Characterization of growth and development of sorghum genotypes with differential susceptibility to Striga hermonthica

Abstract

Two sorghum varieties, Shanqui Red (SQR) and SRN39, have distinct levels of susceptibility to the parasitic weed Striga hermonthica, which have been attributed to different strigolactone composition within their root exudates. Root exudates of the Striga-susceptible variety Shanqui Red (SQR) contain primarily 5-deoxystrigol, which has a high efficiency for inducing Striga germination. SRN39 roots primarily exude orobanchol, leading to reduced Striga germination and making this variety resistant to Striga. The structural diversity in exuded strigolactones is determined by a polymorphism in the LOW GERMINATION STIMULANT 1 (LGS1) locus. Yet, the genetic diversity between SQR and SRN39 is broad and has not been addressed in terms of growth and development. Here, we demonstrate additional differences between SQR and SRN39 by phenotypic and molecular characterization. A suite of genes related to metabolism was differentially expressed between SQR and SRN39. Increased levels of gibberellin precursors in SRN39 were accompanied by slower growth rate and developmental delay and we observed an overall increased SRN39 biomass. The slow-down in growth and differences in transcriptome profiles of SRN39 were strongly associated with plant age. Additionally, enhanced lateral root growth was observed in SRN39 and three additional genotypes exuding primarily orobanchol. In summary, we demonstrate that the differences between SQR and SRN39 reach further than the changes in strigolactone profile in the root exudate and translate into alterations in growth and development.

The Soil Microbiome Reduces Striga Infection of Sorghum by Modulation of Host-Derived Signaling Molecules and Root Development

“…Interestingly, accumulation of suberin was also observed for SRN39, a Striga-resistant sorghum genotype (Fig. 3N, Kawa et al, 2021). Whether this anatomical trait may be an additional postattachment resistance mode of other sorghum genotypes remains to be tested.…”

“…We previously found increased expression of genes associated with fatty acid biosynthesis and a higher abundance of suberin monomers and poly-hydroxy fatty acids in roots of SRN39 as compared to SQR (Kawa et al, 2021). Additionally, polymorphisms in genes related to suberin and wax-ester biosynthesis were previously found in sorghum varieties originating from regions of different levels of Striga infestation (Bellis et al, 2020).…”

“…To explore the existence of Striga soil suppressiveness we selected a soil from the Netherlands, referred to as the "Clue Field" soil (Schlemper et al, 2017). This soil has previously been shown to differentially influence the rhizosphere community composition of two sorghum varieties with distinct susceptibility to Striga hermonthica, (Gobena et al, 2017;Schlemper et al, 2017;Kawa et al, 2021). We gamma-irradiated a batch of this soil for the purpose of sterilization and ensured that gamma sterilization did not affect the physico-chemical properties of the soil (Supplementary Data 1).…”

“…Untargeted analysis was performed as described in (Kawa et al, 2021). Briefly, 5 µL of root exudates (semi-polar and polar fraction) were injected on a Nexera UHPLC system (Shimadzu, Den Bosch, The Netherlands) coupled to a high-resolution quadrupole time-of-flight mass spectrometer (Q-TOF; maXis 4G, Bruker 194 Daltonics, Bruynvisweg 16 /18).…”

The soil microbiome reduces Striga infection of sorghum by modulation of host-derived signaling molecules and root development

“…Root system architecture was analyzed with the DIRT (Digital Imaging of Root Traits) software v1.1 (Das et al, 2015). The total root network area and total network length (to simplify we refer to it as total root area and total root length) used skeleton methods (Bucksch, 2014; Bucksch et al, 2014) as described in (Kawa et al, 2021). Mean root network diameter was calculated as the ratio of network area over network length.…”