Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 − 12 Original article dOi: 10.2478/agri-2022-0001 PHENOTYPIC PERFORMANCE OF NEW PRO-VITAMIN A MAIZE (Zea mays L.) HYBRIDS USING THREE SELECTION INDICES Adesike OlAdOyin kOlAwOle1* And AbiOdun FAtAi OlAyinkA2 1ladoke Akintola university of technology, Ogbomoso, Oyo state, nigeria 2university of Ghana legon, Accra, Ghana kolawole, A.O. and Olayinka, A.F. (2022). Phenotypic performance of new pro-vitamin A maize (Zea mays l.) hybrids using three selection indices. Agriculture (Poľnohospodárstvo), 68(1), 1 – 12. the development of new bio-fortified maize hybrids is crucial for achieving food security and alleviation of micronutrient deficiencies. This study aims at assessing the performance of new pro-vitamin A maize hybrids and identifying potential high-yielding hybrids using base index, multivariate selection index, and rank summation index. twenty-four pro-vitamin A maize hybrids and one hybrid check were evaluated in the rainy seasons of 2018 and 2019 at ladoke Akintola university of technology teaching and Research farm in Ogbomoso, nigeria. Hybrids were planted each year in a 5 × 5 α lattice design with three replications. Data collected on grain yield and agronomic traits were analysed. The hybrids showed significant (P < 0.001) variations for all measured traits except plant aspect and maize streak virus scores. the mean grain yield of hy- brids over two years varied from 1,106 kg/ha (ly1312-12) to 5,144 kg/ha (ly1501-9). the highest yielding hybrid across the years had a 31% yield advantage over the single-cross hybrid used as a check. the base index had the highest selection differential (34%) for grain yield. the rank summation index had a strong correlation with the multivariate selection index (r = ‒0.86+++) followed by base index (r = ‒0.56+++). The three selection indices used identified three superior three-way cross hybrids (ly1409-21, ly1501-9 and ly1501-1) with a slight change in rank order. these outstanding hybrids which combine high productivity with nutrients may be considered for advanced multi-location and on-farm testing before their release to farmers in derived savanna agroecology of nigeria. key words: agronomic traits, breeding programme, rank, selection differential, variation Maize (Zea mays l.) is a staple cereal crop in rietal cross), and conventional maize hybrids (sin- Africa (Musundire et al. 2021) with increasing de- gle, three-way and double-cross). Reif et al. (2003) mand as food, animal feed and industrial products described the development of maize hybrids as the in nigeria (Olaniyan 2015; kolawole et al. 2018). most significant milestone in agriculture because of the ever-increasing human population and demand its uniformity and improved productivity. More so, led farmers in diverse agro-ecological zones of ni- established seed companies targets either the single geria to the cultivation of various maize genotypes or three-way cross hybrids considering the cost of with yield increase over open-pollinated varieties production whereas, resource-limited farmers most- viz., synthetics, composites, non-conventional ly grow the single-cross hybrids for increased pro- maize hybrids (top-cross, double top-cross, and va- ductivity. Adesike Oladoyin kolawole (*Corresponding author), department of Crop Production and soil science, Faculty of Agri- cultural sciences, ladoke Akintola university of technology, Ogbomoso, Oyo state, nigeria. e-mail: aokolawole@lautech. edu.ng Abiodun Fatai Olayinka, west Africa Centre for Crop improvement, university of Ghana legon, Accra, Ghana. e-mail: aolayinka@wacci.ug.edu.gh © 2022 Authors. this is an open access article licensed under the Creative Commons Attribution-nonComercial-noderivs license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 1 Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 − 12 in nigeria, the elderly persons, preschool chil- proposed by Mulumba and Mock (1978) ranks gen- dren, pregnant women, and lactating mothers de- otypes for selected traits in desirable order and the pend mostly on products obtained from either white summed rank for each genotype becomes an index or yellow kernel maize for energy and nutrient in- used for selection. this index is not affected by take. these maize varieties have low nutritional variance among traits, does not require estimation quality when compared with pro-vitamin A (PVA) of genetic parameters and is simple to compute maize (Pixley et al. 2013). Vitamin A is an essential (Crosbie 1980). To increase selection efficiency, micronutrient useful for improved eyesight and en- elston (1963) proposed a multiplicative index, and hanced immune systems in humans (Obeng-bio et wricke and weber (1986) suggested the use of the al. 2019). Thus pro-vitamin A biofortified maize hy- euclidean and Mahalanobis distances as an index. brid with approximately 15 µg/g carotenoids (Men- in addition, a multivariate selection index, which kir et al. 2021) content is beneficial to both humans involves principal components analysis eigenvec- and animals. to enhance maize grain yield potential tors computed from correlation among traits used and nutritive value, the Maize improvement Pro- as weights have also been used effectively in maize gramme (MiP) of the international institute of trop- breeding programmes (Adebayo et al. 2017; Akbar ical Agriculture (iitA), ibadan, nigeria (iitA-MiP) et al. 2018; Anshori et al. 2019). developed diverse PVA enriched maize hybrids with the conditions that determine the usefulness of yellow to orange endosperm colour that combines an appropriate selection index depend on the type of intermediate to late maturity with maize streak virus genetic material and the breeding objectives. Previ- (MsV) resistance. However, the adoption rate for ous studies used diverse selection indices involving these maize hybrids is low. therefore, evaluation, grain yield and other agronomic traits to identify selection, and promotion of outstanding PVA maize genotypes with the highest breeding value in maize hybrids are important to ensure food and nutrition improvement programmes (Zaffar et al. 2005; security. tardin et al. 2007; Ajala 2010; berilli et al. 2013; the selection of superior genotypes with desir- Vieira et al. 2016; Adebayo et al. 2017; Crevelari able agronomic traits requires the utilization of a se- et al. 2018; de santiago et al. 2019; Oloyede-ka- lection index. two main categories of selection in- miyo 2019). In spite of the efficiency of selection dex are used in breeding programmes. the weight- indices, reports on comparison of these indices in based or weight-free selection indices that consti- maize breeding programmes for identification of tute a simultaneous selection of desirable traits superior maize hybrids for a specified agro-ecology have been used by researchers to select outstanding are limited. thus, this study aims at assessing new- genotypes in maize improvement programmes. the ly developed pro-vitamin A enriched maize hybrids weight-based selection indices have been reported for grain yield potential and other agronomic traits, as the most effective methods in the selection of and also compares the efficiency of weight-based superior genotypes (dermail et al. 2022). Howev- and weight-free selection indices in identifying out- er, these indices involve either assigning econom- standing PVA maize hybrids under the derived sa- ic weights or estimating variances (phenotypic and vanna agro-ecology of nigeria. genotypic) and covariance between pairs of traits (smith 1936; Hazel 1943; williams 1962). these indices display certain particularities in their calcu- MAteRiAl And MetHOds lations and inaccuracies may be associated with the variance and covariance matrices (de Azeredo et al. Experimental site 2017). to overcome these bottlenecks, other authors the experiment was conducted during the grow- proposed modified selection indices involving lin- ing seasons of 2018 and 2019 at the teaching and ear combinations of the phenotypic values (brim et Research (t&R) Farm of the ladoke Akintola uni- al.1959; kempthorne & nordskog 1959; Pesek & versity of technology (lAuteCH), Ogbomoso baker 1969; tai 1977; smith et al.1981). (8°10ʹN, 4°10ʹE, and altitude 341 m above sea lev- the weight-free index (Rank summation index) el). the location is in the derived savanna agro-ecol- 2 Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 − 12 ogy of nigeria. the annual mean rainfall of the ex- and well-filled ears, and 5 = rotten, variable, and perimental site ranges between 1,000 and 1,200 mm small ears. Plant aspect was rated on a scale of 1 to while the daily temperature is between 28°C and 5, where 1 = excellent overall phenotypic appeal and 30°C. The soils are characterized as alfisol (usdA 5 = poor overall phenotypic appeal. the number of 1999), which is generally low in nitrogen. ears per plant was determined as the total number of ears divided by the number of harvested plants per Planting materials plot. Foliar diseases (curvularia leaf spot and maize the study evaluated 25 maize genotypes com- streak virus) were rated on a scale of 1 to 5, where prising single and three-way cross hybrids. the 1 = slight leaf infection, and 5 = severe leaf infec- commercial hybrid cultivated in the test environment (Oba super 6) was used as a local check (lC) while the other (24) were intermediate to late (110 ‒ 120 t a b l e 1 days) maturing maize streak virus (MsV) resistant PVA hybrids developed by iitA-MiP (table 1). description of the pro-vitamin A enriched maize hybrids and a local check used in this study Experimental design and cultural practices The maize hybrids were laid out in a 5 × 5 α-lat- entry designation Hybrid type source tice design with three replicates, planted in a single 1 A1702-28 3-way cross iitA row plot of 5 m long, with 0.75 m spacing between 2 A1702-49 3-way cross iitA rows and 0.50 m spacing between hills. three seeds 3 A1702-53 3-way cross iitA were planted per hill, but 2 weeks after planting 4 A1706-2 3-way cross iitA (wAP), thinning was done to keep two plants per hill. A maximum of 22 plants per plot was obtained, 5 A1736-12 3-way cross iitA resulting in an optimum plant density of 53,333 6 A1736-13 3-way cross iitA plants/ha. At the time of sowing, a compound fer- 7 A1736-6 3-way cross iitA tiliser (n:P:k 15:15:15) was applied at the rate of 8 ife Hybrid-3 single-cross iitA 60 kg/ha n, 60 kg/ha of P2O5 and 60 kg/ha of k2O. 9 ife Hybrid-4 single-cross iitA urea was applied as top-dressing at the rate of 60 kg/ha n 4 weeks later. Paraquat and atrazine were 10 ly1001-18 3-way cross iitA applied as pre-emergence herbicides at the rate of 11 ly1001-23 3-way cross iitA 5.0 l/ha each, followed by manual weeding, as and 12 ly1302-9 3-way cross iitA when required, to keep the plots weed-free. 13 ly1312-11 single cross iitA Data collection 14 ly1312-12 single cross iitA data were recorded in each plot for the number 15 ly1312-4 3-way cross iitA of days to anthesis and silking as the number of days 16 ly1409-14 single cross iitA from planting to when 50% of the plants had shed pollen and had emerged silks, respectively. the an- 17 ly1409-21 3-way cross iitA thesis-silking interval was computed as the interval 18 ly1501-1 3-way cross iitA in days between anthesis and silking. Plant and ear 19 ly1501-3 3-way cross iitA heights [cm] were measured as the distance from 20 ly1501-5 3-way cross iitA the base of the plant to the height of the first tassel 21 ly1501-6 3-way cross iitA branch and the node bearing the upper ear, respec- tively. both variables were recorded as an average of 22 ly1501-7 3-way cross iitA 20 competitive plants per plot using the meter rule. 23 ly1501-8 3-way cross iitA Husk cover was rated on a scale of 1 to 5, where 1 = 24 ly1501-9 3-way cross iitA husk tightly arranged and extended beyond the ear 25 Oba super 6 single-cross Ogbomoso tip, and 5 = ear tips exposed. ear aspect was scored (lC) on a 1 to 5 scale, where 1 = clean, uniform, large, IITA ‒ International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria; LC ‒ local check. 3 Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1−12 tion. Grain yield was computed from ear weight per to compute the multivariate selection index plot and converted to kilograms per hectare. A shell- (Msi), eigenvectors from principal component anal- ing percentage of 80% was assumed for all hybrids ysis (PCA) obtained from the correlation among and grain yield was adjusted to 15% moisture con- traits were used as weights (Adebayo et al. 2017; tent using the following formula: Anshori et al. 2019). the multivariate selection in- 100 ‒ MC dex was estimated as: Grain yield [kg/ha] = ear weight [kg/m2] × 10,000 85 Msi1 = Ʃ [a1 (trait 1)1 + a2 (trait 2)1 +…+ an (trait n)1] × × 0.80 plot area [m2] where: (a1 ‒ an) = eigenvectors used as weights. Where: MC ‒ moisture content at harvest. to construct the rank summation index (Rsi), Data analysis rank attached to each maize hybrid for each trait in Analyses of variance (AnOVA) were comput- favourable order was summed (Mulamba & Mock ed for each year of evaluation separately in order 1978; kolawole et al. 2021) resulting in the follow- to test the homogeneity of the mean square error, ing: after which the combined AnOVA was computed R si = Σ (a +b +…+n ) for all traits measured using PROC GlM in sAs 1 1 1 1 (sAs institute 2010). least-squares means for each where: a1 = rank of the mean of the trait “a” of trait were computed and means were separated us- hybrid1, b1 = rank of the mean of the trait “b” of ing Fisher’s least significant difference (LSD) test hybrid1, n1 = rank of the mean of the trait “n” of at 0.05 probability level. For the selection of out- hybrid1. standing maize hybrids, ten agronomic traits which selection differential estimated as a proportion showed significant differences from ANOVA were [%] of the mean of all PVA hybrids were calculated used to rank the performance of the PVA maize for the three selection indices as the difference be- hybrids. two weight-based (base index and multi- tween the mean of the selected top 5 and the overall variate selection index ‒ MSI) and one weight-free mean of PVA maize hybrids to derive the relative (Rank summation index ‒ RSI) selection indices efficiency of the indices for identifying superior hy- were used in this study. to compute the base index brids. (Standardized selection index ‒ SIN), weights were Mean of top 5 hybrids – overall mean assigned based on the relative economic importance selection differential = of the traits. the outstanding genotypes were those × overall mean100 that showed the highest value for the sin (williams spearman’s rank correlation analysis was carried 1962; león et al. 2021). the standardized values out to determine the relationship among the selec- (sV) for each trait was obtained by: tion indices. (χ‒μ) / δ Results And disCussiOn Where: χ is the individual mean for a trait; μ is the overall mean of the trait; and δ is the standard devi- Highly significant differences were observed be- ation value. tween blocks for flowering-related traits, growth-re- the base index was then computed as: lated traits, and grain yield, indicating variation in Base index = Ʃ [a1 (sV trait a) + a (sV trait b) +…+ a the environmental conditions over the years of eval-2 n (sV trait n)] uation. Significant (P < 0.001) mean square of year for all measured traits except for flowering-related where: (a1 ‒ an) represents weights assigned and trait traits implied that the years 2018 and 2019 were means are the standardized values. discriminating enough to enable the detection of genetic differences among the maize hybrids (ta- 4 Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 − 12 5 t a b l e 2 Mean squares of grain yield and other agronomic traits of pro-vitamin A enriched maize hybrids derived from combined AnOVA source trait year Replication block 2 (Rep) (year) (year × Rep) Hybrid Hybrid × year error R [%] CV [%] df = 1 df = 4 df = 24 df = 24 df = 24 df = 72 Anthesis [days] 0.03 11.07+++ 7.46+++ 19.28+++ 6.28+++ 1.90 88 2.27 silking [days] 0.03 9.53++ 14.04+++ 26.89+++ 9.41+++ 2.67 90 2.56 Anthesis-silking interval [days] 0.00 0.35 2.46+++ 3.39+++ 2.58+++ 0.87 82 30.07 Plant height [cm] 114,275.04+++ 39.10 396.42+++ 766.57+++ 387.88+++ 110.36 95 6.04 ear height [cm] 41,660.00+++ 85.65 277.49+++ 240.28+++ 228.84+++ 92.77 91 12.47 Husk cover (1 ‒ 5) 3.08+++ 0.36++ 0.19 0.28++ 0.17 0.11 71 15.83 Plant Aspect (1 ‒ 5) 354.20+++ 0.47 1.05++ 0.56 0.45 0.43 93 18.25 Ear Aspect (1 ‒ 5) 7.94+++ 0.03 0.18 0.63+++ 0.35 0.24 68 21.29 number of ears per plant 5.88+++ 0.59++ 0.21 0.28+ 0.25 0.17 65 37.40 Maize streak virus (1 ‒ 5) 21.66+++ 0.47+ 0.10 0.22 0.25 0.19 73 25.39 Curvularia leaf spot (1 ‒ 5) 48.167+++ 3.14+ 4.51 11.84+++ 11.59+++ 2.75 79 70.02 Grain yield [kg/ha] 3,826,322.40+ 1,261,155.90 1,364,337.40++ 6,736,824.80+++ 4,846,878.10+++ 651,623.2 89 24.12 +,++,++; +, ++, +++ Significant at 0.05, 0.01 and 0.001 probability levels, respectively. R2 ‒ coefficient of determination; CV ‒ coefficient of variation; df – degree of freedom; AnOVA – Analysis of variance Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 −12 ble 2). Similarly, the hybrids showed significant (P < 0.001 and P < 0.05) mean squares for grain yield and other agronomic traits except for plant as- pect and maize streak virus. the observed variabili- ty could be due to the fact that the genotypes evalu- ated which include the single and three-way crosses were from diverse genetic backgrounds. this varia- tion is desirable for the selection of superior hybrids for the test environments, as also reported by em- manuel et al. (2017). the mean square for hybrid by year interaction were significant (P < 0.001) for all flowering-related traits, curvularia leaf spot, grain yield, plant, and ear heights. this implied that the responses of the maize hybrids were different across the years as a result of the edaphic conditions and climatic patterns. this is consistent with the report of tripathi et al. (2016). to ensure the adaptability of the hybrids to the test environment, a multi-envi- ronment trial will be necessary for objective selec- tion of outstanding hybrids. The coefficient of determination (R2) values was very high for all traits. Coefficient of variation (CV) was low (< 20%) for the number of days to anthesis and silking, plant and ear heights, husk cover, and plant aspect scores which shows high precision in the experimentation and data collection procedure. High CVs obtained for anthesis-silking anthesis, the number of ears per plant, and curvularia leaf spot, ranging from 30 to 70% may be a result of inter-en- vironments variability (Guimarães et al. 2021). the two years showed comparable values for the number of days to anthesis and silking, but the hy- brids had a shorter anthesis-silking intervals in 2018 than in 2019 (table 3). the plants were taller with higher ear placement in the year 2018. Ratings for husk cover and ear aspect were generally below 3.0 for all the hybrids in the year 2018 but were on aver- age of 4.0 in the year 2019. Curvularia leaf spot had desirable scores in the year 2019. Grain yield of hy- brids in 2018 ranged between 240.7 kg/ha (ly1001- 18) and 6,458 kg/ha (ly1501-9) with a mean of 3,506.8 kg/ha. this was comparable to the report of ewool et al. (2016) and Ogunniyan et al. (2021). However, the grain yield varied from 1,501.4 kg/ha (ly1501-3) to 4,711.8 kg/ha (ly1501-6) with a mean of 3,186.6 kg/ha in the year 2019. the lower performance of the hybrids in 2019 for most traits could be linked to the duration and fluctuation with 6 t a b l e 3 Means and ranges for grain yield and other agronomic traits of maize hybrids evaluated across years Mean±se Range trait 2018 2019 Combined 2018 2019 Combined LSD (0.05) Anthesis [days] 60.7 ± 0.47 60.8 ± 0.47 60.7 ± 0.42 57.26 ‒ 67.1 57.3 ‒ 66.6 57.90 ‒ 65.4 1.6 silking [days] 63.8 ± 0.62 63.9 ± 0.55 63.8 ± 0.52 59.70 ‒ 71.6 58.8 ‒ 69.5 59.90 ‒ 69.3 1.9 Anthesis ‒ silking interval [days] 3.1 ± 0.29 3.1 ± 0.17 3.1 ± 0.19 0.20 ‒ 6.3 1.5 ‒ 4.6 1.40 ‒ 5.2 1.1 Plant height [cm] 201.6 ± 4.37 146.4 ± 1.90 174.1 ± 2.68 130.20 ‒ 236.6 127.6 ‒ 165.0 135.60 ‒ 196.8 12.1 ear height [cm] 93.9 ± 2.78 60.6 ± 1.06 77.2 ± 1.49 58.30 ‒ 125.2 50.8 ‒ 70.8 57.30 ‒ 91.7 11.1 Husk cover (1 ‒ 5) 2.0 ± 0.04 2.3 ± 0.08 2.1 ± 0.05 1.50 ‒ 2.5 1.6 ‒ 3.3 1.60 ‒ 2.8 0.4 Ear Aspect (1 ‒ 5) 2.1 ± 0.05 2.5 ± 0.11 2.3 ± 0.07 1.50 ‒ 2.7 1.7 ‒ 4.1 1.80 ‒ 3.1 0.6 number of ears per plant 1.3 ± 0.11 0.9 ± 0.02 1.1 ± 0.05 0.40 ‒ 2.6 0.7 ‒ 1.1 0.60 ‒ 1.7 0.5 Curvularia leaf spot (1 ‒ 5) 3.0 ± 0.59 1.8 ± 0.04 2.4 ± 0.31 1.70 ‒ 4.8 1.4 ‒ 2.1 0.30 ‒ 8.6 1.9 Grain yield [kg/ha] 3,506.8 ± 404.25 3,186.6 ± 159.89 3,338.3 ± 244.08 240.7 ‒ 6,458.0 1,501.4 – 4,711.8 1,105.5 – 5,143.8 929.1 SE ‒ standard error; LSD ‒ least significant difference Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 −12 the pattern of rainfall in the second year of evalua- agronomic traits can be considered important grain tion coupled with the armyworm (Spodoptera fru- yield attributes. giperda) infestation in the field. interestingly, the three-way cross hybrid ly1409- Across the years, the hybrids showed a wide 21 showed a similar ranking in performance with range of variations for all traits measured which is an the three selection indices as superior for grain yield opportunity for selection. Grain yield ranged from and other agronomic traits. Additionally, the hybrids 1,105.50 kg/ha for ly1312-12 to 5,143.77 kg/ha ly1501-9 which was the highest yielding (5,143.78 for ly1501-9 with a mean of 3,338.32 kg/ha. in kg/ha) across the years of evaluation cut across the comparison to the commercial hybrid (Oba super three selection indices among the top five outstand- 6) used as a local check in this study, 33% of the ing hybrids. this is contrary to the earlier report of hybrids had a significant (P < 0.05) earlier num- lunezzo de Oliveira et al. (2014) that the highest ber of days to flowering, 29% of the hybrids had yielding hybrids are not necessarily the best for a significant (P < 0.05) earlier number of days to other traits assessed. the only single-cross hybrid silking, 17% of the hybrids had significant a (P < among the top five based on two out of the three 0.05) shorter anthesis-silking interval, 21% of the selection indices used was ife Hybrid-3. the change hybrids were significantly (P < 0.05) taller, 25% of in rank order of hybrids for the three selection indi- the hybrids had a significant (P < 0.05) better husk ces is a reflection of the importance of the weights cover scores, 42% of the hybrids had a significant attached to the traits for the computation of the indi- (P < 0.05) improved overall phenotypic appeal for ces. The three selection indices identified LY1409- the plant and ear aspect and 21% of the hybrids had 21(out-yielded the local check by 18%), ly1501-9 a significant (P < 0.05) superior grain yield. Howev- (out-yielded the local check by 31%), and ly1501-1 er, 50% of the hybrids out-yielded the local check, (out-yielded the local check by 7%) as a three-way but only nine hybrids had a 10% yield advantage cross PVA maize hybrids that may enhance sustain- over the local check (table 4). able productivity in the derived savanna agro-ecol- the selection of outstanding PVA maize hy- ogy of nigeria. brids was based on three selection indices applied selection differentials estimates were used to to ten agronomic traits which showed significant ascertain the effectiveness of the three selection in- variations among the hybrids evaluated. the three dices in identifying the outstanding performance of selection indices used in this study (base index, maize hybrids. there were differences among the multivariate selection index, and rank summation selection differentials estimates for the three selec- index) identified similar maize hybrids among the tion indices (table 6). Positive selection differentials top five superior and poor performers (Table 5). All (0.83 to 33.75%) were obtained for grain yield, the the superior hybrids selected by the three methods number of ears per plant, plant, and ear heights. the of selection had higher selection index values and three selection indices had negative selection differ- out-yielded the commercial hybrid by 7% to 31%. entials for all flowering-related traits, foliar disease, these hybrids depict a combination of favourable and ear aspect score which ranged from ‒2.42 to alleles for plant heights which were important for ‒44.35%. the base index and Msi gave the highest green and dry matter production. the intermediate selection differentials for four traits. Consequently, height for ear placement in these hybrids prevented these two indices appear to be equally efficient in root and stock lodging. earliness to anthesis (57.9 identifying superior PVA maize hybrids as regards days) and silking (63.9 days) allowed short growth the traits considered. Comparing the three selection duration and maturity, while the short number of indices used in this study, the base index had the days for synchronization of pollen shed and silking highest positive and negative selection differentials allowed improved fertilisation and cob fill which for grain yield and curvularia leaf spot respectively. translated into improved (> 1) number of ears per this result corroborates previous studies consider- plant. the phenotypic appeal scores of these hy- ing the identification of potentially high-yielding brids, which determine their acceptability under maize genotypes based on different selection index farmers’ conditions, were also desirable. thus, these methods and found the base index to have a higher 7 Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 −12 8 t a b l e 4 Combined mean performance of grain yield and other agronomic traits of maize hybrids evaluated Hybrid Anthesis silking Anthesis- Plant ear number Maize streak Curvularia [days] [days] silking inter- height height Husk cover Plant aspect ear aspect Grain yield val [days] [cm] [cm] (1 ‒ 5) (1 ‒ 5) (1 ‒ 5) of ears per virus leaf spot plant (1 ‒ 5) (1 ‒ 5) [kg/ha] A1702-28 60.18 ± 0.67 63.93 ± 0.80 3.75 ± 0.46 157.48 ± 5.12 74.93 ± 4.70 1.96 ± 0.16 4.08 ± 0.32 2.72 ± 0.24 1.16 ± 0.20 2.36 ± 0.21 1.76 ± 0.81 3,608.82 ± 393.75 A1702-49 61.73 ± 0.67 64.83 ± 0.80 3.10 ± 0.46 169.00 ± 5.13 79.69 ± 4.70 2.40 ± 0.17 3.55 ± 0.32 2.51 ± 0.24 1.06 ± 0.20 1.86 ± 0.21 2.04 ± 0.81 3,969.08 ± 394.28 A1702-53 61.37 ± 0.67 65.21 ± 0.80 3.85 ± 0.46 167.58 ± 5.12 74.05 ± 4.70 2.32 ± 0.16 4.08 ± 0.32 2.58 ± 0.24 1.70 ± 0.20 1.85 ± 0.21 0.89 ± 0.81 3,552.08 ± 393.71 A1706-2 60.37 ± 0.66 63.17 ± 0.78 2.80 ± 0.45 185.35 ± 5.01 84.08 ± 4.59 1.97 ± 0.16 3.26 ± 0.31 1.99 ± 0.24 0.98 ± 0.20 1.54 ± 0.21 2.35 ± 0.79 4,539.73 ± 385.00 A1736-12 58.30 ± 0.67 61.14 ± 0.79 2.84 ± 0.45 188.24 ± 5.08 79.24 ± 4.66 2.78 ± 0.16 3.73 ± 0.32 2.88 ± 0.24 1.00 ± 0.20 1.67 ± 0.21 3.17 ± 0.80 4,024.42 ± 390.46 A1736-13 59.51 ± 0.65 62.15 ± 0.78 2.64 ± 0.44 180.94 ± 4.99 72.31 ± 4.58 2.26 ± 0.16 3.03 ± 0.31 2.33 ± 0.23 0.65 ± 0.20 1.68 ± 0.21 3.02 ± 0.79 3,277.07 ± 383.70 A1736-6 59.48 ± 0.67 60.83 ± 0.80 1.35 ± 0.46 162.31 ± 5.14 64.27 ± 4.71 2.26 ± 0.17 3.66 ± 0.32 3.13 ± 0.24 0.78 ± 0.20 1.55 ± 0.21 2.45 ± 0.81 3,536.24 ± 394.86 ife Hybrid-3 59.21 ± 0.66 62.40 ± 0.78 3.19 ± 0.45 166.70 ± 5.04 79.98 ± 4.62 1.62 ± 0.16 3.49 ± 0.32 2.58 ± 0.24 1.30 ± 0.20 1.92 ± 0.21 0.39 ± 0.80 4,009.94 ± 387.45 ife Hybrid-4 60.18 ± 0.67 62.60 ± 0.79 2.42 ± 0.45 181.25 ± 5.08 77.89 ± 4.66 2.15 ± 0.16 3.44 ± 0.32 1.96 ± 0.24 0.87 ± 0.20 1.44 ± 0.21 2.48 ± 0.80 2,367.38 ± 390.36 ly1001-18 58.55 ± 0.66 61.31 ± 0.78 2.76 ± 0.45 173.32 ± 5.01 76.38 ± 4.60 1.91 ± 0.16 3.60 ± 0.31 2.15 ± 0.24 1.40 ± 0.20 1.98 ± 0.21 2.54 ± 0.79 1,831.39 ± 385.32 ly1001-23 60.36 ± 0.68 63.93 ± 0.81 3.57 ± 0.46 177.67 ± 5.22 70.97 ± 4.78 2.04 ± 0.17 3.04 ± 0.33 1.81 ± 0.24 1.09 ± 0.21 1.75 ± 0.22 2.13 ± 0.82 5,059.32 ± 400.89 ly1302-9 62.39 ± 0.66 64.25 ± 0.79 1.86 ± 0.45 172.39 ± 5.06 76.10 ± 4.64 1.81 ± 0.16 3.72 ± 0.32 2.67 ± 0.24 0.87 ± 0.20 1.99 ± 0.21 1.93 ± 0.80 1,411.81 ± 388.76 ly1312-11 63.63 ± 0.66 68.80 ± 0.78 5.18 ± 0.44 167.37 ± 5.00 57.32 ± 4.59 1.82 ± 0.16 3.78 ± 0.31 1.96 ± 0.23 1.13 ± 0.20 1.55 ± 0.21 2.28 ± 0.79 2,428.17 ± 384.50 ly1312-12 65.41 ± 0.67 69.28 ± 0.80 3.87 ± 0.46 135.57 ± 5.14 91.69 ± 4.72 1.88 ± 0.17 3.89 ± 0.32 2.69 ± 0.24 0.70 ± 0.20 1.92 ± 0.21 2.19 ± 0.81 1,105.50 ± 395.19 ly1312-4 60.84 ± 0.67 64.96 ± 0.80 4.12 ± 0.46 169.40 ± 5.12 72.18 ± 4.69 2.17 ± 0.16 3.83 ± 0.32 2.16 ± 0.24 0.95 ± 0.20 1.59 ± 0.21 2.56 ± 0.81 3,404.09 ± 393.43 ly1409 -14 63.92 ± 0.66 67.33 ± 0.78 3.41 ± 0.44 179.89 ± 5.00 82.97 ± 4.58 2.32 ± 0.16 3.95 ± 0.31 1.99 ± 0.23 1.30 ± 0.20 1.68 ± 0.21 3.65 ± 0.79 1,241.19 ± 384.25 ly1409-21 57.85 ± 0.67 59.89 ± 0.80 2.04 ± 0.45 172.40 ± 5.11 79.51 ± 4.69 2.07 ± 0.16 3.35 ± 0.32 2.13 ± 0.24 1.54 ± 0.20 1.60 ± 0.21 0.27 ± 0.81 4,301.51 ± 392.74 ly1501-1 60.09 ± 0.66 61.70 ± 0.78 1.61 ± 0.44 173.87 ± 5.00 84.06 ± 4.59 2.02 ± 0.16 3.34 ± 0.31 2.01 ± 0.23 1.49 ± 0.20 1.65 ± 0.21 1.91 ± 0.79 3,810.13 ± 384.36 ly1501-3 65.24 ± 0.66 68.10 ± 0.79 2.86 ± 0.45 160.87 ± 5.05 73.38 ± 4.63 2.29 ± 0.16 4.10 ± 0.32 2.60 ± 0.24 1.05 ± 0.20 1.91 ± 0.21 2.61 ± 0.80 1,851.60 ± 387.78 ly1501-5 59.73 ± 0.67 62.42 ± 0.80 2.69 ± 0.46 179.83 ± 5.14 78.72 ± 4.71 2.29 ± 0.17 3.25 ± 0.32 2.02 ± 0.24 1.19 ± 0.20 1.47 ± 0.21 3.24 ± 0.81 3,524.62 ± 394.61 ly1501-6 59.76 ± 0.69 63.42 ± 0.81 3.66 ± 0.47 176.22 ± 5.24 74.98 ± 4.80 2.37 ± 0.17 3.22 ± 0.33 2.08 ± 0.25 0.88 ± 0.21 1.36 ± 0.22 1.75 ± 0.83 2,968.62 ± 402.52 ly1501-7 59.45 ± 0.68 62.62 ± 0.81 3.17 ± 0.46 196.80 ± 5.21 88.02 ± 4.77 2.41 ± 0.17 3.48 ± 0.33 2.14 ± 0.24 1.04 ± 0.21 1.57 ± 0.22 3.36 ± 0.82 4,583.16 ± 399.98 ly1501-8 61.20 ± 0.66 65.91 ± 0.79 4.71 ± 0.45 196.37 ± 5.05 74.94 ± 4.63 1.82 ± 0.16 3.38 ± 0.32 2.07 ± 0.24 0.83 ± 0.20 1.90 ± 0.21 2.52 ± 0.80 4,569.94 ± 387.98 ly1501-9 58.77 ± 0.66 61.92 ± 0.78 3.14 ± 0.45 186.94 ± 5.02 84.42 ± 4.61 2.09 ± 0.16 3.42 ± 0.31 2.08 ± 0.24 1.14 ± 0.20 1.61 ± 0.21 2.10 ± 0.79 5,143.77 ± 386.04 Grand mean 60.73 ± 0.42 63.84 ± 0.52 3.11 ± 0.19 174.07 ± 2.68 77.17 ± 1.49 2.13 ± 0.05 3.57 ± 0.06 2.30 ± 0.07 1.09 ± 0.05 1.72 ± 0.05 2.44 ± 0.31 3,338.32 ± 244.08 LSD (0.05) 1.59 1.88 1.08 12.09 11.09 0.39 0.76 0.57 0.48 0.50 1.91 929.06 Oba super 6 (lC) 61.14 ± 0.67 64.24 ± 0.79 3.10 ± 0.45 172.20 ± 5.09 79.29 ± 4.66 2.39 ± 0.16 4.26 ± 0.32 2.70 ± 0.24 1.58 ± 0.20 1.78 ± 0.21 0.58 ± 0.80 3,539.00 ± 390.75 LSD ‒ least significant difference; LC ‒ local check Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 −12 t a b l e 5 Overall performance of maize hybrids based on weight-based and weight-free selection indices An- yield An- silking thesis- Plant ear Husk ear number Curvularia Grain increase Hybrid thesis [days] silking height height cover aspect of ears leaf spot yield over [days] interval [cm] [cm] (1 ‒ 5) (1 ‒ 5) per plant (1 ‒ 5) [kg/ha] check [days] [%] base index top 5 ly1409-21 57.9 59.9 2.0 172.4 79.5 2.1 2.1 1.5 0.3 4,301.5 17.7 ly1501-9 58.8 61.9 3.1 186.9 84.4 2.1 2.1 1.1 2.1 5,143.8 31.2 ife Hybrid-3 59.2 62.4 3.2 166.7 80.0 1.6 2.6 1.3 0.4 4,009.9 11.7 ly1001-23 60.4 63.9 3.6 177.7 71.0 2.0 1.8 1.1 2.1 5,059.3 30.0 ly1501-1 60.1 61.7 1.6 173.9 84.1 2.0 2.0 1.5 1.9 3,810.1 7.1 bottom 5 A1736-6 59.5 60.8 1.4 162.3 64.3 2.3 3.1 0.8 2.4 3,536.2 ‒ A1736-12 58.3 61.1 2.8 188.2 79.2 2.8 2.9 1.0 3.2 4,024.4 ‒ ly1501-3 65.2 68.1 2.9 160.9 73.4 2.3 2.6 1.1 2.6 1,851.6 ‒ ly1312-12 65.4 69.3 3.9 135.6 91.7 1.9 2.7 0.7 2.2 1,105.5 ‒ ly1409-14 63.9 67.3 3.4 179.9 83.0 2.3 2.0 1.3 3.6 1,241.2 ‒ Multivariate selection index top 5 ly1409-21 57.9 59.9 2.0 172.4 79.5 2.1 2.1 1.5 0.3 4,301.5 17.7 ly1501-9 58.8 61.9 3.1 186.9 84.4 2.1 2.1 1.1 2.1 5,143.8 31.2 A1736-12 58.3 61.1 2.8 188.2 79.2 2.8 2.9 1.0 3.2 4,024.4 12.1 ly1501-1 60.1 61.7 1.6 173.9 84.1 2.0 2.0 1.5 1.9 3,810.1 7.1 ly1501-7 59.4 62.6 3.2 196.8 88.0 2.4 2.1 1.0 3.4 4,583.2 22.8 bottom 5 ly1312-4 60.8 65.0 4.1 169.4 72.2 2.2 2.2 0.9 2.6 3,404.1 ‒ ly1501-3 65.2 68.1 2.9 160.9 73.4 2.3 2.6 1.1 2.6 1,851.6 ‒ ly1409-14 63.9 67.3 3.4 179.9 83.0 2.3 2.0 1.3 3.6 1,241.2 ‒ ly1312-12 65.4 69.3 3.9 135.6 91.7 1.9 2.7 0.7 2.2 1,105.5 ‒ ly1312-11 63.6 68.8 5.2 167.4 57.3 1.8 2.0 1.1 2.3 2,428.2 ‒ Rank summation index top 5 ly1409-21 57.9 59.9 2.0 172.4 79.5 2.1 2.1 1.5 0.3 4,301.5 17.7 ly1501-1 60.1 61.7 1.6 173.9 84.1 2.0 2.0 1.5 1.9 3,810.1 7.1 ly1501-9 58.8 61.9 3.1 186.9 84.4 2.1 2.1 1.1 2.1 5,143.8 31.2 ife Hybrid-3 59.2 62.4 3.2 166.7 80.0 1.6 2.6 1.3 0.4 4,009.9 11.7 A1706-2 60.4 63.2 2.8 185.3 84.1 2.0 2.0 1.0 2.3 4,539.7 22.0 bottom 5 ly1409-14 63.9 67.3 3.4 179.9 83.0 2.3 2.0 1.3 3.6 1,241.2 ‒ ly1312-11 63.6 68.8 5.2 167.4 57.3 1.8 2.0 1.1 2.3 2,428.2 ‒ ly1312-4 60.8 65.0 4.1 169.4 72.2 2.2 2.2 0.9 2.6 3,404.1 ‒ ly1312-12 65.4 69.3 3.9 135.6 91.7 1.9 2.7 0.7 2.2 1,105.5 ‒ ly1501-3 65.2 68.1 2.9 160.9 73.4 2.3 2.6 1.1 2.6 1,851.6 ‒ 9 Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 −12 t a b l e 6 selection differentials [%] under various selection indices for grain yield and other agronomic traits An- thesis- Plant ear Husk ear number Curvu- estimate Anthesis silking Grain [days] [days] silking height height cover Aspect of ears laria yield interval [cm] [cm] (1 ‒ 5) (1 ‒ 5) per plant leaf spot [kg/ha] [days] (1 ‒ 5) base index Mean of top 5 59.26 61.97 2.71 175.52 79.79 1.97 2.12 1.31 1.36 4,464.93 Grand mean 60.73 63.84 3.11 174.07 77.17 2.13 2.30 1.09 2.44 3,338.32 selection differential [%] ‒2.43 ‒2.93 ‒12.76 0.83 3.40 ‒7.41 ‒7.81 20.86 ‒44.35 33.75 Multivariate selection index Mean of top 5 58.89 61.45 2.56 183.65 83.05 2.27 2.25 1.24 2.16 4,372.60 Grand mean 60.73 63.84 3.11 174.07 77.17 2.13 2.30 1.09 2.44 3,338.32 selection differential [%] ‒3.03 ‒3.74 ‒17.59 5.50 7.62 6.95 ‒2.40 14.23 ‒11.50 30.98 Rank summation index Mean of top 5 59.26 61.81 2.56 177.05 82.41 1.95 2.16 1.29 1.40 4,361.02 Grand mean 60.73 63.84 3.11 174.07 77.17 2.13 2.30 1.09 2.44 3,338.32 selection differential [%] ‒2.42 ‒3.17 ‒17.76 1.71 6.79 ‒8.07 ‒6.24 18.68 ‒42.57 30.64 selection differential for grain yield (Adebayo et al. COnClusiOns 2017; de santiago et al. 2019; silva et al. 2020). the selection differentials under Rsi were highest the results obtained showed wide genetic vari- only for anthesis-silking interval and husk cover rat- ability among the newly developed pro-vitamin A ing, although comparable with the other two indi- (PVA) enriched maize hybrids evaluated under the ces for grain yield and other agronomic. this result derived savanna agroecology. the three selection highlights the efficiency of the weight-free selection indices used in this study identified similar hybrids index (Rsi) which does not require assigning eco- as superior for grain yield and other agronomic nomic weights to each trait, the parameters are easier traits. the base index had good selection differen- to compute and handle (Crosbie 1980; Ajala 2010; tial values for all traits measured indicating its effi- Crevelari et al. 2018). Furthermore, the ranking of ciency in identifying outstanding performance. the values of Rsi had a strong negative correlation with identified superior three-way cross PVA maize hy- the ranking of values of Msi (r = ‒0.86; P < 0.001) brids (ly1409-21, ly1501-9 and ly1501-1) with and base index (r = ‒0.56; P < 0.01). the negative improved productivity and nutrition require further association was due to the ranking method used in evaluations across environments to ascertain the sta- Rsi. with the use of the Rsi approach, the lower bility of their performance and hasten their adop- the rank summed values the better, whereas for the tion by farmers’ in the derived savanna and similar base index and Msi the higher the index values the agro-ecologies. better. The strong significant correlation between these indices indicates the similarity in their ability acknowledgement. the authors appreciate to rank the PVA maize hybrids based on the traits the efforts of the Maize improvement Programme considered. the multivariate index values were not (MiP) of the international institute of tropical Agri- significantly correlated with base index values. culture (iitA), ibadan, nigeria, for the provision of 10 Agriculture (Poľnohospodárstvo), 68, 2022 (1): 1 −12 genetic materials used for this study. they are also hybrids for grain yield and associated traits in three agro- grateful to the students of the department of Crop ecological zones in Ghana. International Journal of Envi-ronment, Agriculture and Biotechnology, 2(4), 2076 ‒ 2087. Production and soil science, Faculty of Agricultural dOi:10.22161/ijeab/2.4.66. sciences for their technical assistance. ewool, M.b., Akromah, R. and Acheampong, P.P. (2016). 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