R. Guncheva1*, M. Panayotov1, P. Tsenov2, Y. Dimitrova2
1Department of Animal Science – Non-ruminants and other Animals, Faculty of Agriculture, Trakiа University, 6000 Stara Zagora, Bulgaria 2Sericulture and Agriculture Experiment Station, 3000 Vratsa, Bulgaria
(Manuscript received 2 July 2016; accepted for publication 22 November 2016)
Abstract. The aim of this paper was to study the influence of the degree of heterosis (compared to higher parent value- HP and mean parental values- MP) on the signs, survival and duration of development in F1 hybrids of Bombyx mori L. from different geographical origin, fed by artificial diet. The study was conducted at the Training Experimental Station of the Sericulture section of the Faculty of Agriculture at Trakia University. A total of 10 hybrids were tested featuring 6 breeds from the genetic bank of Sericulture and Agriculture Experiment Station (SAES)-Vratsa. Silkworms were reared with artificial diet containing 15% powder of dried mulberry leaf produced at SAES-Vratsa and prepared by methods, developed by the manufacturer, whereby 250g of dry substance and 675ml of distilled water are homogenized using a mixer. The mixture is cured thermally in a microwave for 10min. at ~800W. The receptivity of specimens was determined based on the results from the survival and the duration in the I-st age of the larval stage. In heterogeneous crossbreds higher survival rate in the first age is exhibited by hybrids in which a Japanese type breed was used as dam. Homogeneous crossbreds created with the participation of Japanese breeds excel in both analyzed traits those involving a Chinese type. For the survival trait heterosis manifestations to higher parent value (HP) and mean parental values (MP), were detected in the majority of hybrids (90.91%). Regarding the duration of development, heterosis effect to MP was observed in all F1 hybrids, while to HP heterosis is exhibited by 60% of the tested F1 hybrids.