Ecological stability and plasticity of maize hybrids in different groups of ripeness

M. Ilchovska

Maize Research Institute, 5835 Knezha, Bulgaria

(Manuscript received 1 September 2018; accepted for publication 3 December 2018)

Abstract. Ecological stability and plasticity of maize hybrids in different groups of ripeness – Knezha 307, Knezha 435, Knezha 509 and Knezha M625 by the traits grain yield and length of the ear was evaluated. The ecological parameters were determined by using the method of Eberhart and Russell (1966) and of Pakudin and Lopatina (1984). In the period of study (2014-2017) the hybrids demonstrate different plasticity and stability by the examined traits. The results of the analysis of the variances demonstrate reliable differences of the hybrids and the conditions for the two traits and primarily reliable interaction genotype – environment. The variances of the regression Si2 of all hybrids for the trait grain yield reliably differ from their theoretical value which determines them as plastic, i.e. responsive to more favourable conditions of growth. According to the values of bi the hybrid Knezha 435 (bi<1) is stable by the trait grain yield, the hybrids Knezha 307 and Knezha M625 are with values of bi close to one and have relatively medium stability and Knezha 509 with bi>1 is unstable. With reliable values of Si2 for the trait length of the ear is only the hybrid Knezha M625. The ecological stability of the other hybrids was evaluated by the value of the coefficient of regression (bi). Increased stability by this trait is demonstrated by Knezha 435, followed by Knezha 509. Knezha 307 is with medium stability (bi=1.1) by the respective trait.

Testing of new Bulgarian sunflower hybrids under the conditions of Northeast Bulgaria

G. Georgiev*, P. Peevska, E. Penchev
Dobrudzha Agricultural Institute, 9520 General Toshevo, Bulgaria

Abstract. Four new Bulgarian sunflower hybrids were investigated: Veleka and Vokil, which were officially registered in 2013 in Romania; Gaby, which will be registered in Romania in 2014, and Divna, which is now under official testing in Ukraine and Russia. The investigation was carried out at Dobrudzha Agricultural Institute, General Toshevo, Bulgaria during 2011 – 2012 with the aim to follow the phenological specificity of these hybrids under the conditions of Northeast Bulgaria. The hybrids were sown at three crop densities: 40000, 50000 and 60000 plants/ha on two sowing dates. The first one was normal for the conditions of this region – when soil temperature remained permanently above 8°C at depth 10 cm, and the second one was a month later. The investigated traits were duration of flowering (number of days), plant height (cm), diameter of inflorescence (cm), and vegetation period (days).The investigated factors sowing date and crop density in combination with the meteorological conditions over years, had significant effect on the phenological development of the investigated genotypes. With the higher crop densities the mean value of the trait plant height increased at both sowing dates. There was no significant difference in the plant height of the four investigated hybrids, most probably due to the fact that they have the same mother line (217A). The later sowing date was related to higher values of the trait diameter of the inflorescence. This investigation, however, similar to many previous studies, confirmed the rule that with the higher crop densitiestheinflorescencediameterwassmallerregardlessofthesowingdate. Attheoptimalsowingdate,floweringwasthelongestatthehighestcrop density. There was no difference between the individual genotypes involved in the testing. At late sowing the flowering period was shorter for all growing crop densities. The vegetation period depended on the sowing date. At later sowing it decreased with up to two weeks or more.

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Testing of new Bulgarian sunflower hybrids under the conditions of North-East Bulgaria

I. Productivity and traits related to productivity
G. Georgiev, P. Peevska, E. Penchev
Abstract. The investigation was carried out at Dobrudzha Agricultural Institute, General Toshevo during 2011 – 2012. It was aimed at determining the production potential and the values of some of the most important traits of four new Bulgarian sunflower candidate hybrids: Veleka, Vokil, Gabi and Divna, which were enlisted for official varietal testing in different foreign countries. The testing was done by sowing the hybrids on two dates, with three sowing densities. The first sowing date was normal for the conditions of North-East Bulgaria, when soil temperature is permanently above 8oC at 10 cm depth, the second date was one month later. The respective densities were 40000, 50000 and 60000 plants/ha. The following traits were investigated: seed yield (kg/ha), 1000 kernel weight (g), weight of seeds per plant (g), number of seeds per plant, percent of kernel (%), oil content (%). The results showed that the investigated factors – sowing date and crop density in combination with the year conditions during the investigation had significant effect on the productivity of sunflower and some important traits related to it. Hybrid Divna was with the highest seed yield per ha (4055 kg/ha) obtained at the highest crop density, followed by hybrid Vokil (seed yield 3936 kg/ha) obtained at the lowest crop density. Crop density and 1000 kernel weight were in reverse proportion at both sowing dates. The highest absolute weight was demonstrated by hybrid Divna – 62.5 g averaged for the two years at both sowing dates, followed by hybrid Vokil – 57.2 g. The later sowing date was related to decrease of the values of the character number of seeds per plant. At the higher crop densities, the weight of seeds per plant decreased during both years. Higher values were observed at the optimal sowing date during the entire period of investigation. The traits percent of kernel and oil content in seed showed the lowest variation, similar over years, which characterized these traits as stable and with low modification variability.

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