Suitability and use of two molecular markers to track race-specific resistance striga gesnerioides in cowpea (Vigna unguiculata (L.) Walp.)

The obligate root parasitic weed Striga gesnerioides poses a severe constraint to cowpea productivity in the dry savannahs of West and Central Africa, where cowpea is a major crop. At least seven races of S.gesnerioides have been identified within the cowpea-growing regions of West and Central Africa, based onhost differential response and genetic diversity analysis. Molecular markers linked to resistance to  different races of S. gesneriodes have been identified. It was desirable to demonstrate the applicability and efficiency for use in marker-assisted selection (MAS) to fast-track the development of cowpea for resistance to S. gesnerioides. The objective of the study was to determine the suitability of two molecular markers in tracking race-specific S. gesnerioides resistance in cowpea (SG3), the predominant race found in Nigeria. F2 mapping populations and recombinant inbred lines (RILs) derived from the cross involving IT97K-499-35 and a susceptible local landrace (Borno Brown), and another resistant parent B301 with the same susceptible land race (Borno Brown) were assayed using two linked markers. Genetic analysis showed that resistance to S. gesnerioides in cowpea is qualitatively inherited with single dominant gene action. Two SCAR markers, 61RM2 and C42-2B were validated in the same F2 populations and subsequent recombinant inbred lines (RILs). The two markers were able to discriminate between resistance and susceptibility and the genotypic score was quite similar to the phenotypic score with the markers score showing greater efficiency in selection than phenotypic score. The 61RM2 had two bands in resistant cultivars and amplified a ~450 bp fragment with marker efficiency of 98% while C42-2B amplified a single ~250 bp fragment with marker efficiency of 96% in resistant cultivars and absent in susceptible cultivars. The genetic distance between 61RM2 and phenotypic score was 3.5 cM while that of C42-2B and phenotypic score was 8.5 cM. The two marker data set were significantly correlated with the phenotypic data (r=0.95). Based on the tight linkage with the resistant locus, 61RM2 was found to be a utility marker to initiate MAS in cowpea breeding for resistance to S. gesnerioides.Key words: Cowpea, Striga, molecular marker, genetic distance, race-specific, obligate parasitic weed, Vigna unguiculata

Genetic variability and heritability studies of some reproductive traits in cowpea (Vigna unguiculate (L.) Walp.)

The success of most crop improvement programs largely depends upon the genetic variability and the heritability of desirable traits. The magnitude and type of genetic variability help the breeder to determine the selection criteria and breeding schemes to be used for improvement purposes. A screen house experiment was carried out at Samaru, Nigeria in 1999 and 2000 dry seasons to estimate the genotypic variability of some reproductive traits and their heritability in some selected cowpea varieties. Results of the study showed that there was considerable variation among cultivars for duration of reproductive phase and rate of photosynthate partitioning. Genotypic coefficients of variation were also high for days to first flower, 100-seed weight, plant height, and harvest index. Broad-sense heritability estimate (h2) was 98.9% for 100-seed weight, 94% for duration of reproductive phase, 84.5% for days to first flower, 83.9% for days to maturity, and 77.3% for harvest index. This information showed that there is sufficient genetic variance to warrant selection for improvement in the cowpea genotypes studied. We concluded that considerable progress in cowpea breeding could be achieved by exploiting these traits

Effect of imazapyr treated maize on Striga infestation and time of intercropping cowpea in Samaru, Nigeria

Two field experiments were conducted at the research farm of Institute for Agricultural Research (IAR) Samaru, Zaria during the 2011 cropping season, with the aim of determining the effect of imazapyr treated maize on Striga infestation and time of intercropping cowpea in Samaru, northern guinea savannah of Nigeria. There were two sets of experiments: the first experiment consisted of Six (6) hybrids (AS1128-1, AS1128-2, AS1128-3, AS1128-4, AS1128-6 and AS1128-8) of imazapyr resistant (IR) maize seeds treated with imazapyr chemical and intercropped with cowpea at 2, 4 and 6 weeks after sowing (WAS) of maize. The second experiment consisted of the same Six (6) hybrids of IR maize seeds but untreated and also intercropped with cowpea at 2, 4 and 6 WAS of maize. The experiments were laid out in a split plot design with time of intercropping cowpea as main plot and hybrid maize varieties as sub plot, and replicated three times. The cowpea variety used for the trial was IT97K-499-35. Among the treated IR-maize hybrids, only AS1128-1, AS1128-2, AS1128-3 and AS1128-4 germinated while for the untreated, all the six hybrids germinated. The grain yields per hectare of all the treated maize hybrids did not significantly differed whereas grain yields per hectare of the untreated maize hybrids AS1128-1, AS1128-2, AS1128-3 and AS1128-4 were significantly higher than the hybrid AS1128-8. The treated IR  maize hybrids exerted 100% control of Striga while the untreated supported Striga emergence. There was no visible damage symptoms observed on the cowpea intercropped with treated maize at all times of intercropping. It is therefore concluded that the IR-maize hybrids ASII28-1, ASII28-2, ASII28-3 and ASII28-4 should be used in the treated forms for the control of Striga. Moreover, the intercropping of cowpea with imazapyr treated maize can be carried out starting from 2 WAS of maize.Key words: Intercropping, imazapyr resistant maize (IR-maize), cowpea, Striga

Leprosy post-exposure prophylaxis with single-dose rifampicin

_Objective:_ Leprosy post-exposure prophylaxis with single-dose rifampicin (SDRPEP) has proven effective and feasible, and is recommended by WHO since 2018. This SDR-PEP toolkit was developed through the experience of the leprosy postexposure prophylaxis (LPEP) programme. It has been designed to facilitate and standardise the implementation of contact tracing and SDR-PEP administration in regions and countries that start the intervention. _Results:_ Four tools were developed, incorporating the current evidence for SDRPEP and the methods and learnings from the LPEP project in eight countries. (1) th

Response of Soybean Genotypes to Alecta vogelii Infestation under Natural Field Conditions

Field studies were conducted in 1995 and 1996 in the northern Guinea savanna of Nigeria to determine the response of 22 soybean genotypes to Alectra infestation. Significant differences were observed amongst soybean genotypes in number of Alectra shoots that emerged at 9 and 10 weeks after sowing and days to first Alectra emergence. Alectra emergence occurred later in early maturing soybean genotypes [54 days after sowing (DAS)] while with most late maturing genotypes, Alectra emergence started at 50 DAS. Result revealed that sixteen genotypes supported few or no Alectra shoots while six were susceptible. Soybean genotypes that supported high numbers of Alectra shoots recorded lower grain yields than those with fewer Alectra shoots. However, soybean genotypes, SAMSOY2 and TGX1485-1D that significantly supported high numbers of Alectra recorded grain yields similar to those of genotypes that supported few or no Alectra. These findings may be due to three possible mechanisms of resistance of soybean genotypes to Alectra parasitism. The sixteen genotypes, which supported few or no Alectra shoots, may have produced lower amounts of root exudates required for stimulation of germination of Alectra. They may also have prevented the initiation, attachment, and penetration of haustorium from Alectra plants to the roots of the hosts. These mechanism were however, not investigated in this study. Further studies may therefore be necessary to confirm our speculations. Soybean genotypes, SAMSOY2 and TGX1485-1D, which recorded high yield irrespective of high infestation with Alectra may exhibit tolerance to the parasite

Understanding Market Participation Choices and Decisions of Maize and Cowpea Farmers in Northern Nigeria

Alleviating poverty and reducing food insecurity have received close critical attention from many researchers in sub-Saharan Africa. Farmers' participation in agricultural markets has been seen as a potent strategy for improving their livelihoods. This paper applies econometrics to farm survey data from Bauchi and Kano states as major maize and cowpea growing areas hit by one of the most important root parasites known as Striga to determine the factors behind farmers' decisions about participation in the agricultural market and the volume of their output to be marketed. Relevant data was collected from 600 households in both states and results from the Double-Hurdle model indicated that price and non-price constraints played significant roles in determining decisions on participation in the markets for both maize and cowpea. Household and total farm sizes, price and ease of transportation through access to motorized equipment were positively related to decision to participate in the maize market. However, the volume of sale of traded produce was influenced by location-specific variable which underscores socio-economic and population-related factors favoring market access that are present more in Kano than in Bauchi. Age of the household head and total farm size were significantly related to decision to participate in the cowpea market while results of the second stage of the model indicate that access to mobile phone and location variable affect positively the volume of cowpea sold. The role of price was conspicuous in both produce markets as the main incentive for households' participation. The paper concludes with policy implications aimed at providing better market opportunities to farmers thereby improving their welfare in northern Nigeria and other areas with similar socio-economic and bio-physical conditions in West Africa

Effect of phosphorus application and soybean cultivar on grain and dry matter yield of subsequent maize in the tropical savannas of north-eastern Nigeria

Soybean can contribute to soil N, which may partly be used to improve maize production in northeast Nigeria. However, the efficiency of soybean to fix N can be limited by soil P deficiency. This studyevaluated the effect of P application and soybean cultivars on dry matter and grain yield of subsequent maize for two years (2005 - 2006) at Miringa and Azir. Experimental design was a split-plot with threereplications. The main plots contained P levels of 0, 20 and 40 kg P/ha and subplots had four soybean cultivars. Maize was planted in the harvested soybean plots. Application of P to soybean at 20 and 40kg/ha significantly increased dry matter and grain yield of succeeding maize. Differences in grain yield were significant between all P rates in Miringa (2005) and Azir (2006) but only between 0 and 40 kg P/hain Azir (2005) and Miringa (2006). The grain yields of maize following late-maturing soybean cultivars were significantly higher than those following the early maturing cultivars in 2005. The maize yieldincreases could however, not be explained by total soil N, available P, and N and P uptake. Other rotation effects beyond N supply by the preceding soybean may be responsible for the yield increasesof maize