Striga Emergence Research Articles

Genome-wide association analysis of grain yield and Striga hermonthica and S. asiatica resistance in tropical and sub-tropical maize populations

BackgroundGenetic improvement for Striga hermonthica (Sh) and S. asiatica (Sa) resistance is the most economical and effective control method to enhance the productivity of maize and other major cereal crops. Hence, identification of quantitative trait loci (QTL) associated with Striga resistance and economic traits will guide the pace and precision of resistance breeding in maize. The objective of this study was to undertake a genome-wide association analysis of grain yield and Sh and Sa resistance among tropical and sub-tropical maize populations to identify putative genetic markers and genes for resistance breeding. 126 maize genotypes were evaluated under controlled environment conditions using artificial infestation of Sh and Sa. The test genotypes were profiled for grain yield (GY), Striga emergence counts at 8 (SEC8) and 10 (SEC10) weeks after planting, and Striga damage rate scores at 8 (SDR8) and 10 (SDR10) weeks after planting. Population structure analysis and genome-wide association mapping were undertaken based on 16,000 single nucleotide polymorphism (SNP) markers.ResultsA linkage disequilibrium (LD) analysis in 798,675 marker pairs revealed that 21.52% of pairs were in significant linkage (P < 0.001). Across the chromosomes, the LD between SNPs decayed below a critical level (r2 = 0.1) at a map distance of 0.19 Mbp. The genome-wide association study identified 50 significant loci associated with Sh resistance and 22 significant loci linked to Sa resistance, corresponding to 39 and 19 candidate genes, respectively.ConclusionThe study found non-significant QTL associated with dual resistance to the two examined Striga species Some of the detected genes reportedly conditioned insect and pathogen resistance, plant cell development, variable senescence, and pollen fertility. The markers detected in the present study for Sa resistance were reported for the first time. The gene Zm00001eb219710 was pleiotropic, and conditioned GY and SEC10, while Zm00001eb165170 affected SDR8 and SDR10, and Zm00001eb112030 conditioned SDR8 and SDR10 associated with Sh resistance. The candidate genes may facilitate simultaneous selection for Sh and Sa resistance and grain yield in maize after further validation and introgression in breeding pipelines. Overall, we recommend breeding maize specifically for resistance to each Striga species using germplasm adapted to the endemic region of each parasite.

Evaluation of granular formulated strigolactone analogs for Striga suicidal germination.

Striga hermonthica, an obligate root parasitic weed, poses a significant threat to cereal production in sub-Saharan Africa. Lowering Striga seed bank in infested soils is a promising strategy to mitigate infestation levels. The dependency of Striga seed germination on strigolactones opens up the possibility of a 'suicidal germination' approach, where synthetic germination stimulants induce lethal germination in the absence of a host. Implementing this approach requires active germination stimulants with a suitable formulation for field application. Here, we describe the development of slow-releasing granular formulation of two potent germination stimulants 'Methyl Phenlactonoate 3' and 'Nijmegen-1' and the assessment of their activity under Laboratory, greenhouse, mini-field, and field conditions. Under laboratory conditions, the granular formulation of either of the two germination stimulants (1.25 mg per plate, corresponding to 0.09 mg a.i.) induced Striga seed germination at a rate of up to 43%. With 10 mg granular product (0.75 mg a.i.) per pot, we observed 77-83% reduction in Striga emergence under greenhouse pot conditions. Application of the formulated stimulants under artificially or naturally infested fields resulted in approximately 56%, 60%, and 72% reduction in Striga emergence in maize, sorghum, and millet fields in Kenya and Burkina Faso, respectively. Our findings on the newly designed granular formulation of Methyl Phenlactonoate 3 and Nijmegen-1 reveal encouraging prospects for addressing the Striga problem in Africa. These findings underscore several significant advantages of the formulated stimulants, including suitability for the African agricultural context, and, most importantly, their effectiveness in reducing Striga infection. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Screening tropical and sub-tropical maize germplasm for resistance to Striga hermonthica and S. asiatica and yield-related traits

AbstractIdentification of maize germplasm with dual resistance to Striga hermonthica (Sh) and S. asiatica (Sa), could lead to the development of cultivars with stable resistance. 130 tropical and sub-tropical maize germplasms, including checks, were evaluated in a controlled environment for their reaction to Sh and Sa infestations using a 13 × 10 alpha lattice design with two replications over two seasons. Significant differences (P &lt; 0.05) were detected among the assessed genotypes for all the recorded traits in Sh and Sa-infested treatments. Under Sa-infested conditions, mean Striga emergence counts 8 weeks after planting (SEC8) and 10 weeks after planting (SEC10) were 5.00 and 45.50, respectively, while the mean Striga damage rate 8 weeks after planting (SDR8) and 10 weeks after planting (SDR10) were 3.35 and 3.07, respectively. Under Sh-infested conditions, SEC8 and SEC10 mean values were 3.66 and 3.77, respectively, while the SDR8 and SDR10 values were 5.25 and 2.75 respectively. Positive and significant (P &lt; 0.05) correlations were found between anthesis-silking interval (ASI) and SDR8 (r = 0.18) and SDR10 (0.32) under Sa-infested conditions. Negative and significant correlations were recorded between ear per plant (EPP) and SEC8, SDR8, and SDR10, with r = − 0.18, r = − 0.27, and r = − 0.24, respectively. Under Sh-infested conditions, significant and negative correlations were recorded between SDR8 and EPP (r = − 0. 20), EHT and SEC8 (r = − 0.22), EHT and SDR8 (r = − 0.36), PLHT and SDR8 (− 0.48), and PLHT and SDR10 (− 0.22). The results suggest that dual resistance to the two Striga species exists in some tropical and sub-tropical maize lines. The following genotypes have dual resistance to Sa and Sh: CML440, CML566, CML540, CML539, CLHP0343, CLHP0326, TZISTR1248, TZSTRI115, TZISTR25, TZISTR1205, TZSTRI113, TZISTR1119, TZISTR1174 and the OPVs B.King/1421, Shesha/1421, ZM1421, DTSTR-W SYN13, DTSTR-Y SYN14, and 2*TZECOMP3DT/WhiteDTSTRSYN) C2. The identified genotypes are suitable for use as parents in developing high-performing maize varieties with Striga resistance and improved grain yield.

Economic Analysis of Integrated Striga Management for Striga control as Influenced by Trap Crops and Inorganic Fertilizer Application in Sorghum [Sorghum bicolor (L.) Moench] at Fedis District, Eastern Ethiopia

Strigais problematic weed causing difficulty in cultivation of sorghum in areas of eastern hararghe where low and erratic rainfall is prevalent and soils are characterized by poor fertility. Knowing these different options of management has been tried however; its cost benefit has never been studied. Therefore, to assess its economic analysis and effect of integrated Striga management on Striga incidence, a field experiment was conducted during the cropping season of 2015 on heavily Striga-infested field in Fedis District, Boko site to determine the effect of trap crops (cowpea, soybean, desmodium, control) and N fertilizer rates (0, 46, 92 and 138 kg N ha-1) on management of Striga incidence and its economic analysis. The experiment was laid out in a factorial arrangement in a randomized complete block design (RCBD) with three replications. Trap crops were uprooted at maximum above ground fresh biomass. The results indicated significant (P&lt;0.05) main effects of trap crop on emergence of Striga where the lowest (26%) Striga emergence of about was recorded over the control with use of cowpea.Striga count at harvest of sorghum was significantly (P&lt; 0.05) affected by the interaction effect of trap crop and N fertilizer where 46 kg N ha-1 and use of cowpea as trap crop reduced the number of Striga seed bank by about 52.3% over the control treatment. The partial budget analysis also showed that the highest(47998.8 Birr ha-1) net benefit was obtained with the use of cowpea as a trap crop and 46kgN ha-1 application. Thus, the use of cowpea as trap crop and 46 kg N ha-1was found to be promising both agronomical and economically

Cytokinins as an alternative suicidal Striga germination compound

AbstractThe witchweed Striga hermonthica, an obligate and noxious root–parasitic plant, remains a persistent threat to cereal production and poses a great challenge to smallholder farmers in Sub‐Saharan Africa. Inducing suicidal germination of Striga seeds by applying strigolactone analogs is a promising strategy to deplete the Striga seed bank of infested soils. Nevertheless, there is a need to increase the efficiency and improve the applicability of this strategy, which may be achieved by testing further Striga germination stimulants. Herein, we explored the potential of cytokinins in inducing Striga seed germination. We investigated their activity as a suicidal germination agent along with fluridone that inhibits carotenoid biosynthesis and hence reduces abscisic acid formation and facilitates breaking of seed dormancy. Under lab conditions, application of fluridone (at 100 μM) or cytokinins (at 100 μM) showed 19% and 63% Striga germination, respectively, while combining different cytokinins with fluridone led to above 93% germination of treated seeds, with thidiazuron as the most active cytokinin. Using rice (cv IAC‐165), we also show that co‐application of fluoridone and thidiazuron to Striga infested pots before planting the host led to up to 86%–100% reduction in Striga emergence. In summary, cytokinins, particularly thidiazuron, could be useful suicidal agents to induce Striga seed germination and ultimately deplete the seedbank in Striga‐infested regions.

Effective Striga control and yield intensification on maize farms in western Kenya with N fertilizer and herbicide-resistant variety.

Maize production in western Kenya is limited by the spread of parasitic weed Striga hermonthica and depletion of soil nutrient stocks. Nitrogen (N) fertilizer and imidazolinone resistant (IR) maize are key elements in the agronomic toolbox to control infestations and enhance yields. The circumstances under which their use, individually or combined, is most effective on farmer fields have not been well documented. Inappropriate management decisions and low returns on investments arise from this knowledge gap, causing hunger and poverty in smallholder communities to persist. Experiments were carried out on 60 fields in three different agroecosystems of western Kenya using full-factorial treatments with non-herbicide treated maize (DH) and herbicide treated maize (IR), and N fertilizer omission and application. Trials were stratified on a field with low and high soil fertility within individual farms and repeated over two seasons. Cultivating IR maize instead of DH maize decreased the emergence of Striga with 13 shoots m-2 on average while applying N fertilizer on DH maize led to a reduction of 5 shoots m-2 on average. Decreases of Striga by use of IR maize and N fertilizer were between 6 and 23 shoots m-2 larger at the site with high levels of infestation than at the sites with medium or low emergence. Input of N fertilizer increased grain harvests by 0.59 ton ha-1 on average while use of IR maize enhanced the productivity with 0.33 ton ha-1 on average. Use of N fertilizer had similar yield effects in all three sites, whereas use of IR maize at the site with high Striga emergence increased maize production by 0.26-0.39ton ha-1 more than at the sites with medium or low emergence. The greater Striga responses to IR maize and the greater yield responses to N fertilizer demonstrate their use could be optimized according to field conditions and management goals. Combining IR maize and N fertilizer has larger added yield benefits where their individual effects on grain productivity are smaller. Findings from this study indicate that farmers in western Kenya require guidance on how to align the use of herbicide resistant maize and inorganic N inputs with the level of Striga infestation and maize yield on their fields for effectively controlling the pernicious weed and enhancing food production.

Influence of Sorghum-legume Intercropping on Striga Control and Sorghum Performance

Striga hermonthica (Del.) Benth is an important parasitic weedon cereals in the semi-arid tropics. Intercropping, particularly of cerealswith cowpea (Vigna unguiculata), is a common practice in many parts ofthe semi-arid zone. The main objectives of this study were to determinethe influence of sorghum-legume intercropping on striga control in centralSudan, and to assess the effect of such association on crop performance.Field experiments were conducted in striga-infested plots at theAgricultural Research Corporation (ARC) farm at Wad Madani, Sudan,during the 2009/2010 and 2010/2011 seasons. Sorghum cultivarsArfagadamk and Wad Ahmed were intercropped with four legumes.Treatments were arranged in randomized complete block design with 3replicates. Striga emergence was significantly reduced by 37.7% - 85.6%in sorghum-legume intercropping compared to sole sorghum, irrespectiveof variety and season. The highest reduction in striga emergence wasobtained with the sorghum cv. Arfagadamk-legume intercropping, whichreduced striga emergence by 72.5% - 85.6% compared to sole non-fertilized sorghum. Striga dry weight was high in sole sorghum incomparison with sorghum intercropped with legumes. Sorghum cv.Arfagadamk intercropped with lablab bean, brown-seed cowpea, andwhite-seed cowpea significantly reduced striga dry weight by 95%, 90%,and 73%, respectively. The total biological yield of both sorghumcultivars per unit area was generally higher in the intercropping

Effects of Rotation with Trap Crops on Striga (Striga hermonthica Del. Benth) Incidence, its Seed Bank and Sorghum Growth and Yield

A trial was conducted for three consecutive seasons (2006/07,2007/08 and 2008/09) in a field artificially infested by Striga hermonthicain the Experimental Farm of the Faculty of Agriculture, University ofSinnar. The effects of a two seasons’ crop rotation on striga incidence, itsseed bank and growth and yield of subsequent sorghum crop wereinvestigated. The rotation comprised the trap crops, cowpea (Vignaunguiculata), millet (Pennisetum glaucum), sesame (Sesamum indicum),sunflower (Helianthus annuus) and fallows, in assorted combinations. Asorghum monoculture, for the three seasons, was included as a control.All treatments reduced striga emergence significantly in comparison tosorghum monoculture. Sunflower and sesame grown for two consecutiveseasons caused the maximum reductions (80%), while a fallow followedby sorghum resulted in the least reduction (42%). Significant reduction instriga capsules (37%) was caused by two consecutive sesame crops. In thesecond season, all treatments significantly reduced striga seed bank,. Twoconsecutive fallows and two consecutive crops each of cowpea, millet andsunflower resulted in the highest reductions in striga incidence (80% -92%), while a fallow followed by sorghum exhibited the least reduction(51-65%). None of the treatments had adverse effects on sorghum standearly in the season; however, at harvest significant reduction wasobserved. Sorghum monoculture resulted in the lowest stand, whilesunflower planted subsequent to a fallow and two successive sunflowercrops affected the highest stands. Among all treatments, sorghum

Parental evaluation, polymorphic loci marker survey and allelism study of earliness in cowpea (Vigna unguiculata (L.) Walp)

The objectives of this study were to confirm genetic variability of three early-to-medium and three extra-early maturing cowpea genotypes selected from the previous studies, identify polymorphic loci markers between the two maturity groups, and investigate the allelism among the earliness genes in the three extra-early maturing genotypes. The parental genotypes were sowed on the Striga hotspot field of the CSIR-Savana Agricultural Research Institute, in a Randomized Complete Block Design with three replications. Data were collected on the number of days to first flower appearance (DFFA), days to 50% flowering (DFF), days to 95% pod maturity (DNPM), Striga emergence, Aphids infestation, grain yield and hundred seed weight. Leaf samples were taken from individual plants, and DNA extracted and genotyped for the polymorphic marker survey. Crosses were made among the three extra-early maturing genotypes to generate F 1 populations, and hybridity test conducted. The successful ones were advanced to F 2 and evaluated for DFFA and DNPM. The results showed significant differences between the genotypes, and two main clusters were identified for pod maturity. Polymorphic loci markers between the parental pairs were identified. These markers would play a significant role in the hybridity testing and could also be used with other markers to map the earliness genes in cowpea. The study also showed that earliness gene(s) in CB27 is non-allelic to those of Tobonaa and Sanzi-Nya. CB27 could be used to introgress earliness and large seed size into improved varieties lacking these two important traits.

Striga hermonthica Suicidal Germination Activity of Potent Strigolactone Analogs: Evaluation from Laboratory Bioassays to Field Trials.

The obligate hemiparasite Striga hermonthica is one of the major global biotic threats to agriculture in sub-Saharan Africa, causing severe yield losses of cereals. The germination of Striga seeds relies on host-released signaling molecules, mainly strigolactones (SLs). This dependency opens up the possibility of deploying SL analogs as “suicidal germination agents” to reduce the accumulated seed bank of Striga in infested soils. Although several synthetic SL analogs have been developed for this purpose, the utility of these compounds in realizing the suicidal germination strategy for combating Striga is still largely unknown. Here, we evaluated the efficacy of three potent SL analogs (MP3, MP16, and Nijmegen-1) under laboratory, greenhouse, and farmer’s field conditions. All investigated analogs showed around a 50% Striga germination rate, equivalent to a 50% reduction in infestation, which was comparable to the standard SL analog GR24. Importantly, MP16 had the maximum reduction of Striga emergence (97%) in the greenhouse experiment, while Nijmegen-1 appeared to be a promising candidate under field conditions, with a 43% and 60% reduction of Striga emergence in pearl millet and sorghum fields, respectively. These findings confirm that the selected SL analogs appear to make promising candidates as simple suicidal agents both under laboratory and real African field conditions, which may support us to improve suicidal germination technology to deplete the Striga seed bank in African agriculture.

A New Formulation for Strigolactone Suicidal Germination Agents, towards Successful Striga Management.

Striga hermonthica, a member of the Orobanchaceae family, is an obligate root parasite of staple cereal crops, which poses a tremendous threat to food security, contributing to malnutrition and poverty in many African countries. Depleting Striga seed reservoirs from infested soils is one of the crucial approaches to minimize subterranean damage to crops. The dependency of Striga germination on the host-released strigolactones (SLs) has prompted the development of the “Suicidal Germination” strategy to reduce the accumulated seed bank of Striga. The success of aforementioned strategy depends not only on the activity of the applied SL analogs, but also requires suitable application protocol with simple, efficient, and handy formulation for rain-fed African agriculture. Here, we developed a new formulation “Emulsifiable Concentration (EC)” for the two previously field-assessed SL analogs Methyl phenlactonoate 3 (MP3) and Nijmegen-1. The new EC formulation was evaluated for biological activities under lab, greenhouse, mini-field, and field conditions in comparison to the previously used Atlas G-1086 formulation. The EC formulation of SL analogs showed better activities on Striga germination with lower EC50 and high stability under Lab conditions. Moreover, EC formulated SL analogs at 1.0 µM concentrations reduced 89–99% Striga emergence in greenhouse. The two EC formulated SL analogs showed also a considerable reduction in Striga emergence in mini-field and field experiments. In conclusion, we have successfully developed a desired formulation for applying SL analogs as suicidal agents for large-scale field application. The encouraging results presented in this study pave the way for integrating the suicidal germination approach in sustainable Striga management strategies for African agriculture.

STRIGA HERMONTHICA SUICIDAL GERMINATION ACTIVITY OF TEN SOYABEAN, COWPEA AND GROUNDNUT VARIETIES IN NIGER STATE, NIGERIA

The obligate hemiparasite Striga hermonthica is one of the major global biotic threats to agriculture in sub-Saharan Africa, causing severe yield losses of cereals. The germination of Striga seeds relies on host-released signaling molecules, mainly Strigolactones (SLs). Strigolactones (SLs) are plant hormones that regulate the branching of plants and seed germination stimulants of root parasitic plants. Striga hermonthica’s non-hosts stimulate parasite seed to germinate without getting infected because the non-hosts produce unique germination stimulants Strigolactones). This phenomenon called suicidal seed germination is greatly used in S. hermonthica control. For improved efficiency of the suicidal seed germination method in S. hermonthica control, detailed analysis of comparative ability of potential trap crops to stimulate germination is critical. This study was undertaken with the aim to screen 10 genotypes each of soybean, cowpea and groundnut as trap crops for Striga: the potential ability of their root exudates to stimulate germination of Striga seed was evaluated. The results indicate that soyabean varieties TGX 1019-2EB and TGX 1448-2E delayed Striga emergence in 2013 and 2014 respectively compared to other varieties. In the results of the Striga count, plant height and grain yield, Soyabean variety TGX 1448-2E generally performed better than other varieties. 2.5 g Striga level gave better results in all the parameters measured compared to 5 g Striga level. Cowpea varieties IT04K-339-1 and IT07K-25-3-3 delayed Striga emergence in 2013 and 2014 respectively, while in Striga count and plant height, cowpea variety IT04K-217-5 performed better than other varieties but higher grain yield was recorded in cowpea variety IT04K-339-1 compared to other varieties. Groundnut varieties TES, QH 243C, RMP-12 and RMP-91 delayed Striga emergence compared to other varieties in 2014. Groundnut variety RMP-91 performed better in Striga count, plant height and grain yield in both planting years 2013 and 2014 compared to other varieties.

Efficacy of "PESTA" Granular Formulation Myco-herbicides of Aspergillus niger spores in Striga hermonthica (Del.) Benth Biocontrol

Aspergillus niger spores were isolated from diseased Striga plants at the Demonstration Farm Faculty of Agriculture, Shambat was used as a mycoherbicide for the biocontrol of Striga hermothica plant.Sterilized dried sorghum straw, Alfalafa hay and sucrose were used, as solid state substrates for growth and multiplication. These were used in different formulations coated to sorghum seeds or mixed with soil or added after Striga emergence to spores of Aspergillus niger .The results indicated that the formulation camposed of %07sterilized sorghum straw , %57 alfalfa hay formulation and 57sucrose was the best as it yielded the highest number of spores as compared to other formulations. Therefore, this formulation was selected for further application and was applied for inoculation of Striga seeds in the presence of its host (sorghum) seeds in different ways in the glass house at Shambat, Faculty of Agriculture.

Characterization of Maize Genotypes (Zea mays L.) for Resistance to Striga asiatica and S. hermonthica and Compatibility with Fusarium oxysporum f. sp. strigae (FOS) in Tanzania

Striga species cause significant yield loss in maize varying from 20 to 100%. The aim of the present study was to screen and identify maize genotypes with partial resistance to S. hermonthica (Sh) and S. asiatica (Sa) and compatible with Fusarium oxysporum f. sp. strigae (FOS), a biocontrol agent. Fifty-six maize genotypes were evaluated for resistance to Sh and Sa, and FOS compatibility. Results showed that FOS treatment significantly (p &lt; 0.001) enhanced Striga management compared to the untreated control under both Sh and Sa infestations. The mean grain yield was reduced by 19.13% in FOS-untreated genotypes compared with a loss of 13.94% in the same genotypes treated with FOS under Sh infestation. Likewise, under Sa infestation, FOS-treated genotypes had a mean grain yield reduction of 18% while untreated genotypes had a mean loss of 21.4% compared to the control treatment. Overall, based on Striga emergence count, Striga host damage rating, grain yield and FOS compatibility, under Sh and Sa infestations, 23 maize genotypes carrying farmer preferred traits were identified. The genotypes are useful genetic materials in the development of Striga-resistant cultivars in Tanzania and related agro-ecologies.

EVALUATION MULTI-SITE DE LEFFET DU PARASITISME AU STRIGA GESNERIOIDES (WILLD) VATKE SUR LES TRAITS FONCTIONNELS DES VARIETES DE NIEBE

Cowpea(Vigna unguiculata (L.) Walp) is a major legume crop in West African farming systems. Although cowpea is a drought tolerant crop, its production level is very low due to biotic constraints such as Strigagesnerioides parasitism. The present study aims to assess the effect of S. gesnerioides(Willd.) Vatkeon photosynthesis efficiency of cowpea varieties. Multilocal trialwas carried out rural areas during the 2017 rainy season to assess the number of Striga emergence likely to cause a change in photosynthetic efficiency on a panel of 26 cowpea varieties and to determine tolerant varieties. The observations were made on six experimental sites along a south-north climatic gradient representative ofMaradi region agro-ecological zones.The results showed a marked decrease of relative chlorophyll content when the number of visible Strigaemergence exceeded five per plant. Likewise, the LEF * PAR saturation curve is higher when the plants showed no visible attack of Striga. The Striga emergence have declined CRC in varieties CS001 and CS127 and led in rapid saturation in variety CS133.

Effects of Chlorsulfuron 75% WDG Herbicide and Varieties on Striga Control and Sorghum Yield in Tigray, Ethiopia

Sorghum [Sorghum bicolor (L.)Moench] is widely cultivated but the productivity is very low due to different factors such as Striga hermonthica. Field trails were carried out at Humera location to determine the management of striga to different rates of herbicide application to increase sorghum yield during 2017 cropping season. The trail consisted of eight treatments; 0 (control), 10, 15 and 20gha-1 rates of Chlorsulfron. The herbicide rates were assigned to the main plot while sorghum varieties were assigned to subplots, replicated three times in a split plot design. The data of days to 50%emergence, 50%flowering, plant height at maturity, Panicle length, panicle weight (g), yield per panicle (g), 1000 seed weight (g), grain yield (kg ha-1), above ground dry biomass (kg ha-1) and striga data days to first striga emergence, days to first flowering, number of striga count, branch number per striga plant, striga count per sorghum plant, striga height and biomass (kg/m2 respectively. Partial budget analysis was computed to assess the economic visibility of herbicide application where recorded. Result showed that application of herbicide rates and varieties increased plant height, panicle length, number of heads harvested per plot, panicle weight, yield per panicle, 1000 seed weight and grain yield over the control. Maximum grain yield (3725kg ha-1) was obtained from application of 15 g ha-1 Chlorsulfron with variety Deber. Days to first flowering, striga count per sorghum plant, stand counts of striga at 45DAP, 65 DAP and 85DAP M-2, branch number per plant, plant height and biomass of striga were significantly (P&lt;0.01) affected with the application of herbicide rates and varieties. The partial budget showed that an investing of 1.0 birr on application of herbicide with varieties earn 2.34 birr. Generally, application of Chlorsulfuron75% WDG and use local variety with high yielder could be an advantage to obtain highest yield and profit for the farmers in striga infestation areas.

Push-pull technology improves maize grain yield and total aboveground biomass in maize-based systems in Western Kenya

Abstract Push-pull is one of the sustainable intensification technologies for the control of stem-borers, striga weed and fall armyworm. Even though the effectiveness of push-pull in addressing these constraints has been evaluated under different agro-ecological conditions and on research stations, performance of the technology relative to other common maize-based cropping systems in farmers’ fields and the impact of the push-pull age is not yet understood. We hypothesized that, a) maize grain yield and aboveground biomass from push-pull system is higher than other common maize farming systems; b) duration of use of push-pull, and climatic conditions have an influence on its efficacy; and c) the presence of legumes in maize farms positively affects system performance. We compared maize grain yield, aboveground biomass and striga emergence of push-pull system with common maize farming systems: (1) maize monocrop (2) maize-bean intercrop, (3) maize-cowpea intercrop, (4) maize-green gram intercrop, and (5) maize-groundnut intercrop in 45 farms in three contrasting sites (Vihiga, Siaya and Bondo) in western Kenya. Push-pull increased maize grain yield by 2.33 and 1.77 Mg ha−1 in Vihiga in 2017 long and short rains, and 2.15 Mg ha−1 in Bondo in 2018 long rains, and aboveground biomass by between 2.84 Mg ha−1 in Vihiga in 2018 long rains and 8.94 Mg ha−1 in Bondo in 2018 long rains. Striga emergence declined in push-pull systems by up to 100 % and its performance varied with sites and seasons. Farms that had practiced push-pull for less than 2 years had a higher number of striga than farms which had practiced it for more than 2 years for the first season; the number decreased and was similar to that for farms which had practiced push-pull for above 2 years in the two subsequent seasons. Farms with legumes had similar maize grain and aboveground biomass as maize monocrop in all sites and seasons, and higher number of striga in Siaya in 2017 short rains and 2018 long rains, and Vihiga in 2018 long rains. These findings show that push-pull is similar or superior to other maize farming systems in terms of maize grain and biomass production; and that while its performance is influenced by agro-ecological conditions, its efficacy in controlling striga increases over time, and its productivity is not compromised over time on the same farm.

The effectiveness of local strains of Fusarium oxysporium f. Sp. Strigae to control Striga hermonthica on local maize in western Kenya.

Striga hermonthica weed infestation continues to persist among smallholder poor farmers in Kenya who depend on traditional maize (Zea mays L.) seeds for their livelihood. The purpose of this study was to evaluate the efficacy of five local Fusarium oxysporum f. sp. Strigae strains (FK1, FK2, FK3, FK4, and FK5) to control Striga on susceptible local maize cultivar “Rachar” in three farmer field sites in Siaya County, Kenya. A complete randomized block design was used in each site. Statistical analysis was done using SAS 9.1 software, and means for different strains were tested with Fisher's LSD. The strains differentially reduced the number of emerged Striga and infected most of the emerged Striga, which affected performance of the local maize. Striga emergence and infection rates were significantly different (p < .05) between different strains of F. oxysporum f. sp. strigae. FK1 and FK2 strains had the least pathogenicity, while FK5 strain had the highest pathogenicity on Striga. Soil and climatic factors influenced the rate of infection for the tested strains and maize performance. Improvement in yield during the short rains was attributed to the persistence of Fusarium strains in the soil. Based on Striga emergence and infection rates, and maize yield, FK5 was the most effective strain to curb Striga menace. Adoption of local F. oxysporum strains will increase maize yield in Siaya County's Striga‐infested fields from a dismal average of 0.95 t/ha to about 1.95 t/ha. The observed significant differences in the tested strains between sites for the infection and emergence rates revealed the importance of considering pathogens on a field‐to‐field basis. Further studies should be carried out to establish the relationship between soil properties and the five fungal strains.

Genetic Variation for Striga hermonthica Resistance and Yield Among Sorghum Accessions in Nigeria

Striga hermonthica (Delile) Benth., commonly referred to as witch weed, is a major constraint to sorghum (Sorghum bicolor (L.) Moench) production in the Northern region of Nigeria because of high yield losses due to infestation. To identify parental lines useful in breeding for S. hermonthica resistant sorghum genotypes adapted to Nigeria, twenty-five sorghum accessions were evaluated in Nigeria across three test environments. Both phenotypic and genetic components influenced the variation observed in the sorghum accessions. The estimates for the genetic coefficient of variation, heritability and genetic advance for the area under Striga number progress curve (ASUNPC), Striga emergence counts, yield and other agronomic traits, obtained in this study revealed that genetic gain for resistance to S. hermonthica could be realized through selection. Based on the performance of the 25 sorghum accessions SRN39, Danyana, Sepon82, and SAMSORG40 were the top four accessions found to be most resistant to S. hermonthica. Assessment of resistance was based on the low Striga emergence counts and the ASUNPC values. These accessions can be used as donor sources of S. hermonthica resistant genes for introgression into cultivars adapted to Nigeria, followed by recombination breeding for pyramiding the different resistance mechanisms.

Combining ability of extra-early biofortified maize inbreds under Striga infestation and low soil nitrogen.

Striga hermonthica (Del.) Benth parasitism, low soil N, and nutritional deficiencies of normal‐endosperm maize (Zea mays L.) threaten maize yield and exacerbate nutritional problems in sub‐Sahara Africa (SSA). This study was conducted (a) to evaluate genetic variation among extra‐early maturing maize hybrids with provitamin A and quality protein characteristics, (b) to investigate gene action governing the inheritance of Striga resistance, grain yield, low N tolerance, and other measured traits under low‐N, high‐N, and Striga‐infested environments, and (c) to identify hybrids with high yield and stability across environments. One hundred and fifty hybrids developed using North Carolina Design II were evaluated with six checks under low‐N, high‐N, and Striga‐infested environments in Nigeria. Mean squares for hybrids were highly significant (P < .01) for grain yield and other traits across environments. Only general combining ability (GCA) for female and/or male mean squares were significant for measured traits under low N. In addition to significant GCA effects for most traits, specific combining ability was significant (P < .05) for Striga emergence count under Striga infestation, and ear height and ears per plant under high N, indicating that additive and nonadditive genetic effects controlled the inheritance of few traits under Striga and high N, whereas additive genetic effect governed the inheritance of the traits under low N. Hybrids TZEEIORQ 55 × TZEEIORQ 26, TZEEIORQ 49 × TZEEIORQ 75, and TZEEIORQ 52 × TZEEIORQ 43 were high yielding and stable across environments and have potential for improving nutrition and maize yields in SSA.