Assessments of genetic diversity and anthracnose disease response among Zimbabwe sorghum germplasm

Abstract

The USDA-ARS National Plant Germplasm System maintains a Zimbabwe sorghum collection of 1235 accessions from different provinces. This germplasm has not been extensively employed in US breeding programmes due to the lack of phenotypic and genetic characterization. Therefore, 68 accessions from Zimbabwe were phenotyped, and evaluated for their anthracnose response for two consecutive years, and genetically characterized with 21 simple sequence repeat markers. Phenotypic analysis showed significant differences among accessions with plant height and panicle length being the most variable traits. Likewise, 25 accessions were anthracnose resistant, nine showed variable responses and 34 were susceptible. Genetic analysis identified 174 alleles with an average of 8.3 alleles and 11.8 genotypes per locus and a polymorphic information content of 0.60. These results reflect a moderate genetically diverse germplasm. Neighbour-joining clustering analysis revealed that the majority of anthracnose-resistant accessions showed high genetic relatedness; therefore, this germplasm might represent one to six new sources of resistances. Results presented herein show that the Zimbabwe collection contains valuable germplasm for breeding programmes and is an important source of anthracnose resistance.

Population structure of the NPGS Senegalese sorghum collection and its evaluation to identify new disease resistant genes

“…Of the 12,880 pairwise genetic distances, only one was larger than 0.90 (PI 514299 vs. PI 514301). The average observed heterozygosity (0.25) was greater than that reported in previous studies with sorghum landraces from the NPGS collection [ 6 , 23 , 42 ]. However, this could be attributed to the fact that the SSRs were selected based on their previously reported high PIC value among Senegalese germplasm collections [ 29 ].…”

“…The high humidity of West and Central Africa may have driven the evolution towards and selection for anthracnose resistance responses. For instance, the frequency of resistant accessions is low in the Northeastern [Ethiopia (7%), Sudan (24%)] and Southern [Botswana (34%) and Zimbabwe (37%)] regions of Africa [ 23 , 24 , 27 ]. Similarly, the average seed rating and germination in the Senegal germplasm is higher than that observed in Sudan [ 47 ] and South Africa [ 19 ].…”

“…The deployment of multiple resistance genes is therefore necessary to control the disease. Recent evaluation of germplasm from China, Ethiopia, Mali, Mozambique, Botswana, Malian, Sudan, Uganda, and Zimbabwe identified resistant lines [ 19 , 20 , 23 – 27 ]; however, the lack of knowledge about genetic relationships between resistant germplasm and its mode of inheritance limits the use of these resources in breeding programs. In this regard, the identification and selection of the most genetically diverse and exotic germplasm for inheritance studies is the first step towards its introgression into breeding programs.…”

Assessment of genetic diversity among cultivated Pearl millet (Pennisetum glaucum, Poaceae) accessions from Benin, West Africa

“…Among these, Single Sequence Repeat (SSR) or microsatellite markers, which target tandem repeats of ditri-or tetra-nucleotide DNA motifs, are both highly polymorphic within populations and randomly distributed throughout the genome in both transcribed and nontranscribed sequences (Saghai-Maroof et al, 1994;Manzelli et al, 2007). SSR markers have been successfully used to evaluate genetic diversity in several crop species such as wheat (Fufa et al, 2005), Pennisetum purpureum (Azevedo et al, 2012), Capsicum (Nicolai et al, 2013), Sorghum (Cuevas et al, 2014), barley (Shakhatreh et al, 2015), Vigna subterranea (Molosiwa et al, 2015), maize (Salami et al, 2016) and some underutilized species such as buckwheat and wild melon (Roy et al, 2012;Zhang and Zao, 2013). For pearl millet characterization, several SSR markers were developed (Mariac et al, 2006;Stich et al, 2010;Nepolean et al, 2012) and used to evaluate its genetic diversity at the regional scale in west Africa.…”

Genomic Dissection of Anthracnose (Colletotrichum sublineolum) Resistance Response in Sorghum Differential Line SC112-14

“…Several sources of anthracnose resistance have been identified in tropical and temperate-adapted germplasm. The screening of the U.S. National Plant Germplasm System (NPGS) sorghum germplasm collection resulted in multiple sources of resistance being identified Erpelding 2011;Prom et al 2011;Erpelding 2012;Cuevas et al 2014b;Cuevas et al 2016). Most of these resistance sources are, however, tropical germplasm that cannot be integrated into U.S. sorghum breeding programs without conversion through introgression of photoperiod insensitivity using dwarfing and early maturity genes (Thurber et al 2013).…”