A high resolution genetic linkage map of cassava published in G3

Cassava roots affected by cassava brown streak diseases - the linkage maps will help breeders in their efforts to develop varieties resistant to this deadly disease.
Cassava roots affected by cassava brown streak diseases – the linkage map will help scientists in their efforts to develop varieties resistant to this and other  deadly diseases.   Photo by J. Legg

A high-resolution linkage map and chromosome scale-genome assembly for cassava by a group of international researchers, including some from IITA, has been published in G3 Genes Genomes Genetics, and highlighted by the Genetics Society of America (http://www.g3journal.org/content/5/1/133.full).

The linkage map was generated by combining 10 genetic maps from 14 diverse parents from African cassava breeding projects including those of IITA in East Africa and Nigeria. It was a collaborative effort  aomg researchers from  IITA, the Agricultural Research Institute (ARI) of Tanzania, National Crops Resources Research Institute (NaCRRI) in Uganda, National Root Crops Research Institute (NRCRI) in Nigeria and the University of Berkeley/ Joint Genome Institute, USA.

It was accomplished through two collaborative projects funded by the Bill & Melinda Gates Foundation. One of them, administered by IITA, focuses on the development of mapping populations, and the other, by  University of Arizona, focuses on improving the cassava genome sequence.

According to Dr Morag Ferguson, IITA’s Cassava Molecular Geneticist, the maps have allowed the aligning of DNA sequence fragments into larger fragments or scaffolds, so that now 90% of the cassava genome assembly is contained in only 30 large fragments, whereas previously it was made up of approximately 13,000 pieces.

“This will be a valuable tool in a number of research areas from diversity assessments to functional genomics and will ultimately assist researchers to efficiently identify and use genetic variation for improved productivity, disease resistance, enhanced nutrition and to develop varieties for industrial processing amongst other applications,’ she said.

This is good news for small-holder farmers in sub-Saharan Africa where currently the crop’s production is greatly threatened by two viral diseases, cassava mosaic disease (CMD) and cassava brown streak disease (CBSD).

DTMA trains field technicians and seed specialists

IITA, in collaboration with CIMMYT, has organized a one-week training course for field technicians, seed specialists of public institutions, and production managers of seed companies participating in the Drought Tolerant Maize for Africa (DTMA) project. This is in recognition of the need for Africa to raise production to meet the world level of maize—a highly sought-after crop with industrial and local consumption benefits both for people and animals.

The training titled “Conduct and Management of Field Trials for Seed Production of Open-pollinated and Hybrid Seed” was held in Ibadan 4-8 August.

Participants in the DTMA trainingin IITA, Ibadan, Nigeria.
Participants in the DTMA trainingin IITA, Ibadan, Nigeria.

During the opening, Dr Robert Asiedu, IITA’s Research for Development Director for West Africa, urged participants to learn all that they could during the training. “Make use of this opportunity by sharing your experiences and also learning new things from your instructors,” he said.

Dr Dele Fakorede, a breeder, who was also present, added that efforts being made by research institutes and their partners would be futile if seed companies did not reach out to farmers with available technologies.

Twenty six trainees took part in the practical course which aimed at upgrading the technical capabilities and skills of the participants, particularly in quality hybrid maize seed production, variety testing, profitable seed marketing, community-based seed production, and the management of seed production fields.

The training also provided participants an opportunity to fully grasp the limiting factors and mitigation strategies for maize seed production and deployment in West Africa with much emphasis on drought and the parasitic weed Striga hermonthica.

Giant strides in IITA plantain breeding for West Africa


Amah during her contract review seminar
Amah during her contract review seminar

IITA has made significant progress in its plantain research in West Africa with the generation of seedlings from crosses with in vitro induced tetraploids from diploids―a first for the Institute.

The IITA Regional Banana Breeding Manager, Delphine Amah, who supervised execution of the crosses in IITA-Ibadan, said the crosses were vital for plantain improvement in West Africa in the years ahead.

Delivering her contract review seminar titled: Support to Banana and Plantain Breeding―Updates on West Africa, Amah said the Banana Unit had recorded giant strides in the recent years.

For instance, as part of a revised pre-breeding strategy to produce improved parents while shortening the breeding cycle for plantain, the unit was now producing tetraploids which have four sets of chromosomes from diploids (which have two) using optimized in vitro doubling techniques.

In addition, tissue culture techniques have been employed to generate seedlings from crosses through embryo culture and mass propagation of plants for clonal evaluation.

The unit is also promoting the use of macropropagation and field propagation techniques for the production of clean planting material and good agronomy practices.

So far, Amah and her team have produced and distributed thousands of Agbagba plantain plantlets to the IITA farm unit and Youth Agripreneur project for propagation and distribution.

Furthermore, they have established pollination blocks with female fertile plantain landraces and Black Sigatoka resistant tetraploid plantain hybrids for accelerated breeding.

The team has established recently imported Musa acuminata ssp. banksii accessions for evaluation and use as parents in crosses to breed for plantains with high provitamin A content.

They have also established a propagation scheme for the production of plantlets for pollination blocks and planned trials to enable registration of new IITA hybrids.

All these activities are aimed at rejuvenating plantain breeding in IITA for efficient delivery of improved varieties to farmers, she said.