Stability of total carotenoid concentration and fresh yield of selected yellow-fleshed cassava (Manihot esculenta Crantz)

The effects of genotype (G), environment (E), and G x E interaction on carotenoid concentration and yield of 25 yellow-fleshed (YF) and three white-fleshed (WF) cassava genotypes were investigated at five locations in Nigeria for two consecutive cropping seasons. The locations represented the major cassava growing agroecologies in the country and the objective was to identify stable cassava clones for yield and carotenoid levels. Location (L) and G main effects, and year (Y) x L and G x L interactions were significant (p> 0.001) for fresh yield and total carotenoid concentrations; G x L was the largest component of G x E. AMMI analysis revealed that carotenoid concentration is a stable trait, while yield is relatively unstable. The most stable genotypes for total carotenoid concentration with levels above the overall mean were 01/1277, 01/1235, 01/1371, 01/1413, and 01/1442. Likewise, the most stable clones for yield with above average performance were 01/1235, 94/0006, and 01/1206. The high G and low E effects, and the relatively low GEI on total carotenoid concentration imply that evaluation and selection can be effectively done in fewer environments to distinguish clones with high and stable performance while yield requires early testing in diverse and multiple environments to identify genotypes with broad and specific adaptations. Our results suggest that it is possible to breed cassava with high and stable performance for both yield and carotenoid contents

Agronomic traits and tuber quality attributes of farmer grown cassava landraces in Nigeria

Article purchasedEleven Nigerian cassava landraces with desirable pest and disease resistance were evaluated for 18 agronomic and tuber quality traits along with two popularly grown cultivars including an improved genotype. The improved cultivar TMS 30572 gave the highest yield, but had certain undesirable quality attributes such as high cyanogenic potential (12.86 mg HCN equivalent/100g fresh tuber weight) and low mealiness (non-poundable). Conversely, the landraces had lower cyanogenic potential (1 to 5 mg HCN equivalent/100g fresh tuber weight, considered non-toxic) and high mealiness (2.0 to 2.5 scored on a scale of 0 to 3) of boiled tubers. All cultivars exhibited relatively high dry matter percentage (33.2 to 39.2%). Taste, colour, and fibre content of boiled tubers were generally sweet to bland, white to cream, and low to moderate respectively for all cultivars. Although the landraces gave less yield than the elite cultivars, they carried genes for adaptation to local conditions, and have preferred tuber quality attributes that can be introgressed into elite germplasm development

Field evaluation of root rot disease and relationship between disease severity and yield in cassava

Open Access Article; Published online: 15 July 2005eports of cassava root rot disease from different African countries have increased in recent times. Field studies were conducted from July 1998 to October 1999 to determine a reproducible disease assessment method that would allow the comparison of results from different locations and an evaluation of the relationship between disease severity and root yield. Single point disease assessments at 6, 9, 12 and 15 months after planting (MAP) were compared to multiple points assessment based on the area under a disease progress curve (AUDPC). Single point assessments at 12 and 15 MAP, and the AUDPC identified continuous variation (p≤0.01) among the genotypes. However, a consistent result across trials was obtained only with the assessment based on AUDPC. Root dry yield (DYLD) at 15 MAP showed a strong negative correlation with AUDPC (r=−0.74). Regression analysis also confirmed the negative relationship between yield and root rot severity. The five genotypes compared were separated into resistant (91/02324, 30572 and 92/0427) and susceptible (92/0057 and TME-1) groups. It was concluded that root rot disease may cause significant yield loss; however, the magnitude of the yield loss will depend on the susceptibility of the cassava genotype

SSR markers reveal genetic variation between improved cassava cultivars and landraces within a collection of Nigerian cassava germplasm

Open Access JournalThirty-one improved cultivars and five Nigerian landraces of cassava were assessed at genomic DNA level with 16 SSR primers for genetic diversity study. The minimum number of SSR primers that could readily be used for identification of the 36 cassava genotypes was also determined. For the genetic diversity study, the similarity coefficients generated between improved cultivars and Nigerian landraces ranged from 0.42 to 0.84, and 12 distinct DNA cluster groups were identified at 0.70 coefficients using Numerical Taxonomy and Multivariate Analysis System software package. For the genotype identification study, the 16 SSR primers were screened by their polymorphic information content (PIC) values. Five SSR primers that have PIC values between 0.50 and 0.67 were selected and further assessed using simple arithmetic progression combination method. The results obtained revealed a combination of these 5 primers from SSR primers collection at IITA that could readily distinguish the 36 cassava genotypes at 0.93 similarity coefficient. These five primers clustered the 36 cassavas into 16 groups at 0.70 similarity coefficient. Application of this few SSR primers would ultimately reduce the cost and time of research for genetic diversity and genotype identification studies for the genetic improvement program of cassava

Effect of staking and non-staking systems on disease severity, yield and quality attributes of yams (Dioscorea alata)

Aims: The aim of this study was to evaluate the effect of staking and non-staking systems on disease severity, yield and quality attributes of yams. Methodology: High costs and lack of planting materials, labour, staking and inappropriate knowledge on production techniques are major constraints of yam production in Sierra Leone. A total of seven promising hybrid genotypes of yams from International Institute of Tropical Agriculture and one local cultivar, Pulli, were evaluated for yield, reaction to local pest and disease and desirable market traits during 2011 and 2012 in three agro-ecological zones of Sierra Leone. The experiment was laid out in randomized complete block replicated thrice at the experimental sites of the Njala Agricultural Research Centre. Results: Results revealed higher disease pressure in non-staked plots compared to staked plots. Fresh tuber yields were significantly higher in staked plots than the non-staked plots. Five genotypes with yields ranging between 11.8 and 14.7 t.ha-1 significantly out-yielded Pulli (9.1 t.ha-1) in the staked plots, while only genotype TDa 02/00012 (11.9 t.ha-1) significantly out-yielded Pulli (7.1 t.ha-1) in the non-staked plots. Farmers’ preferences for all genotypes were similar to that of the local cultivar. Staking contributed 30.5% mean yield increase compared to non-staking. Makeni had the highest percent mean yield increase due to staking (38.5%) compared to Njala (29.7%) and Kenema (26.4%). Conclusion: Staking is beneficial in yam production contributing an average of 28.2% more fresh tuber yields than non-staking. Genotypes in staking system were more tolerant to in-field local diseases, thereby significantly out-yielding those in non-staking system. Genotypes TDa 98/01174, TDa 98/01176, TDa 02/00012, TDa 98/01168 and TDa 00/00194 had stable resistance to in-field diseases in the staking system and desired food quality traits compared to the check variety, Pulli. Findings have good implications for multiple disease resistance breeding for various production systems as the different genes controlling these traits could be pyramided into an ideotype. Similar technique could be used to breed for yield and other desired food quality traits

Carotenoids content of yellow-fleshed cassava genotypes grown in four agroecological zones in Nigeria and their Retinol Activity Equivalents (RAE)

Vitamin A deficiency (VAD) is a serious and widespread public health problem in developing countries. Therefore, it is essential to identify and improve provitamin A content of staple food crops that may be promoted for health improvements. Cassava (Manihot esculenta) is an important food crop in the tropics. Twenty-two yellow-fleshed and three white-fleshed cassava genotypes were grown in a randomized complete block design with two replications at five locations representing the major cassava-growing agro-ecological zones in Nigeria. The objective was to determine the quantity and quality of carotenoids in cassava storage roots. The varieties were harvested at 12 months after planting and analyzed for moisture content using a standard oven method and carotenoid content using HPLC. Results obtained indicate trans β-carotene was the major component of total carotenoids in cassava (53.5%), followed by α-carotene and 9-cis β-carotene (both at 19.3%). Other components were 15-cis β-carotene (14.9%), zeaxanthin (3.1%), α-cryptoxanthin (2.7%), 13-cis β-carotene (2.4%), and lutein (0.4%). The results revealed that 90% of the carotenoids in cassava is β-carotene. The mean Retinol Activity Equivalent for the genotypes across locations was 0.40, and the genotype TMS 01/1371 had Retinol Activity Equivalent of 0.63. The results from this study provide information that may be used in breeding programs to further enhance the carotenoid content of cassava storage roots

Quantitative variation and interrelationship between factors influencing cassava yield

Objective: Cassava is a crop with largely unexplored and unexplained potentially valuable genetic variability. This study aimed to investigate interrelationship between factors that control cassava yield. Methodology and results: Fourteen quantitative characteristics were assessed in ten cassava genotypes at three locations (Namulonge, Bulisa and Kapchorwa) during two seasons in Uganda. Highly significant (P<0.001) influence of the environment and genotype by environment interactions were observed in most of the plant traits evaluated. Broad sense heritability was relatively moderate for storage roots and dry matter content (h2=0.39 and 0.56, respectively) while it was high for petiole length (h2=0.82). The most productive in storage root yield was clone Migyera at all locations during the first season. Storage root performance decreased during the second season and clones SS4, TMS82/01635 and TMS I 91/0057 led at Namulonge, Bulisa and Kapchorwa, respectively. Dry yield production per clone was high at Bulisa in season one while it was high at Namulonge during second season. Phenotypic correlations were significant between dry root yield with storage root number (r=0.53, p<0.001), storage root size (r=0.37, p<0.001), storage root girth (r=0.54, p<0.001), stem girth (r=0.38, p<0.05), leaves and stems biomass (r=0.38 and 0.58, p<0.05, respectively). The leaf area, petiole length, storage root number, root size, root girth, stem weight, and starch content gave the best equation for yield prediction (R2=0.69, C (P) =5.6). Conclusion and application of findings: Indirect path analysis revealed that selection of high potential clones could be achieved based on storage root number, storage root size and storage root diameter as the main yield components contributing factors to yield enhancement in cassava, and could be used as selection criteria for higher storage root yield potential. Results from multiple regression and path analysis suggested, however, that the model does not fully explain the complex interrelationship of factors determining cassava yield and this will need additional research to understand better yield factors