Identification of candidate virulence loci in Striga hermonthica, a devastating parasite of African cereal crops

Parasites have evolved suites of proteins, Virulence Factors (VFs), that are delivered into host plants to facilitate colonization. Whilst VFs mediating plant-microbe and plant-nematode interactions have been characterised extensively, less is known about VFs mediating parasitic plant interactions with their hosts. Striga hermonthica is an obligate, root-parasitic plant capable of parasitizing multiple cereal hosts in sub-Saharan Africa, causing devastating losses in yields. An understanding of the molecular nature and allelic variation of VFs in S. hermonthica is essential for breeding durable resistance and delaying the evolution of parasite virulence. To address this issue, we assembled a genome for Striga hermonthica and identified candidate VFs by combining in silico prediction of secreted proteins with pooled sequencing of parasites growing on a susceptible and a strongly resistant rice host. Consistent with predictions for parasites, like S. hermonthica, that can interact with multiple hosts, we identified multiple loci, potentially with a wide range of functions, implicated in overcoming host resistance. Extremely different allele frequencies were observed at 152 non-secreted and 38 putatively secreted VFs between S. hermonthica parasitising the resistant and susceptible rice varieties. Our candidate, secreted VFs encompassed functions such as host cell wall modification, protease inhibitors, oxidoreductase and kinase activities, as well as several with unknown functions. Consistent with maintenance of variation at virulence loci by balancing selection the candidate loci had significantly higher Tajima’s D on average than the genomic background. Our results show that diverse strategies are used by S. hermonthica to overcome different layers of host resistance. Understanding the maintenance of variation at virulence loci by balancing selection will be critical to managing the evolution of virulence as a part of a sustainable control strategy.

Effect of the fortilizer nitrophoska on sorghum Sorghum bicolor L. parasitized by witchweed (Striga Hermonthica Del Benth)

Effect of the fortilizer nitrophoska on sorghum Sorghum bicolor L. parasitized by witchweed (Striga Hermonthica Del Benth) Nitrophoska (NPK), a compound fertilizer, showed significant effects in stimulating yield components of Sorghum bicolor L. cultivar Tabat and in depressing the parasitism of Striga hermonthica Del. Benth. Over all treatments nitrophoska at N3 (54 kg N/F) gave 160, 105,121 and 120% increases in yield components over the control for head weight, plant height, 1000 grain weight and straw yield/ m2 of sorghum. Nitrophoska scored 83% and 80% decrease in striga dry shoot weight / m2 and striga density / m2, respectively less than the control at N1 (18 kg N/F). To maximize the yield components of sorghum, higher levels of nitrophoska (N2. N3) were recommended to be used; while lower levels of nitrophoska (N1) were recommended to combat the menace of striga in fields of sorghum

Association analysis for resistance to Striga hermonthica in diverse tropical maize inbred lines

Striga hermonthica is a widespread, destructive parasitic plant that causes substantial yield loss to maize productivity in sub-Saharan Africa. Under severe Striga infestation, yield losses can range from 60 to 100% resulting in abandonment of farmers’ lands. Diverse methods have been proposed for Striga management; however, host plant resistance is considered the most effective and affordable to small-scale famers. Thus, conducting a genome-wide association study to identify quantitative trait nucleotides controlling S. hermonthica resistance and mining of relevant candidate genes will expedite the improvement of Striga resistance breeding through marker-assisted breeding. For this study, 150 diverse maize inbred lines were evaluated under Striga infested and non-infested conditions for two years and genotyped using the genotyping-by-sequencing platform. Heritability estimates of Striga damage ratings, emerged Striga plants and grain yield, hereafter referred to as Striga resistance-related traits, were high under Striga infested condition. The mixed linear model (MLM) identified thirty SNPs associated with the three Striga resistance-related traits based on the multi-locus approaches (mrMLM, FASTmrMLM, FASTmrEMMA and pLARmEB). These SNPs explained up to 14% of the total phenotypic variation. Under non-infested condition, four SNPs were associated with grain yield, and these SNPs explained up to 17% of the total phenotypic variation. Gene annotation of significant SNPs identified candidate genes (Leucine-rich repeats, putative disease resistance protein and VQ proteins) with functions related to plant growth, development, and defense mechanisms. The marker-effect prediction was able to identify alleles responsible for predicting high yield and low Striga damage rating in the breeding panel. This study provides valuable insight for marker validation and deployment for Striga resistance breeding in maize.

Evaluation De L’activité Anthelminthique Des Extraits Aqueux De Striga Hermonthica (Del.) Benth Et Ceratotheca Sésamoïdes Endl Sur Deux Stades Biologiques De Haemonchus Contortus

Medicinal plants with anthelmintic properties are an alternative to the chemical fight against small ruminant’s gastrointestinal nematodes. In order to broaden the spectrum of medicinal plants with anthelmintic properties, ovicidal activity and L3 larvae exsheathment of C. sesamoïdes Endl and S. hermonthica (Deli) Benth, aqueous extracts has been done on H contortus egg and L3 larvae. Three concentrations, 3.12 mg / ml, 6.25 mg / ml, 12.5 mg / ml of each plant extract were used to assess the inhibition of fresh egg hatching and larval paralysis as well as the 'inhibition of L3 larvae exsheathment. A negative control (PBS1x) and a positive control (levamisole, 2.5 mg / ml) were constituted for the fresh egg hatching inhibition assessment while only the negative control (PBS1x) was constituted to evaluate the inhibition of L3 Larvae exsheathment.1 ml of each concentration was contacted with 1 ml of the egg solution and then incubated for 48 hours at 27 ° C in petri dishes (60X15 Cm) for hatching test inhibition.1 ml of each extract concentration was contacted with 1 ml of the embryonated egg solution after 24 hours of incubation at 27 ° C for the larval paralysis test.

Production Potential of Allelopathic Rice, Cymbopogon, Desmodium, Mucuna and Maize

Allelochemicals regulate the productivity of crop ecosystems. A screen house experiment was conducted (2016) at the National Crops Resources Research Institute, Namulonge, Uganda to determine the effects of NERICA 1 rice (an interspecific hybrid between Oryza sativa and O. glaberrima species), Cymbopogon nardus (C), Desmodium uncinatum (D), Mucuna pruriens (Mc) and LONGE 6H, Zea mays (Mz) on crop relative growth rates (RGR), nitrogen (N), phosphorus (P) and potassium (K) nutrient levels. One field study was conducted on a farm (2017) to establish the allelopathic interactive effects of RCDMcMz on Striga hermonthica (a parasitic weed), crop competition and productivity. Data was collected on striga, RMz growth, nutrient levels and yield. Potted rice reduced (30%-47%) in root length but Mz leaf length increased (31% & 15%) with Mc & D. RMc reduced (73%) striga and increased rice RGR (14-42 days). RD similarly reduced (67%) striga. RC increased (96%, 44% & 73%) rice NPK uptake, RGR (14-42 days), reduced (57%) striga and increased (1.56) the combined land equivalent ratio (CLER) and rice grain yields. RMz reduced (16%, 38% & 38%) rice NPK reserves, RGR (14-42 days), CLER (1.0), grain yields and increased (36%) striga. RD recorded higher CLER (1.56). MzMc reduced (15% & 27%) maize P uptake and NP uptake increased (42% & 9.3%) under MzC & MzD (73% & 29%). RMc increased rice RGR (14-42 days). Maize RGR (14-28 days) increased under MzD, MzMc & MzC and reduced (28-42 days) under MzD, RC & MzMc.. The ecosystems’ productivity was attributed to allelopathy.

Agronomic Performance Of S1 Maize Lines Derived From A Bi-Parental Cross Under Infested And Striga Free Environments

Striga hermonthica, causes up to 100% yield loss in maize production in sub-Saharan Africa. Developing Striga resistant maize cultivars could be a major component of integrated Striga management strategies. This study aims at assessing the agronomic performance of S1 breeding lines in improving maize for Striga resistance. Two hundred S1 lines have been evaluated under artificial infestation Striga and Striga-free conditions in Benin for two years during 2018 and 2019 growing seasons using alpha-lattice design (51 x 4) with two replicates. Twelve agro-morphological and Striga adaptive traits have been assessed. The tested lines have displayed high genetic variability for most agronomic and Striga adaptive traits. The S1 lines exhibited high grain yield than their parents with averages of 2,552.72±593 kg ha-1 and 2,965.67±635.86 kg ha-1 under Striga artificial infestation and Striga-free conditions, respectively. Grain yield has displayed high positive and significant genetic and phenotypic correlations with ears per plant and high negative correlations with days to 50% silking, ears aspect, and Striga damage rating at 8 and 10 weeks after planting (WAP). Useful traits like ears per plant, days to 50% silking, ears aspect, number of emerged Striga plants and Striga rating at 10 WAP could assist for indirect selection under Striga conditions. Based on the selection index, a total of 15 S1 lines have been identified as top ranking and can be used as sources of resistance or tolerance genes to Striga and further improvement in maize breeding in future.