties are characterized by better technological properties (low content of impurities) and earlier attainment of technological maturity.
Since sugar beet variety trials are usually harvested at the end of the growing period, information about effect of harvest date on yield and quality of sugar beet root can be very valuable.Jozefyová et al. 2003, Filipović et al. 2009) did not offer the full explanation about interaction between genotype and harvest date.One group determined the existence of significant interaction between genotype and harvest date for root yield, sugar content and sugar yield.In contrast to them, 2005, Heidari et al. 2008) considered that there is no interaction between genotype and harvest date and that all genotypes react similarly with the delay of harvest date.
In the last years, sugar beet harvesting campaign in Serbia starts at the end of August.Duration of campaign is dependent on climatic conditions and can last for more than three months.Having that in mind, the aim of this research was to determine influence of early harvest dates on sugar beet root yield and quality in five hybrid varieties.Weather conditions were very different during the three growing seasons (Tab.1).The average temperature during the vegetation was higher than the long term average.In the first two years there term average.Distribution of precipitation in the first two years were very similar, until September, and in 2009 only 13.1 mm.Average temperature in July and August of 2009 were higher by 1°C and in of precipitation in these two years was reflected in reduced yields.In the third year of there was very high amount of precipitation, twice as much than 2008 and 2009.The difference in precipitation between the 2009 and 2010 was 412.1 mm.Because of these weather conditions in 2010 there was a reduction in the quality of sugar beet roots.
All results were processed in the statistical software Statistica for Windows v. 10, Statsoft Inc. by ANOVA as two-factorial (genotype / harvest date) and three-factorial trial (genotypes / harvest date / year).
Because of the specific weather conditions during the study, such as severe drought in 2009 and heavy rainfall in 2010, yield and quality of sugar beet root extremely varied, and therefore the results of variance analysis varied between the years (Tab.2).
Influence of harvest date on the measured traits was significant in the first and third years of study, while in 2009 those differences were not significant.This result is a direct consequence of severe drought in August and September of 2009.In those conditions there was a reduction in the phenotypic variation of studied traits, al. 2005).Effect of genotype also varied from year to year: there were differences between genotypes in 2008 for root yield and raw sugar yield, and in   2. Mean values of the analyzed sugar beet traits and ANOVA results 2009 only for sugar content.Interaction between genotype and harvest date was significant only for sugar content in 2008.In other years there was no interaction for all traits.These results are where the interaction between these two factors occurred sporadically and only for certain traits.
With the delay of harvest date, root yield increased during 2008 and 2010, as reported by and Filipović et al. ( 2009) (Tab.2).Sugar content was under influence of weather conditions before harvest date.Because of the heavy rainfalls in September 2008 sugar content had lowest value in the last harvest date.In 2010 sugar content was for this decline in sugar content is the combined impact of weather conditions (heavy rainfall) and Raw sugar yield increased with the delay of harvest date during 2008 and 2010.Average increase of raw sugar yield for three years of research between the first and last harvest dates was 1.13 t ha -1 , which is consistent with result of Jozefyová et al. (2003), -1 for 27 days.Comparing varieties in 2008, variety Drena had the highest root yield and raw sugar yield in all three harvest dates (Tab.2), confirming the results Significant differences between genotypes in sugar content were determined only in 2009, and variety Vera had highest value, which was expected because it belongs to sugar (Z) type of sugar beet varieties Results of analysis variance for three-factorial trial showed that effect of year, harvest date, genotype and interaction between year and harvest date were significant for all quantitative traits (Tab. 3).Interaction between year and genotype was significant (p < 0.01) only for sugar content.Effect of interaction between genotype and harvest date was significant at level of probability 0.05 also for interactions between genotype and environment in sugar beet are exceptionally low comparing to other field crops.Main reason for absence of interaction is that root and quantitative traits of root are estimated in commercial production of sugar beet.Root grows in vegetative phase of sugar beet development and in contrast to other field crops does not pass through sensitive stages filling (Hoffmann et al. 2009).Although analysis of variance showed that effect of year was most important in total sum of squares for sugar content effect of year was behind effect of harvest date and genotype effect.These results are consistent with those of Oldemeyer et al. (1977) who concluded that the harvest date had a greater effect on most studied traits than genotype.

Table 3 .
Results of analysis of variance, partitioning sums of squares (SS) and mean squares (MS) of the analyzed traits