Twelve corn varieties and inbred lines [BP1] showing resistance to ear rot caused by the fungal pathogen Fusarium have been identified from the screening of 43 white corn lines/populations and Lagkitan in a study conducted by the University of the Philippines Los Baños (UPLB).

Among these lines or genotypes, three exhibited potentially most resistant, which will be subject to further confirmatory tests. These potential lines can be used as donor in developing resistant varieties of white corn, according to the DA Biotechnology Program, which provided funds for the research.

Fusarium ear rot is a common corn disease that is more widespread in tropical and subtropical regions. Data from the UPLB-Institute of Plant Breeding indicate that during the 2007 wet season, 35% of ears harvested was infected with the pathogen and the degree of infection ranged from 5-60%.

Efficient breeding strategies for disease-resistant white corn varieties are viewed to be beneficial to local corn industry since corn is the second most important crop in the Philippines. It is estimated that 14 million Filipinos prefer white corn as their main staple.

Using biotechnology, the study also resulted in the development and validation of a reliable detection method. Using this method, the researchers have confirmed what has long been suspected that there is a widespread occurrence of the ear rot pathogen in corn growing regions in the Philippines.

The study utilized samples from all over the country collected in collaboration with the Department of Agriculture regional field office, local government units, and state universities and colleges.

The result of a two-year study by a UPLB research team led by Dr. Cecilia Pascual and Dr. Eureka Teresa Ocampo were reported in the paper “Fusarium ear rot of maize: Fumonisin-producing Fusarium species and host resistance” that presented during the 2014 Annual Meeting of the Phytopathological Society of Japan.

Their findings are hoped to contribute to existing efforts to develop resistant corn varieties, implement more active efforts for detection and develop effective control mechanisms for the disease.

The widespread occurrence fusarium ear rot in different regions in the country cause concern, especially in cases when infection of corn from the pathogen is symptomless or not readily apparent. These infected corn may still enter the food chain and affect consumers and livestock.

Some species of the pathogen produce fumonisin, a family of mycotoxins, which can cause serious animal and human diseases, including esophageal cancer and neural tube birth defects in humans and lethal horse disease and porcine pulmonary edema in animals.

The most predominant fumonisin-producing Fusarium species causing Fusarium ear rot in the Philippines is F. verticillioides.  Two other species, F. proliferatum and F. graminearum, were also present in specific areas but in less than 1% of the total isolate collection. 

Fusarium isolated from the collected samples underwent morphological (form and structure) characterization as well as DNA analysis using biotechnology tools such as Polymerase Chain Reaction (PCR) and Enzyme-Linked Immunosorbent Assay (ELISA).

PCR is a laboratory tool commonly used to detect the presence of specific microorganisms through DNA analysis while ELISA specifically detects proteins such as the Fusarium mycotoxins.

Preliminary results of the study based on the physical traits and genetic diversity of the ear rot pathogen suggest that it is highly diverse and able to adapt under local conditions, suggesting a high possibility of the rapid evolution of resistance against the current control measures such as application of fungicides. Increased humidity, hot weather and drought conditions favor the proliferation of Fusarium.

The DA Biotech Program supports research initiatives that utilize biotechnological tools and generate beneficial technologies and novel information to help enhance genetic improvement of agricultural commodities and their production. (DA-BPO).