Figure Legends
Figure 1: Genetic structure of the sorghum accession panel (SAP): (a)Striga hermonthica range in Africa overlapping with sorghum origin (b) A distribution map showing the collection points of sorghum (174 georeferenced samples collection from Africa) genotypes, races are represented by color-coded dots (c) Phylogenetic relatedness of 373 sorghum accessions measured by Neighbor-joining technique. Phylogenetic tree nodes are color coded according to sorghum races.
Figure 2: Identification and characterization of new low germination stimulant 1 (lgs1 ) sorghum. (a) Sulfotransferase marker analysis of the lgs1 loci. Presence of a single band characterized by a 223bp PCR product indicates the presence of the resistance allele (lgs1 ) (b) Liquid Chromatography Tandem-Mass Spectrometry (LC-MS/MS) quantification of strigolactones: (upper panel) orobanchol and 5-deoxystrigol peaks of some representative sorghum lines in LC-MS/MS analysis (lower panel) Orobanchol and 5-deoxystrigol mass transitions. (c) Orobanchol quantification (pg per sample) in various sorghum lines. (d) 5-Deoxystrigol quantification (pg per sample) in sorghum lines. The strigolactones collected from the root exudates of various sorghum lines quantified through LC-MS analysis. Data means±SE (n=6). The treatments with various letters denote significance (one-way ANOVA, Tukey’s post hoc test, P <0.05). (e) Strigolactone proportion of SAP lines. LGS1 genotypes had high proportions of 5-deoxystrigol. In contrast, lgs1 genotypes had high proportions of orobanchol.
Figure 3: Striga resistance in SAP low germination stimulant 1 sorghum (a) Bioassay to measure Striga resistance by germination frequency induced by root exudates of resistant (blue, SAPlgs1-1 ) and susceptible (orange, SAP LGS1). (b) Measurement ofStriga germination using germination frequency showing low germination stimulation in most SAP lgs1 -1 accessions. (c) Agar gel assay to measure Striga stimulation activity by sorghum rootsin vitro . (d) Measurement of Striga emergence using pot experiments. Most lsg1 genotypes had a low number ofStriga attachments. (e) Striga emergence pot experiments. Notable low emergence was observed in most lgs1 lines and in the LGS1 line PI6506054.
Figure 4: Performance of SAP low germination stimulant 1 sorghum under natural Striga infestation. (a) Striga emergence measured as area under Striga number progressive curve (AUSNPC) at 98 after planting (b) Correlation of Striga emergence (AUSNPC) at 98 days after planting with relative yield loss as a measure of sorghum tolerance (c) Heatmap showing Striga resistance levels of sorghum genotypes based on ranked summation index (RSI) of yield, days to 50 % flowering and emergence counts. (d) Striga resistance phenotypes. Wild type LGS1 sorghum with high number of emergedStriga seedlings growing next to lgs1 mutant in aStriga hermonthica infested field in Alupe, western Kenya.Striga resistance evaluation of SAP lgs1 genotypes showed that here was notable infestation on SAP LGS1 PI533839 but not in one of the Striga resistant SAP lgs1 genotype PI561071.