Suresh Lingadahalli Mahabaleswara

Northern leaf blight (NLB), caused by Exserohilum turcicum , threatens maize production in Ethiopia, with yield losses of 15.0%–70.0%. This two‐year study (2023–2024) evaluated three dual‐mode fungicides—Opera Max (pyraclostrobin + epoxiconazole), Amistar Top (azoxystrobin + difenoconazole) and Artea 330 EC (propiconazole + cyproconazole)—applied at stem elongation (GS30), tasselling (GS51) and early grain filling (GS51 + 3w) across two agroecological sites. Disease severity was quantified using percent severity index (PSI) and area under the disease progress curve (AUDPC). Fungicide application at GS51 significantly reduced disease progression ( F _9,110 = 18.44, p < 0.001). Opera Max at GS51 achieved the lowest AUDPC (328%‐days) and final PSI (28.9%), representing 49.0% and 59.5% reductions versus controls, respectively. This treatment increased seed yield by 34.0% (4.24 vs. 3.16 t/ha) and thousand‐seed weight by 22.0% (316 vs. 258 g). Two‐way ANOVA confirmed significant main effects of fungicide chemistry ( F _2,99 = 5.83, p = 0.004) and application timing ( F _2,99 = 43.73, p < 0.001), with no significant interaction ( p = 0.89), indicating that timing is more critical than product selection. Regression analysis showed each 1.0% increase in R4 severity reduced yield by ~28 kg/ha ( R ² = 0.42, p < 0.001). Economic analysis prioritized Opera Max at GS51, delivering a marginal rate of return of 258.0% and net benefits of $1704/ha. These findings underscore the importance of precision timing for sustainable intensification of Ethiopian maize production.

Maize lethal necrosis (MLN) is a severe disease caused by the combined infection of maize chlorotic mottle virus (MCMV) and a potyvirus, most often sugarcane mosaic virus (SCMV). This disease seriously threatens food security across sub-Saharan Africa (SSA). We investigated a major-effect quantitative trait locus for resistance on chromosome 6, named the maize lethal necrosis susceptibility locus 1 ( qMLNS1 ), derived from the Thai line KS23-6. Fine mapping and CRISPR-Cas9 editing of the candidate genes within the narrowed 105 kb interval revealed a peroxisomal peptidase as the underlying cause of susceptibility. Confocal microscopy confirmed the localization of the MLNS1 protein within peroxisomes. Targeted knockout of the Mlns1 gene in the susceptible elite line CML536 from SSA conferred resistance comparable to KS23-6 in field trials conducted in Naivasha, Kenya. This knockout specifically blocked MCMV accumulation without affecting SCMV. The edited lines showed no yield penalty or agronomic defects under disease-free conditions. Our findings uncover a mechanistic link between a peroxisomal enzyme and viral susceptibility. They also establish a rapid, scalable gene editing strategy for incorporating MLN resistance into elite germplasm, offering a model for combating similar viral diseases in staple crops globally.

Maize (Zea mays L.) ear rot is an important disease hindering maize production, and Fusarium species have been implicated as a primary cause worldwide. The disease causes substantial yield loss and often results in mycotoxin contamination of grain. In the present study, a preharvest maize ear rot survey was conducted in Ethiopia’s 10 major maize-growing zones during the 2020 and 2021 cropping seasons. The goal was to identify the main Fusarium spp. associated with preharvest ear rots and determine if they could cause stalk rot of maize in Ethiopia. Based on morphological characteristics, 775 Fusarium isolates were recovered and grouped into four main Fusarium species complexes (FSCs). Ninety-two representative FSC isolates belonging to eight Fusarium spp. were identified by molecular phylogenetic analysis using concatenated partial sequences of translation elongation factor-1α and RPB2. The analysis of variance showed isolates selected from all eight identified Fusarium spp. caused maize stalk rot disease symptoms with significant differences in disease severity (P < 0.001) when tested in a pathogenicity assay. Furthermore, F. falciforme, F. oxysporum f. sp. ciceris, and F. cf. tjaetaba are reported for the first time as possible causal agents for maize ear rot in Ethiopia. Knowledge of the possible agents (pathogens) associated with maize ear rot and their potential to cause maize stalk rot disease will help develop effective integrated management strategies for these diseases in Ethiopia.

A systematic evaluation of maize hybrid performance and combining ability was conducted to enhance resistance to maize lethal necrosis (MLN), drought tolerance, and grain yield (GY) in eastern and southern Africa. Thirty-eight early- to intermediate-maturing maize inbred lines, including MLN-tolerant and high-yielding genotypes with drought tolerance and resistance to multiple foliar and insect pests, were crossed with 29 single-cross testers to generate 437 testcross hybrids. These hybrids were evaluated under managed MLN inoculation, drought stress, and optimum conditions across multiple locations. Continuous variation in GY, disease severity, and agronomic traits confirmed quantitative inheritance, with strong positive correlations between GY and ears per plant and negative correlations between MLN severity and yield. Variance analyses revealed highly significant genotypic and genotype × environment interactions, with additive effects predominating across environments (Baker’s ratios 0.85–0.99; heritability 0.69–0.88), supporting effective selection based on general combining ability (GCA). Superior MLN-tolerant hybrids, such as (CKLMARSI0037/CKLTI0139)//CKDHL120312, achieved up to 5.75 t ha ⁻ ¹ under MLN, exceeding commercial checks by over fivefold. Under optimum and drought conditions, top hybrids maintained high yield, foliar disease resistance, short anthesis–silking intervals, and delayed senescence. Specific combining ability (SCA) effects highlighted stress-specific non-additive interactions, particularly under drought, underscoring the need for targeted parental selection. GCA analyses identified across environment and environment-specific favorable parents, including CKDHL120312, CKDHL140910, CKLMARSI0037/CKLTI0139, and CML322/CML543, while GGE biplots confirmed tester discrimination and representativeness. These findings demonstrate that integrating MLN resistance, drought tolerance, and high yield is achievable without compromising other agronomic performance. The study provides a robust framework for selecting elite parents and testers, exploiting additive and non-additive genetic effects, and developing resilient, high-performing maize hybrids for sub-Saharan Africa.

Northern leaf blight (NLB), caused by Exserohilum turcicum , is a major foliar disease constraining maize productivity in sub‐Saharan Africa. This study aimed to (i) estimate combining ability effects, (ii) elucidate the nature of gene action, and (iii) identify superior parents and hybrids for NLB resistance and grain yield (GY). Ten diverse inbred lines were crossed in a half‐diallel design to generate 45 F ₁ hybrids, which were evaluated with three checks at three locations in Ethiopia under natural NLB pressure. Combined analysis of variance revealed highly significant ( p < 0.001) genotypic differences for all traits. The ratio of general combining ability (GCA) to specific combining ability (SCA) mean squares exceeded unity for NLB severity (2.73), GY (2.51), ear aspect (EA) (3.19), number of ears (NE) (2.63), and ear rot (ER) resistance (2.59). However, Baker’s ratio revealed that nonadditive gene action predominated for most traits, with dominance variance accounting for 58%–100% of total genetic variance. Notable exceptions were NE (Baker’s ratio = 0.75), where additive gene action predominated, and EA (0.42), ER (0.34), NLB resistance (0.38), and GY (0.33), which exhibited a mixed genetic architecture where dominance variance exceeded additive variance but the additive component remained sufficient to support GCA‐based selection. Parents CML202 and BK2019DArT196 showed the most favorable GCA values for both NLB resistance (−1.40, −1.35) and yield (0.83, 0.52); crosses BKL22 × SC22 (SCA‐NLB = −1.36, SCA‐GY = 2.62) and VL121146 × CML202 (SCA‐NLB = −1.22, SCA‐GY = 2.18) showed high SCA for both traits. NLB severity and GY were strongly and negatively correlated ( r = −0.75, p < 0.001). The top hybrid, VL121146 × BK2019DArT120, yielded 7.92 t ha ⁻¹ with low NLB severity (2.67), outperforming the best check, BH520, by 15.3%. Narrow‐sense heritability was moderate for NLB resistance ( h ² = 0.30 ± 0.18) and GY ( h ² = 0.27 ± 0.17) on an entry‐mean basis. The mixed genetic architecture for key traits advocates for an integrated breeding strategy combining recurrent selection for additive improvement with strategic hybrid exploitation of dominance variance. Elite parents CML202 and BK2019DArT196 are valuable for the simultaneous improvement of productivity and resistance. The superior specific crosses identified offer immediate potential for hybrid development, demonstrating that the yield–disease trade‐off can be overcome through strategic parent selection and exploitation of complementary gene action.

A systematic evaluation of maize hybrid performance and combining ability was conducted to enhance resistance to maize lethal necrosis (MLN), drought tolerance, and grain yield (GY) in eastern and southern Africa. Thirty-eight MLN-tolerant, lines were crossed with 29 single-cross testers to generate 437 testcross hybrids, evaluated under managed MLN inoculation, drought stress, and optimum conditions across multiple locations. Continuous variation in GY, disease severity, and agronomic traits confirmed quantitative inheritance, with strong positive correlations between GY and ears per plant and negative correlations between MLN severity and yield. Variance analyses revealed highly significant genotypic and genotype × environment interactions, with additive effects predominating across environments (Baker’s ratios 0.85–0.99; heritability 0.69–0.88), supporting effective selection based on general combining ability (GCA). Superior MLN-tolerant hybrids, such as (CKLMARSI0037/CKLTI0139)//CKDHL120312, achieved up to 5.75 t ha⁻¹ under MLN, exceeding commercial checks by over fivefold. Under optimum and drought conditions, top hybrids maintained high yield, foliar disease resistance, short anthesis–silking intervals, and delayed senescence. Specific combining ability (SCA) effects highlighted stress-specific non-additive interactions, particularly under drought, underscoring the need for targeted parental selection. GCA analyses identified across environment and environment-specific favorable parents, including CKDHL120312, CKDHL140910, CKLMARSI0037/CKLTI0139, and CML322/CML543, while GGE biplots confirmed tester discrimination and representativeness. These findings demonstrate that integrating MLN resistance, drought tolerance, and high yield is achievable without compromising other agronomic performance. The study provides a robust framework for selecting elite parents and testers, exploiting additive and non-additive genetic effects, and developing resilient, high-performing maize hybrids for sub-Saharan Africa.

Fusarium ear rot (FER) and Gibberella ear rot (GER) caused by Fusarium species are major diseases affecting maize production in Ethiopia. In addition to reducing quality and yield, these fungi can produce mycotoxins that contaminate maize kernels and, thereby, pose health hazards to humans and livestock. A survey was conducted in 10 administrative zones of Ethiopia within the major maize-growing regions of the country to identify the species of Fusarium associated with ear rot. Twenty kernels were sampled from ears randomly collected from each zone (12 ears per field, 24 fields per zone). Ninety-two fungal isolates recovered from the kernels were tentatively identified as Fusarium based on morphological traits. Subsequently, the species identity of each isolate was determined by DNA sequence analysis of a portion of the translation elongation factor 1-α gene and two noncontiguous fragments of the RNA polymerase II subunit gene. Based on phylogenetic analysis of the data, 37.3% of the isolates recovered from maize kernels were from three species that have not been reported previously in Ethiopia: Fusarium boothii (4.3%), F. meridionale (10.2%), and F. temperatum (22.8%). Completion of Koch’s postulates with selected isolates confirmed that these three species can cause maize ear rot. Information on causal agents of maize ear rots in Ethiopia should be taken into consideration when developing disease management strategies, including breeding for resistance.

Maize (Zea mays L.) is one of the most widely cultivated grain crops globally. In sub-Saharan Africa (SSA), it plays an important role in ensuring both food and income security for smallholder farmers. This study was conducted to (i) assess the performances of testcross hybrids constituted from maize lethal necrosis (MLN) tolerant doubled haploid (DH) lines under various management conditions; (ii) estimate the combining ability effects and determine the nature of gene action in the DH lines; and (iii) identify DH lines and testcross hybrids for resistance to MLN, high grain yield, and other important traits. Eleven DH lines were crossed with 11 single-cross testers using the line-by-tester mating design, and 115 successful testcross hybrids were generated. These hybrids, along with five commercial check hybrids, were evaluated across four optimum management conditions, two MLN artificial inoculations, and one managed drought environment in Kenya. Under each management condition, the effects of genotypes, environments, and genotype-by-environment interactions were significant for grain yield (GY) and most other traits. Hybrids T1/L3, T10/L3, and T11/L3 exhibited higher grain yields under at least two management conditions. A combining ability analysis revealed that additive gene effects were more important than non-additive effects for GY and most other traits, except for leaf senescence (SEN) and MLN disease severity score. DH line L3 exhibited a desirable general combining ability (GCA) effect for GY, while L5 was the best general combiner for anthesis date (AD) and plant height (PH) across all management conditions. DH lines L2, L6, and L7 showed negative GCA effects for MLN disease severity. Single-cross testers T11 and T10 were good general combiners for GY under all management conditions. Hybrids T2/L11, T9/L10, and T2/L10 demonstrated high specific combining ability (SCA) effects for GY under all conditions. This study identified DH lines and testers with favorable GCA effects for grain yield, MLN resistance, and other agronomic traits that can be used in breeding programs to develop high-yielding and MLN-resistant maize varieties. Better-performing testcross hybrids identified in the current study could be verified through on-farm testing and released for commercial production to replace MLN-susceptible, low-yield hybrids grown in the target ecologies.