The experiment was conducted in the experimental area of Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka during March to June, 2014 to study the genetic variability, correlation and path coefficient analysis for yield and yield contributing characters of maize. In this experiment 25 maize genotypes were used as experimental materials. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. Mean performance, variability, correlation matrix and path analysis on different yield contributing characters and yield of maize genotypes were estimated. The highest grain yield/plant (272.21 g) was recorded in the genotype of BARI Hybrid Maize-6, whereas the lowest grain yield/plant (180.40 g) from the genotype of NZ-003. Phenotypic coefficient of variation was higher than the genotypic coefficient of variation for all the yield contributing traits. In correlation study, significant positive association was recorded for grain yield/plant of maize genotypes with plant height (0.235), tassel height (0.359), number of grains/cob (0.854), cob length (0.390), cob diameter (0.313) and weight of 1000-grains (0.689). Path analysis revealed that days to initiation of male flower had positive direct effect (0.132), days to initiation of female flower had negative direct effect (-0.254), days to maturity had positive direct effect (0.178), plant height had positive direct effect (0.314), tassel height had positive direct effect (0.234), ear length had positive direct effect (0.197), number of grains/cob had negative direct effect (-0.095), cob length had positive direct effect (0.167), cob diameter had positive direct effect (0.168) and that weight of 1000-grains had positive direct effect (0.217) on yield / plant.

Twenty one F1s produced from 77 diallel mating along with the 7 parents were evaluated to notice the inheritance and combining ability of different traits to obtain high heterotic crosses. Genetic analysis and combing ability were analyzed following Hayman's and Griffing's diallel analyses, respectively. Hybrids projecting positive or negative potency ratio with >1.0 value for those traits is also the sign of incidence of over-dominance in desirable direction, and heterosis breeding is important to improve those traits in maize. Hayman's approach indicated dominance variance and the proportion of +/genes was higher than additive variance in all characters. Griffing's analysis also demonstrated the presence of over-dominance governing the traits. The preponderance of dominant gene action coupled with low heritability observed for days to silking, ear length and grain yield suggests the importance of heterosis breeding. Substantial differences in general combing ability and specific combining ability were noticed in all the studied traits except 1000-grain weight. The parental line CML-509 was found to be the best general combiner for days to tasseling and silking, CML-498 for plant height, ear height and grain yield, CML-395 for ear length and grain yield. The crosses CML-498×CML-376, CML-498×CML-395 and CML-376×CML-247 showed significant positive specific combining ability effect for grain yield along with higher mean values over commercial check varieties.

Seven lines of baby corn were crossed with 3 testers in a Line × Tester (L × T) mating design and the resulting 21 crosses along with parents and standard check 'Baby Star' were evaluated to develop high yielding baby corn hybrids during rabi, 2014-15. Variance due to sca was larger than gca variance for all the characters indicating the preponderance of non additive gene action in the expression of various traits. Among the parents, BCP/S 4 -29, BCP/S 4 -31 and tester VS/S 3 -1 and VS/S 3 -26 were found as good general combiners for baby corn yield and important yield contributing characters. Considering baby corn yield, number of cobs/plant and other performances, the crosses BCP/S 4 -2×VS/S 3 -1, BCP/S 4 -5×VS/S 3 -8, BCP/S 4 -10×VS/S 3 -8, BCP/S 4 -22×VS/S 3 -26 and BCP/S 4 -29×VS/S 3 -1 were selected as promising baby corn hybrids.

A line × tester analysis comprising forty eight test-crosses generated by crossing 24 S3 inbred lines derived from commercial maize hybrid 981 with two testers. Heterosis study of these crosses against two standard checks was evaluated at Bangladesh Agricultural Research Institute, Gazipur during rabi 2015-16. The objectives of the study were to estimate general and specific combining ability effects of the inbred lines and to assess the test cross performance and estimate the amount of standard-heterosis of the hybrids for grain yield and yield related characters. Highly significant genotypic differences were observed indicated wide range of variability present among them. Five lines viz. Line 11, Line 14, Line 17, Line 24 and Line 30 were good general combiner for grain yield and possessed high means. Nine crosses showed (Line 18 × BIL22, Line 23 × BIL22, Line 27 × BIL22, Line 7 × BIL28, Line11 × BIL28, Line14 × BIL28, Line 24 × BIL28, Line 25 × BIL28 and Line 30 × BIL28) significant and positive specific combining ability effect for grain yield. The information on the nature of gene action with respective variety and characters might be used depending on the breeding objectives. These crosses, Line 24× BIL28 (11.40 t/ha), Line 18 × BIL22 (11.30 t/ha) and Line 25 × BIL28 (11.20 t/ha) showed higher yield, could be utilized in maize breeding activities. Estimation of heterosis was carried out using two commercial hybrids BARI Hybrid Maize-9 (BHM-9) and NK-40. The percent heterosis for grain yield varied from -23.39 to 4.6% against BHM-9. Among the 48 crosses, 13 crosses exhibited significant positive heterosis for grain yield. Bangladesh J. Agril. Res. 46(4): 469-489, December 2021

Twenty-eight hybrids of Zea mays L. produced in 2015-16 from 8×8 half diallel mating design were evaluated along with their parents in 2016-2017 under saline condition to find out genetic action and potency ratio of some agronomic and yield contributing traits. Genetic action and potency ratio were analyzed following Hayman's diallel analyses and Smith's formula, respectively. Genetic parameter like additive variance (D), dominance variance (H 1), proportion of positive and negative genes in the parents (H 2), relative frequency of dominant and recessive alleles in the parents (F), dominance effect over all loci in heterozygous phase (h 2) suggested that traits like days to tasseling, days to silking, anthesis silking interval, ear height and number of grains/plant are governed by dominant alleles in these traits. Contrariwise, the data of plant height and 100-grain weight were shown to have higher frequency of recessive alleles. Proportion of genes with positive and negative [(4DH 1) 0.5 + F]/[(4DH 1) 0.5-F] effects suggested the asymmetrical distribution of dominant and recessive alleles for all the traits except yield/plant. Under saline condition heritability in narrow sense (h 2 n) was found very low which indicates a possible strong influence of stress in the growing environment. These parameters along with Vr-Wr graphs and potency ratio indicated overdominance in desirable direction, and thus, heterosis breeding is important to improve those traits in maize under salinity.