Abstract
The present investigation was undertaken to study the inheritance of lodging resistance and its associated traits related to dwarfing gene effects in bread wheat. The experiments were conducted within the period of 1997- 98 to 2000-2001 at Wheat Research Center, Dinajpur and Rajshahi. Gene action, combining ability, heterosis, and heritability for lodging related attributes were studied in both F1 and F2 generations of a 9 x 9 diallel cross without reciprocal. Detailed gene actions were also studied in six selected crosses for lodging related traits. Relationships between lodging and lodging attributes were also studied.
From the collected thirty-four wheat genotypes, only nine were selected for detailed studies on the basis of their field performance covering different lodging groups. Gibberellic Acid (GA3) insensitivity test for the selected nine genotypes confirmed that Baviacora, Rayon, Seri 82, Siete Cerros and Alpha/ Adam Tas // SST 825 # 34 contained Rht gene, Pavon, Aghrani and Sonora 64 contained Rht2 gene and Kheri with the rht gene. Significant effects of nitrogen were observed for stem length, unit stem weight and breaking strength of second and third internodes, plant height, spikes per plant, main shoot weight, grains per plant, biomass per plant, grain yield per plant and lodging score. Nitrogen x genotype interaction was significant for spikes per plant, head/shoot ratio, biomass, grain yield per plant and lodging score. Among the parental nine genotypes, Baviacora had higher internodal diameter, wall thickness, unit-stem weight and consequently higher breaking strength and resistance to lodging. Both the tallest (Kheri) as well the shortest (Sonora 64) genotypes with lower straw-strength were found most susceptible to lodging over locations. Baviacora and Alpha/Adam Tas// SST 825 # 34 did not lodge in any plot at all levels of nitrogen but their lodging angle as well as lodging score increased with the increase of nitrogen level. Lodging susceptible genotypes responded more to nitrogen than lodging resistant genotypes. Internode breaking strength decreased with the increase of N levels and consequently lodging increased but its effects were different in different genotypes.
The genetic nature of length, diameter, unit-stem weight and breaking strength of second and third internode, plant height and head/shoot ratio was additive in both F1 and F2 generations. The genetic nature of second and third internode wall thickness was additive in F1 generation but nonadditive in F2 generation. Whereas, spikes per plant, main shoot weight, grains per spike, biomass and grain yield per plant was additive in F2 generation but nonadditive in F1 generation. These traits might be controlled by both additive and non-additive gene actions. So, both additive and non-additive gene actions were found important in controlling the young stem characters as well as post harvest characters contributing to lodging resistance. Siete Cerros, Aghrani and Sonora 64 were good combiners for head/shoot ratio. Kheri showed significant GCA effects for internodal length, plant height and spikes per plant. Considering the performances in F1 and F2 generations, Baviacora and Alpha/ Adam Tas// SST 825 # 34 were found good general combiners for most of the young stem characters and post harvest characters related to lodging resistance.
Expressions of the non-additive gene action through heterosis were not similar in F1 and F2 generations. Most of the crosses, which expressed significant SCA effects in F1, did not express the same in F2 generation except in a few crosses. The inconsistent nature of the SCA effects between F1 and F2 generations were non-significant for all characters studied except plant height. The second internode length, second internode wall thickness, plant height, main shoot weight, biomass and grain yield per plant showed significant average heterosis in both F1 and F2