Hermonthica Infestation Research Articles

Screening pearl millet genotypes for resistance to Striga hermonthica and compatibility to Fusarium oxysporum f.sp. strigae

Pearl millet (Pennisetum glaucum [L.] R. Br., 2n = 2x = 14) is a nutritionally rich and climate-resilient food crop cultivated globally. It is a crucial staple crop in Burkina Faso and the dry Sahel region, encompassing Niger, Mali, and Senegal. However, the yield of pearl millet is relatively low in the region (<0.85 tons ha−1) due to Striga hermonthica (Sh) infestation, bird damage, insect pests, diseases, and low-yielding open-pollinated landrace varieties. The study aimed to screen genetically diverse pearl millet accessions for Sh resistance and compatibility to a Striga bio-control agent, Fusarium oxysporum f. sp. Strigae (FOS), to select contrasting and promising parents for resistance breeding and production. One hundred and fifty genotypes were evaluated in Sh hotspot fields in the rain-fed and greenhouse conditions using an alpha lattice design and two replications in Burkina Faso. Significant differences were recorded among the tested pearl millet genotypes for the assessed agro-morphological and Striga resistance. Days to flowering was significantly delayed in the assessed genotypes due to Sh infestation. Applying FOS on pearl millet seed significantly reduced the mean Striga number in Sh-infested conditions. The following genotypes: IP-3098, IP-6112, IP-9242, IP-10579, and IP-11358 were identified as exhibiting Sh resistance and were compatible to FOS. The pearl millet genotypes supported few to none Sh emerged plants with comparatively low values under the Striga number progress curve. The selected genotypes are useful parents to breed for Striga resistance and integrated management in Burkina Faso and related agroecologies.

Towards Striga-resistant Gene pool in Nigerian Pearl millet landraces

Parasitism of crop plants by Striga species is a major constraint in the savannah zones of West Africa. A germplasm collection comprised of 240 accessions of pearl millet was screened under natural Striga hermonthica infestation to identify sources of Striga resistance. Data were collected at different time points, specifically at 70, 90 and 140 days after planting for Striga count, Striga vigour and Striga severity. Number of panicles, panicle weight and Grain yield were also measured. The results revealed significant variation in the resistance of pearl millet genotypes to Striga. Fifteen genotypes identified as the most resistant were free of emerged Striga shoots, 10 genotypes supported 14 Striga shoots but with appreciable yield and 15 genotypes with 1-4 Striga shoots and low grain yield. Principal Component and cluster analyses grouped these genotypes into 3 main clusters medium yielding tolerant to Striga, low yielding susceptible to Striga and medium to high yielding resistant to Striga. The high level of resistance observed in some breeding lines enabled the selection of suitable parents for population development.

Hydroxamic acids: New players in the multifactorial mechanisms of maize resistance to Striga hermonthica

Striga hermonthica is the most widespread and destructive plant parasite infesting maize and other major crops in sub-Saharan Africa where it causes severe yield losses and threatens food security. Several tolerant maize lines supporting reduced S. hermonthica emergence have been deployed. However, the molecular bases of such resistance are yet poorly understood. Based on a time course comparative gene expression analysis between susceptible and resistant maize lines we have confirmed resistance mechanisms known to be activated upon plant parasite infestation and identified potential novel players worth further investigation e.g. iron homeostasis and mitochondrial respiration-related genes. Most intriguingly, we show a previously unknown strategy of maize post-attachment resistance based on DIMBOA accumulation in S. hermonthica-infested maize roots. S. hermonthica infestation triggers positive regulation of gene expression in the hydroxamic acid (HA) pathway culminating with an accumulation of benzoxazinoids (BX), known for their antifeedant, insecticidal, antimicrobial, and allelopathic activities. We demonstrate that HA root content is positively correlated with S. hermonthica resistance in the resistant parent and its progenies and in unrelated maize lines. Downregulation of HA genes causes increased susceptibility to S. hermonthica infestation in loss-of-function maize mutants. While the mechanism of BX action in parasitic plant resistance is yet to be uncovered, the potential of this discovery for developing effective control and breeding strategies is enormous.

Enhancing Genetic Gains in Grain Yield and Efficiency of Testing Sites of Early-Maturing Maize Hybrids under Contrasting Environments.

The major challenges of maize production and productivity in Sub-Saharan Africa (SSA) include Striga hermonthica infestation, recurrent drought, and low soil nitrogen (low N). This study assessed the following: (i) accelerated genetic advancements in grain yield and other measured traits of early-maturing maize hybrids, (ii) ideal test environments for selecting early-maturing multiple-stress tolerant hybrids, and (iii) high-yielding and stable hybrids across multiple-stress and non-stress environments. Fifty-four hybrids developed during three periods of genetic enhancement (2008-2010, 2011-2013, and 2014-2016) were evaluated in Nigeria, The Republic of Benin, and Ghana under multiple stressors (Striga infestation, managed drought, and Low N) and non-stress environments from 2017 to 2019. Under multiple-stress and non-stress environments, annual genetic gains from selection in grain yield of 84.72 kg ha-1 (4.05%) and 61 kg ha-1 (1.56%), respectively, were recorded. Three mega-environments were identified across 14 stress environments. Abuja was identified as an ideal test environment for selecting superior hybrids. The hybrid TZdEI 352 × TZEI 355 developed during period 3 was the most outstanding under multiple-stress and non-stress environments. On-farm testing of this hybrid is required to verify its superior performance for commercialization in SSA. Considerable progress has been made in the genetic improvement of early-maturing maize hybrids for tolerance of multiple stressors and high yield. The identified core testing sites of this study could be used to enhance the testing and selection of promising hybrids.

Combining ability of extra-early maturing pro-vitamin A maize (Zea mays L.) inbred lines and performance of derived hybrids under Striga hermonthica infestation and low soil nitrogen.

Low soil nitrogen (low-N), Striga hermonthica infestation and vitamin A deficiency in normal endosperm maize are major challenges confronting maize production and nutrition of the people of sub-Saharan Africa (SSA). Development of pro-vitamin A (PVA) maize hybrids with combined resistance/tolerance to the two stress factors is crucial in mitigating the food insecurity and nutrition challenges resulting from low-N deficiency and Striga infestation. One hundred and fifty hybrids plus six hybrid checks were evaluated under low-N, Striga-infested and optimal conditions in Nigeria for two years. The study examined the combining ability of the PVA inbreds in contrasting environments, classified them into heterotic groups, examined the inter-relationships of grain yield and other agronomic traits of the inbreds in hybrid combinations and assessed the performance and stability of the PVA hybrids across environments. Additive gene action conditioned the inheritance of grain yield under Striga infestation and optimal conditions while non-additive gene action played the major role in the inheritance of grain yield under low-N. Hybrids TZEEIOR 217 × TZEEIOR 197 and TZEEIOR 245 × TZEEIOR 195 were the top-yielding under Striga and low-N conditions, respectively. Inbred lines were classified into three heterotic groups. Inbreds TZEEIOR 195 and TZEEIOR 221 were identified as testers while TZEEIOR 197 × TZEEIOR 82, TZEEIOR 132 × TZEEIOR 195 and TZEEIOR 205 × TZEEIOR 221 were identified as single-cross testers. Ear aspect had direct contribution to grain yield, justifying its inclusion in the multiple trait base index used for selection of Striga resistant and low-N tolerant maize genotypes in SSA. Hybrids TZEEIOR 195 × TZEEIOR 149, TZEEIOR 195 × TZEEIOR 150, TZEEIOR 245 × TZEEIOR 195, TZEEIOR 30 × TZEEIOR 150 and TZEEIOR 245 × TZEEIOR 30 were high-yielding and stable across test environments. These hybrids should be tested extensively in on-farm trials and commercialized to contribute to food security in SSA.

Estimating genetic gains for tolerance to stress combinations in tropical maize hybrids.

Maize is a strategic food crop in sub-Saharan Africa. However, most maize growing tropical savannas particularly in West and Central African experience the occurrence of frequent droughts and Striga infestation, resulting in 30-100% yield losses. This production zones need maize cultivars that combine tolerance to the two stresses. IITA in collaboration with national partners has thus employed a sequential selection scheme to incorporate both drought tolerance and Striga resistance in topical maize hybrids using reliable screening protocols. The main objective of the present study was therefore to use grain yield and other agronomic traits recorded in regional collaborative hybrid trials conducted for 8years under manged stressful and non-stressful conditions and across rainfed field environments to estimate genetic gains in grain yields using mixed model analyses. The results showed significant (p < 0.05) annual yield gains of 11.89kgha-1 under manged drought stress (MDS) and 86.60kgha-1 under Striga infestation (STRIN) with concomitant yield increases of 62.65kgha-1 under full irrigation (WW), 102.44kgha-1 under Striga non-infested (STRNO) conditions and 53.11kgha-1 across rainfed field environments. Grain yield displayed significant but not strong genetic correlation of 0.41 ± 0.07 between MDS and STRIN, indicating that gene expression was not consistent across the two stress conditions. Furthermore, grain yield recorded in MET had significant moderate genetic correlations of 0.58 ± 0.06 and 0.44 ± 0.07It with MDS and STRIN, respectively. These results emphasize the need to screen inbred linens under both stress conditions to further enhance the rate of genetic gain in grain yield in hybrids for areas where the two stresses co-occur. Nonetheless, this study demonstrated that the sequential selection scheme has been successful in generating hybrids with dependable yields that can reduce chronic food deficits in rural communities experiencing simultaneous presence of drought and S. hermonthica infestation in their production fields.

Constraints to Pearl Millet (Pennisetum glaucum) Production and Farmers’ Approaches to Striga hermonthica Management in Burkina Faso

Pearl millet (Pennisetum glaucum) is a staple food crop in Burkina Faso that is widely grown in the Sahelian and Sudano-Sahelian zones, characterised by poor soil conditions and erratic rainfall, and high temperatures. The objective of this study was to document farmers’ perceptions of the prevailing constraints affecting pearl millet production and related approaches to manage the parasitic weeds S. hermonthica. The study was conducted in the Sahel, Sudano-Sahelian zones in the North, North Central, West Central, Central Plateau, and South Central of Burkina Faso. Data were collected through a structured questionnaire and focus group discussions involving 492 participant farmers. Recurrent drought, S. hermonthica infestation, shortage of labour, lack of fertilisers, lack of cash, and the use of low-yielding varieties were the main challenges hindering pearl millet production in the study areas. The majority of the respondents (40%) ranked S. hermonthica infestation as the primary constraint affecting pearl millet production. Respondent farmers reported yield losses of up to 80% due to S. hermonthica infestation. 61.4% of the respondents in the study areas had achieved a mean pearl millet yields of &lt;1 t/ha. Poor access and the high cost of introduced seed, and a lack of farmers preferred traits in the existing introduced pearl millet varieties were the main reasons for their low adoption, as reported by 32% of respondents. S. hermonthica management options in pearl millet production fields included moisture conservation using terraces, manual hoeing, hand weeding, use of microplots locally referred to as ‘zaï’, crop rotation and mulching. These management techniques were ineffective because they do not suppress the below ground S. hermonthica seed, and they are difficult to implement. Integrated management practices employing breeding for S. hermonthica resistant varieties with the aforementioned control measures could offer a sustainable solution for S. hermonthica management and improved pearl millet productivity in Burkina Faso.

Genetic Characterization Of Early Generation Lines Using SNPS Makers And Agronomic Traits For Resistance To Striga Improvement In Maize

The characterization of a greater number of lines hence potentially increase the efficiency of maize breeding programs. This study aims to assess the genetic variation and relationships existing within a population of 177 lines and the two parental lines, using 8,883 SNPs markers obtained from sequencing genotyping (GBS) and four agronomic traits. Two hundred S 1 lines and four checks including the two parents have been evaluated under Striga hermonthica infestation in Benin Republic and Nigeria for two years during 2018 and 2019 growing seasons using 51 x 4 lattice design with two replicates. The UPGMA phylogeny, was used to group the progenies based on their genetic similarity. The tested lines have displayed high genetic variability for all the agronomic traits. Analysis molecular revealed that the polymorphism information content has been varied from 0.047 to 0.50, with average of 0.37, and 63% of the SNP makers were highly polymorphic. The population has displayed a moderate diversity with average genetic diversity of 0.44. The estimated genetic distance has been varied from 0.01 to 0.79 and the highest distance has been observed between the two parental lines. UPGMA clustering based on the Gower dissimilarity matrix grouped the 177 lines into two clusters (I and II) at 30% genetic similarity threshold. The estimated genetic distances between lines showed that all the progenies were genetically related to the two parental lines; and have the potential to provide new favorable alleles for the development of high-performing, Striga-resistant and/or Striga-tolerant maize populations.

Genotypic Variation in Cultivated and Wild Sorghum Genotypes in Response to Striga hermonthica Infestation.

Striga hermonthica is the most important parasitic weed in sub-Saharan Africa and remains one of the most devastating biotic factors affecting sorghum production in the western regions of Kenya. Farmers have traditionally managed Striga using cultural methods, but the most effective and practical solution to poor smallholder farmers is to develop Striga-resistant varieties. This study was undertaken with the aim of identifying new sources of resistance to Striga in comparison with the conventional sources as standard checks. We evaluated 64 sorghum genotypes consisting of wild relatives, landraces, improved varieties, and fourth filial generation (F4) progenies in both a field trial and a pot trial. Data were collected for days to 50% flowering (DTF), dry panicle weight (DPW, g), plant height (PH, cm), yield (YLD, t ha−1), 100-grain weight (HGW, g), overall disease score (ODS), overall pest score (OPS), area under Striga number progress curve (ASNPC), maximum above-ground Striga (NSmax), and number of Striga-forming capsules (NSFC) at relevant stages. Genetic diversity and hybridity confirmation was determined using Diversity Arrays Technology sequencing (DArT-seq). Residual heterosis for HGW and NSmax was calculated as the percent increase or decrease in performance of F4 crossover midparent (MP). The top 10 best yielding genotypes were predominantly F4 crosses in both experiments, all of which yielded better than resistant checks, except FRAMIDA in the field trial and HAKIKA in the pot trial. Five F4 progenies (ICSVIII IN × E36-1, LANDIWHITE × B35, B35 × E36-1, F6YQ212 × B35, and ICSVIII IN × LODOKA) recorded some of the highest HGW in both trials revealing their stability in good performance. Three genotypes (F6YQ212, GBK045827, and F6YQ212xB35) and one check (SRN39) were among the most resistant to Striga in both trials. SNPs generated from DArT-seq grouped the genotypes into three major clusters, with all resistant checks grouping in the same cluster except N13. We identified more resistant and high-yielding genotypes than the conventional checks, especially among the F4 crosses, which should be promoted for adoption by farmers. Future studies will need to look for more diverse sources of Striga resistance and pyramid different mechanisms of resistance into farmer-preferred varieties to enhance the durability of Striga resistance in the fields of farmers.

Field Screening of Sorghum [Sorghum bicolor (L.) Moench] Inbred Lines for Resistance to Striga [Striga hermonthica (Del.)] in East Hararghe, Ethiopia

Drought and the obligate Striga root parasite are two of the most important constraints to sorghum production in the northern and north eastern parts of Ethiopia. This study assessed the field reaction of selected advanced lines under Striga hermonthica infestation condition. Twenty-two sorghum genotypes with two resistant checks (Gobiye and SRN-39) and one susceptible check (Teshale) were evaluated under Striga hot spot area at Fadis Agricultural Research Center, Boko research station (Ethiopia) in the 2016 season using a 5x5 triple lattice design. During the field experiment, 11 parameters were measured among which Striga count emerged on each genotype was the indicator of resistance genotypes. Genotypes differed significantly in all measured parameters in their reactions to Striga. Genotypes 2006 MW 6044, ETSC 300003, ETSC 300081, 05 MW 6019, and ETSC 300080 showed Striga resistance in the field. Thus, these genotypes were the most promising sources of resistance to S. hermonthica. From field experiments, it could be suggested that genetic variability for resistance and tolerance is available in a range of genotypes, which could be used for future breeding and production in Striga infested areas. Keywords: genotypes, germination stimulant, parasitic weed, resistant, screening techniques DOI: 10.7176/FSQM/105-01 Publication date: February 28 th 2021

Impact of Trichoderma harzianum and bacterial strains against Striga hermonthica in Sorghum

A series of laboratory and green house experiments were conducted to investigate the efficacy of Trichoderma harzianum fungi, bacteria ( Flavobacterium, Bacillus megatherium var. phosphaticum (BMP) and Azomonas ) on Striga hermonthica early developmental stages , incidence and sorghum growth under laboratory and greenhouse conditions. The first laboratory experiment results showed that application of BMP + Flavobacterium significantly inhibited S. hermonthica seeds germination during and after conditioning in response to GR24 concentrations as compared to medium control. In the second laboratory experiment, application of the filtrate of T. harzianum alone or in combinations with bacteria significantly inhibited S. hermonthica germination and haustorium initiation as compared to the corresponding control. From greenhouse experiment results, S. hermonthica emergence significantly reduced by T. harzianum and insignificantly by the combination of Flavobacterium + BMP + T. harzianum . T. harzianum followed by the combination of Flavobacterium + BMP gave the highest increment in plant height. T. harzianum significantly increased sorghum number of leaves as compared to the infested control. The combination of Flavobacterium + BMP + T. harzianum gave the highest number of leaves. The combination Flavobacterium + BMP gave the highest sorghum shoot dry weight, followed by T. harzianum . While the highest sorghum root dry weight was obtained from the combination of Flavobacterium + BMP + T. harzianum . Generally, the combination of T. harzianum + Flavobacterium + BMP reduced S. hermonthica infestation and enhanced sorghum growth in comparison to the infested control.

Contrasting Response Mechanisms of Maize Lines to Striga hermonthica

Strigahermonthica (Del.) Benth is a parasitic weed that devastates cereals in Sub-Saharan Africa. Several control measures have been proposed for the parasite, of these, host plant resistance is considered the most cost-effective for poor farmers. Some tolerant/resistant lines have been developed and these lines display tolerance/resistance mechanisms to the parasite. A series of studies was done to investigate some of the mechanisms through which a resistant (TZISTR1108) and a susceptible (5057) maize line responds to S. hermonthica infestation, as well as the effects of parasitism on these lines. In this study, TZISTR1108 stimulated the germination and attachment of fewer S. hermonthica plants than 5057, both in the laboratory and on the field. In TZISTR1108, the growth of the S. hermonthica plants, that successfully attached, was slowed. When compared to the un-infested plants, the infested resistant plants showed fewer effects of parasitism than the infested susceptible plants. The infested TZISTR1108 plants were more vigorous, taller and resembled their un-infected counterparts. There were substantial reductions in the stomatal conductance and nitrogen content of the 5057 upon infestation. The resistant inbred line showed multiple mechanisms of resistance to S. hermonthica infestation. It thrives better than the susceptible line by reducing the attachment of S. hermonthica and it delays the parasite’s development.

Mitigating Striga hermonthica parasitism and damage in maize using soybean rotation, nitrogen application, and Striga-resistant varieties in the Nigerian savannas

AbstractStriga hermonthica infestation causes significant losses of maize yield in the Nigerian savannas and several technologies have been developed and promoted to control Striga in maize. However, since no single technology has been found to be effective against Striga, integrated management is needed to achieve satisfactory and sustainable Striga control. Both on-station and on-farm trials were undertaken from 2013 to 2015 in Bauchi and Kano States of Nigeria to evaluate the performance of integrated Striga control technologies. In the on-station trials, a soybean–maize rotation did not suppress Striga in maize in either location. However, nitrogen application suppressed and reduced Striga infection, except in Bauchi in 2014. The soybean–maize rotation accompanied by N application reduced Striga damage in both locations. On farmers’ fields, rotating soybean with maize significantly reduced Striga infection. At the same time, the use of maize varieties with a combined tolerance to drought and resistance to Striga parasitism also increased maize grain yield on farmers’ fields, probably due to three factors: a reduction in Striga infection, reduced effects of a mid-season moisture deficit, and increased uptake of nutrients from the soil. We concluded that the use of Striga-resistant maize varieties in combination with the application of N fertilizer and rotation with soybean could increase the productivity of maize in Striga-infested fields in the Nigerian savannas.

Stacking Tolerance to Drought and Resistance to a Parasitic Weed in Tropical Hybrid Maize for Enhancing Resilience to Stress Combinations.

Maize is a food security crop cultivated in the African savannas that are vulnerable to the occurrence of drought stress and Striga hermonthica infestation. The co-occurrence of these stresses can severely damage crop growth and productivity of maize. Until recently, maize breeding in International Institute of Tropical Agriculture (IITA) has focused on the development of either drought tolerant or S. hermonthica resistant germplasm using independent screening protocols. The present study was therefore conducted to examine the extent to which maize hybrids simultaneously expressing resistance to S. hermonthica and tolerance to drought (DTSTR) could be developed through sequential selection of parental lines using the two screening protocols. Regional trials involving 77 DTSTR and 22 commercial benchmark hybrids (STR and non-DTSTR) were then conducted under Striga-infested and non-infested conditions, managed drought stress and fully irrigated conditions as well as in multiple rainfed environments for 5 years. The observed yield reductions of 61% under managed drought stress and 23% under Striga-infestation created desirable stress levels leading to the detection of significant differences in grain yield among hybrids at individual stress and non-stress conditions. On average, the DTSTR hybrids out-yielded the STR and non-DTSTR commercial hybrids by 13–19% under managed drought stress and fully irrigated conditions and by −4 to 70% under Striga-infested and non-infested conditions. Among the DTSTR hybrids included in the regional trials, 33 were high yielders with better adaptability across environments under all stressful and non-stressful testing conditions. Twenty-four of the 33 DTSTR hybrids also yielded well across diverse rainfed environments. The genetic correlations of grain yield under managed drought stress with yield under Striga-infestation and multiple rainfed environments were 0.51 and 0.57, respectively. Also, a genetic correlation between yields under Striga-infestation with that recorded in multiple rainfed environments was 0.58. These results suggest that the sequential selection scheme offers an opportunity to accumulate desirable stress-related traits in parents contributing to superior agronomic performance in hybrids across stressful and diverse rainfed field environments that are commonly encountered in the tropical savannas of Africa.

English

Sorghum (Sorghum bicolor (L) Moench) is the fifth most important staple food crop after wheat, rice, maize and barley. Sorghum is consumed by more than 70% of the population. Striga hermonthica is a serious biotic constraint to cereal production in the dry savannas of sub-Saharan Africa. Striga infestation in sorghum is reported to be higher in Nigeria than in other West African countries with about 80% (8.7 million ha) of land cropped to sorghum infested by this weed. Field trials were conducted in 2012 and 2013 to evaluate the effect of seed treatment, sowing date and trap crop in the management of S. hermonthica. During the investigation in two sorghum (resistance and susceptible) which involved intercropping with soyabean, seedtreatment with parkia biglobosa pulp and sowing at different dates (June and July), these were found to reduce the infestation of sorghum by S. hermonthica. The results showed that the effect of shading by soyabean, putative allelopathic mechanism effect of parkia material and high relative humidity due to established rainfall in July showed some benefits against S. hermonthica infestation. Growth of S. hermonthica was almost completely suppressed and yield increased with the resistant sorghum intercropped with soyabean, primed at 66 g/L parkia and planted in July. Key words: Shading, soyabean, allelopathy, Parkia pulp, sorghum, Striga. &nbsp

Consistency of performance of early-maturing maize cultivars in Striga-infested and Striga-free environments

Badu-Apraku, B., Yallou, C., Oyekunle, M., Akinwale, R., Aweke, G. and Kamara, A. 2015. Consistency of performance of early-maturing maize cultivars in Striga-infested and Striga-free environments. Can. J. Plant Sci. 95: 1073–1084. Despite the immense potential of maize (Zea mays L.) in savannas of West and Central Africa (WCA), production and productivity is constrained by Striga hermonthica parasitism. Sixteen early-maturing cultivars were evaluated at two locations in Nigeria and three locations in the Republic of Benin from 2007 to 2009 to assess the grain yield, stability and the consistency of the rankings of the cultivars under Striga-infested and Striga-free environments. The combined analysis of variance showed significant (P&lt;0.01) cultivar and cultivar×environment interactions for grain yield and other traits under Striga-infested and Striga-free environments. The test of concordance was significant (P&lt;0.001) for grain yield (W=0.68), number of emerged Striga plants (W=0.74) and Striga damage (W=0.56) under Striga infestation, indicating stability of resistance in the cultivars developed from diverse sources under artificial S. hermonthica infestation across environments. There was high consistency of the rankings of the cultivars for grain yield and other Striga-resistance traits under Striga-infested and Striga-free environments in Benin and Nigeria. The additive main effects and multiplicative interaction (AMMI) biplot analysis for grain yield revealed POOL15SR/ACR94TZECOMP5-W/ACR94TZECOMP5-W and 2004 TZE-Y Pop DT STR C4 as the most stable cultivars with above-average mean grain yield in Striga-infested environments and they can be combined with other crop management options to control the parasite in the Striga endemic environments. Cultivars TZE Comp 5-W C7F2 and TZE Comp5-Y C6 S6 (Set B) had less Striga damage and number of emerged Striga plants across test environments. These cultivars could therefore serve as unique sources of favorable alleles for improving Striga resistance in maize in different production environments and farming systems.

Assessment of the relationship between soil properties, Striga hermonthica infestation and the on-farm yields of maize in the dry Savannas of Nigeria

A study was conducted in Kano and Bauchi States in the dry Savanna of northern Nigeria to determine Striga incidence and infestation and relate these to soil fertility status and yield of maize. A three-stage sampling technique was used to select communities and fields in targeted Local Government Areas in the two States. The soils in the two States were generally of low fertility, characterized by low levels of total N, organic C, available P and exchangeable bases. In Kano State, Striga incidence ranged from 0 to 100%. One hundred percent of the maize fields sampled in Bauchi State had Striga. In general, Striga population was more than twice higher in Bauchi State [3.1 plants m−2] than in Kano State [1.4 plants m−2]. There were differences in Striga population and severity of attacks between the States and between communities within States. In Kano State, the Striga population was negatively related to latitude, total N, and exchangeable K and was positively related to sand and silt. In Bauchi State, Striga was negatively related to clay, exchangeable K, and Ca, and was positively related to pH and latitude. In both states, the Striga population was negatively correlated with maize grain yield. Up to 75% of the variations in maize grain yield in Kano State could be explained by Striga population and soil organic C. Management of Striga usually requires several measures, however, improving the levels of soil fertility should be the central component of any integrated Striga management approach.

Assessment of level, extent and factors influencing Striga infestation of cereals and cowpea in a Sudan Savanna ecology of northern Nigeria

Infestation of cereals and cowpeas by Striga species constitute a major constraint to increased crop productivity in the savannas of northern Nigeria. Field surveys were undertaken in Jigawa State, Nigeria in 2012 to assess (i) the level and extent of Strgia infestation of cereal and cowpea fields (ii) the severity of Striga attack on crops and (iii) to determine the factors associated with Striga infestation of crop fields. The study was conducted in 48 communities. Eight farmer's fields were sampled in each community along two intersecting transects. Striga hermonthica incidence ranged from 58 to 100% in sorghum fields and from 0 to 100% in millet fields. In sorghum and millet fields, number of emerged Striga plants ranged from 4750 to 431,500 and 0 to 251,750plantsha−1 respectively. For cowpea, S. gesnerioides population ranged from 1625 to 105,375plantsha−1. The severity of Striga attack on sorghum was devastating in all the communities studied. Except in a few cases, all cowpea plants in fields surveyed in most communities were attacked by S. gesnerioides. Field infestation was largely related to poor soil fertility. Stepwise multiple regression identified latitude, pH, available P, Cu and exchangeable K as potentially most important in explaining observed variations in S. hermonthica infestation in sorghum fields. For millet fields, soil pH, available P, Zn and latitude accounted for most of the variations in Striga population whereas latitude, total N, organic C, exchangeable Ca, ECEC, pH, available Mn and Cu accounted for most of the observed variations in S. gesnerioides population in cowpea fields. Our study showed that Striga is a major problem in Jigawa State with almost all the cowpea, sorghum and millet fields infested with the parasite. Improved soil fertility management technologies and Striga-resistant crop varieties are needed to address the menace of Striga in the State.

Cumulative effects and economic benefits of intercropping maize with food legumes on Striga hermonthica infestation

The parasitic weed Striga hermonthica, commonly known as striga, is a major biotic constraint to maize production in sub-Saharan Africa (SSA) where it causes serious food insecurity and poverty in smallholder farming communities. We previously discovered an effective control method for it involving intercropping cereals with fodder legumes in the genus Desmodium, commonly known as desmodium. The objectives of the current study were to evaluate cumulative effects of intercropping maize with the commonly grown food legumes on striga infestation, and to establish any economic benefits of the same. Treatments comprised maize plots planted in monocrop stands or intercropped with five different food legume species or desmodium. Intercropping maize with desmodium gave the most consistent and significant suppression of striga. Out of the food legume intercrops, only crotalaria, groundnut and greengram intercrops had significantly lower striga counts and only in some of the cropping seasons. Grain yields were consistently and significantly higher with desmodium intercrop, although they were also increased with food legume intercrops compared to maize monocrop, thus confirming superiority of intercropping with legumes over maize monocrop. Although production costs in terms of total labor and variable costs were significantly higher for the intercrops than for the maize monocrop, total revenue and net benefits were significantly higher in the former, especially for desmodium. The desmodium intercrop gave the highest economic benefits followed by crotalaria and greengram intercrops. These results confirmed the effectiveness of desmodium in suppressing striga and improving yields and economic returns to smallholder farmers. They also showed that it is profitable to invest in food legume intercrop systems, especially the crotalaria and greengram systems, and indicate that intensifying maize cropping systems through integration of these food legumes in combination with other approaches can contribute to an integrated management of striga and provide a more sustainable and profitable productive system to smallholder farmers.

Effects of mulching, N-fertilization and intercropping with Desmodium uncinatum on Striga hermonthica infestation in maize

The parasitic weed Striga hermonthica is a major constraint to maize production in sub-Saharan Africa and causes serious food insecurity. We discovered serendipitously an effective control method for the weed that involves intercropping cereals with the fodder legume, silverleaf desmodium, Desmodium uncinatum (Jacq.) DC., through mechanisms that involve soil shading and nitrogen fixation. In the current study we investigated long-term effects of inorganic nitrogen (N), mulching and D. uncinatum, singly and in combinations, on S. hermonthica infestation, maize plant growth and grain yields. Treatments comprised sole maize with and without 120 kg N/ha; sole maize plots covered with maize straw (i.e. mulching), with and without N; and maize–D. uncinatum intercrop, with and without N. Intercropping maize with D. uncinatum gave the most significant suppression of S. hermonthica, with addition of N only minimally enhancing its effect. Similarly, mulching significantly suppressed S. hermonthica, although to a much less extent. Application of N both to sole maize and mulched plots reduced seasonal S. hermonthica infestations but the effect was largely insignificant. The effect of D. uncinatum was again notable as it dramatically increased maize plant height and grain yields, with the addition of N only minimally improving both effects. Application of N and mulch, singly and in combination, to the sole maize crop generally enhanced plant height and grain yields, although to a less extent, with the effect of N on grain yields being statistically insignificant during most of the cropping seasons. These results confirm the efficacy of D. uncinatum in S. hermonthica suppression leading to better growth and yields of maize. The effects of N application, mulching and a combination of both treatments in S. hermonthica control in maize were also observed, although these effects were much weaker. The results and their implications are discussed in the context of smallholder cropping systems in the region.