Symbiotic fungus dramatically enhances drought tolerance in maize
Increasing the level of Trichoderma, a fungus that occurs naturally in soils around the world, makes some varieties of maize more drought tolerant, as well as boosting yield and general plant health.
That’s the finding of Ayanda Ngema, a plant pathology masters student who is being supervised by ACCI director, Professor Mark Laing. Ngema, who grew up in Hluhluwe, has been investigating the influence of Trichoderma on drought-tolerant maize varieties obtained from the Agricultural Research Commission (ARC) and Water Efficient Maize for Africa (WEMA) program. A few normal maize varieties were also included in the study.
Trichoderma is a genus of fungi in the family Hypocraeceae, found in all soils and on the surface of plant roots. It forms a symbiotic presence inside the roots of compatible plants, including maize, soybean and groundnuts. However, some crops are not compatible and do not let the fungus invade its roots, including wheat.
Used as a supplement, it promotes growth by boosting a plant hormone called indole acetic acid (IAA) that regulates many aspects of development, including the production of lateral roots. Trichoderma also increases disease resistance and actively acts fungi that feed on plant roots.
“We got drought-tolerant maize, inoculated it with Trichoderma asperellum and then subjected it to drought stress, to see if drought tolerance was increased,” says Ngema, explaining her experiment. “We were looking at whether the Trichoderma increased root volume, shoot growth and chlorophyll content.”
Drought tolerance is measured by chlorophyll content — an indicator of plant health—and root mass. Here the dry weight is measured and is significant because when plants are subjected to drought stress the root system increases to maximise the chance of finding water.
Trichoderma was applied in the form of a product manufactured by Plant Health Products (PHP) called Eco-T, which was mixed with maize seeds and a 2% substance call guar gum, which helps the powder to adhere to the seeds. The Trichoderma sticks to the roots of the plant as it grows, forming a symbiotic relationship with the plant.
In the field trial six different maize cultivars were used—four drought tolerant and two ‘normal’. The cultivars were all subjected to three levels of water stress — none, moderate and severe— and the results showed that chlorophyll content and root yield increased at all three levels with with the application of Trichoderma, depending on the cultivar used.
Interestingly, under severe stress the chlorophyll content of one drought-tolerant cultivar showed the greatest increase — a whopping 39%. This variety also showed the second-highest increase (46%) for root yield, with another drought-tolerant variety increasing by 49%.