| Wheat Information Service Number 70: 4 - 6 (1990) 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 homo- or heterozygous form, cause necrosis (Hermsen 1 963). 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:
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, many 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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