Abstract
Genotypic and phenotypic correlation coefficients were worked out for grain weight per spike, harvest index, economic yield and biological yield in six strains/varieties of wheat to select the genotypes efficient in apportioning their biomass into grain yield and vegetative part in proper proportion. The variety LU2OS was found to be the most efficient and possessed the highest harvest index of 33.59%, followed by strain 1697-1 (32.28%). Positive and significant associations ex-isted among almost all the characters studied except between grain weight per spike and harvest index where relationship was positive though non-significant. Path-coef-ficient analysis indicated that the direct effect of harvest index on economic yield was remarkable.
INTRODUCTION
The biological yield of a cereal crop is the total of plant material and harvest index is the ratio of the yield of grain to the bio-logical yield (Donald, 1962). Selection based on high harvest index may have value for improving grain yield of cereal crops (Rostelle and Frey, 1975). This improve-ment in grain yield of high yielding semi-dwarf wheat varieties is due to increased harvest index with a change in biological yield (Bhatt, 1976). Donald and Hamblin (1976) reported the harvest index as breed-ing criterion in cereals. The objective of the present stuk was to select physiologically the most efficient genotypes having the highest harvest index for further breeding programme.
MATERIALS AND METHODS
The studies were conducted in the Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad during 1989-90. The experimental material corn-
prised six wheat strains/variety viz., LU26S, 1697-1, K-1595, 4362, 4072 and 4125 planted in triplicated randomized complete block design. Plot size used was 1.5 m2. Inter-row and inter-plant distance was kept at 15 cm. Regularity of spacing and uniformity of sowing depth were achieved by sowing with the help of a template. To avoid edge ef-fects, the central 1 x 1 in area from each plot was harvested at maturity to record data on biological yield, economic yield and harvest index. The randomly selected plants from this marked area were used to measure the grain weight per spike. Phenotypic correlation coefficients were worked out by method described by Steel and Torrie (1960) while genotypic cor-relations were calculated according to the formula given by Fischer 0963), Path-coef-ficient analysis was performed according to the procedure delineated by Dewey and Lu (1959) using genotypic correlation coeffi-cients to estimate the direct and indirect ef-fects of different variables on economic
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