![]() The probability to find high polymorphisms around target genes has significantly increased with SNPs given that they are highly abundant in the genomes and provide highest map resolution when compared with other marking systems 22. However the strong limitations attached to the earlier molecular markers were a drag in the effective dissection of traits in cassava with a large paucity of markers which did not permit good genome coverage and prediction of crop performance in the first set of genetic maps developed for cassava up to 2010 as SNPmarkers hadn’t been developed for this crop. ![]() The integration of the early developed molecular markers for cassava has fast tracked the discovery of novel genes such as CMD1, CMD2, CMD3 18, 19, 20, 21 that has improved breeding and development of CMD resistant varieties. This soon resulted in the development of several molecular markers such as RFLP, ESTs, RAPDs, ESTs and SSRs 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18. Cassava benefited from such molecular tools leading to the development of the first molecular map 8. Advancement of biotechnology has resulted in the development of molecular tools to increase breeding efficiency in crops. Although, classical breeding has resulted in moderate improvement of cassava for several traits up to the late 90s, this often not at efficient pace leading to long breeding cycle. Breeding for such complex traits can be very challenging due to its multigenic nature given that drought tolerance/productivity under stress is a complex phenomenon as it is driven by several morphological, physiological and yield-component traits 6, 7. Development of varieties that can withstand moderate stress or sever stress conditions are critical to enhance higher productivity in marginal environments. The most limiting abiotic constraint to cassava production is drought 2, 5. ![]() The rapid expansion of cassava production into non-traditional ecologies of the savannas in the last two or more decades have necessitated need to breed for more adapted varieties. In recent years, cultivation has expanded to transitional belts/savannas with increasing need for more food (due to population pressures). Cassava has been historically grown in the humid and sub humid zones of Africa where amount of rainfall distribution is between 10 mm 3, 4. It is one of the most important source of energy in the diet of Africans 1, 2. The availability of KASPar SNPs are anticipated to improve the implementation of MB for the development of high performing drought-tolerant cassava varieties in Africa.Ĭassava is an important food and starch crop, with excellent adaptability to multiple environments typically grown from 18 to 24 months in the dry environments. Composite interval mapping using 267 F 1 progeny in initial QTL mapping identified 27 QTLs for productivity traits in the dry savannah of Nigeria. To aid molecular genetic analysis of traits, a linkage map covering 1582.8 cM with an average resolution of 3.69 cM was constructed using 505 polymorphic SNP markers distributed over 21 linkage groups. ![]() This study was conducted to explore KASpar SNPs to generate more molecular tools to enhance genetic dissection of elite African germplasm for improved cassava productivity in dry environments of Africa where molecular resources are highly limited for crop improvement. Unfortunately, the dearth of molecular tools for decades has hampered molecular breeding (MB) to improve cassava productivity. Yield is a complex trait and often difficult to manipulate for genetic gain in conventional breeding. While its production has rapidly expanded to the dry savannahs of the continent, productivity is low in this ecology due to drought by farmers, extending the growth cycle from 12 months to 18, and sometimes 24 months to ensure better harvests. Cassava is an important staple in Sub-Sahara Africa. ![]()
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