A tropical root-crop that is a daily staple food to hundreds of millions of people in Africa and increasingly being used by small-holder farmers in commercial production, cassava has historically been difficult for plant breeders to improve in part because of delayed and poor production of flowers. The new studies funded by the NextGen Cassava project and led by scientists at Cornell University and the International Institute of Tropical Agriculture provide plant breeders with potential best practices to overcome poor (particularly low numbers of female flowers) or delayed flower production.
The lead authors on both papers are Deborah Oluwasanya, Ph.D ‘20 and Tim Setter, professor of soil and crop science in Cornell’s School of Integrative Plant Science.
“Rigorous scientific research into cassava is helping to optimize production in Africa and better ensure a food-secure future,” said Chiedozie Egesi, director of NextGen Cassava, adjunct professor in the Department of Global Development and senior scientist at IITA.
“These studies into cassava flowering open new insights to improve the lives and livelihoods of Africa’s farmers.”
The first study, published May 21 in Frontiers in Plant Science, aims to better understand the factors regulating cassava flowering and its low ratio of female to male flowers. The natural tendency is for cassava to produce several more males than females whereas for breeding to be effective, more females are required as they become seeds bearing improved traits from breeding. Combinations of plant growth substances and pruning treatments were examined for their effectiveness in improving flower production. Through various trials, a three-input combination was eventually found to promote flowering with an increased ratio of female to male flowers.
First, specific pruning methods stimulated flower growth; second, application of a compound called silver thiosulfate (STS) also increased flower abundance; third, applications of a synthetic plant hormone called benzyladenine (BA) also feminized flowers. Combining pruning and STS treatments led to an increase in flower abundance. With the addition of BA, over 80% of flowers were female. This three-way treatment combination of pruning+STS+BA also led to an increase in fruit.
“We saw an additive effect when treatments are layered upon each, providing new insights into how cassava production can be increased," said Oluwasanya. "Our findings give clear direction, which is not always the case in science."