Curriculum Vitae

EDUCATION:

Ph.D. in Plant Pathology, 1984, Purdue University, West Lafayette, Indiana

EXPERIENCE:

Interim Chair, Agronomy & Resource Sciences, TAMUK (January - May 2005)
Professor, Texas A&M University-Kingsville (TAMUK) Citrus Center, 312 N. International Blvd, Weslaco, TX (1999 to present)

Referred Journal Publications (past 3 years)

● Madhurababu Kunta and Mani Skaria. 2006. Molecular characterization of Phytophthora in the Lower Rio Grande Valley (LRGV) citrus orchards. Subtropical Plant Science 59: 000-000 (Accepted).
● Kunta, J.V. da Graca, and Mani Skaria. 2006. Molecular Detection and Prevalence of Citrus Viroids in Texas. HortScience 42: 000-000 (Accepted).
● S.R. Palle, H. Miao, M. Seyran, E.S. Louzada, J.V. daGraca, and M. Skaria. 2005. Evidence for Association of Citrus psorosis virus with Symptomatic trees and an Olpidium-like Fungus in Texas. Proceedings, 16th Conference of the International Citrus Virologists: 423-426.
● C.J. Kahlke, J.W. Watson, N. Solis-Gracia, M.Skaria, and J.V. daGraca. 2005. The Texas Citrus Budwood Certification program. Proceedings, 16th Conference of the International Citrus Virologists: 480-483.
● T.R. Gottwald, S.R. Palle, H. Miao, M. Seyran, M.Skaria, and J.V. da Graca. 2005. Assessment of the Possibility of Natural Spread of Citrus Psorosis Disease in Texas. Proceedings, 16th Conference of the International Citrus Virologists: 000-000.
● C.M. Herron, T.E. Mirkov, N. Solis-Gracia, C.J. Kahlke, M.Skaria, and J.V. daGraca. 2005. Severity of Citrus tristeza virus isolates from Texas. Plant Disease 89:575-580.
● Reginald S. Fletcher, David E. Escobar., and Mani Skaria. 2004. Evaluating airborne normalized difference vegetation index imagery for citrus orchard surveys. HortTechnology 14: 91-94.
● R. S. Fletcher, D. E. Escobar., and M. Skaria. 2004. Response of ratio vegetation indices to foot rot-infected citrus trees. Int. J.Remote Sensing. 25: 1-6.
● Q. Du, J. Victor French, Mani Skaria, Chenghai Yang, and James H. Everitt, “Citrus pest stress monitoring using airborne hyperspectral imagery,” Proceedings of 2004 International Geoscience and Remote Sensing Symposium, vol. 6, pp. 3981-3984, Anchorage, AK, Sep. 2004.
● Mani Skaria, Yin-Tung Wang and Larry Barnes. 2004. What Causes Those Spots? Microscopic Study of Leaf Lesions of Oncidium Sharry Baby ‘Sweet Fragrance,’ Orchids 73:54-56.

OFFICES HELD (1996-present)

Chair, Mycology Committee, The American Phytopathological Society (APS), 2006; Member, Teaching Committee, APS; President 2002, The Rio Grande Valley Horticultural Society; Elected to the University Faculty Senate (2001-2004) Fruit Section Director, Rio Grande Valley Hort. Soc. 1998; Fruit Section Director, Rio Grande Valley Hort. Soc. 1996; Chairman, Tropical plant pathology, American Phytopathological Society, 1996; Member, task force on Texas budwood program; Texas Dept. Agric. (TDA); Member, task force on Texas root weevil eradication, TDA.; Member of all citrus industry committees related to tristeza virus in Texas. Member of National Citrus Research Council; Chairman, Poster Committee, Rio Grande Valley Hort. Soc.(4 years); Member, Environmental Plant Quality Committee, APS ; Co-Chair, Cultural Diversity Committee, 2002. APS. Task Force Member, Committee on Indoor Air Quality in Schools (Appointed by the Texas Department of Health).

Current Research Projects

Membrane filter technique for citrus nematode assay: Membrane filter (MT) technique is a standard procedure used worldwide to assess bacterial contamination in water. This technique is simple and has use in several different applications, in addition to bacteriology. This technique allows filtration of a large volume of water to retain microorganisms and particulates on a MT placed on a filter holder with a seal to prevent water leak. We have adapted the bacterial MT technique to screen a large volume of soil samples to assay for citrus nematode, Tylenchulus semipenetrans. In addition, we successfully stored the MFs for several weeks in a refrigerator. The stored MFs can be kept in a refrigerator for months and can be re-used for counting, photography, and/or scanning.

Postharvest fruit decay control: This is a project that is very important to the growers and packers. Many packinghouses in the Valley experience stem-end rot problem as a result of ethylene de-greening. Well-regulated, air quality parameters in degreening rooms are necessary to control stem-end rot disease. If the degreening rooms are not properly designed and air quality parameters not monitored; the conditions can reach levels that are damaging to fruit. High carbon monoxide, carbon dioxide, and ethylene concentrations may cause serious economic damage and human health issues. Ethylene oxide reacts with carbon dioxide to produce carbon monoxide.

Citrus psorosis virus work. We have been studying the natural transmission of Citrus psorosis virus and the role of Olpidium. A graduate student completed his Master degree on this subject. The study topics are: 1. “Preliminary evidence for natural transmission of citrus psorosis virus by an Olpidium-like fungus.” and “Assessment of the possibility of natural spread of citrus.”

Phytophthora nicotianae growth in viroid-infected and non-infected citrus baits: Citrus exocortis viroid(CEVd) and other viroids are harmful pathogens when trifoliate orange and its hybrid rootstocks are used. Resistance to fungus, Phytophthora nicotianae in citrus trees infected with viroids has been reported by some scientists. We studied the growth and development of P. nicotianae in leaf, root, and bark tissue of Rio Red grapefruit, compared to non-infected controls. A significant reduction of P. nicotianae sporangia was found in viroid-infected baits when viroid-infected and healthy controls were used as bait tissue challenged with the fungus. Phenolic acids were extracted from roots of CEVd-infected roots and the extract was used to study the growth of P. nicotianae in control and viroid-infected baits. Salicylic acid, gentisic acid, ferulic acid and flavone concentrations differed among viroid-
and P. nicotianae-infected plants, alone and in combination, compared to control plants.

Molecular characterization of citrus viroids: Citrus viroids are commonly found in all commercially important citrus cultivars grown in the Lower Rio Grande Valley. Most trees are non-symptomatic carriers of more than one viroid and are grown on sour orange rootstock. Detection of viroids through biological indexing on sensitive indicator plants is the gold standard. However, we developed a conditional use of RT-PCR as an efficient and alternative detection method of citrus viroids. This is especially useful in the Texas virus-free citrus budwood certification program. We were able to detect, clone, and sequence full-length viroids of Citrus exocortis viroid (CEVd), Hop stunt viroid (HSVd) (both cachexia and non-cachexia variants), Citrus viroid-III, and Citrus viroid-IV from a collection of viroid-inoculated grapefruit plants. Based on our results, RT-PCR can be a conditional substitute for biological indexing of mother trees in foundation block trees and shoot-tip grafted trees in the virus-free budwood program.

3. Effect of Harpin on citrus growth under nematode pressure: A higher proportion of plants treated with 1X and 1/2X harpin protein showed good plant vigor. In these two treatments, the mean plant height was 42.3 and 40.7 respectively. Shoot vigor was decreased with an increase in dilution. Plants treated with 1/32X and 1/64X dilution did not exhibit vigor, and the average shoot height decreased between 11 and 22 percent as compared to the undiluted. Shoot height in plants treated with 1/32X and 1/64X was comparable to water treatment. Shoot diameter also showed a similar trend with an increase in dilution. The citrus nematode (Tylenchulus semipenetrans) inoculation technique was successful. Harpin has a significant, positive effect on the growth of the root and the shoot system even with a high citrus nematode population. A follow-up study result also confirms the positive effect of Harpin.

Mycosphaerella citri inoculation technique: Citrus greasy spot caused by the fungus Mycosphaerella citri, is a serious disease in citrus producing areas that have high temperatures and high relative humidity. The fungus causes yellow mottling on the upper side and brown to black blisters on the lower side of the infected leaves. Fallen, decomposing leaves infected with M. citri produce fruiting bodies called ascocarps. Both rainfall and irrigation help the ascocarps to rupture and release ascospores into the air. The ascospores are two-celled, straight or slightly curved, usually 2-3 by 6-12 micrometer. The disease cycles are initiated by ascospores which land on the under surface of young leaves when the relative humidity is nearly 100%. Studies to understand the disease development in young leaves require a system to inoculate young leaves with a known number of ascospores. In my laboratory, I am trying to develop a system to: a) harvest mature ascocarp containing leaves from the field, b) release ascospores, c) inoculate detached young leaves, and d) follow the ascospore development and disease progress using fluorescence microscopy.

Molecular Characterization of Citrus Phytophthora isolates: Phytophthora infections of citrus causing foot rot, root rot, and gummosis are common in the Lower Rio Grande Valley. No previous studies have been conducted to characterize this fungus using molecular methods. We characterized twenty two Phytophthora isolates from several root and soil samples using the polymerase chain reaction. First round PCR with Ph2 and ITS4 primers resulted in a 700 base pair fragment. Primers Pn5B-Pn6 and Pc2B-Pc7 are highly specific for P. nicotianae and P. citrophthora, respectively. A highly sensitive nested PCR produced a 120bp fragment with primers Pn5B-Pn6 and no amplification with primers Pc2B-Pc7. This fragment was sequenced and a similarity search at GenBank showed 100% identity with P. nicotianae. These results reveal that P. nicotianae is the most prevalent species in LRGV citrus and it confirms the results of non-molecular identification completed previously.