Genotypic Variation and Seed Morphological Determinants of Maize (Zea mays L.) Performance and Resistance to Bacterial Streak in a Naturally Infected Field

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Bukola Ojo Adediran¹ , Oluwafemi Michael Adedire² , Olufemi Stephen Olaoye³

¹Department of Crop Production Technology, School of Agriculture, Federal College of Agriculture, Ibadan, Nigeria

²Department of Microbiology, School of Applied Sciences, Federal College of Agriculture, Ibadan, Nigeria

³Department of Animal Production Technology, School of Agriculture, Federal College of Agriculture, Ibadan, Nigeria

Corresponding Author Email: bukoladoriginal@gmail.com

DOI : https://doi.org/10.51470/JPB.2026.5.1.11

Abstract

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Introduction

Maize (Zea mays L.) is one of the world’s most important cereal crops, serving as a primary source of food, feed, and industrial raw material. Maize (Zea mays) cultivation and exploration have been at their all-time high in Nigeria and indeed, all parts of the globe [2]. In many maize-growing regions, particularly in tropical and subtropical environments, productivity is constrained by a wide range of biotic stresses, among which bacterial diseases have gained increasing importance [19]. One of the emerging bacterial diseases affecting maize is Bacterial Leaf Streak (BLS), caused by Xanthomonas vasicola pv. vasculorum (Xvv) [14]. The disease is characterized by elongated, water-soaked lesions on leaves that coalesce to form streaks, leading to reduced photosynthetic area, premature senescence, and ultimately yield losses. In endemic areas, especially where climatic conditions favor disease development, bacterial streak has become a major challenge to sustainable maize production [20].

Chemical and cultural management strategies for bacterial streak are largely ineffective or uneconomical due to the limited availability of effective bactericides and the polycyclic nature of the pathogen [12]. Consequently, host-plant resistance remains the most viable and environmentally friendly approach for disease management [7]. However, the genetic basis of tolerance to bacterial streak in maize is complex, and resistance levels among available germplasm are variable [13]. Identifying and selecting genotypes that combine superior agronomic performance with tolerance to bacterial streak is therefore critical for breeding programs targeting disease-prone environments.

Field evaluation of maize genotypes under natural disease pressure provides an opportunity to assess both yield performance and resistance stability under realistic agronomic conditions [9]. Such assessments help distinguish genotypes that can maintain acceptable productivity despite infection pressure, making them valuable candidates for further breeding and deployment in endemic regions [6]. Furthermore, understanding the interaction between the performance of released maize genotypes from research institutes like the Institute of Agricultural Research and Training (IAR&T) and disease intensity contributes to the development of selection indices that integrate yield potential, seed morphology, and disease tolerance [8]. The present study was therefore undertaken to evaluate the agronomic performance of eight (8) maize genotypes released by IAR&T, Ibadan, in a bacterial streak endemic field in order to identify promising genotypes and grain size that combine high yield potential with stable tolerance.

Materials and Methods

The experiment was conducted at the Teaching and Research Farm of Cocoa Research Institute of Nigeria (CRIN), Ibadan, Oyo State. Seeds of eight genotypes of maize used for the experiment were obtained at the seed store of IAR&T, Ibadan, Oyo State (Table 1). The experiment was carried out during the early cropping season of 2023 (May – August) on a bacterial streak endemic field [3]. Maize seeds (500 g) of each cultivar were sorted into three different sizes (big, medium, and small) [24][17]. One hundred seeds were randomly selected from each category to determine seed morphometrics through the use of a digital variety caliper (Table 2).

The experiment was laid out in a randomized complete block design (RCBD), replicated three times. The experimental field was laid out in three blocks, and each block comprised three replicates. Inter-block spacing was 2.0 m, inter-row spacing was 0.75 m while intra-row spacing was 0.50 m and seeds were sown at 2 cm depth.

Data were collected on five randomly selected plants to study the agronomic traits: Plant height at 95% maturity (cm), leaf area (cm²), stem girth (cm), cob length (cm), cob girth (cm), total grain weight (kg), cob weight/fruit (kg), grain yield per hectare (kg), harvest index (calculated as percentage of grain weight divided by total biomass), shelling percentage was calculated as percentage of grain weight divided by cob weight (%), 1000-seed was the average weight of 1000 seeds obtained from five shelled cobs (kg). The data collected were subjected to analysis of variance (ANOVA) using statistical analysis software [22]. Means were separated using Duncan’s multiple range test (DMRT) at 5% probability.

Isolation of Xanthomonas vasicola and characterization of bacterial streak

Affected portions (5 mm sections) of infected leaves were inoculated on Nutrient Agar for isolation of the streak pathogen (X. vasicola). Samples were surface-sterilised with 2% sodium hypochlorite, rinsed thrice with sterile water, drained, and inoculated on prepared agar plates [2]. Microbial strains were isolated from infected tissue samples on Nutrient Agar, and bacterial streak disease was eventually characterized in the maize genotypes as reported by Malvick et al., 2024 [15].

A modified disease severity scale (0-5) for maize streak was used Mushayi et al., 2025 [16], while percentage incidence [18] of the disease was determined as described below:

Resistance and tolerance to bacterial wilt were determined according to the rating class described by Borisade et al., 2017 [5] as < 1% and ≤ 25% severity measures, respectively.

Results and Discussion

Performance of maize genotypes

The mean performance of growth characters evaluated in the eight varieties of maize is presented in Table 3. There was no significant difference among the varieties in terms of their stem girth and seed sizes, although variety ART-98-SWI (Small) recorded the highest mean of 6.26 cm. There was no significant difference in the plant height of maize; however, plant height for small seed size was lower, considering seed size. This was in concordance with the result observed in a collection of soybean varieties [27]. Mean performance of yield and yield components evaluated in the eight (8) varieties of maize is presented in Table 4. With reference to cob length, there was no significant difference in the varieties and seed sizes. However, variety Suwan-1 (Large) recorded the longest cob length (28.20 cm) while ALT-98-SW6 (Small) recorded the least cob length (23.49 cm). For cob girth, there were significant differences among the varieties; variety ALT-98-SW6 (Large) recorded the widest average cob (17.83 cm), while the shortest cob girth was recorded for variety LNTP (Small).

For 1000-seed weight, a significant difference was observed among the varieties and their seed sizes. Variety DMR-LSR-Y (Small) recorded the heaviest weight (0.38 kg). Variety LNTP (Medium) recorded the heaviest/largest total grain yield (0.23 kg). PRO-VIT-A (Medium) recorded the largest grain yield/hectare (99.749 tonnes). Variety PRO-VIT-A (Small) expressed a superior performance in harvest index (73.83%) and biomass measurement (0.13%). Both medium and small seed size PRO-VIT-A had the highest shelling percentage (78.01%) when variety BR-9928 (Large) recorded the least performance (55.52%). Small and medium maize seed fractionation performed significantly better than the large seed size [24]. Contrary results by Wang et al., 2025 [27] were obtained in soybean, where larger seed size performed better in pod yield and 100-seed weight than the smaller sizes.

The significant variety effect on 1000-seed weight, total grain weight, shelling percentage, harvest index, biomass measurement, and grain yield/hectare suggests that differences in varieties and seed sizes were responsible for variation in these characters. The result indicates that dissimilar maize cultivars exhibited significantly different yield characteristics. It is in agreement with the study carried out by Adediran et al., 2025 [1] on okra genotypes. Differences in evaluated yield and yield components for seed sizes (Large, Medium, and Small) showed that different fractions of seed size did influence the yield of the maize plant [24].

A similar trend of outcome was obtained by Sulewska and Kaziora 2006 [23] in an experiment with maize cv. Clarica, in which grain yield from plants grown from a large fraction declined when compared with that of plants grown from the small and medium sizes. Graven and Carter (1990) [11] showed a downward trend in large maize seeds compared to plants grown from smaller seeds. Royo et al., 2006 [21] revealed that the effect of durum wheat plants grown from large grains was higher (16% increment) compared with plants grown from small seeds. Contrary to the study, however, EmayatGlolizadeh et al., 2012 [10] showed that by increasing maize seed size, commercial yield increased and the seed with higher vigour and size produced stronger seedlings, thus increasing the establishment.

Incidence and severity of bacterial streak disease among maize genotypes

All the selected genotypes of maize were tolerant to bacterial streak, disease severity varied significantly among the eight maize genotypes evaluated under endemic field conditions, with severity scores (on a 0–5 scale) ranging from 0.80 to 1.60 (Table 5). However, large grain sizes of ART-98-SW6, PRO-VIT-A, and ART-98-SW1 with severity measures less than 1 (0.80, 0.93, and 0.93, respectively) appeared more resistant to the disease than other genotypes, but their symptom were not significantly better compared to other varieties. ART-98-SW6 large grain size was less susceptible to bacterial streak, as it manifested a significantly lower severity than the small and medium grain plants. Leaves infected with X. vasicola were characterised with brown to light brown streak lesions, manifesting between the leaf veins.

Disease incidence ranged from 2.33% to 6.67%, indicating generally low infection levels across the genotypes. Among the genotypes, BR-9928 and LNTP consistently exhibited the lowest mean disease incidence (2.33%) in large-grained plants; however, infected plants expressed severity higher than 1.00. In contrast, ART-98-SW6 (medium grain) recorded the highest disease incidence (6.67%); it equally exhibited a corresponding higher severity score (1.27), indicating worse susceptibility to X. vasicola. Similarly, small-grained variants of ART-98-SW6 and PRO-VIT-A recorded the highest severity values (1.60), signifying that grain size may influence the plant’s response to bacterial streak infection.

Across genotypes, large-grained plants generally showed lower incidence and severity compared to medium and small-grained forms. This observation suggests that grain size may be associated with physiological or structural factors conferring partial resistance, possibly due to better resource allocation or stronger cell wall composition that limits bacterial penetration. These findings align with previous studies that reported genotypic and morphological influences on disease tolerance in maize and other cereals under bacterial and fungal stress.

Tasnim et al., 2025 [26] investigated the influence of morphological properties of maize genotypes on drought tolerance. This study identified BHM-7, BHM-14, and BHM-15 as genotypes with superior drought tolerance at the reproductive stage, while Black, Violet, and White Vutta showed resilience at the seedling stage, exhibiting greater plant vigor under drought stress. A similar relationship was observed between bacterial streak tolerance and seed size of maize in the current study. Recognizing the relationship between phenotypic classifications of maize genotypes and their resistance to biotic and abiotic stressors was therefore proposed as a significant step toward breeding programmes for food security and sustainable agriculture [26].

In a similar study, genotypic differences in maize root morphology were associated with their response to low-nitrogen stress [25]. Advancements in breeding have led to modern hybrid maize genotypes characterized by smaller yet more responsive root systems under low-nitrogen (low-N) conditions. For instance, the root phenotypes of Zhengdan958 and Xianyu335 maize genotypes were determined by distinct genetic architectures, while in the B73 genotype, crown roots, rather than embryonic roots, exhibit greater functional activity in adapting to low-N stress [25]. Furthermore, shoot nitrogen concentration serves as an indicator of the plant’s internal nitrogen status, which exerts a regulatory influence on root morphogenesis, disease tolerance, and developmental plasticity [4].

Overall, while variations existed among grain sizes within genotypes, the differences were not statistically significant (p > 0.05) for most comparisons. Nevertheless, the consistently low incidence and severity observed in large-grained genotypes (especially, ART-98-SW6, PRO-VIT-A, and ART-98-SW1) highlight these plants as promising candidates for further evaluation and possible use in resistance breeding programs against bacterial streak disease.

Conclusion

Evaluation of agronomic performance of maize genotypes in disease-endemic fields is imperative in order to identify promising genotypes and grain size that combine high yield potential with stable tolerance. This study established the performance and tolerance of 8 maize genotypes, further classified into different grain sizes (large, medium, and small), to bacterial streak disease. The yield of maize genotypes was dependent on the seed fraction used, and it decreased with an increase in the size of the seeds. However, variety LNTP performed best in total grain weight. The genotypes were all tolerant to streak disease, while large grain size genotypes manifested more tolerance than medium and small grain-plants, particularly in ART-98-SW6, PRO-VIT-A, and ART-98-SW1. These findings provide useful insights for maize improvement programs and inform the influence of grain size in strategies for managing bacterial streak through host resistance, especially in endemic fields.

Recommendation

The released maize hybrids by IAR&T, Ibadan appeared to be tolerant to bacterial streak disease.

However, genotypes PRO-VIT-A and ART-98-SW1 (large grains) should be selected for subsequent breeding programmes for disease resistance and screening for resistance genes. Furthermore, LNTP with outstanding performance can be recommended for maize researchers and farmers to obtain optimum yield, especially in a bacterial streak-free environment.

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