| Hybrid necrosis in wheat R.K. CHOWDHURY* Haryana Agricultural University Regional Research Station, Bawal, 123501, India. Hybrid necrosis is the pre-mature gradual death of leaves and leaf sheaths in certain wheat hybrids. Some of the Indian wheat varieties like C 306, C 286, C 273 and NP 890 have been reported to give complete or partial necrosis with the genes present in Maxican germplasm (NARULA et al. 1966; ANAND et al. 1969; GILL et al. 1969, 1972; CHOWDHURY, 1982). HERMSEN (1963) opined that two complimentary genes Ne1 and Ne2 when brought togather either in homo- or hetero-zygous condition could lead to hybrid necrosis, the degree of necrosis in F1 plants varying considerably due to multiple alleles (s, m and w) of Ne1 and Ne2. Therefore, he distinguished 9 grades of necrosis viz.: 0-3: Weak necrosis (normal seeds) 3-6: Moderate necrosis (pre-mature seeds) 6-9: Severe (No seed) Indian varieties as mentioned above, have been referred to be as the probable source of Ne1 gene while Maxican varieties are supposed to have Ne2 gene. This has been the major barrier encountered by the plant breeders in bringing togather desirable genes of some of the desirable cutlivars. For instance variety C 306, having good quality grains and drought resistance may not be included in many combinations when the other variety in combination carries Ne2 gene. During the year 1980-81, with a view to transfer drought/rust resistance into high yielding genotypes, a crossing programme was initiated at this centre in which four high yielding genotypes namely; P48-B, WH 157, P 1206 and Raj 1482, were crossed with a number of varieties having drought/rust resistance in a 'line x tester' design. P 1206 strain has very long ears with more number of spikelets per ear while WH 157 and Raj 1482 are approved high yielding varieties for timely sown, high fertility irrigated conditions. Strain P48-B is a double dwarf with high yield potential. All the F1 hybrids were grown in the field during the year 1981-92. Among these hybrids, seedlings of nine hybrids started yellowing at 2-3 leaves stage and finally died at 4-6 leaves stage without producing any ear showing the characteristic symptoms of severe necrosis of grade 7 as described by HERMSEN (1963). The whole material was sown under six different irrigation levels to see the impact of management, if any, to improve the growth of seedlings. The average mean for different traits under different irrigation levels have been given in Table 1. It is obvious from this table that all the hybrid plants died between 4-6 leaves stage. There was no obvious effect of irrigation levels on number of leaves. Similar was the case for tiller number per seedling. This shows that the death of the hybrid plants was genetically determined at this stage of plant growth. On the other hand, the plant height and joints per tiller were maximum under rainfed condition and minimum in fully irrigated conditions. Though there was no marked difference under various irrigation levels on these traits, however, there was reduction towards higher number of irrigations. |
| * Present address: Economic Botanist (Wheat), Department of Plant Breeding, Haryana Agricultural University, Hissar-215004, India. |
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