Hybrid necrosis in bread wheat. III.
R.P. SINGH, I. SINGH and R.K. CHOWDHURY
Department of Plant Breeding, Haryana Agricultural
University, Hisar-125004, India
Hybrid necrosis is the pre-mature gradual death of leaves
and leaf sheaths in certain crosses of wheat and is the
major barrier in combining desirable traits into hybrid
combinations. Based on the earlier studies, two
complementary genes, namely, Ne1 and
Ne2 when brought together in hybrid
combination, either in home- or heterozygous form, cause
necrosis (HERMSEN 1963). The degree of necrosis in
F1 plants varies depending on the multiple
alleles (s, m and w) of these two genes
(Ne1 and Ne2). HERMSEN
(1963) has given 0 - 9 grades of necrosis in hybrids
(F1) depending on different combinations of the
three alleles of Ne1 and
Ne2 genes as:
0 - 3 Weak necrosis (Hybrids produce normal seeds)
3 - 6 Moderate necrosis (Hybrids produce pre-mature
seeds)
6 - 9 Severe (No seed obtained from hybrids)
Indian varieties have been reported to be generally having
Ne1 gene, while Mexican varieties are
supposed to have Ne2 genes (GILL et
al. 1969, ANAND et al. 1969, CHOWDHURY 1981,
1983). Because of these reasons, many times it becomes
cumbersome to combine desirable traits of Indian varieties
with that of Mexican, if the genotypes in combination have
Ne1 and Ne2 genes,
respectively. This problem has already been experienced in
case of variety C306, which is one of the top drought
tolerant varieties and has good quality grains. Since it
carries Ne1 gene, therefore, may of its
crosses with Mexican wheat varieties fail, when the other
parent has Ne2 gene, though some way-outs
have been suggested to overcome the necrosis in
F1 generations of such crosses (DHALIWAL et
al. 1986).
While breeding of high yielding and drought/rust resistant
varieties, we at Haryana Agricultural University are
attempting a number of crosses in bread wheat every year and
screening their hybrid generations. While doing so, we came
across many of the crosses showing necrotic behaviour in
F1 generation. We have already published two
lists of such crosses (CHOWDHURY 1981, 1983). Here we have
compiled the third list of bread wheat crosses showing
necrosis. Depending on the gene combination we have
sorted-out wheat genotypes having Ne1 or
Ne2 genes. Other varieties have also been
listed which have given indication of non-carrier of either
Ne1 or Ne2 or both
(Table 1). The data on
morphological features like plant height and number of
leaves (green as well as dry) per tiller of some of the
necrotic F1 hybrids have been given in Table
2.
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