Abstract
Cassava mosaic geminiviruses (CMGs) and cassava brown streak viruses (CBSVs) cause the highest yield losses in cassava production in Africa. In particular, cassava brown streak disease (CBSD) is and continues to be a significant constraint to optimal cassava production in Eastern and Southern Africa. While CBSD has not been reported in West Africa, its recent rapid spread and damage to cassava productivity in Eastern, and Southern Africa is alarming. The aim of this study was to evaluate Nigerian cassava genotypes in order to determine their responses to CBSD, in the event that it invades Nigeria, the world’s largest cassava producer. The study gathered information on whether useful CBSD resistance alleles are present in the elite Nigerian cassava accessions. A total of 1,980 full-sib cassava seedlings from 106 families were assessed in the field at the seedling stage for a year. A subset of 569 clones were selected and assessed for another year at the clonal stage in Namulonge, central Uganda, a known hotspot for CBSD screening. Results indicated that foliar and root incidences and severities varied significantly (p ≤ 0.01, p ≤ 0.001) except for CBSD foliar incidence at 6 months (CBSD6i). Highest and lowest plot-based heritability estimates for CBSD were registered for CBSD root severity (CBSDrs) (0.71) and CBSD6i (0.5). Positive and highly significant correlations were noted between CBSD root incidence (CBSDri) and CBSDrs (r = 0.90***). Significant positive correlations were also noted between CBSD foliar severity at 3 months (CBSD3s) and CBSD foliar incidence at 6 months (CBSD6i) (r = 0.77***), CBSD3s and CBSDrs (r = 0.35***). Fresh root weight (FreshRW) negatively correlated with CBSDri and CBSDrs, respectively (r = −0.21*** and r = −0.22***). Similarly, CBSD3s correlated negatively with cassava mosaic disease severity at 3 (CMD3s) and 6 months (CMD6s), respectively (r = −0.25*** and r = −0.21***). Fifteen clones were selected using a non-weighted summation selection index for further screening. In conclusion, results revealed that the elite Nigerian accessions exhibited significant susceptibility to CBSD within 2 years of evaluation period. It is expected that this information will aid future breeding decisions for the improvement of CBSD resistance among the Nigerian cassava varieties.
Highlights
Cassava (Manihot esculenta Crantz) is a perennial plant cultivated as an annual crop
About 0.01% of genotypes were lost by the 6th month, and by the 12th month, an additional 15% of genotypes had succumbed to cassava brown streak disease (CBSD) pressure
This study was initiated on the premise of determining the field reaction of Nigerian cassava genotypes to CBSD
Summary
Cassava (Manihot esculenta Crantz) is a perennial plant cultivated as an annual crop It originated in Latin America and is widely grown across the subtropical and tropical regions of the world. The crop is amenable to piecemeal harvesting for a period between 8 and 24 months after planting, an attribute that makes it popular among smallholder farmers. These inherent characteristics make cassava one of the most resilient food security crops of the 21st century. 70% of cassava is currently grown in Africa and Asia, with an estimated cultivated area of more than 22 million hectares (Food and Agricultural Organization of the United Nations [FAOSTAT], 2020). Africa accounts for 61% of 277 million tons of cassava production worldwide, most of which comes from Nigeria with an estimated 59 million tons (Food and Agricultural Organization of the United Nations [FAOSTAT], 2020)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
