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Wheat Information
Service
Number 72: 9-11 (1991)
Hybrid
weakness in Triticum dicoccum Schubl.
S. M. S. Tomar*, M. Kochumadhavan and P. N. N. Nambisan*
Indian Agricultural Research Institute, Regional Station
Wellington-643 231, The Nilgiris, India
Introduction
Genetical traits such as hybrid necrosis and hybrid chlorosis are
controlled by two independent genetic systems. In both kinds of
hybrid weakness the F1 hybrids are lethal or semi-lethal
resulting in gradual death or debility. Hybrid necrosis and hybrid
chlorosis are frequently met with in inter- and intraspecific wheat
crosses and are serious barriers to the transfer of genes in a
planned hybridization programme. Hybrid necrosis is governed by two
complementary genes, Ne1 and Ne2, located
on chromosomes 5B and 2B respectively (Tsunewaki 1960) while
hybrid chlorosis is controlled by two complementary genes
Ch1 located on 2A (Hermsen & Waninge 1972) and
Ch2 on 3D (Tsunewaki & Kihara 1961). The present
investigations were carried out to identify the genes for necrosis
and chlorosis in nine Indian varieties of Triticum
dicoccum.
Materials and Methods
Nine varieties of Triticum dicoccum were crossed to two
T. aestivum testers, C 306
(Ne1ne2ch1Ch2) and Sonalika
(ne1Ne2ch1Ch2 ). The F1
hybrids and parents were raised in the greenhouse under optimum
conditions of growth. The F1 hybrids were critically
observed for the occurrence of hybrid necrosis and hybrid chlorosis
and genotype of the parents with respect to the genes for necrosis
and chlorosis were determined from the phenotype of the F1
hybrids.
Results and Discussion
The results obtained in the study are presented in
Table1.
With the exception of HW 178-A and HW 489, all the varieties of T.
dicoccum when crossed to C 306 (Ne1Ch2-carrier)
produced strong chlorotic F1 hybrids, indicating that the
varieties carry the Ch1 gene.The F1 hybrid plants
between Sonalika (Ne2Ch2 -carrier) and four
T. dicoccum varieties, namely, HW 43, HW 1018, HW 1046 and
Khapli-53 Yellow expressed the symptoms of both necrosis and
chlorosis simultaneously, indicating that these varieties also carry
the gene Ne1. The variety HW 178-A produced normal and
necrotic F1 offspring when crossed to C 306 and Sonalika
respectively. Results indicate that the variety is non-carrier for
chlorosis gene while it carries the gene Ne1. Normal
F1 hybrids were obtained in the crosses of HW 489 with
both the testers indicating that this variety is a non-carrier for
both necrosis and chlorosis genes
(ne1ne2ch1).
*Present address: Division
of Genetics, IARI, New Delhi, India
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