Genetic analysis of low-n traits in maize (Zea mays L) using triple test cross

Low-N maize variety is developed for its ability to tolerate low nitrogen soil environment. This experiment was conducted to study the genetic implication of Low-N maize variety for grain yield and related traits under low nitrogen soil conditions triple test cross analysis. Inbred lines used for the study were generated from twelve low nitrogen tolerance open pollinated maize varieties after six generations of selfing. Two inbred lines along with their F1 were used as testers for ten inbred lines in a triple test cross pattern to generate 30 crosses. The 30 crosses, their parents and the testers to State University, Ado-Ekiti during 2017 planting season. The experimental design was a Randomized Complete Block Design (RCBD). Data were collected on plant height, ear height, days to 50% anthesis, days to 50% silking, incidence of curvularia leaf spot, blight, plant aspect, ear aspect, ear rot, stay green, cob per plant, ear weight, grain moisture content and grain yield. All data were subjected to analysis of variance and complete genetic estimates. Additive and dominants were significant (P < 0.05) for all traits; however, epitasis estimates were not significant for all the traits tested. The degree of dominance component indicated partial dominance for all the traits. Correlation coefficients for days to 50% anthesis and 50% silking, plant height, ear height, number of cobs per plant and grain yield were positive and significant (P < 0.05). Since both additive and dominance gene actions were important for low-N traits, the use of reciprocal recurrent selection procedure can be adopted in incorporating the trait into elite maize varieties.

Detection of Epistasis and Genetic Parameters of Some Quantitative Traits Through Triple Test Cross Analysis in Chickpea (Cicer Arietinum L.)

Triple test cross analysis was carried out to detect the epistasis of thirteen yield and yield components in five chickpea (Cicer arietinum L.) crosses. Total epistatic effect was found to be non-significant for all the studied traits. Partitioning of total epistasis indicated the involvement of ‘i’ type (additive × additive) epistasis for DFF, PHFF, PWH, NPd/P, PdW/P, NS/P and SW/P in cross-1; NPBFF and NSBFF in cross-3 and for PHFF, DMF, PHMF and NSBMF in cross-5. The magnitude of additive component (D) was higher than that of the dominance component (H). Partial degree of dominance (√H/D) was observed for most of the traits. Both broad (h2b) and narrow (h2n) sense heritability were found to be moderately high. Positive and significant correlation between sums and differences indicated the direction of dominance towards decreasing parents and vice-versa. Bangladesh J. Bot. 50(2): 351-358, 2021 (June)

Revelation of Epistasis through Triple Test Cross (TTC) Analysis in Rice (Oryza sativa L.)

Background: An investigation was performed to identify epistasis, additive, dominance components of genetic variation and yield and yield variability attributing characteristics by triple test cross testing involving three testers (P1, P2 and F1) and ten rice lines.Methods: The study materials consisted of F1 seeds of three crosses, involving six parents namely, ASD16, ADT47, ASD18, CO51, TKM9 and MTU 7029. They are evaluated in randomized complete block design with three replications. Observations were reported for seven traits, namely plant height, number of tillers per plant, number of productive tillers per plant, length of panicle, number of grains per panicle, weight of 1000 grains and yield of grain per plant on five randomly selected plants per replication.Result: The segregating population of three crosses exhibited wide range of variability for most of the traits. The difference between GCV and PCV was low for most of the characters indicated less influence of environment. Among the three crosses ASD18 x CO15 recorded high percent of heritability and genetic advance for grain yield per plant. The estimate of total epistasis revealed that i type of epistasis (additive x additive) was highly significant for number of tillers per plant, number of productive tillers per plant, panicle length and 1000 grain weight. The effect of the additive (D) variance was very important for all the traits except the number of grains per panicle. Across all traits, the degree of dominance (H / D)1/ 2 was less than unity ( less than 1) suggesting, partial of dominance. Since, the pre dominance component of epistasis in autogamous crop is additive x additive (i type), it was suggested that the selection may be post ponded to later generation until all the non-additive components of variance has been mitigated to additive components.

Relationship Between Combining Ability, Genetic Components And Genetic Diversity Using Triple Test Cross

Background: The target of this study is to investigate the relationship between genetic components, combining ability and genetic diversity among twenty six cotton crosses derived from a cross between thirteen contrasting inbred lines with two testers in three replications using modified triple test cross model.Results: All the genotypes showed highly significant differences for twelve yield and fiber quality traits reflecting genetic variability between lines, testers and crosses. Giza 86 is considered as a good combiner for yield and its components traits, while Giza 45 is the best combiner for fiber fineness and fiber strength, which classified in unique cluster. Most of the combinations having significant SCA effects were belonging to genetically diverse parents. The mean squares for the deviations revealed the presence of significant epistasis for all the studied traits except, seed index and fiber reflectance. While, significant mean squares were shown for sums and differences except lint index for additive and uniformity ratio and fiber reflectance for dominance. The fixable type (i) of epistasis was larger than non-fixable (i + l) type for the inheritance of the studied traits. The traits had significant mean squares for both fixable and non-fixable gene action, also showed significant GCA and SCA among 15 parents and 26 cotton crosses, respectively. Additive genetic component was larger than dominance for all the studied traits. So, most of the studied traits had significant GCA and degree of dominance was less than unity for all the studied traits, indicating partial or incomplete dominance. The correlation coefficient between the sums and difference were found to be insignificant indicating the genes with positive and negative effects were equally distributed among the genotypes.Conclusions: Genetic correlation between three genetic components revealed that both additive and epistasis play a great role among some studied traits suggesting common genetic pool. Thus, selection based on additive gene action based on indirect selection could improve cotton yield. The genotypes which have large genetic diversity could produce significant general or specific combining ability which may be reflecting its genetic behavior.

Genetic Dissection of Low-N Traits using Triple Test Cross Analysis in Maize (Zea mays L.)

Low-N maize is bred for its ability to tolerate low soil nitrogen (N) by growing and producing grain that compares appreciably to conventional varieties. This experiment was conducted to study the genetic effects of grain yield and other agronomic traits in Low-N maize using triple test cross analysis. Twelve low-N open pollinated maize varieties were converted to the inbred line after six generations of selfing and used for the experiment. Two inbred lines along with their F1 were used as testers for ten inbred lines in a triple test cross pattern to generate 30 crosses and along with their parents and testers to make a total of 43 entries which were evaluated at the Teaching and Research Farms of Ekiti State University, Ado-Ekiti during in 2017. The design was a Randomized Complete Block Design (RCBD). Data was collected on plant height, ear height, days to 50% anthesis, days to 50% silking, the incidence of Curvularia leaf spot, blight, plant aspect, ear aspect, ear rot, stay green, cob per plant, ear weight, grain moisture content and grain yield. All data was subjected to analysis of variance and complete genetic estimates made. Additive and dominants were significant (P0.05) for all traits, however, epitasis estimates were not significant for all the traits. The degree of dominance component indicated partial dominance for all the traits. Correlation coefficients for days to 50% anthesis and 50% silking, plant height, ear height, number of cob per plant and grain yield were positive and significant (P0.05). Since both additive and dominance gene actions were important for low-N traits, the use of reciprocal recurrent selection procedure can be adopted in incorporating the trait into elite maize varieties.

Detection of epistasis through triple test cross (TTC) analysis in maize (Zea mays L.)

The present study was carried out to detect the epistasis present in two cross of maize through triple test cross (TTC) analysis. The mean squares due to total epistasis was highly significant at P≤0.01 for all the characters in both C-I and C-II, except for ear length in C-I. The i type of epistasis was highly significant for the traits such as days totasseling, days to silking, earlength, ear circumference, kernels row-1,100 grain weight and shelling percentage in C-I and in C-II, ‘i’ type was non-significant for ASI, ear length, kernels row-1and grain yield plot-1. Both j type and l type of epistasis were significant for all characters in both C-I and C-II, except for ear length in C-I and days to silking in C-II. The estimate of additive genetic component (D) was highly significant for all characters in both C-I and C-II. Epistasis played a significant role in the inheritance of all the characters in both C-I and C-II except for ear length in C-I. Both additive and dominance components of genetic variance with a predominance of dominance genetic variance played an important role in the inheritance of all the quantitative traits except ear length in C-I and kernel rows ear-1 in C-II.