Analysis of Constraints to Agricultural Production in the Sudano Savanna Zone of Cameroon and Implication for Research Priority Setting

A participatory rural appraisal (PRA) survey approach was used to identify the major constraints to agricultural production and to describe the major production systems in the sudano savanna and sudano sahelian zone of northern Cameroon. Relative emphasis was placed on the household level characterization to have a better understanding of the land use system, farmers' constraints to production and opportunities, so as to better target agricultural technologies and interventions in this vast agro-ecological zone. It was noted that, large variations exist in agriculture management practices between agro-ecological zones, among villages and households in terms of access to resources, such as labour, fertilizers, livestock, farm equipment, and land. Intensive and extensive farming practices might co-exist within the same village and households. The mains sources of vulnerability were identified. Results are used to set research priorities which will be directed towards the need of the majority of area's population; the improvement of sustainable food and feed crop production

Combining ability studies in tropical sorghum (Sorghum bicolor (L.) Moench)

Sorghum varieties grown in West Africa usually have low production potential. Information on combining ability of diverse open-pollinated cultivars and gene pools is needed for efficient choice of breeding methods and parental materials to use in developing breeding programs to increase production. Twenty parental lines including 15 restorers and 5 male-sterile A-lines were mated. The 20 parents were sampled from elite germplasm available for cultivar development in the region. Combining ability studies were conducted on these parents along with their F1 hybrids for grain yield, days to anthesis, plant height, inflorescence length, threshing percentage, and seed mass in 2 years and in two locations. Each location-year combination was considered as an environment. For each trait, general combining ability (GCA) and specific combining ability (SCA) effects were estimated using the line-tester method of analysis. Highly significant GCA effects of males were found for all traits under study. Significant SCA was detected in all traits except inflorescence length. From the ratio of general combining ability to specific combining ability non-additive gene action was predominant for most traits. Parental lines with good performance per se and good performance in crosses for most agronomic traits included: ICSA 902 NG, NR 71182-2, NR 71182-3, CS 144, and Damougari. Both additive and non-additive gene effects are involved in variations observed among crosses. Hybrid breeding could contribute to sorghum improvement in the dry land agriculture of West Africa. Importance of genotype-environment interaction underlines the necessity of evaluating breeding materials under broad range of conditions. The various traits studied can be improved through breeding procedures using a range of different intra-population and inter-population selection procedures. In hybrid breeding procedures, testing of parent lines for general combining ability should be supplemented by evaluation of individual F1 hybrids for specific combining ability

Genetic and Phenotypic Association between Yield Components in Hybrid Sorghum (Sorghum bicolor (L.) Moench) populations

The magnitude of genetic expression and associations among traits are important for the prediction of response to selection in diverse environments and provide the basis for planning and evaluating breeding programs. In this regard, a cross classification mating design was used to produce hybrid sorghum populations, which were evaluated in a randomized completed block design with three replications at four environments in Northern Cameroon. Data on grain yield, days to anthesis, plant height, inflorescence length, threshing percentage and seed mass were collected and subjected to statistical genetic analyses. Significant genotype × environment interaction effects were observed for all traits. Genetic variance was essentially attributed to additive gene effects, with dominance variance for grain yield being negligible. However, the reverse was observed for threshability. Genetic variance components were much higher for plant height and grain yield than for days to anthesis, seed mass and threshability. Heritability estimates for plant height and inflorescence length were high (77 and 54 percent respectively) while the estimates for grain yield and threshability were low (14 and 5 percent respectively). Grain yield had positive genotypic correlation with most of the traits. Days to anthesis were negatively correlated with vegetative and reproductive traits. These results suggest that improvement of days to anthesis, plant height, and inflorescence length should be faster because of higher heritabilities and greater phenotypic variation. However, selection for earliness and reduced plant height would not be possible without hampering grain yield. Selecting for yield primary components namely inflorescence length and seed weight would be effective for increasing production. In addition, optimizing agronomic practices and improved experimental design would increase the selection efficiencie

Genetic variation and interrelation of agronomic character in landraces sorghum (Sorghum bicolor (L.) Moench)

No Abstract. JCAS Vol. 7 (1) 2007: pp. 3-1

Combining ability in medium-maturity maize genotypes adapted to mid-altitude and lowland tropical environments

Maize (Zea mays L.) is grown in different agro-ecological zones in the semi-arid tropical regions. Breeding for high production requires information on the combining ability and the magnitude of useful genetic variances among adapted genotypes. This study was conducted to determine the combining ability among tropical lowland and mid-altitude medium-maturity maize genotypes, provide information to clarify the relationship among them and identify suitable lines for distribution to growers. Six mid-altitude adapted maize inbred lines and six lowland adapted maize inbred lines were crossed in a full diallel mating system. The resulting 132 crosses, excluding the parental lines were evaluatedin four environments for grain yield, days to silking, plant height, ear height, ear weight and grain moisture at harvest. The subdivision of treatment effects in the general (GCA) and specific (SCA) combining ability were performed according to Griffing’s diallel analysis method 3, model 2. Both GCA and SCA were significant for all traits. The reciprocal meansquares were significant for ear height, ear weight, grain moisture and grain yield. Both additive and nonadditive gene effects were involved in combining ability between maize germplasm from different ecologies. Additive genetic effects were more important than nonadditive effects in controlling expression of the various traits evaluated. Positive GCAeffects for yield were observed with the lines EXP124, NCREGP1103, NCREGP28, and TZUT57 among the lowland and the lines TZMI308, 87036 among the mid-altitude lines. Crosses involving parents of different adaptation ecologies yielded hybrids with good agronomic performances and high estimates of SCA for all assessed traits. Crosses with atleast one mid-altitude female parent were better than lowland x lowland and mid-altitude x mid-altitude crosses in all environments. Mid-altitude maize germplasm may hold potential for use as source populations for both mid-altitude and lowland ecologies. These results emphasize the need to exploit the full potential of interpopulation crosses ofmaize genotypes

Heterosis and Combining Ability for Grain Yield and its Components in Induced Sorghum Mutants

Heterosis, general combining ability (GCA) and specific combining ability (SCA), and their effects were studied for five major traits in a design II mating system in pure sorghum lines obtained by induced mutation. Significant genotype effect was detected for all traits. GCA effects were highly significant for all traits studied. Effects due to SCA were of less magnitude except on plant height. Some parents were identified having high GCA for grain yield and low or negative GCA for days to anthesis, which were considered as good combiners. The ratio of general combining ability to specific combining ability indicated that additive gene effect was the predominant type of gene action for most yield contributing traits. High positive heterosis for grain yield and its components, including days to anthesis and plant height, as found for more than half of the hybrids studied. Some pure lines evaluated may be used directly as male parents of hybrids and as breeding lines for incorporation into selection programs. The results demonstrate for this set of genotypes the considerable potential that exists for improving the yield performance of sorghum in Western Africa. Importance of genotype x environment interaction underlines the necessity of evaluating breeding materials under a broad range of dry land conditions. This research would assist decisions on parental selection for more extensive study of heterozygosity involving large numbers of genotypes

Heterosis and combining ability for grain yield and its components in induced sorghum mutants

No Abstract. African Crop Science Journal Vol. 13(2) 2005: 143-15

Genetic and phenotypic association between yield components in hybrid sorghum (Sorghum bicolor (L.) Moench) populations

The magnitude of genetic expression and associations among traits are important for the prediction of response to selection in diverse environments and provide the basis for planning and evaluating breeding programs. In this regard, a cross classification mating design was used to produce hybrid sorghum populations, which were evaluated in a randomized completed block design with three replications at four environments in Northern Cameroon. Data on grain yield, days to anthesis, plant height, inflorescence length, threshing percentage and seed mass were collected and subjected to statistical genetic analyses. Significant genotype × environment interaction effects were observed for all traits. Genetic variance was essentially attributed to additive gene effects, with dominance variance for grain yield being negligible. However, the reverse was observed for threshability. Genetic variance components were much higher for plant height and grain yield than for days to anthesis, seed mass and threshability. Heritability estimates for plant height and inflorescence length were high (77 and 54 percent respectively) while the estimates for grain yield and threshability were low (14 and 5 percent respectively). Grain yield had positive genotypic correlation with most of the traits. Days to anthesis were negatively correlated with vegetative and reproductive traits. These results suggest that improvement of days to anthesis, plant height, and inflorescence length should be faster because of higher heritabilities and greater phenotypic variation. However, selection for earliness and reduced plant height would not be possible without hampering grain yield. Selecting for yield primary components namely inflorescence length and seed weight would be effective for increasing production. In addition, optimizing agronomic practices and improved experimental design would increase the selection efficiencies

Yield stability of sorghum hybrids and parental lines

Seventy-five sorghum hybrids and twenty parental lines were evaluated for two consecutive years at two locations. Our objective was to compare relative stability of grain yields among hybrids and parental lines. Mean grain yields and stability analysis of variance, which included linear regression coefficient (bi) and deviation from regression (S2d) were used to determine relative stability. Genotypes x environment interactions were significant. Significant hybrids x environment interactions were also detected. Hybrids and parental lines had significantly different regression coefficients, as indicated by hybrid-environment (linear) mean squares. Hybrids showed significantly higher mean yield compared with parental lines and the yield advantage generally increased with increasing environmental yield potential. Hybrids bi values were significantly higher (0.02 - 2.14) than for parental line (-0.82 - 1.52). Deviations from regression for hybrids were higher than those of parental line. Crosses between hybrids ICSA 38 x Damougari, and ICSA 39 x Damougari produced the highest grain yields. Their bi values were not significantly different from unity, but S2d estimates were significantly greater than zero. Thirteen hybrids recorded bi values close to unity, small S2d and grain yields higher than the mean of all the hybrids. Based on our findings it is apparent that in the dry land agriculture of west Africa, selection of hybrids for superior yields across environments should be emphasized first, and then the relative stability of these hybrids over environment should be determined

Etude génétique de l’indice de récolte des lignées pures et hybrides F1 du niébé (Vigna unguiculata [L.] Walp.) en zone des hautes savanes guinéennes de l’Adamaoua, Cameroun

En vue de sélectionner les variétés du niébé (Vigna unguiculata [L.] Walp) adaptées en zone de hautes savanes guinéennes, un essai en champ a permis de mesurer l’indice de récolte (IR), d’établir ses corrélations avec les paramètres de rendement et d’évaluer l’hétérosis chez huit lignées pures et quatre hybrides F1 dans les conditions environnementales de Ngaoundéré. Après les croisements en pots, ce matériel a été évalué en champ dans un dispositif en blocs complètement randomisé. La parcelle élémentaire était de 2.5 × 6.0 m. Les résultats indiquent des différences significatives au seuil de 5% pour l’indice de récolte (12,40 à 46,21%). L’analyse de variance montre un effet génotypique important aussi bien pour le rendement en graines que pour le nombre de gousse par plante. La comparaison des hybrides F1 avec leurs parents montre un hétérosis pour l’indice de récolte (IR), le rendement et ses composantes à l’exception du nombre de graines par gousse. Le contrôle génétique suggère l’implication des gènes à effets dominants et additifs ; toutefois, la valeur de l’hybride F1 dépend de la valeur propre des géniteurs. Parailleurs, aucune corrélation n’a été trouvée entre IR au seuil de 5%, les paramètres du rendement mesurés et les critères de prédiction. Cette étude montre que la sélection pour l’IR devra privilégier les géniteurs possédant des valeurs individuelles élevées.Mots clés : Vigna unguiculata, indice de récolte, rendement, hétérosis, sélectionIn order to select varieties of cowpea (Vigna unguiculata [L.] Walp) adapted to the high guinea savannah region, a trial was carried out to determine the harvest index (HI), establish the correlation between yield components and evaluate the heterosis of eight pure lines and four F1 hybrids under the environmental conditions of the Ngaoundere area. Following controlled crossing in pots, the resulting hybrids were evaluated in a randomized complete block design, the experimental plot measuring 2.5 × 6.0 m. Results showed significant (