1022-7954/04/4009- © 2004
Russian Journal of Genetics, Vol. 40, No. 9, 2004, pp. 990–994. Translated from Genetika, Vol. 40, No. 9, 2004, pp. 1209–1214.
Original Russian Text Copyright © 2004 by Boyko, Sukhanov, Shakhbazov.
Many hypotheses and theories have been advanced
concerning the mechanisms of the heterosis effect .
However, owing to the complexity of this phenomenon,
there is still no general theory which would explain the
advantage of hybrid organisms over the parental forms.
The studies which could extend current understanding
of the heterosis effect are therefore of particular impor-
tance. Comparative analysis of the responses of inbred
and hybrid organisms to the effect of physical factors is
one of the promising lines in the study of heterosis .
On the other hand, the widespread application of the
sources of electromagnetic (EM) ﬁelds has recently led
to a signiﬁcant increase of the general background of
low-intensity EM radiation. The stimulating effect of
low-intensity EM radiation on living organisms shown
in a number of studies is widely used in treatment and
prophylaxis of various human diseases and in plant and
animal breeding . Nevertheless, the mechanisms of
the EM-ﬁeld effect on the biological objects remain
still unclear . Some evidence suggests that irradia-
tion effects are inherited in generations , but the
mechanisms of this phenomenon are unknown. The
above considerations motivated our study on such a
convenient biological model as silkworm.
Silkworm heterosis hybrids have been long used in
sericulture . Therefore, analysis of the expression of
quantitative traits in silkworms exposed to EM radia-
tion is not only of theoretical but also of practical
importance. In addition, it is possible to study the effect
of the reproduction type on the putative inheritance of
irradiation effects in the parthenogenetic silkworm gen-
The aims of this study were comparative analysis of
the effects of heterosis in the silkworm hybrids, intact
and exposed to EM effect and estimation of the role of
sexual reproduction in the inheritance of the irradiation
MATERIALS AND METHODS
The subject of this study was silkworm
L. The following clone breed combinations were
used: parthenoclone Ukrainskaya-27 (Ukr.-27),
Ukrainskaya-15 breed (Ukr.-15), the clone breed hybrid
Ukr.-15, and the interbreed combinations Belo-
cocoon-1 improved (B-1
), Belococoon-2 improved
), and interbreed hybrids B-1
The experimental grain (silkworm eggs) was irradi-
ated with electromagnetic waves for 10 and 20 min on
the second day of the postdiapause embryonic develop-
ment. The control grain was not exposed to irradiation.
The source of irradiation was an SHF-ﬁeld genera-
= 1.6 cm, power rate 700
The silkworm breeding was conducted according to
the standard techniques .
The parthenoclones were obtained using artiﬁcial
ameiotic parthenogenesis .
According to the methods generally used in silk-
worm breeding, the following quantitative parameters
were estimated: larval yield from eggs, larval viability,
male and female cocoon weight, male and female silk
shell weight, male and female silk yield. In combina-
Ukr.-15, Ukr.-27, and Ukr.-15, only
female cocoon parameters were estimated, because the
Ukr.-27 clone is represented solely by females.
In each variant, 500 eggs were examined (50 eggs in
ten replications) and 300 larvae (100 larvae in three rep-
lications); 30 cocoons have been weighted individually.
The Effect of Heterosis and Inheritance of Quantitative Traits
in Silkworm Exposed to Electromagnetic Irradiation
Ye. A. Boyko
, S. V. Sukhanov
, and V. G. Shakhbazov
Sericultural Institute, Ukrainian Academy of Agrarian Sciences, Merefa, 62472 Ukraine;
fax: (057)748-68-74; e-mail: firstname.lastname@example.org
Kharkov National University, Kharkov, 61077 Ukraine
Received May 6, 2003; in ﬁnal form, October 27, 2003
—The effect of heterosis was studied in several quantitative traits of clone breed and interbreed silk-
worm hybrids exposed to electromagnetic irradiation (
= 1.6 cm, power density 700
) during postdi-
apause embryonic development. The inﬂuence of the type of reproduction on the manifestation of irradiation
effects in the next generation was also examined. In hybrids, the resistance to low-intensity high-frequency irra-
diation was higher than in the parental forms. Unlike the latter, the hybrids showed no signiﬁcant modiﬁcation
of the traits after the exposure to electromagnetic irradiation. In the second generation, the modifying effect of
irradiation is retained in the case of parthenogenetic silkworm development but not after mating.