| dc.description | Wheat is one of the most important cereal crops in the world. Cultivated wheat
belongs to the genus Triticum, family Gramineae. Triticum includes diploid
(2n = 2x = 14), tetraploid (2n = 4x = 28) and hexaploid (2n = 6x = 42) species. The
genomic constitution of diploid, tetraploid and hexaploid groups are AA, AABB
and AABBDD (Sears, 1944) respectively. The Triticum includes two commercially
cultivated species Triticum aestivum L. and Triticum durum L. Triticum aestivum
is of two types winter and spring wheat. In Bangladesh only spring wheat are
commercially grown. | en_US |
| dc.description.abstract | Present study was performed on conmbining ability, heterosis and gene actions for yield and yield
contributing characters from a diallel cross population, and other was selection response of different yield
contributing characters in two crosses of spring wheat.
The analysis of variance studied in the diallel cross populations, showed that, there were significant
variations among the genotypes for the characters plant height, tillers per plant, spike length, spikelets per
spike, grains per spike, 100-grain weight and grain yield per plant. Both general combining ability (GCA)
and specific combining ability (SCA) variances were significant for all characters except grains per spike.
This character had only significant GCA variance. This suggests that both additive and non additive gene
actions were involved in the inheritance of them. The parent Rawal was best general combiner for grain
yield and some yield contributing characters. The crosses Gourav x Anja , Kanchan x Rawal, Rawal x
Moyoor, Moyoor x Kheri and Chyria x Kheri showed positive and significant SCA effects for grain yield and
some yield contributing characters.
The crosses Gourav x Anja, Rawal x Moyoor and Chyria x Kheri exhibited significant and positive mid
parent heterosis for grain yield per plant. Maximum heterosis of grain yield per plant was 155. 94% in the
crosses Gourav x Anja. A positive relationship was observed between heterosis of the crosses with their
corresponding SCA effects for yield and yield contributing characters.
Study of Wr-Vr graph showed that partial dominance was observed for plant height, tillers per plant, spike
length and 100-grain weight. Over dominance was noticed for spikelets per spike and grains per spike.
Tillers per plant, grains per spike and grain yield per plant expressed presence of epistasis.
Analysis of relationship between yield and yield contributing characters revealed that spike length, spikelets
per spike and 100-grain weight were the most important yield contributing characters. They directly
contributed to grain yield and had high correlation at genotypic level.
High heritability estimates in both broad and narrow sense were obtained for plant height, spike length,
spikelets per spike and 100-grain weight. Medium heritability in broad sense but poor heritability in narrow
sense were observed for tillers per plant and grains per spike. Grain yield per plant was highly heritable in
broad sense and poorly heritable in narrow sense.
Study of response to selection showed that the characters tillers per plant, 100-grain weight and grain yield
per plant in the cross Nk-5 x Opata and tillers per plant, spikelets per spike, grains per spike and grain yield
per plant in the cross Rawal x SA-92 gave good response to selection. These characters had also positive
realized heritability. The other characters in both crosses had negative response to selection and that might
be due to the cause of genotype-environment interaction. | en_US |
