Squash (Cucurbita pepo L.), one of the most important vegetable crops for human nutrition all over the world, is infected by many diseases, particularly powdery mildew caused by Podosphaera xanthii (syn. Sphaerotheca fuliginea), which is considered the most serious disease causing yield losses. This research study was conducted to investigate the role of Bacillus subtilis, Bacillus chitinosporus, Bacillus pumilus, Bacillus megaterium, Bacillus polymexa, Trichoderma harzianum, and Trichoderma viridi on squash leaves infected with P. xanthii under laboratory and greenhouse conditions. Results indicated that all treatments significantly inhibited the conidial germination of P. xanthii than the control. A significant decrease in the disease symptoms, severity, and the area under disease progress curve (AUDPC) was registered in squash plants sprayed with the tested bio-agents, particularly B. subtilis, B. pumilus, and T. harzianum. The activity of defense-related enzymes, i.e., catalase (CAT), peroxidase (POX), and polyphenol oxidase (PPO), were significantly upregulated as results of most treatments. Light and scanning electron microscopic (SEM) investigation showed that the morphological shape of P. xanthii was abnormal and the pathogen growth was limited in bio-agent-treated plants compared to control plants that showed dramatic infection. Bio-agent treatments significantly increased growth and yield attributes of squash plants over control. Overall, the results showed possibility of using the tested bio-agents to control squash powdery mildew disease as an alternative to fungicides' use that is harmful for human health and polluting the environment.

Tomato late blight caused by Phytophthora infestans (Mont.) de Bary, also known as the Irish famine pathogen, is one of the most destructive plant diseases. Wild relatives of tomato possess useful resistance genes against this disease, and could therefore be used in breeding to improve cultivated varieties. In the genome of a wild relative of tomato, Solanum habrochaites accession LA1777, we identified a new quantitative trait locus for resistance against blight caused by an aggressive Egyptian isolate of P. infestans. Using double-digest restriction site–associated DNA sequencing (ddRAD-Seq) technology, we determined 6,514 genome-wide SNP genotypes of an F2 population derived from an interspecific cross. Subsequent association analysis of genotypes and phenotypes of the mapping population revealed that a 6.8 Mb genome region on chromosome 6 was a candidate locus for disease resistance. Whole-genome resequencing analysis revealed that 298 genes in this region potentially had functional differences between the parental lines. Among of them, two genes with missense mutations, Solyc06g071810.1 and Solyc06g083640.3, were considered to be potential candidates for disease resistance. SNP and SSR markers linking to this region can be used in marker-assisted selection in future breeding programs for late blight disease, including introgression of new genetic loci from wild species. In addition, the approach developed in this study provides a model for identification of other genes for attractive agronomical traits.

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Pea (Pisum sativum L.) is subjected to attack by certain soil-borne phylogenetic of fungus-like eukaryotic microorganisms such as Pythium debaryanum and soil-borne fungi Rhizoctonia solani and Fusarium solani which cause damping-off diseases. Isolation of associated fungi and P. debaryanum and three species of Trichoderma was carried out from soil rhizosphere of pea plants. Antagonistic effect of Rhizobium leguminosarum combined with Trichoderma lignorum, T. longibrachiatum and T. koningii against pathogenic fungi was investigated in vitro and in vivo under greenhouse conditions. The effect of combinations between the tested Rhizobium sp. and the other tested Trichoderma spp. on the disease incidence caused by the pathogenic microorganisms was evaluated when used as seed and soil treatments. Disease assessments, nitrogen fixation and yield parameters after 50 and 90 days from sowing in comparison with un-treated and fungicide treatments were recorded. Mycoparasitic activity of the tested Trichoderma spp. against each of the pathogenic fungi and Pythium debaryanum was studied using scanning electron microscope. Results showed that the soil treatments were more effective in controlling damping-off disease than seed treatments in overall experiments. Combination of R. leguminosarum with T. longibrachiatum gave the best results in reducing percentage of post-emergence damping-off (13.33 and 6.67%) and root rot (14.72 and 9.58%) caused by P. debaryanum and R. solani, respectively. Survived plants, nitrogen fixation and yield parameters were also increased. Treatment of R. leguminosarum combined with T. koningii against infection by F. solani gave the best results in reducing percentages of post-emergence damping-off (6.67%) and root rot (13.06%) with increment of survived plants, nitrogen fixation and yield parameters. In conclusion, combinations of R. leguminosarum with the Trichoderma species were effective than application of each one alone against pea damping-off disease.