Shokry Ramadan Bayoumi

Bacterial wilt caused by Ralstonia solanacearum race 1 is one of the most destructive diseases of tomato, resulting in severe yield losses worldwide. This study evaluated the individual and combined effects of humic acid (H) and arbuscular mycorrhizal fungi (AMF) with or without NPK supplementation on tomato growth, nutrient uptake, defense activation, and suppression of bacterial wilt. Disease severity was highest in inoculated controls (60.4%), while integrated treatments markedly reduced wilt incidence, with the triple combination (NPKHM+) achieving the lowest severity (23.2%). Growth performance and nutrient uptake of N, P, and K were enhanced, particularly when combined with humic acid and AMF, which improved biomass, chlorophyll content, and nutrient assimilation under both healthy and infected conditions. Biochemical and molecular analyses revealed that phenol accumulation, peroxidase (POX), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) enzyme activities, as well as the expression of POX, PPO, PAL, and PR-2 genes, were highly upregulated in treated plants. The NPKHM⁺ treatment produced the highest biochemical and transcriptional responses, which coincided with maximal wilt suppression and improved plant vigor. These findings demonstrate that the integration of mineral nutrition with organic and microbial amendments synergistically enhances tomato resistance to bacterial wilt while promoting growth, providing a sustainable and effective strategy for disease management.

Background The interaction of various treatments such as abscisic acid (ABA), polyamines (PS), and biological control with Trichoderma against Meloidogyne incognita was evaluated to assess their impact on pathological indices, growth metrics, and defense mechanisms in tomato cultivars. Methods The study assessed Meloidogyne incognita root tomato disease (number of galls and egg masses) and growth parameters (shoot, root system, and fruit weight) in two tomato cultivars (1077 and Dania 85), along with the activities of defense enzymes; peroxidase (POD), polyphenol oxidase (PPO) and expression of defense genes (POD, PPO and PR2). Specifically, the study evaluated abscisic acid (ABA; 10 µM), potassium silicate (5 g/L), and biological Trichoderma harzianum (10⁸ CFU/ml) treatments under greenhouse conditions 45 days post-inoculation. pathological indices, including the number of galls and egg masses, were measured, along with defense enzyme activities and gene expression levels. Results Among the treatments applied, the 1077 cultivar demonstrated the highest resistance, exhibiting the lowest number of galls and egg masses. All treatments (ABA, PS, and Trichoderma) significantly increased growth parameters compared to the nematode-infected untreated control. Specifically, PS treatment showed the strongest enhancement in shoot fresh weight across both cultivars (1077 and Dania 85). Enzyme activities of PPO and POD, along with the gene expressions of POD, PPO and PR2, were elevated across all treatments. PS was the most effective treatment, followed by ABA and Trichoderma, significantly boosting both enzyme activities and gene expressions relative to the untreated control. The 1077 cultivar the resistant hybrid consistently outperformed Dania 85 in enzyme activities and gene expression. Conclusions PS and ABA significantly enhanced growth (≤ 57.4%↑) and defense (≤ 3.3-fold↑), with 1077 exhibiting superior resistance (48–53%↓ pathology). This hybrid is already marketed as a resistant cultivar, underscoring the potential for integrated disease management strategies.

Three isolates of Streptomyces scabies (St.1, St.2, and St.3) were examined for virulence on potato mini tubers, necrosis initiation on potato slices, inhibition of radish seedling length, production of thaxtomin A, and the presence of thaxtomin A (txtA) and nec1 genes. The three isolates, St.1, St.2, and St.3, were classified as highly virulent, moderately virulent, and weakly virulent, respectively. The St.1 isolate showed the highest scab severity index on potato mini tubers and necrosison potato slices, while the St.3 had the lowest, and St.2 had intermediate values. The St.1reduced radish seedling length by 82.35% and produced the highest toxin level (3.1 mg/ml), while the St.3 isolate reduced seedling length by 63.5% and produced the lowest level of toxin (1.18 mg/ml). The three isolates were positive for the presence of thaxtomin A (txtA) gene and produced a specific gene band at 500bp. However, St.1 and St.2 isolates were able to create a particular band at 700bp associated with thenecrosis gene (nec1), while the isolate St.3 lacked this band. Based on the total protein profile analysis, the three S. scabies isolates clustered into two groups which diverged at a similarity index of 0.78. The St.2 and St.3 virulent isolates were located in the same group with 0.86 similarity, while the highly virulent isolate St.1 was located in a separate group.Current findings highlight the correlation between the presence of thaxtomin A and necrosis virulence factors and S. scabies pathogenicity.

Chocolate spot disease caused by Botrytis fabae is a major problem that limits faba bean production in Egypt. The in vitro antifungal activity of chitosan and its ability to elicit defense responses in two faba bean cultivars Giza 416 (resistant) and Giza 40 (susceptible) against this fungus were evaluated. Seven isolates of B. fabae were cleaned from infected leaves. All isolates were pathogenic to Giza 40 cultivar, with isolate 3 (Bf-3) was the most virulent. Chitosan inhibits the mycelial growth of B. fabae (Bf-3) in concentration-dependent manner. At 0.75 % and 1 %, chitosan completely inhibits the growth of B. fabae. Under greenhouse conditions, two fab bean cultivars, Giza 416 (resistant) and Giza 40 (susceptible) were sprayed with 0.5% chitosan. Treatment with chitosan 0.5% reduced the chocolate spot disease severity for both cultivars compared with untreated infected control. Plants of both cultivars treated with chitosan showed a lower rate of lipid peroxidation and higher levels of chlorophyll and total phenols compared with untreated infected control. Chitosan stimulated the activity of defense enzymes such as peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL). Furthermore, chitosan treatment increased the expression levels of three pathogenesis related (PR) genes including PR1, PR2 (β-1,3-glucanase), and chitinase. The resistant cultivar (Giza 461), whether treated or untreated with chitosan displayed weaker symptoms, and enhanced values for all physiological and molecular responses than the susceptible cultivar (Giza 40). The findings show that chitosan has a high potential for protecting faba bean plants from B. fabae by regulating biochemical, physiological and molecular responses in faba bean plants under infection

Bacterial wilt, caused by Ralstonia solanacearum (Rs), is one of the most important plant diseases, especially on potato. In this study, the molecular mechanisms of potato resistance against Rs were compared between cv. Diamant (susceptible) and cv. Lady Bedford (partially resistant). The results indicated that potato cv. Lady Bedford was significantly more resistant (24.3% wilt) to Rs than cv. Diamant (83.8% wilt). The inoculated cv. Diamant plants exhibited the highest decrease in photosynthetic pigment compared to the cv. Lady Bedford. Three differentiated expressed cDNA fragments that present in inoculated plants of the partially resistant cv. Lady Bedford were selected for sequencing and identified as 1-D-deoxyxylulose 5-phosphate synthase gene (StDXS1), polyphenol oxidase (PPO) gene and WRKY transcription factor (StWRKY) from potato genome. The expression level of the POD (peroxidase), PPO, StWRKY and StDXS1 genes were induced by inoculation with Rs compared to the non-infected plants. The highest gene expression level on the two cultivars was recorded at 12, 24, 24 and 12 hpi for the four genes, respectively, and it was significantly higher in the partially resistant cultivar than the susceptible one. POD and PPO, enzymes activity significantly increased After inoculation with Rs in the both cultivars. cv. Lady Bedford had a higher enzymes activity and peaked at 12 and 24 hpi for POD and PPO, respectively, while, cv. Diamant peaked at 6 and 12 hpi for the same enzymes. These clear transcriptional responses suggested that these genes and enzymes participates in the basal defense of potato to Rs.

Abscisic acid (ABA), a plant hormone involves in various plant physiological processes including, response to biotic and abiotic stress conditions. ABA was tested to study its ability to enhance disease resistance of two potato cultivars i.e., Nicola and Spunta, to the infection by the early blight fungus Alternaria solani (A. solani) under greenhouse conditions. Treatment with ABA solution (10 μM) reduced the early blight disease severity for both cultivars compared to the untreated infected plants. Differential display gene analysis for treated plants revealed three clear bands. These bands showed significant homology to well-known genes in the GenBank database and identified as superoxide dismutase (CuZnSOD), WRKY transcription factor (StWRKY) and Endoglucanase from potato genome. Real-Time PCR was used to detect the changes in gene expression of CuZnSOD and WRKY-type genes after infection with A. solani for both Nicola and Spunta potato cultivars and in different time intervals. The expression level of CuZnSOD and WRKY genes in potato leaves of both cultivars were increased for ABA treated and infected plants and for untreated/infected plants compared to the untreated/uninfected plants. Both genes were over expressed in infected plants treated with ABA than untreated ones and reached the maximum level of expression after two days of inoculation. The highest increase of both genes expression was observed in potato leaves of cv. Nicola compared to cv. Spunta.

Two maize populations (GE440 × Sd7 and NC300 × Gm1002) were used in this study. Molecular markers like simple sequence repeat (SSR) and sequence-tagged site (STS) were used to identify resistance genes linked to Fusarium ear rot (Fusarium verticillioides). Also, quantitative trait locus (QTL) mapping was used to detect resistance genes on maize chromosomes. The co-dominant microsatellite markers (bnlg1063, umc2082, bnlg1621, umc2013, bnlg1740, umc2059 and SSR85) and STS (STS06) were amplified polymorphic bands and candidate markers linked to Fusarium ear rot resistance genes in maize. Seven QTLs were identified ranging from 2 to 7 for each trait. QTLs were distributed on two chromosomes and associated with grain yield/main ear and 100 kernel weight. The present study indicated that microsatellite and STS primers might be useful for developing improved cultivars.