| Performance and selection of wheat mutants for some
quantitative characters A.S. LARIK Department of Botany and Plant Breeding, Sind Agricultural University, Tandojam Pakistan Plant height, culm diameter and tillers per plant have evolutionary significance (LARIK, 1978) and are important from breeders point of view because of their direct influences on crop yield (ROMERO and FREY, 1973; JOPPA, 1973; SHUKLA, 1974). At present, in breeding programmes concentration is being made on the development of semi-dwarf selection with one gene only (ALLAN and PRITCHETT, 1973). Semi-dwarf and stiff straw traits, are doubly beneficial in wheat production because short plants are lodging resistant and have high grain-straw ratio (VOGEL et al, 1956). Semi-dwarf lines also produce more tillers than the tall lines, and as expected, environments have large effects on the number of tillers. Environments that induce the highest number of tillers also produce the highest yields (JOPPA, 1973). The present studies are concerned with an evaluation of phenotypically stable wheat mutants for plant height, culm diameter and tillers per plant, isolated from one locally bred cultivar and two cultivars of Mexican origin. Such studies can be instrumental in producing genotypes and populations with high genetic homeostatis (LERNER, 1954) and ultimately in enhancing the yield of bread wheat. The magnitude of genetic variability and response to selection among these mutants are also reported. Materials and Methods The material originated from different doses of gamma rays (20, 25 and 35 kR) and ethyle methane sulphonate (EMS) of varieties C-591 (locally bred), Nayab and Indus-66 (Mexican origin) of bread wheat Triticum aestivum L. Phenotypically stable mutants were evaluated for plant height, culm diameter and tillers per plant in M9 generation grown in the field in Tandojam during Rabi 1977-78. Seeds of these genotypes were procured from the Department of Botany and Plant Breeding, Sind Agricultural University, Tandojam. Sowing of homogeneous seeds of mutants and cultivars was done by dibbling single seed per hole at 30.5 cm intervals, in single rows each 3.1 m long with 30.5 cm interrow distance with path ways 1.0 m wide between blocks of a plot in randomized block design with four replications. Thus 50 plants were studied from each mutant genotype and cultivars respectively. Mean values for the mutant populations for each character were compared with the control means by using t tests. To make effective and efficient use of mutant genotypes in advanced generations through selection, estimates of broad sense heritability and expected genetic advance with selection intensity of five percent have been computed for these quantitative characters. The broad sense heritability (h) of a character was estimated similarly to LARIK (1978) as under: %h=(sigma2g/sigma2t) x 100 where sigma2g=induced genetic variance and sigma2t is the total phenotypic variance calculated from mutant population. The estimates of genetic advance (GA) at 5% selection intensity was based on the relation suggested by LARIK (1978) and computed by the following formula: GA=(K)(sigmap)(H) where sigmap=phenotypic standard deviation from the mean performance of mutant population, H=heritability coefficient and K=2.06 constant for selection differential. |
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