| Genetic architecture of characters related to lodging
in wheat O. P. LUTHRA Department of Genetics, Haryana Agricultural University, Hisar, India Informations on the genetic architecture of attributes related to lodging in wheat are very scanty. Therefore, the investigation was conducted to understand the nature of gene effects governing the inheritance of attributes related to lodging. Materials and Method Seven genotypes viz. Sonalika, WG377, WH147, WH157, UP368, HD2160 and C281 were crossed in all possible combinations to produce 21 crosses in diallel fashion excluding reciprocals. The genotypes were selected on the basis of visual observations for variation in lodging behaviour. The 28 progenies (21 F1 crosses plus 7 parents) were grown in randomised block design with three replications. Observations were recorded on ten competitive plants from each genotype in each replication for plant height (cm), Mother-shoot weight (g), shoot weight (g), root weight (g), straw strength (g) and length of second internode (cm). Data were subjected to diallel cross analysis as outlined by Hayman (1954). Heritability in narrow sense was estimated by using the formulae of Crumpacker and Allard, 1962. Results and Discussion According to the analysis of variance for randomised block design, the differences among parents and crosses were statistically signiflcant in respect of all the attributes related to lodging under study. Before carrying out the genetic analysis for diallel cross, however, it was considered advisable to test the validity of the hypothesis underlying diallel analysis. Using the formula which yields uniformity of Vr and Wr and testing the value of t2 against the table value of F (4,5 d.f) showed that this estimate was not statistically significant for all the attributes except straw strength and length of second internode. As such it was assumed that hypotheses of diallel analysis were largely satisfied. Even when a trait exhibits partial failure of the assumptions, estimates of population parameters for that trait are still possible (Hayman 1954), though the results for such a trait are less reliable than what these would have been if all the assumptions are fulfilled. The estimates of components of genetic variation according to Hayman (1954) and some derived parameters in respect of the different characters are presented in Table 1. The additive variance component D was significant and so was the dominance variance component H1. The relative magnitude of the former was higher than the latter. The estimate of average degree of dominance (H1/D)1/2 was less than one which indicated partial dominance for all the traits. This suggested that as the inheritance of quantitative characters become more complex, the contribution of dominant gene effects to the inheritance becomes greater. Under such situation rapid improvement in component characters may be expected through standard selection procedure which may exploit the fixable genetic variance most effectively. Simultaneously care should be taken that dominance variance is not dissipated rather they should be concentrated. Heritability in narrow sense was high for length of second internode, mother shoot weight followed by root weight and plant height. Thus it was seen that out of the six traits studied for their genetic architecture, length of second internode, plant height and mother shoot weight appeared to be better attributes from the viewpoint of a practical plant breeder. References HAYMAN, B. 1954. Genetics, 39: 789-809. CRUMPACKER, D. W. and ALLARD, R. W. 1962. Hilgardia. 52: 275. |