Evaluation of dwarf mutants of bread wheat (Triticum aestivum L.)

Y.G. KHAMANKAR

Genetics Division Indian Agricultural Research Institute, New Delhi 110012, India

The search for shorter varieties has long been a pre-occupation of wheat breeders. Less and less height appears historically as an essential characteristics of the most productive varieties destined for farmers using more and more intensive cultivation. However, not all the dwarf varieties give equally higher yields and are no better than tall varieties (Jain et al. 1974). In the present investigation, the effect of further diminishing the height of semidwarf varieties on different yield components have been studied.

Material and Methods

Two dwarf mutants, one each of the varieties Sonalika and Arjun, owe their origin to 25 KR gamma rays (Co⁶⁰) treatment. Phenotypically stable mutants were evaluated in M₇ generation.

Homogeneous seeds of the mutants and respective control were sown in a plot of uniform fertility. Seeds were drilled in three rows, of six meter length with 22.5 cm inter-row spacing in a randomised block design with five replications.

Observations on ten plants per replication for the characters height, spike length, spikelets per spike, seeds per spike were recorded. Tiller number in a meter length and yield of a middle row was recorded. For thousand kernel weight, random sample of seed was considered. The data was analysed and phenotypic correlations worked out.

Results and Discussion

Analysis revealed that the dwarf mutants differed for all the characters except for tillering capacity. Spike length, spikelets per spike, seeds per spike, thousand kernel weight and tillers per unit area are reliable measure of yielding ability (Borojevic and Borojevic, 1972). As seen from Table-1, the dwarf mutant of Sonalika showed reduction in spike length, spikelets per spike, and seeds per spike. However, the mutant showed increase in kernel weight. The reduction in seed number per spike can be attributed to the reduction in the spikelength and number of spikelets per spike. There was no change in tillering capacity and yield of the mutant.

Dwarf mutant of Arjun showed decrease in spikelets per spike, kernel weight and yield, but no change in spike length, number of seeds per spike and tillering capacity.

It is known that the yield components seeds per spike, unit grain weight and number of tillers per unit area in wheat are negatively correlated (Sikka and Jain, 1958; Gandhi et al. 1964 Knott and Talukder, 1971). Thus, it was observed that the increase in kernel weight in case of dwarf mutant of Sonalika has resulted in the decrease in number of seeds per spike. Since yield is the product of number of kernels per spike, kernel weight and number of tillers, all assume importance in efforts to attain new level of productivity in wheat. Any gain in a single yield component offset by decrease in one or both of the other components would produce no gain in the total yield. This is the reason why the dwarf mutant of Sonalika showed comparable yield to control. In case of dwarf mutant of Arjun the reduction in one of the important yield components kernel weight has resulted in the loss of yield. The observations are in agreement with the earlier findings that the mutants have generally reduced vitality (Gaul 1965; Siddiqui & Araih 1974).

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