SummaryAegilops tauschii is the diploid progenitor of the wheat D subgenome and a valuable resource for wheat breeding, yet, genetic analysis of resistance against Fusarium head blight (FHB) and the major Fusarium mycotoxin deoxynivalenol (DON) is lacking. We treated a panel of 147 Ae. tauschii accessions with either Fusarium graminearum spores or DON solution and recorded the associated disease spread or toxin‐induced bleaching. A k‐mer‐based association mapping pipeline dissected the genetic basis of resistance and identified candidate genes. After DON infiltration nine accessions revealed severe bleaching symptoms concomitant with lower conversion rates of DON into the non‐toxic DON‐3‐O‐glucoside. We identified the gene AET5Gv20385300 on chromosome 5D encoding a uridine diphosphate (UDP)‐glucosyltransferase (UGT) as the causal variant and the mutant allele resulting in a truncated protein was only found in the nine susceptible accessions. This UGT is also polymorphic in hexaploid wheat and when expressed in Saccharomyces cerevisiae only the full‐length gene conferred resistance against DON. Analysing the D subgenome helped to elucidate the genetic control of FHB resistance and identified a UGT involved in DON detoxification in Ae. tauschii and hexaploid wheat. This resistance mechanism is highly conserved since the UGT is orthologous to the barley UGT HvUGT13248 indicating descent from a common ancestor of wheat and barley.

Mycorrhiza is obtained from two Greek expressions, namely: mykes (fungus) and rhiza (root). In otherwise, mycorrhiza means fungus-root as coined by Frank in 1885. So, mycorrhiza association is defined as the mutual relationship between fungus and plant root in which the fungus derive carbon from its host plant while the host plants obtain minerals from the fungus. Mycorrhizas are found in different biomes ranging from high latitudes and altitudes, deserts, lowland tropical forest to aquatic ecosystems. It is a known fact that several plants cannot thrive in their natural habitats without this mutualism, as 95-99 % of all plant species have been estimated to belong to genera that generally form mycorrhizas. It is only three families of plant that do not enter into mutual relationship with fungus. These families are as follows: Cyperaceae, Chenopodiaceae, and Brassicaceae. There are now seven types of mycorrhizas among which are arbuscular (AM) endomycorrhiza, ericoid endomycorrhizas, arbutoid endomycorrhizas, monotropoid endomycorrhizas, orchidaeous endomycorrhizas, ectomycorhizas and ectendomycorrhizas. The benefits of mycorrhiza association cannot be overemphasized as studies have shown that it improves nutrient supply of carbon, phosphorus and nitrogen to both plant and fungus that might not normally be made available to plant roots in large amount. It also enhances the performance of plant growing in soils with high amounts of heavy metals and water absorption of desert plants.

Plant breeding experiments require the use of appropriate experimental designs that will efficiently block variation due to wide heterogeneity nature of tropical soils. The primary objective of this study was to assess the effectiveness of eight different alpha-lattice designs relative to randomized complete block design for evaluating 108 genotypes of maize under rainforest agro-ecology. The maize genotypes were field-tested using three replications at two locations. Data were collected on grain yield and other agronomic traits. Data collected were subjected to analysis of variance (ANOVA) assuming randomized complete block design (RCBD) and eight alpha-lattice designs. Pearson's correlation and stepwise multiple regression analyses were used to analyze relationship among different designs and efficiency of the lattice designs over RCBD was computed. Result showed that all the alpha lattice designs except 27 × 4 were effective in evaluating the genotypes for plant height. There was significant difference (p < 0.001) among genotypes for grain yield only when data were analyzed based on 9 × 12 alpha lattice design. In addition, results showed that the proportion of variation due to blocking and R-square values of the model increased with increase in the number of blocks for grain yield. In contrast, coefficient of variation decreased with increase in the number of blocks. The result showed an increase in efficiency of the alpha lattice designs as the number of blocks increased. It could then be concluded that the more the number of blocks within replicate, the proportion of total variation due to blocking increased, the coefficient of variation (CV) reduced, coefficient of determination (R-square) increased and thus, effectiveness increased. Appropriateness of designs was trait dependent. The 9 × 12 alpha lattice design was identified to be the best in the evaluation of grain yield for the maize genotypes.

Proper understanding of the mode of gene action in open-pollinated varieties (OPVs) maize parents helps breeder in the choice of appropriate breeding method to improve its genetic value. The objectives of the present study were to determine gene action controlling grain yield and other agronomic traits of late maturing elite OPVs and classify the varieties into heterotic groups. Ninety-one hybrids generated from 14 elite OPV parents using diallel mating design were evaluated with their parents plus three commercial checks under marginal rainfall, drought, and optimal environments in Nigeria from 2017 to 2018. The experiment was laid out in a 9 × 12 alpha lattice with three replications in each environment. Results showed that there were significant mean squares for grain yield and most agronomic traits. Significant general combining ability (GCA) and specific combining ability (SCA) mean squares for some of the traits indicated that additive and non-additive genetic gene actions were important in the inheritance of yield and those traits among this set of genotypes. However, non-additive genetic effects were more important than additive for grain yield and other agronomic traits in all research environments. Only TZL Comp-3 C3 DT had significant and positive GCA effects (0.336*) while three hybrids had significant and positive SCA for grain yield across research environments. Because of the preponderance of non-additive gene action over additive gene action, distinct heterotic groups could not be identified but four tester groups were identified by HSGCA (Heterotic grouping based on Specific and General Combining Ability) and three groups by HGCAMT (Heterotic grouping based on the GCA of Multiple Traits). Results of grouping were not related to the endosperm colour but grouping based on HGCAMT was related to the Open Access Received: 09 July 2020 Accepted: 01 December 2020 Published: 28 January 2021 Copyright © 2021 by the author(s). Licensee Hapres, London, United Kingdom. This is an open access article distributed under the terms and conditions of Creative Commons Attribution 4.0 International License. Crop Breeding, Genetics and Genomics 2 of 24 pedigree of the varieties. In conclusion, this study has demonstrated preponderance of non-additive gene action over the additive gene action for all measured traits. The presence of the non-additive gene action present in the studied materials can enhance identification of outstanding varietal hybrids and population testers that can serve as base genetic materials for future maize improvement through reciprocal recurrent selection program in SSA.

A sound breeding program for maize improvement is very important to meet the demands of the growing population. Therefore, combining ability and heterosis were studied in a 4 x 4 full diallel cross in maize for growth attributes, yield and its contributing traits. Randomized Complete Block Design (RCBD) with four replicates was used to study the general combining ability of parents, specific combining ability of F1s (including reciprocals) and heterosis of the F1s over commercial check variety on selected agronomic characters. Genotype was highly significant for all the traits studied. The combining abilities (GCA and SCA) and reciprocal mean squares were highly significant for most studied characters. The ratio of GCA/SCA was not less than unity for studied traits excepted for days to anthesis and ear height. The results indicated that the additive genetic effects were more important and played major role in studied traits. Thus, results revealed GCA effects for the parental lines (PL). Where ‘PL2’ was excellent combiner for number of tassels and cob circumference and ‘PL3’ was good combiner for days to silking and grain yield (t.h-1). While ‘PL4’ for short height. Majority of the F1s from the GCA effects showed high SCA effects. This F1 (PL2 x PL3) performed best amongst. However, several reciprocals were not desirable. Heterosis estimation was carried out using a commercial check, Oba super II. When commercial check was used, the percent heterosis especially on grain yield varied from -8.89 to 22.62%. Among the twelve F1s, nine of the crosses exhibited significant positive heterosis for grain yield (t.h-1). Those F1s that showed significant positive and/or negative desirable traits for SCA effects and significant positive heterosis could be used for varietal development in maize breeding. And conservation of those parents that exhibited high GCA effects be considered as well.

In the maize producing regions of Sub-Saharan Africa (SSA), compounding effects of genotype-by-environment interaction have necessitated breeding maize for outstanding performance and stability across varying environments. This study was conducted to assess the performance and stability of late-maturing cultivars and their respective hybrids evaluated under contrasting environments in the tropical rainforest region. We evaluated 108 genotypes in field trials under three different growing conditions in 2018 involving 14 open-pollinated parents and their hybrids derived from a diallel mating design. The genotypes were evaluated under field conditions using 9 × 12 alpha lattice design with three replications in six environments. The genotypes were divided into three groups, containing either the parents, hybrids or checks, for estimating the stability variance and grain yield. The difference between the lowest and highest yielding environment was 3.9 t ha −1 , while the repeatability of the grain yield trials ranged from 39 to 80%. The average grain yield of the hybrids (2.33 t ha −1 ) was significantly higher than that of the parents (2.19 t ha −1 ) and the check varieties (2.03 t ha −1 ). The hybrids were more stable than both the parents and the checks. They also showed a higher stability against a common group of the parents and checks. The results of this study suggest that high yielding and stable population hybrids can be utilized in breeding programmes aiming to provide improved varieties for the large number of rural maize farmers in the SSA zone, who often lack access or the capacity to purchase commercial hybrids.

The genetic variability and inter-relationships between yield and associated traits in some taro genotypes were investigated in two years across two locations. The experiment was laid out as randomized complete block design with three replications in each location. Data were collected on the growth and yield attributes of taro. The genetic variability of the attributes measured in both locations was studied to estimate the genotypic (GCV) and phenotypic (PCV) coefficients of variation, broad sense heritability (h 2 b) and genetic advance (GA). Considering GCV, h 2 b and GA simultaneously as the best estimators of the amount of advance expected from selection, number of secondary shoots/plant and number of leaves/plant gave the highest values in each of the locations. This shows that a satisfactory selection program for improvement of these genotypes through these traits is possible at each specific location. Correlation analysis showed that all the traits measured were significantly and positively correlated with taro yield except corm and cormel lengths. Number of cormels/plant had the strongest positive correlation with taro yield (r = 0.699**) followed by cormel weight (r = 0.624**). Path-coefficient analysis and stepwise multiple regression analysis revealed cormel weight and number of cormels/plant as the biggest determinants of taro yield, both contributing about 72% of the total variation in yield. This suggests that these two characters are important selection indices for taro yield improvement.