Biplot Analysis of Line × Tester Data of Maize (Zea mays L.) Inbred Lines under Stress and Nonstress Environments

The GGE biplot tool has potential for determining combining ability effects, identifying distinct heterotic groups and efficient testers in a line × tester study. However, its use for such analysis has not been adequately explored. The objectives of this study were to (i) assess combining ability of extra-early maturing lines (80–85 days to physiological maturity) and testers for grain yield (ii) classify lines into heterotic groups and (iii) identify most efficient testers using GGE biplot. Sixty-three lines crossed to four testers were evaluated under Strga-infested, drought and nonstress environments for 2 years in Nigeria. Results of GGE biplot analyses of combining ability and heterotic patterns of yield of lines, grouping and identification of testers were close to those of the conventional line × tester method. Testers TZEEI 13, TZEEI 21 and TZEEI 29 were highly efficient in grouping lines under stress environments while testers TZEEI 21 and TZEEI 29 were best under nonstress environments. The GGE biplot identified tester TZEEI 13, TZEEI 21 and TZEEI 29 as most efficient across stress environments and TZEEI 21 and TZEEI 29 across nonstress environments

Interrelationships between grain yield and other physiological traits of cowpea cultivars

Adequate knowledge of the interrelationships among physiological traits is essential in planning and evaluating breeding programmes for cowpea improvement. The objective of this study was to determine the interrelationships among physiological traits of thirty cowpea cultivars and identify suitable traits for indirect selection for improved crop yield. The study was conducted for two consecutive growing seasons at the Obafemi Awolowo University, Teaching and Research Farm, Ile-Ife in Nigeria. Combined analysis of variance, cluster analysis and genotype-bytrait (GT) analysis were carried out on the measured traits. Results showed significant genotype differences for all phenological and morphological traits, except grain yield and associated yield components. The GT biplot analysis revealed close associations among the phenological traits. Grain yield was positively correlated with all morphological traits except the two peduncle traits and negatively correlated with flowering traits. IT98-131-1 was the best cultivar based on multiple traits and was identified as the ideal cultivar that can be used as a reference check. Seed growth rate, yield growth rate, yield per plant, and pod weight were identified as traits that are most appropriate for indirect selection for improved grain yield of cowpea.La connaissance ad\ue9quate des relations mutuelles parmi les traits physiologiques est essentielle dans planification et l\u2019\ue9valuation des programmes d\u2019am\ue9lioration du petit pois. L\u2019objectif de cette \ue9tude \ue9tait de d\ue9terminer les relations mutuelles parmi les traits physiologiques de trente cultivars de petit pois et d\u2019identifier des traits appropri\ue9s pour la s\ue9lection indirecte de cultures \ue0 rendement am\ue9lior\ue9. L\u2019\ue9tude \ue9tait conduite en deux consecutives saisons de culture \ue0 l\u2019Universit\ue9 Obafemi Awolowo, une Ferme de Recherche et d\u2019\ue9ducation, Ile-Ife au Nigeria. L\u2019analyse de la variance combine, l\u2019analyse par groupement et l\u2019analyse du g\ue9notype par trait, \ue9tait conduit sur les traits m\ue9sur\ue9s. Les r\ue9sultats ont montr\ue9 des diff\ue9rences g\ue9notypiques significatives pour tous les traits ph\ue9nologiques et morphologiques, except\ue9 le rendement en grain et les composants associ\ue9s aux rendements. L\u2019analyse de biplot GT a r\ue9v\ue9l\ue9 des associations proches parmi les traits ph\ue9nologiques. Le rendement en grain \ue9tait positivement corr\ue9l\ue9 avec tous tous les traits morphologiques except\ue9 les deux traits de p\ue9doncules et n\ue9gativement correl\ue9 avec les traits de floraison. IT98-131-1 \ue9tait le meilleur cultivar bas\ue9 sur de traits multiples et \ue9tait identifi\ue9 comme un cultivar ideal qui peut \ueatre utilis\ue9 comme un mat\ue9riel de reference. Le taux de croissance, le taux de rendement, le rendement par plant, et le poids de gousses \ue9taient identifi\ue9s comme des traits appropri\ue9s \ue0 la s\ue9lection indirect pour l\u2019am\ue9lioration du rendemen en grain du petit pois

Assessing the suitability of stress tolerant early-maturing maize (Zea mays) inbred lines for hybrid development using combining ability effects and DArTseq markers

Open Access Article; Published online: 27 Jan 2023Identification of hybrids for commercialization is crucial for sustainable maize production in sub-Saharan Africa (SSA). One hundred and ninety test crosses, 10 tester × tester crosses + 10 hybrid checks were evaluated across 11 environments, 2017 to 2019. Inheritance of grain yield under Striga infestation, optimal and across environments was influenced by additive genetic action, but there was greater influence of nonadditive gene action under drought stress conditions. Nine, seven and two inbreds had significant and positive general combining ability (GCA) effects for grain yield under Striga-infested, optimal and drought stress environments, respectively, and would contribute high grain yield to their progenies. Heterotic grouping methods based on specific and GCA, GCA effects of multiple traits and DArTseq markers classified the inbreds into five, three and two heterotic groups, respectively, across research conditions. The DArTseq markers method that classified the inbred lines into two major heterotic groups and was one of the most efficient methods should be adopted for practical purposes in maize breeding programmes in SSA. Hybrids TZEI 7 × TZdEI 352, TZEI 1238 × TZEI 7 and TZEI 1252 × TZEI 7 had outstanding grain yield under contrasting environments and should be tested on-farm for commercialization in SSA

EVALUATION OF STRIGA-RESISTANT EARLY MAIZE HYBRIDS AND TEST LOCATIONS UNDER STRIGA-INFESTED AND STRIGA-FREE ENVIRONMENTS

Emergence of several seed companies in the West Africa sub-region during the last decade has necessitated intensified efforts towards hybrid development and extensive testing. The objectives of the present study were to evaluate selected Striga-resistant maize ( Zea mays L.) hybrids for grain yield and stability of performance based on multiple traits. Thirty Striga-resistant single\u2013cross maize hybrids plus two checks were evaluated under artificial Striga infestation and Striga-free conditions at 2 locations in Nigeria in 2008 and 2009. The two test locations possessed high discriminating ability. More promising genotypes were identified under Striga infestation based on multiple traits than based on yield per se, suggesting that grain yield alone is not a precise predictor of Striga resistance. Based on both biplot analyses, TZEI12 x TZEI25 was identified as the most outstanding in performance under both research conditions. Furthermore, TZEI11 x TZEI127 and TZEI80 x TZEI2B were identified as the most outstanding under Striga-infested conditions and TZEI60 x TZEI87 under Striga-free conditions by the two biplot methods. The hybrids with outstanding performance should undergo extensive multilocational testing and promotion for adoption for commercial production.L\u2019\ue9mergence de plusieurs companies de semence dans la sous r\ue9gion weste africaine durant la derni\ue8re decades a n\ue9cessit\ue9 des efforts intensifi\ue9s en d\ue9veloppement d\u2019hybrides et essais extensifs. Les objectifs de la pr\ue9sente \ue9tude \ue9taient d\u2019\ue9valuer des hybrides s\ue9lectionn\ue9s de ma\uefs ( Zea mays L.) r\ue9sistants au striga pour le rendement en grains et la stabilit\ue9 de sa performance sur base de multiples traits. Trente hybrides de ma\uefs r\ue9sistants \ue0 un seul croisement ainsi que deux t\ue9moins \ue9taitent \ue9valu\ue9s en condition artificielle d\u2019infestation et dans des conditions sans Striga dans deux milieux du Nigeria en 2008 and 2009. Les deux milieux en tests possedaient une aptitude discriminatoire \ue9lev\ue9e. Plus de g\ue9notypes promettants \ue9taient identifi\ue9s en condition d\u2019infestation du Striga, en se basant sur des traits multiples plut\uf4t que sur base du rendement, sugg\ue9rant que seul le rendement en grain n\u2019est pas un pr\ue9dicteur pr\ue9cis de la r\ue9sistance du striga. Bas\ue9 sur les analyses biplot, TZEI12 x TZEI25 \ue9tait identifi\ue9 comme le plus remarquable en performance sous conditions de recherche. En plus, TZEI11 x TZEI127 et TZEI80 x TZEI2B \ue9taient identifies comme \ue9tant les plus remarquables en conditions d\u2019infestation du Striga et TZEI60 x TZEI87 sous conditions non infest\ue9es du Striga par deux methods biplot. Des \ue9tudes extensives multilocales des hybrides \ue0 performance remarquable ainsi que la promotion de l\u2019adoption pour une production commerciale sont recommend\ue9es

Detection of non-additive gene action within elite maize populations evaluated in contrasting environments under rainforest ecology in Nigeria

Open Access Journal; Published online: 28 Jan 2021Proper 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 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

Inheritance of seed quality traits and concentrations of zinc and iron in maize topcross hybrids

Information about the mode of inheritance of maize ( Zea mays L.) seed quality traits is crucial in planning for improvement programmes for such traits. The objective study was to determine mode of inheritance and interrelationships between seed quality traits, and Fe and Zn contents in maize. Twenty-six maize genotypes were considered for evaluation in this study. Additive gene action was prevalent for most seed quality traits (>50%); while non-additive gene action was preponderant for Fe and Zn concentrations. Inbreds TZEEI82 and TZEEI64 were outstanding in terms of GCA male effects for conductivity (-0.13** and -0.06*), root number (0.79** and 0.30*), and root fresh weight (0.90*). Genotypes TZEEI81, DTE-STR-Y-SYN-POP-C3, 2009-TZEEI-OR1-STR and 2009-TZEE-OR1-STR-QPM were identified as excellent pollen parents for Fe concentration; and TZEEI58 and TZEEI64 for Zn concentration. In addition, only germination index had a significant additive genetic relationship with Fe content (r=0.57*); while both shoot fresh and dry weights had significant positive correlations with Zn content (r=0.45*, 0.53*). Overall, it is clear that different modes of gene action control inheritance of seed quality traits and Fe and Zn concentrations.L\u2018 information sur le mode de transmission des caract\ue8res de qualit\ue9 des semences de ma\uefs ( Zea mays L.) est cruciale dans la planification d\u2019un programme d\u2019am\ue9lioration de ces caract\ue8res. L\u2019objectif de cette \ue9tude \ue9tait de d\ue9terminer le mode d\u2019h\ue9r\ue9dit\ue9 et les relations entre les caract\ue8res de qualit\ue9 des semences et les teneurs en Fe et Zn du ma\uefs. Vingt-six g\ue9notypes de ma\uefs ont \ue9t\ue9 \ue9valu\ue9s pour les caract\ue8res de qualit\ue9 des semences ainsi que pour les teneurs en Fe et Zn. L\u2019action des g\ue8nes additifs \ue9tait pr\ue9dominante pour la plupart des caract\ue8res de qualit\ue9 des semences (> 50%); tandis que l\u2019action g\ue9nique non additive \ue9tait pr\ue9pond\ue9rante pour les concentrations de Fe et de Zn. Les consanguines TZEEI82 et TZEEI64 ont \ue9t\ue9 remarquables en termes d\u2019effets GCA m\ue2les pour la conductivit\ue9 (-0,13 ** et -0,06 *), le nombre de racines (0,79 ** et 0,30 *) et le poids des racines fra\ueeches (0,90 *). Les g\ue9notypes TZEEI81, DTE-STR-Y-SYN-POP-C3, 2009-TZEEI-OR1-STR et 2009-TZEE-OR1-STR-QPM ont \ue9t\ue9 identifi\ue9s comme d\u2019excellents parents de pollen pour la concentration de Fe; et TZEEI58 et TZEEI64 pour la concentration de Zn. De plus, seul l\u2019indice de germination avait une relation g\ue9n\ue9tique additive significative avec la teneur en Fe (r = 0,57 *); tandis que les poids frais et secs des pousses avaient des corr\ue9lations positives significatives avec la teneur en Zn (r = 0,45 *, 0,53 *). Dans l\u2019ensemble, il est clair que diff\ue9rents modes d\u2019action g\ue9nique contr\uf4laient l\u2019h\ue9r\ue9dit\ue9 des caract\ue8res de qualit\ue9 des semences et des concentrations de Fe et Zn

Genome-wide association study of Striga resistance in early maturing white tropical maize inbred lines

Open Access Journal; Published online: 11 May 2020Background: Striga hermonthica (Benth.) parasitism militates against increased maize production and productivity in savannas of sub-Saharan Africa (SSA). Identification of Striga resistance genes is important in developing genotypes with durable resistance. So far, there is only one report on the existence of QTL for Striga resistance on chromosome 6 of maize. The objective of this study was to identify genomic regions significantly associated with grain yield and other agronomic traits under artificial Striga field infestation. A panel of 132 early-maturing maize inbreds were phenotyped for key agronomic traits under Striga-infested and Striga-free conditions. The inbred lines were also genotyped using 47,440 DArTseq markers from which 7224 markers were retained for population structure analysis and genome-wide association study (GWAS). Results: The inbred lines were grouped into two major clusters based on structure analysis as well as the neighborjoining hierarchical clustering. A total of 24 SNPs significantly associated with grain yield, Striga damage at 8 and 10 weeks after planting (WAP), ears per plant and ear aspect under Striga infestation were detected. Under Striga-free conditions, 11 SNPs significantly associated with grain yield, number of ears per plant and ear aspect were identified. Three markers physically located close to the putative genes GRMZM2G164743 (bin 10.05), GRMZM2G060216 (bin 3.06) and GRMZM2G103085 (bin 5.07) were detected, linked to grain yield, Striga damage at 8 and 10 WAP and number of ears per plant under Striga infestation, explaining 9 to 42% of the phenotypic variance. Furthermore, the S9_154,978,426 locus on chromosome 9 was found at 2.61 Mb close to the ZmCCD1 gene known to be associated with the reduction of strigolactone production in the maize roots. Conclusions: Presented in this study is the first report of the identification of significant loci on chromosomes 9 and 10 of maize that are closely linked to ZmCCD1 and amt5 genes, respectively and may be related to plant defense mechanisms against Striga parasitism. After validation, the identified loci could be targets for breeders for marker-assisted selection (MAS) to accelerate genetic enhancement of maize for Striga resistance in the tropics, particularly in SSA, where the parasitic weed is endemic

Identification of early and extra-early maturing tropical maize inbred lines resistant to Exserohilum turcicum in sub-Saharan Africa

Open Access Article; Published online: 12 Sept 2020Northern corn leaf blight (NCLB) incited by the fungus Exserohilum turcicum is a foliar disease that significantly limits maize production and productivity in West and Central Africa (WCA), particularly in the mid-altitudes but during the last decade it has become a menace in lowland agro-ecologies. The most economical and environmentally friendly disease management strategy is the cultivation of maize varieties resistant or tolerant to NCLB. However, no early maturing (EM) and extra-early maturing (EEM) NCLB resistant varieties are commercially available in WCA. One hundred inbred lines each of EM and EEM derived from tropical maize germplasm were inoculated with a virulent isolate of E. turcicum at five locations in Nigeria during the 2017 and 2018 growing seasons. The objective of the study was to identify promising NCLB resistant lines and to investigate inter-relationships among the traits. Analysis of variance revealed highly significant genotype and genotype by environment (G × E) interactions for disease severity, grain yield (GYLD), and other agronomic traits. The average disease severity (TURC) values ranged from 1.9 to 5.8 and 2.9 to 5.7 for the EM and EEM inbred lines, respectively. The levels of reaction of the inbred lines to NCLB ranged from highly resistant to highly susceptible. Stepwise regression analysis showed that ears per plant, ear and plant aspects were significantly influenced by the disease scores. Ears per plant, ear and plant aspects, TURC and GYLD traits were employed to develop a base index (BI) for selecting NCLB resistant inbred lines for hybrid development. TZEI 135 and TZEEI 1 were outstanding in GYLD and also had the highest positive BI values in the EM and EEM inbred lines, respectively. The identification of NCLB resistant lines in this study has set the premise for development of NCLB resistant hybrids for WCA as well as the improvement of tropical maize breeding populations for NCLB resistance

Use of GGE biplot for targeting early maturing maize cultivars to mega-environments in West Africa

Maize (Zea mays L.) is an important staple food consumed by people with varying food preferences and socio-economic backgrounds in West Africa (WA). Genotype by environment interactions (G 7E) exist in WA implying the need for extensive testing of cultivars in multiple environments over years before cultivar realistic recommendations can be made. This study examined the effect of G 7E on the performance and stability of early cultivars and to identify core test locations in the mega-environments of WA. Across locations, 2004 TZE-W Pop STR C4 produced the highest grain yield and was the most stable cultivar. DMR-ESRW QPM produced the lowest yield. The test environments contributed about 83.4% of the total variation in grain yield, while genotypes accounted for 1.5% and G 7 E, 11%. Test environments were classified into four mega-environments, namely, Katibougou, Sotouboua, Ejura, and Bagou as the first group; the second group consisted of Manga, Nyankpala, Bagauda, Yendi, Angaredebou, Mokwa, Katibougou, and Zaria; while the third group comprise of Ativeme, and Ikenne; and the fourth, Ina. Test locations Ejura, Sotouboua and Bagou and Katibougou were highly correlated in their ranking of the genotypes in group 1, suggesting that a promising early maturing cultivar selected in one of these locations in one country will also be suitable for production in the other locations within the same mega-environments in different countries. Kita was identified as the ideal location, while Zaria was close to the ideal location.Le ma\uefs (Zea mays L.) est une nourriture principale consomm\ue9 par des personnes \ue0 pr\ue9f\ue9rence alimentaires et un pass\ue9 socio-\ue9conomique vari\ue9s en Afrique de l'Ouest. Une interaction G\ue9notype et Environnement (G 7E) \ue9tait trouv\ue9e, impliquant ainsi le besoin en test extensive des cultivars sur plusieurs ann\ue9es avant toute recommandation. Le but de cette \ue9tude \ue9tait d'examiner l'effet G 7E sur la performance et la stabilit\ue9 des cultivars pr\ue9coces, ainsi que d'identifier le test principal de milieu dans les m\ue9ga-environnements de l'Afrique de l'Ouest. A travers les milieux, 2004 TZE-W Pop STR C4 avait produit le rendement en grain le plus \ue9lev\ue9 et \ue9tait le cultivar le plus stable. DMR-ESRW QPM avait induit le rendement le moins \ue9lev\ue9. La contribution du test d'environnements \ue9tait d'environ 83.4% de la variation totale du rendement en grain, pendant que les g\ue9notypes et G 7 E pr\ue9sentaient 1.5% et 11%, respectivement. Les tests d'environnements \ue9taient classifi\ue9s en quatre m\ue9ga-environnements \ue0 savoir, Katibougou, Sotouboua, Ejura, and Bagou comme premier groupe; Manga, Nyankpala, Bagauda, Yendi, Angaredebou, Mokwa, Katibougou, and Zaria comme deuxi\ue8me groupe, alors que le troisi\ue8me groupe comprenait Ativeme, et Ikenne et le quatri\ue8me, Ina. Le test de milieux Ejura, Sotouboua, Bagou et Katibougou \ue9taitent hautement corr\ue9l\ue9 sur le plan ranking des g\ue9notypes au sein du groupe 1, sugg\ue9rant qu'un cultivar pr\ue9coce promettant s\ue9lectionn\ue9 dans un de ces milieux dans un pays sera appropri\ue9 pour la production dans d'autres milieux au sein des m\ueames m\ue9ga-envoronnements dans diff\ue9rents pays. Kita \ue9tait identifi\ue9 comme un milieu ideal, alors que Zaria \ue9tait proche du milieu ideal