Collection and characterization of cassava germplasm in Comoros

Genet Resour Crop Evol https://doi.org/10.1007/s10722-023-01626-4 RESEARCH ARTICLE Collection and characterization of cassava germplasm in Comoros M. E. Ferguson · P. Ntawuruhunga · M. O. Fouad · O. K. M. A. Hassane · M. A. Charmila · A. A. Hamza · N. A. Mohamed · I. Dieng · E. Njukwe · T. M. Shah Received: 20 March 2023 / Accepted: 31 May 2023 © The Author(s) 2023 Abstract In Comoros, cassava plays a major food security role, however yields are low as few modern cultivars are grown. Prior to the introduction of new cultivars, and as a germplasm resource for breeders, germplasm collection missions were undertaken in the three largest islands; Ngazidja, Ndzouani and Mwali; and associated farmer knowledge documented. Cassava landraces were collected from 34 farms, and 17 key informant interviews conducted. Stakes of 79 collected landraces were planted for agro-morphological characterization. All landraces Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/s10722-023-01626-4. M. E. Ferguson (*) · T. M. Shah International Institute of Tropical Agriculture (IITA), P.O. Box 30709, 00100 Nairobi, Kenya e-mail: T. M. Shah e-mail: P. Ntawuruhunga IITA, Lusaka, Zambia e-mail: M. O. Fouad · O. K. M. A. Hassane · M. A. Charmila · A. A. Hamza · N. A. Mohamed Institut National de Recherche pour l’Agriculture, la Pêche et l’Environnement (INRAPE), Ngazidja, Comoros e-mail: O. K. M. A. Hassane e-mail: were genotyped using DaRTSeq technology and data analysed to identify duplicates. Genetic fingerprints of 46 unique landraces were co-analysed with 402 previously genotyped landraces and improved cultivars from Tanzania. From this set only one match was made with a very old cultivar, Aipin Valenca, from the Northern Zone in Tanzania. According to SNP data, germplasm from the three islands of Comoros were similarly related to one another, and more distantly related to germplasm from Tanzania. They were most closely related to germplasm from the Northern Zone in Tanzania, suggesting a possible historical introduction of germplasm from this area. Lower levels of diversity were observed on these M. A. Charmila e-mail: A. A. Hamza e-mail: N. A. Mohamed e-mail: I. Dieng IITA, Ibadan, Nigeria e-mail: E. Njukwe IITA, Kigali, Rwanda e-mail: Present Address: E. Njukwe CORAF, Dakar, Senegal Vol.: (0123456789) 13 Genet Resour Crop Evol islands, as well as the islands of Pemba and Zanzibar. This implies limited introduction and movement of cassava germplasm into the islands. Introductions of improved germplasm to Comoros is recommended with the simultaneous conservation of collected unique landraces. Two landraces with high market demand and reported tolerance to diseases were identified for further evaluation with a view to multiplication and distribution and incorporation into the breeding program. Keywords Farmer knowledge · Morphological descriptors · Genotyping · Diversity Introduction Africa depends on the climate-resilient, starchy root crop, cassava (Manihot esculenta Crantz), to feed a substantial proportion of its’ population. Annual production in sub-Saharan Africa is estimated at 178 million tons, which is 61% of global production (FAOSTAT 2022). Cassava serves as a food security crop because of its concentrated source of carbohydrate, ability to produce a yield under diverse climatic conditions, ability to remain in the soil without deteriorating until needed, and its amenability to staggered harvesting (De Vries and Toenniessen 2001). It can also be used for animal feed and industrial applications for income generation (Li et al. 2017). Nevertheless, on-farm yields in Africa are low; 8.62 Mt/ ha in 2020 compared to 14.6Mt/ha in Latin America in the same year (FAOSTAT 2022). This is largely due to farmers growing traditional landraces, which are often inherently low yielding and susceptible to widespread virus diseases, including cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) (Legg et al. 2014). Landraces of cassava, often referred to as farmer-cultivars or heirloom cultivars, have been grown for many years, being subject to natural and artificial selection by farmers, and represent an important source of genetic variation for plant breeding. It is important that this diversity is collected, evaluated, and conserved as some of these landraces may be vulnerable to extinction through susceptibility to viruses or replacement by modern cultivars. In Comoros, cassava is the main food crop after banana, a major source of calories and the most Vol:. (1234567890) 13 resilient of local food crops. The Comoros is a group of islands located at the northern end of the Mozambique Channel of the Indian Ocean, between Madagascar and the southeast African mainland, about 290 km off the eastern coast of Africa. Agriculture contributes 35.6% to the country’s GDP and employs 68% of the country’s labor force and accounts for 90% of exports (IFAD 2016). Cassava germplasm in these islands comprise both landraces and improved cultivars that could have been introduced from neighboring countries, or when cassava was first introduced to the East African coast in the 17th or eighteenth centuries (Carter et al. 1992). A first step in improving cassava production in Comoros is to collect and conserve existing landraces and farmer knowledge. By being cognisant of this information, breeders are more likely to breed or introduce appropriate improved cassava cultivars that respond to the intricacies of farmers’ preferences with implications for positive varietal adoption. After collection of landraces, it is important to identify duplicates in the collection as farmers often give different names to the same cultivar and thus define a unique set of germplasm for conservation and for breeders to utilize. In addition, germplasm must be evaluated, to rapidly identify any obvious, interesting characteristics, and to determine any genetic structure, or relationship to germplasm from neighboring regions. Although traditional agro-morphological characterization is useful to assess general features of the germplasm, and identify any landraces with striking characters, molecular characterization provides a far greater number of makers that are more stable and less influenced by the environment for diversity assessment (Tiago et al. 2016). Several molecular marker technologies have been used to characterize cassava germplasm to identify genetic variability. These include Random Amplified Polymorphic DNA (Asante and Offei 2003), Amplified Fragment Length Polymorphism (Roa et al. 1997), microsatellites (Hurtado et al. 2008) and more recently, Single nucleotide polymorphic (SNP) markers (Kawuki et al. 2009; Ferguson et al. 2019, 2021; Pierre et al. 2022). The objectives of the present study were to (1) document farmers’ knowledge relating to the genetic material collected, (2) assess the cassava genetic variability and diversi (...truncated)