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

Abstract

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.

Genetic diversity analysis of East African sorghum (Sorghum bicolor [L.] Moench) germplasm collections for agronomic and nutritional quality traits

“…The phenotypic, genotypic, and environmental variances denoted as σ 2 p, σ 2 g, and σ 2 e, respectively, were computed from the expected mean square values as described by Federer and Searle (1976) . The phenotypic, genotypic, and environmental coefficients of variation denoted as PCV, GCV, and ECV, respectively, were calculated according to Muchira et al. (2021) .…”

Genotypic Yield Stability of Wild and Landrace Sorghum Species Under Drought Stress and Striga Infestation

“…The F 4 populations were derived as generation of crosses between the 43 wild and cultivated accessions as shown in Table 1. This germplasm was chosen for evaluation of yield stability because it contains previously tested and proven sources of drought tolerance and striga resistance by different authors (Kebede et al, 2001;Hausmann et al, 2002;Rodenburg et al, 2005;Muchira et al, 2021;Ochieng et al, 2020).…”

“…Wild sorghum genotypes have demonstrated resistance to Striga over the years and are likely to harbor resistance genes which if exploited may assist in the improvement of adapted sorghum varieties (Muraya et al, 2011;Magomere et al, 2015). Known sources of resistance to striga, include N13, SRN 39, Framida, IS9830 (Rodenburg et al, 2005) landraces and wild relatives recently identified by Muchira et al (2021).…”

“…Interaction between striga resistance and drought tolerance has been reported (Muchira et al, 2021) which suggested that most consistent top-yielding genotypes under natural and artificial striga infestation were from generation of crosses with drought-tolerant genotypes, such as LODOKA, B35, and E36-1 (Muchira et al, 2021).…”

Striga Biology and Its Management in Maize: A Review

“…In contrast, S. hermonthica is a highly out-crossing species, thus it is expected to show greater diversity within a population than seen in related autogamous species [21]. All except S. gesnerioides preferentially parasitize cereal crops such as maize (Zea mays), sorghum (Sorghum bicolor), rice (Oryza sativa) and millet [22]. Striga has been found attaching to non-traditional host crops such as Eragrostis tef, barley (Hodeum vulgare) and wheat (Triticum aestivum) [23].…”