Magdy S. Montasser

Application of plant growth-promoting rhizobacteria (PGPR) in combination with a mild strain of Cucumber mosaic virus (CMV) associated with viral satellite RNAs to enhance growth and protection against a virulent strain of CMV in tomato

Abstract An indigenous strain of Cucumber mosaic virus (CMV) associated with a naturally occurring benign viral satellite RNA (345 bp long), referred to as CMV-KU1, although effective as a protective biocontrol agent against the damaging effects of the virulent CMV-16 strain, produced negative side-effects such as mild stunting, vigour reduction and about 20% yield loss in tomato (Solanum lycopersicon L.) plants. The efficacy of using a mixture of two plant growth-promoting rhizobacteria (PGPR) strains, Pseudomonas aeruginosa and Stenotrophomonas rhizophilia, to compensate for vegetative and yield loss caused by CMV-KU1 in tomato plants, was evaluated in greenhouse experiments. In addition to promoting plant growth, PGPRs are known to enhance systemic defences in plants against foliar pathogens such as viruses that attack tissues distant to PGPR sphere of activity. The use of PGPR and CMV-KU1 together successfully promoted vegetative growth and fruit yield in tomato plants to values equivalent to that of the healthy controls. The combination used also enhanced overall protection of the plants against the severe CMV-16 virus with about 91.3% disease prevention. Serological analysis using enzyme-linked immunosorbent assay (ELISA) also indicated a lower incidence of CMV-16 infection in protected test plants.

Effect of Tomato yellow leaf curl bigeminivirus (TYLCV) infection on tomato cell ultrastructure and physiology

Abstract Tomato yellow leaf curl bigeminivirus was isolated in Kuwait and therefore designated as TYLCV-K. The virus was found to be transmitted by whiteflies (Bemisia tabaci Genn.), and produced the characteristic external symptoms on tomato (Solanum lycopersicum L.) test plants. Electron microscopy of ultra-thin sections of infected leaves showed alterations in the ultrastructure of some organelles and uneven thickenings of the cell wall of the phloem tissue associated with severe damage in chloroplasts and abnormal building up of oily inclusions and empty vacuoles. The causal virus was characterized as a whitefly-transmitted monopartite Geminivirus. Viral genomic DNA fragment of 1.1 kb was successfully amplified from TYLCV-K infected tissues using polymerase chain reaction (PCR). The virus identity was confirmed by using Southern and dot-blot hybridizations. Chemical components of tomato leaves, such as photosynthetic pigments, especially chlorophyll a and b, total lipids, saturated and unsaturated fatty acids, reducing sugars and proteins, decreased in infected leaves when compared with healthy leaves of tomato test plants. On the other hand, total phenols accumulated to a greater extent in infected leaves. However, concentration of ascorbic acid (an antioxidant), leaf extract pH and total fatty acids were not dramatically affected by TYLCV-K. The level of increase or decrease of these constituents varied with different stages of plant growth (depending upon the developmental stages of the leaf at the time of infection). Our study showed that the level of some of the chemical constituents in tomato leaves changed in response to TYLCV-K infection.

Histopathology of Chloroplast Ultrastructure and Inclusion Bodies in CMV-Infected Plant Tissues Using Electron Microscopic Examination and ImageJ Analysis

Histopathology of Chloroplast Ultrastructure and Inclusion Bodies in CMV-Infected Plant Tissues Using Electron Microscopic Examination and ImageJ Analysis Cucumber mosaic virus (CMV) is an economically important virus that causes wide-spread diseases damaging crops worldwide. Two strains of the virus were detected using ELISA with specific antibodies, and isolated from Kuwait environment designated CMVKU1 and CMV-KU2. The KU1 is a mild strain and is associated with a benign viral satellite RNA, while KU2 isolate, is a severe strain and lacking viral satellite RNA. Both strains were used in a comparative study to investigate the effects of CMV infection on the ultrastructure of chloroplasts and inclusion bodies in test plants of tomato (Lycopersicon esculentum) and squash (Cucurbita pepo). Transmission electron microscopy (TEM) was used to determine the extent of infection and damage caused by virus isolates on chloroplast structure, and cellular inclusions including plastoglobules, and starch granules. Chloroplasts, the photosynthetic apparatus of plants, in infected tissues were severely affected with KU2 strain that caused a reduction and damage of their main structure, number, size, and inclusion bodies compared to the benign strain of KU1 and healthy control plants. Electron micrographs of ultra-thin sections proved the presence of the viral nanoparticles. The formation of viral crystalline bodies, chloroplast damage and malformation due to the viral infection. As the infection progressed, chloroplasts were destroyed and grana were disorganized and scattered into the cytoplasm that causes reduction in chlorophyll contents in plant tissues. ImageJ freeware analysis were used to determine the extent of infection and host-virus interactions and damage caused by virus isolates...

Biological Control of a severe viral strain of Cucumber Mosaic Virus(CMV) using a mild strain of CMVassociated with viral satRNA combined with a mixture of plant growth promoting rhizobacteria (PGPRs)

The effect of using plant growth promoting rhizobacteria (PGPR) as compensatory agents to nullify the detrimental growth effects that occur when using satRNA mediated protective technology were studied in greenhouse grown chilli pepper. A benign cucumber mosaic virus strain (CMV) associated with satRNA, CMV-KU1, was successfully used as a biological control agent to combat infections caused by another severe strain of CMV , CMV-16. However, despite its protective capability, CMV-KU1 caused certain vegetative and yield loss to the plants to which it was applied. A mixture of two known PGPR strains, Pseudomonas aeruginosa and Stenotrophomonas rhizophilia were used in this investigative study to see if this loss can be reversed or compansated. Additionally, three different routes of PGPR application to the plants were also tested to determine which would provide the best result in promoting plant growth and reducing infections. The three PGPR application pathways tested were i) application directly to the rhizosphere of the plants by injection to the roots, ii) coating of the seeds with PGPRs before sowing, and iii) mixing of the PGPRs with the soil before sowing. Observations were made based on the manifested symptoms of the infected plants, fruit yield and ELISA readings. The resulting data were statistically analysed. The results indicated that the presence of PGPRs significantly improved the plant growth, yield, fruit number and fruit set rate in chilli pepper compared to using satRNA alone. Moreover, the best results were obtained when PGPRs were directly inoculated into the rhizosphere compared to the two other alternative application methods tested.