Acta agriculturae Slovenica, 117/2, 1–8, Ljubljana 2021 doi:10.14720/aas.2021.117.2.1944 Original research article / izvirni znanstveni članek Early detection of sources of resistance to the fall armyworm in some tropically-adapted maize varieties in Southern Nigeria Qudrah Olaitan OLOYEDE-KAMIYO*, Oluwakemi Oluwaseyi ODEYEMI Received October 29, 2020; accepted April 29, 2021. Delo je prispelo 29. oktobra 2020, sprejeto 29. aprila 2021. Early detection of sources of resistance to the fall armyworm in some tropically-adapted maize varieties in Southern Nige- ria Abstract: The outbreak of fall armyworm (FAW), Spodop- tera frugiperda, in Nigeria since 2016 had caused serious socio- economic problem to farmers. Twenty maize varieties adapted to the agro-ecologies of Nigeria were evaluated in five envi- ronments to identify varieties with resistance to the FAW for possible improvement and deployment. The evaluations were under artificial and natural infestation between 2017 and 2018. Data were collected weekly after infestation on severity and in- cidence of FAW and plant height. All trials were terminated at six weeks after sowing. Varieties SUW AN 1 SR, BR LNTP-Y C 6 , AMA TZBR-W C 4 and TZBR ELD 4 C 2 are good sources of re- sistance to FA W which could be used in improvement program. Key words: crop improvement; fall armyworm; insect in- festation, maize; pest resistance, Africa. Institute of Agricultural Research and Training (IAR&T), Obafemi Awolowo University, P .M.B. 5029, Moor Plantation, Apata, Ibadan, Nigeria. * Corresponding author: Qudrah Olaitan Oloyede-Kamiyo Address: Maize Improvement Programme for Southern ecology, IAR&T, Moor Plantation, Ibadan, Nigeria Email address: qudratkamiyo@gmail.com Tel. No.: +2348060993930 Orcid ID: 0000-0002-9409-0259 Zgodnje odkrivanje na ameriško koruzno sovko (Spodoptera frugiperda [J. E. Smith, 1797]) odpornih in tropom prilagoje- nih sort koruze v južni Nigeriji Izvleček: Močan pojav ameriške koruzne sovke (Spo- doptera frugiperda [J. E. Smith, 1797]) kmetom v Nigeriji od leta 2016 povzroča resne socio-ekonomske težave. V pričujoči raziskavi je bilo ovrednotenih dvajset sort koruze, prilagojenih agro-ekološkim razmeram v Nigeriji. Na petih lokacijah so pre- učevali odpornost sort na škodljivca, z namenom njihovega izboljšanja in uvajanja v pridelavo. Ocenjevanja so potekala v letih 2017 in 2018 v naravnih razmerah in v rastlinjaku. Podatki o pojavu škodljivca, obsegu poškodb zaradi gosenic in višini rastlin so se zbirali tedensko. Vsi poskusi so bili končani šest te- dnov po setvi. Sorte kot so SUW AN 1 SR, BR LNTP-Y C 6 , AMA TZBR-W C 4 in TZBR ELD 4 C 2 so se izkazale kot dober vir od- pornosti na škodljivca in bi lahko bile uporabljene v programih za izboljšanje učinkovitosti zatiranja ameriške koruzne sovke. Ključne besede: izboljšanje poljščin; ameriška koru- zna sovka; napadenost z žuželkam i; koruza; odpornost na škodljivce; Afrika. Acta agriculturae Slovenica, 117/2 – 2021 2 Q. O. OLOYEDE-KAMIYO, O. O. ODEYEMI 1 INTRODUCTION Maize (Zea mays L.) yield is limited by several bi- otic and abiotic stresses. Insect pests are one of the major biotic stresses contributing to yield losses of crops in the field with high socio-economic impact. Various control measures are employed which include use of chemicals, cultural control and use of bio-pesticides. For instance, entomopathogenic nematodes have been reported to sig- nificantly reduce number of larvae of Colorado potato beetles, but high cost of the agent limits its use (Laznik et al., 2010). Stem borers used to be the common insect pests of maize especially in the forest zone of Nigeria causing between 20-40 % yield losses (Oloyede-Kamiyo et al., 2011). The fall armyworm (FAW), Spodoptera fru- giperda (J.E. Smith) (Lepidoptera: Noctuidae) also of the family Lepidoptera, has been in Africa for approximately 10 years but in the early 2016, there was an outbreak of the pest on maize in southwest Nigeria. A survey car- ried out in 2016 by Institute of Agricultural Research and Training (I.A.R.&T), Ibadan showed that the pest is widespread, especially in the southwest and some south- ern states. By the end of that year, it has spread to the northern part of the country causing majority of farm- ers to abandon their farms. The larvae of the pest were observed to have caused as high as 100 % damage on maize fields, attacking virtually all the growth stages of the maize crop, from the vegetative stage to cob forma- tion. The menace of this pest has caused loss of millions of dollars especially to commercial farmers who invest with loan from banks, hence posing a serious econom- ic threat to the food security of the country. The report commissioned by the Department for International De- velopment, indicates that the arrival of fall armyworm in Africa has the potential to cause maize yield losses in a range of 8.3 to 20.6 million tonnes per annum, in the ab- sence of any control measure in just 12 maize-producing countries. (Abrahams et al., 2017). FAW has recorded long history of resistance to pesticides and GM toxins (Huesing, 2017). Several insecticides have been tested on the insect since its arrival in Nigeria in 2016 with little success. The heavy dose of different types of insecticide used has long-term effect on the health of maize farm- ers and even the end-users. Development of resistance lines is very crucial to combat the menace and eliminate the health hazard of persistent use of insecticides. In de- veloping FAW resistant maize varieties, there is need to identify resistant source from the existing varieties. Some promising lines have been identified and validated by CIMMYT and KALRO, Kiboko, Kenya (Prasanna, 2018). There is need to identify varieties with resistance to the FAW among the varieties adapted to the agro-ecologies of Nigeria for possible improvement and deployment. This study therefore aims at detecting maize vari- eties with resistance to the FAW at early growth stage among the adapted varieties in Southern Nigeria. 2 MATERIAL AND METHODS Twenty open-pollinated maize varieties were evalu- ated in five environments at different out-stations of the Institute of Agricultural Research and Training (IAR&T), Ibadan, Nigeria, under natural and artificial FA W infesta- tion between 2017 and 2018. The varieties were sourced from the International Institute of Tropical Agriculture (IITA), and Institute of Agricultural Research and Train- ing (IAR&T), Ibadan, Nigeria. Some of varieties used have undergone cycles of recurrent selection for resist- ance to stem borer species, Sesamia calamistis (Hamp- son) and Eldana saccharina (W alker). The maize varieties used with their attributes are presented in Table 1. Out of the five environments, one was under arti- ficial infestation in the screen house in Ibadan (Lat.7 o 24 / 7.06 // N, Long. 3 o 55 / 2.33 // E, 225m above sea level) in November 2017. The remaining four environments were under natural infestation on the field at Amakama in the humid rain forest (Lat. 5 o 26 / 40 // N, long. 7 o 28 / 49 // E, 154.25 m above sea level), Ikenne in rain forest (Lat. 6 o 51 / 57 // N, Long. 3 o 42 / 55 // E, 70 m above sea level), and ear- ly and late seasons in Ibadan in derived savanna of Nige- ria. The field evaluated commenced in April 2018 (early season in Ibadan), June 2018 in Ikenne and Amakama, and in October 2018 for late season in Ibadan. The ex- periment was laid out in a randomized complete design in three replications. Each plot on the field was a two-row plot of 5 m long with plant spacing of 75 cm between rows and 50 cm within rows with two plants per stand. No insecticide was used to control S. frugiperda, being the only major pest around. However, other agronomic practices were carried out appropriately. Pre-emergence herbicide, comprising mixture of atrazine (Southern AG) and paraquat (Syngenta, United states) was used a day after planting, with one manual weeding at four weeks after planting. NPK fertilizer and urea were applied at 10 days and 4 weeks after planting, respectively at the rate of 60 kg N ha -1 each. For the artificial infestation in the screen house, each plant was infested with average of six first instar larvae at two weeks after planting using camel hair brush. Data collection started in the screen house at a week after infestation, while data commenced on the field at a week after the first notice of infestation on the plants. Plant height was taken in centimeter on five tagged plants per plot using ruler. Severity of infestation was rated per plot on a scale of 1-9 based on the level of feeding on the Acta agriculturae Slovenica, 117/2 – 2021 3 Early detection of sources of resistance to the fall armyworm in some tropically-adapted maize varieties in Southern Nigeria leaves, presence of frass, and overall effects on the plants (Prasanna, 2018). Incidence of infestation was taken by counting the number of plants infested by the pest per plot and expressed as percentage of plant stands per plot. All data were taken weekly till termination of the experi- ment. The trials were terminated at six weeks after sow- ing (W AP). Percentage data were transformed using arcsine before analysis. Means were separated using least sig- nificant difference (LSD). Combined analysis of variance was performed using SAS, version 9.2. Rank Summation Index (RSI) of Mulumba and Mock (1978) was used to rank the varieties according to their level of resistance us- ing severity and incidence at 1 and 4 weeks after infesta- tion as selection criteria. Principal component analysis was conducted to determine the contribution of the traits to the observed variation. The traits contributing most were then used to perform cluster analysis. Similarities were measured based on Euclidean distance. Table 1: Maize varieties used for the study with their attributes *The attributes are from the names of the varieties. The source indicated the producers of the varieties. TZBR: Tropical Zea Borer Resistance; SR: Streak Resistance; DMRSR: Downy Mildew Resistance Streak Resistance; ELD: Eldana; IITA: International Institute of Tropical Agriculture; IAR&T: Institute of Agric. Research and Training s/n Name Kernel colour *Source *Attribute 1 TZBR COMP 1-Y C 3 Ye l l ow IITA  Stem borer resistant 2 SUW AN-1-SR-Y Ye l l ow IITA  Streak resistant 3 TZBR COMP-1-W C 2 White IITA  Stem borer resistant 4 TZPB-SR-W White IITA   Streak resistant 5 TZBR COMP-2-Y C 3 Ye l l ow IITA  Stem borer resistant 6 ART/98/SW1 Ye l l ow IAR&T  High protein maize 7 TZBR ELD 4-Y C 2 Ye l l ow IITA Resistant to stem borer (Eldana sp.) 8 ART/98/SW6-OB White IAR&T  Quality protein maize 9 TZBR COMP-2-W C 2 White IITA  Stem borer resistant 10 TZE-COMP5 White IITA Striga resistant 11 BR9928 DMRSR Ye l l ow IAR&T Resistant to stem borers, downy mildew and streak 12 ART/98/ILE-1-OB White IAR&T  Quality protein maize 13 AMA TZBR-Y C 1 Ye l l ow IITA  Stem borer resistant 14 DMR-ESR-Y Ye l l ow IAR&T Downy mildew and Streak resistance 15 BR LNTP-Y C 6 Ye l l ow IITA  Stem borer resistant, tolerant to low soil nitrogen 16 PRO-VIT. A Ye l l ow IAR&T Provitamin A enriched 17 AMA TZBR-W C 4 White IITA  Stem borer resistant 18 TZE BR-ELD3-W White IITA Resistant to stem borer (Eldana sp.) 19 TZBR ELD 4-W C 2 White IITA Resistant to stem borer (Eldana sp.) 20 BR9943 DMRSR White IAR&T Resistant to stem borers, downy mildew and streak Acta agriculturae Slovenica, 117/2 – 2021 4 Q. O. OLOYEDE-KAMIYO, O. O. ODEYEMI 3 RESULTS The weekly FAW severity and incidence level is pre- sented in Table 2. Severity was high at early stage (1-2 weeks after infestation) but reduced as the plant grow older. FAW incidence varied among the maize varieties. It increased over time in some, while it reduced in some. The level of severity and incidence was more pronounced under artificial infestation than natural infestation. Se- verity was the least in ‘TZBR ELD 4-W C 2 ’ under natu- ral infestation, and in ‘TZBR COMP2-Y C 3 ’ under arti- ficial infestation. FAW incidence reduced drastically in ‘BR9943 DMRSR’ from 1-4 weeks after infestation (23.6 %, 15.6 %, 5.8 % and 4.2 % respectively) under natural in- festation, and in ‘TZPB SR-W’ under artificial infestation (83.3 %, 58.3 %, 16.7 % and 0 % respectively). Mean square of variety was significant for severity and plant height at one week after infestation under ar- tificial infestation (Table 3), while under natural infesta- tion (Table 4), mean square of environment and mean square of variety were significant for almost all the traits. Mean squares of environment by variety interaction was also significant for severity at 3 weeks after infestation, incidence at 2 and 4 weeks after infestation, and plant height at 1and 3 weeks after infestation (Table 4). The top 25 % maize variety selected using RSI is presented in Table 5. Three of the five maize varieties se- lected under artificial infestation are stemborer resistant varieties. The BR LNTP-Y C 6 selected as the best resistant variety under artificial infestation has been tested at IITA to be resistant to the FAW . ‘ ART/98/SW6-OB’ is a quality protein maize. Variety developed by IAR&T, while SUW AN 1 SR is an old variety, resistant to streak. All the maize selected under natural infestation are stem borer resistant varie- ties except ‘SUW AN 1 SR-W . SUW AN 1 SR-W’ , ‘ AMATZ- BR-W C 4 ’ and ‘TZBR ELD 4’ were commonly selected under both conditions although the white version of ‘TZBR ELD 4’ was selected under natural infestation. The result of principal component analysis revealed that PCA 1, 2 and 3 accounted for 85.5 % and 87.9 % of the variations observed under artificial and natural in- festation respectively (Table not shown). The variables responsible for the observed variation under artificial infestation were incidence at 1, 2, 3 and 4 weeks after infestation, while incidence at 1, 2, 3 and 4 weeks after infestation and plant height at 3 and 4 weeks after infes- tation were responsible for the variations under natural infestation. At 50 % similarity distance, 9 distinct groups were formed under artificial infestation (Figure 1). Varieties TZBR Comp 1-W (G1), BR LNTP-Y C 6 (G5), SUW AN 1 SR (G6), BR9928 DMRSR (G7) and TZPB SR (G9) stood alone in their groups. ‘ ART/98/SW6-OB’ and ‘TZBR ELD 4-Y C 2 ’ clustered together in a group (G4). Other varie- ties clustered in three different groups. However, at 50 % similarity distance, six distinct groups were formed under natural infestation (Figure 2). Varieties BR9943D- MRSR (G1), TZEBR ELD 3-W (G3), AMATZBR-Y C 1 (G5) stood alone in their groups. ‘BR LNTP-Y C 6 ’ , ‘ AM- ATZBR-W C 4 ’, ‘DMRESR-Y’, ‘TZBR Comp-Y C 3 ’ and ‘TZBR ELD 4-W C 2 ’ clustered together in a group (G2), while others clustered in two other groups. It is worth noting here that the top varieties selected by RSI under artificial infestation fell in the best groups in the dendrogram (G4, 5 & 6). Similar result was ob- served under natural infestation. The varieties selected by RSI clustered in G1 and G2 in the dendrogram in cluster analysis. 4 DISCUSSION The economic effect of the fall armyworm could be determined on the field at early growth stage of maize plant through random sampling on the field, location of infestations in the field, larval size, and where the larvae are feeding on the plant. Hence, levels of infestation at this stage, especially under artificial infestation or hot spots suggest the inherent resistance of each maize vari- ety to the pest. In the present study, it was observed that severity and incidence level reduced over time in some of the varieties although at different pace. The resistance check, ‘BR LNTP-Y C 6 ’ had its severity and incidence level reduced to 1 and 8 % respectively, after 4 weeks of infestation. This was comparable to what was observed in some other varieties such as ART/98/ SW6-OB, TZPB SR and TZBR ELD 4-Y C 2 . Ni et al. (2011) had similar observation in some of the germplasms evaluated. This observation suggested that the varieties had the ability to tolerate/overcome the effects of FAW . Hence, substan- tial level of resistance to the fall armyworm was indicated in them. Williams et al. (1998) reported that maize that is resistant to FAW sustained less leaf-feeding damage, and larvae feeding on resistant maize grew more slowly. Some promising CIMMYT maize inbreds identified and validated in Kiboko, Kenya had their leaf damage ratings between 2.0 and 6.0 (Prasanna, 2018). This rating was similar to what was obtained in the present study. The significant mean squares of environment, vari- ety and the environment by variety interaction for most of the traits under natural infestation was similar to those observed by Giaveno et al. (2004), Giaveno and Ferrero (2003) and Ni et al. (2011). The significant environment by variety interaction observed for incidence and sever- ity of FAW could be due to erratic performance across Acta agriculturae Slovenica, 117/2 – 2021 5 Early detection of sources of resistance to the fall armyworm in some tropically-adapted maize varieties in Southern Nigeria Table 2: Mean performance of the 20 maize varieties for resistant traits under FAW infestation in the five environments between 2017 and 2018 W AI: weeks after infestation; Scale 1-9: 1 no infestation, 9 severe infestation; SE: Standard error; CV: coefficient of variation NI: Natural infestation; AI: Artificial infestation Entry Severity 1W AI (1-9)  Severity 2W AI (1-9)  Severity 3W AI (1-9)  Severity 4W AI (1-9)  Incidence 1W AI (%) Incidence 2W AI (%) Incidence 3W AI (%) Incidence 4W AI (%)   NI AI NI AI NI AI NI AI NI AI NI AI NI AI NI AI AMA TZBR-W C4 3.67 4.33 3.11 4.00 1.67 2.00 1.67 1.33 25.62 100.00 18.67 83.33 14.54 58.33 16.67 16.67 AMA TZBR-Y C1 4.50 4.67 3.56 5.33 1.83 2.67 3.67 2.00 37.46 91.67 22.98 91.67 22.54 75.00 45.83 33.33 ART/98/SW1-Y 3.83 5.33 3.88 4.67 2.80 3.00 3.00 1.33 30.75 91.67 33.47 83.33 31.17 58.33 29.17 16.67 ART/98/SW6-OB-W 4.50 5.67 4.11 4.67 2.83 2.00 4.33 1.00 33.89 83.33 38.16 83.33 29.52 50.00 41.67 0.00 BR 9943 DMRSR 3.17 5.33 2.56 3.67 1.60 2.00 1.67 1.33 23.57 91.67 15.57 83.33 5.78 50.00 4.17 25.00 BR LNTP-Y C6 4.00 4.67 3.00 3.33 2.00 2.00 2.00 1.00 23.06 75.00 19.27 66.67 11.56 58.33 16.67 8.33 BR9928 DMRSR 3.50 6.00 3.00 3.33 2.50 2.00 2.67 1.33 29.63 58.33 25.95 50.00 17.90 33.33 33.33 16.67 DMR-ESR-Y 3.67 5.33 3.56 4.67 2.17 2.33 2.00 1.00 42.53 100.00 30.75 83.33 20.97 66.67 16.67 8.33 ART/98/ILE-1-OB 5.20 5.00 3.78 4.67 2.33 3.33 3.00 1.33 33.47 100.00 31.00 100.00 24.56 83.33 29.17 33.33 PRO-VIT. A 4.17 4.67 3.22 4.00 2.00 2.67 2.00 2.33 38.08 75.00 23.18 50.00 15.85 41.67 25.00 33.33 SUW AN-1-SR-Y 3.00 4.33 2.89 4.00 2.17 2.67 2.33 1.67 16.04 50.00 17.76 75.00 26.57 66.67 17.46 25.00 TZBR COMP-1-W C2 3.67 4.67 3.67 4.00 3.00 2.67 2.00 2.33 22.44 83.33 17.67 75.00 28.12 66.67 25.72 50.00 TZBR COMP-2-W C2 4.17 6.67 4.00 5.00 3.33 2.33 3.33 1.67 33.78 100.00 35.95 75.00 27.28 50.00 37.50 8.33 TZBR COMP-2-Y C3 3.00 3.00 3.00 3.33 3.33 1.33 4.67 2.00 26.07 75.00 26.85 58.33 31.77 25.00 45.83 41.67 TZBR COMP 1-Y C3 3.20 4.33 3.00 4.67 1.33 2.33 1.67 1.67 24.38 91.67 16.10 66.67 13.76 41.67 10.00 25.00 TZBR ELD 4-W C2 2.17 4.67 2.22 4.00 1.50 1.33 1.67 1.33 25.94 66.67 24.06 66.67 17.63 33.33 12.50 33.33 TZBR ELD 4-Y C2 2.67 4.33 2.78 4.33 2.50 2.33 4.00 1.00 23.30 100.00 22.71 91.67 29.87 41.67 50.00 0.00 TZE BR-ELD3-W 3.50 4.00 3.13 4.00 2.00 1.33 2.00 2.00 26.39 75.00 17.61 58.33 0.00 25.00 16.67 41.67 TZE-COMP5 3.50 6.33 3.29 5.00 1.50 2.67 3.33 1.33 26.19 100.00 29.40 91.67 21.43 50.00 29.17 25.00 TZPB-SR-W 4.00 6.00 3.89 4.00 3.17 0.67 3.33 1.00 27.95 83.33 39.77 58.33 24.73 16.67 42.59 0.00 Mean 3.64 5.00 3.28 4.23 2.30 2.18 2.72 1.50 28.58 84.58 25.41 74.58 20.83 49.58 27.29 22.08 SE 0.27 0.15 0.19 0.17 0.12 0.15 0.19 0.09 2.98 2.92 2.12 3.23 2.29 3.73 3.43 3.31 LSD (0.05) 2.68 1.54 2.33 2.41 1.35 1.90 1.56 1.03   30.04 33.50  32.55 41.54 42.0  44.89   39.2 40.65 cv (%) 45.24 18.70 43.72 34.47 36.21 52.70 35.40 41.46 64.70 23.96 78.84 33.70 108.18 54.77 70.98 111.40 Acta agriculturae Slovenica, 117/2 – 2021 6 Q. O. OLOYEDE-KAMIYO, O. O. ODEYEMI Table 3: Mean squares from analysis of variance for the traits studied under artificial infestation in Ibadan in 2017 Table 4:. Mean squares from analysis of variance for the traits studied under natural infestation in the four environments in 2018 Table 5: The top maize varieties selected under artificial and natural SVR 1,2,3&4: FAW severity (scale1-9) at 1,2,3&4 weeks after infestation; INC 1, 2 , 3 & 4: FAW incidence (%) at 1, 2, 3 & 4 weeks after infestation; PH 1, 2, 3 & 4: Plant height at 1, 2, 3 & 4 weeks after infestation; df: degree of freedom; *,** : Significant at p = 0.05 and 0.01 respectively SVR 1, 2, 3 & 4: FAW severity (scale1-9) at 1, 2, 3 & 4 weeks after infestation; INC 1, 2, 3 & 4: FAW incidence (%) at 1, 2, 3 & 4 weeks after infestation; PH 1, 2, 3 & 4: Plant height at 1, 2, 3 & 4 weeks after infestation; df: degree of freedom; *,** : Significant at p = 0.05 and 0.01 respectively FAW infestation using RSI (25 % selection intensity) *Selection under natural infestation is based on the pooled data for the four environments Source df INC 1 INC 2 INC 3 INC 4 SVR 1 SVR 2 SVR 3 SVR 4 PH 1 PH 2 PH 3 PH 4 Variety 19 0.17 0.13 0.18 0.16 2.31** 1.02 1.25 0.58 13.24* 29.1 42.26 52.11 Rep 2 0.20 0.07 0.39 0.44 2.62 3.22 1.52 0.65 1.01 25.54 18.60 38.90 Error  38 0.10 0.15 0.14 0.13 0.86 2.13 1.32 0.39 7.08 16.93 26.23 39.41 Source df SVR 1 SVR 2 SVR 3 SVR 4 INC 1 INC 2 Env 3 701.53** 362.98** 4.54** -- 22.54** 8.37** Variety (V) 19 2.40 2.2 9.98** 20.42** 0.08 0.19* Rep (Env) 8 2.44 2.03 2.15** 2.75** 0.64** 0..31** Env x V 57 2.2 1.92 2.16** 0.001 0.10 0.16** Error 152 2.71 2.06 0.69 0.92 0.10 0.09 Source INC 3 INC 4 PH 1 PH 2 PH 3 PH 4 Env 5.78** 20.67** 1416.84** 8009.34** 12091.77** 24084.52** Variety (V) 0.74** 0.75** 83.92** 16.29 624.76** 120.10* Rep (Env) 0.14 0.24** 3.12 375.66** 54.89** 1032.16** Env x V 0.13 0.25** 6.10* 27.65 60.41** 83.09 Error 0.11 0.09 3.26 20.57 23.97 76.48 s/n Artificial infestation Natural infestation* 1 BR LNTP-Y C6 BR 9943 DMRSR 2 ART/98/SW6-OB-W TZBR ELD 4-W C2 3 SUW AN-1-SR-Y TZBR COMP 1-Y C3 4 AMA TZBR-W C4 AMA TZBR-W C4 5 TZBR ELD 4-Y C2 SUW AN 1-SR Y Acta agriculturae Slovenica, 117/2 – 2021 7 Early detection of sources of resistance to the fall armyworm in some tropically-adapted maize varieties in Southern Nigeria Figure 1: Dendrogram of the 20 maize varieties under artificial fall armyworm infestation based on Euclidean similarity distance Figure 2: Dendrogram of the 20 maize varieties under natural FAW infestation based on Euclidean similarity distance environments (Giaveno et al., 2004) or variation of the buildup of the pest in different environments used for this study. The significant mean squares of variety showed high level of variability among the varieties for resistance to FAW . Oliveira et al. (2018) working on popcorn under fall armyworm reported significant differences among genotypes for both nutritional and physical traits. The result of RSI corroborates the outcome of clus- ter analysis under both conditions. Three of the top 5 se- lected varieties under artificial infestation using RSI are stem borer resistant and also belong to the best groups under cluster analysis. Under natural environment, four of the selected varieties are stem borer resistant. Some of the varieties selected by RSI clustered in the same group with the resistant check ‘BR LNTP-Y C 6’ , while some stood alone in distinct groups. This study suggested some levels of relationship between stem borer resistance and FAW resistance. Hence, multiple insect resistance could be developed in these varieties. Ni et al. (2011) recorded similar observation in the western corn rootworm resist- ant variety, CRW3(S1) C6 which showed resistance to the FAW. Previous reports on multiple insect resistance has been limited to similar plant tissues, such as multiple leaf-feeding insects (Wilson et al., 1995; Abel et al., 2000), and multiple ear-feeding insects and ear-colonizing dis- eases (Ni et al., 2007; Ni et al., 2008). It is worthy to note that ‘ ART/98/SW6-OB’ and ‘SU- WAN 1-SR’ selected by RSI, and also grouped with the resistant check in cluster analysis are non-stem borer re- sistance varieties. ‘ ART/98/SW6-OB’ is a quality protein maize developed by the Institute of Agricultural research and Training (IAR&T), while ‘SUWAN 1 SR’ is a streak resistant maize variety. Acta agriculturae Slovenica, 117/2 – 2021 8 Q. O. OLOYEDE-KAMIYO, O. O. ODEYEMI 5 CONCLUSION This study suggested that there is a relationship be- tween resistance to stem borer and FAW . It also revealed that varieties BR LNTP-Y C 6 , AMA TZBR-W C 4 and TZBR ELD 4 C 2, ART/98/SW6-OB and SUW AN 1-SR are good resistant source which could be used in a breeding program for resistance to FAW . 6 REFERENCES Abel, C.A., Berhow, M.A., Wilson, R.L., Binder, B.F . & Hibbard, B.E. (2000). Evaluation of conventional resistance to Eu- ropean corn borer (Lepidoptera: Crambidae) and western corn rootworm (Coleoptera: Chrysomelidae) in experi- mental maize lines developed from a backcross breeding program. Journal of Economic Entomology, 93, 1814-1821. https://doi.org/10.1603/0022-0493-93.6.1814 Abrahams, P., Bateman, M., Beale, T., Clottey, V., Cock, M., Colmenarez, Y . . ,., (2017). Fall armyworm: Impacts and Im- plications for Africa. Department of Biosciences, University of Exeter. CABI, UK. Giaveno, C.D & Ferrero, J. (2003). Introduction of tropical maize genotypes to increase silage production in the cen- tral area of Santa Fe, Argentina. Crop Breeding and Applied Biotechnology, 3, 203-208. https://doi.org/10.12702/1984- 7033.v03n02a01 Giaveno, C.D., Paravano, A.S., Curis, M.C. & Portmann, E. (2004). Breeding maize for resistance to fall armyworm (Spodoptera frugiperda) in Argentina: genetic and environ- mental effects. Crop Breeding and Applied Biotechnology, 4, 434-440. https://doi.org/10.12702/1984-7033.v04n04a09 Huesing, J. (2017). Fall Armyworm in Africa: A Guide for Inte- grated Pest Management. SDSN carbon-free e-conference ‘Responding to Fall Armyworm in Africa’, 22-26 October 2017. USAID Washington DC, USA. Laznik, Z., Toth, T., Lakatos, M.,Vidrih, S. &Trdan, S. (2010). Control of the Colorado potato beetle (Leptinotarsa de- cemlineata [Say]) on potato under field conditions: a com- parison of the efficacy of foliar application of two strains of Steinernema feltiae (Filipjev) and spraying with thiametox- am. Journal of Plant Diseases and Protection, 117, 129-135. https://doi.org/10.1007/BF03356348 Mulumba, N.N & Mock, J.J. (1978). Improvement of yield po- tential of Eto Blanco maize (Zea mays L.) population by breeding for plant traits. Egyptian Journal of Genetics and Cytology, 7, 40-51. Ni, X. Z., Chen, Y. G., Hibbard, B. E., Wilson, J. P., Williams, W. P., Buntin, G. D., Ruberson, J. R. & Li, X. C. (2011). Foliar resistance to fall armyworm in corn germplasm lines that confer resistance to root- and ear-feeding in- sects. Florida Entomologist, 94(4), 971-981. https://doi. org/10.1653/024.094.0434 Ni, X., Krakowsky, M.D., Buntin, G.D., Rector, B.G., Guo, B. & Snook, M.E. (2008). Identification of multiple ear-coloniz- ing insect and disease resistance in CIMMYT maize inbred lines with varying levels of silk maysin. Journal of Econom- ic Entomology, 101, 1455-1465. https://doi.org/10.1093/ jee/101.4.1455 Ni, X., Xu, W., Krakowsky, M.D., Buntin, G. D., Brown, S. L., Lee, R.D. & Coy, A.E. (2007). Field screening of experimen- tal corn hybrids and inbred lines for multiple ear-feeding insect resistance. Journal of Economic Entomology, 100, 1704-1713. https://doi.org/10.1093/jee/100.5.1704 Oliveira N.C., Suzukawa, A.K., Pereira, C.B., Santos, H.V., Hanel, A., De Albuquerque, F.A. & Scapim, C.A. (2018). Popcorn genotypes resistance to fall armyworm. Ciência Ru- ral, Santa Maria, 48(2), 1-6. https://doi.org/10.1590/0103- 8478cr20170378 Oloyede-Kamiyo, Q.O., Ajala, S.O. & Akoroda, M.O. (2011). Variability for resistance to the pink stem borer (Sesamia calamistis Hampson) and the sugarcane borer (Eldana sac- charina Walker) in two tropical maize populations. May- dica ,56, 257-264. Prasanna, B.M. (2018). Breeding for Native Genetic Resistance to Fall Armyworm. CIMMYT. Hohenheim; Sept 11, 2018. Williams, W. P., Davis, F. M., Buckley, P. M., Hedin, P. A., Baker, G. T. & Luthe, D. S. (1998). Factors associated with resistance to fall armyworm (Lepidoptera: Noctuidae) and southwestern corn borer (Lepidoptera: Crambidae) in corn at different vegetative stages. Journal of Economic Entomolo- gy, 91(6), 1471-1480. https://doi.org/10.1093/jee/91.6.1471 Wilson, R. L., Abel, C. A., Wiseman, B. R., Davis, F. M., Wil- liams, W . P ., Barry, B. D. & White, W . H. (1995). Evaluation for multiple pest resistance in European corn borer, Ostrin- ia nubilalis resistant maize accessions from Peru. Journal of Kansas Entomological Society, 68, 326-331.