engleski

Environmental and genetic influences on sugar beet seed largeness and germination

The moderate climate in Croatia is suitable for seed sugar beet growing, which seriously began following the establishing of Belje Plant Breeding Station in Baranya province, 75 years ago. Currently our annual status is about 27000 ha (close to 2% of the arable land in Croatia) of sugar beet growing area, while seed sugar beet occupies 280 ha. Main characteristics of our sugar beet crop management practice are dry farming system (without irrigation) use and sowing of monogerm hybrids seeds in amount from 120 to 180 thousands seed/ha. Also, we use dry farming system in sugar beet seed production. We tested sugar beet seed quality (germination and percent share of individual fractions) of four monogerm triploid hybrids (Os Nada, Os Stela, Os Sana, Os Ana) which were grown as seed crops (18 fields of individual area about 10 ha) during three growing seasons (1994, 1995 and 1996) on high-fertile soils of eastern Croatia. Four individual seed samples (2 kg weight) were collected from each seed material. They were separated in six fractions (designated from A to E, according to range of seed diameter in mm) as follows: under 3.25 (A), from 3.25 to 3.75 (B), from 3.75 to 4.25 (C), from 4.25 to 4.75 (D), from 4.75 to 5.50 (E) and above 5.50 (F). The shares of the individual fraction were as follows (3-year means): 25.0%, 20.4%, 20.5%, 15.3%, 13.4% and 5.4%, for the fractions A, B, C, D, E and F, respectively. In general, fractions between 3.75 and 4.75 mm of seed diameter (C+D) have the best characteristics because of the highest share of germination and monogermity. Also, they are most suitable for receiving of optimal dimension of covered monogerm seed. The shares of these fractions in total weight of seed was 35.8% (3-year mean), while in the individual years of testing it was similar: from 34.3% to 36.7%. The remaining fractions of the lower diameter (A+B) and the higher diameter (E+F) participated 45.4% and 18.8% of the total weight of seed (3-year means), respectively. In the first year of testing, the share of the A+B fractions was 50.9% and E+F fractions 12.4%, while in the remaining two years of testing these relations were similar (mean 42.6% and 22.0%, respectively). Also, seed largeness (comparison of shares of the A and C+D fractions) depended on hybrid (for example: 29.0% and 34.2% for Os Nada; 18.0% and 40.7% for Os Ana). In our study, germination was in close connection with seed fraction and it was as follows (3-year means): 44%, 73%, 79%, 85%, 87%, 88%, for the fractions A, B, C, D, E and F, respectively. This trend was similar in individual years of testing. The mean values of tested fraction germination were 78%, 76% and 75%, for 1994, 1995 and 1996, respectively. Weather conditions play an important role in sugar beet seed growing in Croatia because of the application of dry farming systems. For this reason, rainfall and temperature regimes during the flowering and grain filling stages are important factors of sugar beet seed yield and its quality. In that respect, the growing season 1996 was more favorable in comparison with 1994. For example, unfavorable weather conditions during the 1994 growing season - rainfall shortage in grain filling stage and heat stress - (Osijek Weather Bureau: from 21 June to 10 August = 19 mm rainfall and average air-temperature 24.5 oC) had influences on the higher share of less desirable A+B fractions (50.9%). More favorable weather conditions at the same period of 1996 growing season (135 mm rainfall and 19.6 oC mean air-temperature) reflected on the lower share of the A+B fractions (43.5%).

sugar beet; seed yield; largeness; germination

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