Genetic diversity of maize genotypes with variable resistance to Striga asiatica based on SSR markers

Genetic diversity among breeding populations is key in plant breeding programs. This study aimed to determine the extent of genetic diversity among 37 diverse maize genotypes using simple sequence repeat (SSR) markers. The maize genotypes were selected based on their variable resistance to Striga asiatica. Maize genotypes were fingerprinted using 18 polymorphic SSR markers. Marker and population diversity parameters were computed. A total of 191 alleles were detected and the number of effective alleles varied from 2 to 21 per locus with a mean of 11. The polymorphic information content (PIC) of the SSR markers varied from 0.59 to 0.96, with a mean of 0.80. Significant differences were observed among populations, individuals and within individuals. Within and among individual variances accounted for 85% and 13% of the total gene diversity. The genotypes were grouped into three main genetic clusters, which were not influenced by genotype origin. Mean genetic distance (0.43) and low geneflow (0.18) were observed among the populations. High mean genetic identity (0.65) was recorded, indicating potential genetic ‘bottleneck’ among the selected germplasm. The following open pollinated varieties; Border King, Colorado, CIMMYT’s ZM OPVs, Mac Pearl, Shesha, Nel Choice, Natal 8Lines, Nel Choice QPM, Hickory King, Kep Select, Obatanpa and the Striga resistant synthetic variety DSTRYSYN15 were selected from different clusters for breeding

Socio-Economic Factors and Water Footprint in Smallholder Irrigation Schemes in Zimbabwe

Despite the need to grow crops with low water consumption needs, given the increasing water stress across many regions of the globe, assessments of crop water footprint (WFP) values have not received significant research attention in Zimbabwe. This unique study is the first of its kind to assess the mediation effect between socio-economic factors and crop WFP among smallholder irrigation schemes in Zimbabwe. A total of 317 farmers from three schemes in Midlands Province in Zimbabwe participated in this study. The following were the main findings in terms of the examined variables: (1) Schemes (p p p < 0.1) all decreased WFP_Maize; (2) education showed a reduction effect on the link between scheme maintenance and WFP_Maize; (3) secondary education has a higher impact on the magnitude of Maint on WFP_Maize; and (4) Maint and WFP_Maize have a positive correlation. This study illustrates the interaction of socio-economic factors on WFP and has substantial implications for simultaneously addressing the sustainable consumption of water for crop production, food security, and malnutrition in a changing climate

Socio-Economic Factors and Water Footprint in Smallholder Irrigation Schemes in Zimbabwe

Despite the need to grow crops with low water consumption needs, given the increasing water stress across many regions of the globe, assessments of crop water footprint (WFP) values have not received significant research attention in Zimbabwe. This unique study is the first of its kind to assess the mediation effect between socio-economic factors and crop WFP among smallholder irrigation schemes in Zimbabwe. A total of 317 farmers from three schemes in Midlands Province in Zimbabwe participated in this study. The following were the main findings in terms of the examined variables: (1) Schemes (p &lt; 0.01), Gender (p &lt; 0.05), and Maint (p &lt; 0.1) all decreased WFP_Maize; (2) education showed a reduction effect on the link between scheme maintenance and WFP_Maize; (3) secondary education has a higher impact on the magnitude of Maint on WFP_Maize; and (4) Maint and WFP_Maize have a positive correlation. This study illustrates the interaction of socio-economic factors on WFP and has substantial implications for simultaneously addressing the sustainable consumption of water for crop production, food security, and malnutrition in a changing climate

Variance components and heritability of traits related to root: shoot biomass allocation and drought tolerance in wheat

Enhanced root growth in plants is fundamental to improve soil water exploration and drought tolerance. Understanding of the variance components and heritability of root biomass allocation is key to design suitable breeding strategies and to enhance the response to selection. This study aimed to determine variance components and heritability of biomass allocation and related traits in 99 genotypes of wheat (Triticum aestivum L.) and one triticale (X. Triticosecale Wittmack) under drought-stressed and non-stressed conditions in the field and greenhouse using a 10x10 alpha lattice design. Days to heading (DTH), days to maturity (DTM), number of tillers (NPT), plant height (PH), spike length (SL),shoot and root biomass (SB, RB), root to shoot ratio (RS), thousand kernel weight (TKW) and yield (GY) were recorded. Analyses of variance, variance components, heritability and genetic correlations were computed. Significant (p70%) for RS observed in this population constitute several bottlenecks for improving yield and root mass simultaneously. However, indirect selection for DTH, PH, RB, and TKW, could help optimize RS and simultaneously improve drought tolerance and yield under drought-stressed conditions

Variance components and heritability of traits related to root : shoot biomass allocation and drought tolerance in wheat

Enhanced root growth in plants is fundamental to improve soil water exploration and drought tolerance. Understanding of the variance components and heritability of root biomass allocation is key to design suitable breeding strategies and to enhance the response to selection. This study aimed to determine variance components and heritability of biomass allocation and related traits in 99 genotypes of wheat (Triticum aestivum L.) and one triticale (X. Triticosecale Wittmack) under drought-stressed and non-stressed conditions in the field and greenhouse using a 10x10 alpha lattice design. Days to heading (DTH), days to maturity (DTM), number of tillers (NPT), plant height (PH), spike length (SL),shoot and root biomass (SB, RB), root to shoot ratio (RS), thousand kernel weight (TKW) and yield (GY) were recorded. Analyses of variance, variance components, heritability and genetic correlations were computed. Significant (p70%) for RS observed in this population constitute several bottlenecks for improving yield and root mass simultaneously. However, indirect selection for DTH, PH, RB, and TKW, could help optimize RS and simultaneously improve drought tolerance and yield under drought-stressed conditions

Analysis of population structure and genetic diversity in a Southern African soybean collection based on single nucleotide polymorphism markers

Abstract Soybean is an emerging strategic crop for nutrition, food security, and livestock feed in Africa, but improvement of its productivity is hampered by low genetic diversity. There is need for broadening the tropical germplasm base through incorporation and introgression of temperate germplasm in Southern Africa breeding programs. Therefore, this study was conducted to determine the population structure and molecular diversity among 180 temperate and 30 tropical soybean accessions using single nucleotide polymorphism (SNP) markers. The results revealed very low levels of molecular diversity among the 210 lines with implications for the breeding strategy. Low fixation index (FST) value of 0.06 was observed, indicating low genetic differences among populations. This suggests high genetic exchange among different lines due to global germplasm sharing. Inference based on three tools, such as the Evanno method, silhouette plots and UPMGA phylogenetic tree showed the existence of three sub-populations. The UPMGA tree showed that the first sub-cluster is composed of three genotypes, the second cluster has two genotypes, while the rest of the genotypes constituted the third cluster. The third cluster revealed low variation among most genotypes. Negligible differences were observed among some of the lines, such as Tachiyukata and Yougestu, indicating sharing of common parental backgrounds. However large phenotypic differences were observed among the accessions suggesting that there is potential for their utilization in the breeding programs. Rapid phenotyping revealed grain yield potential ranging from one to five tons per hectare for the 200 non-genetically modified accessions. Findings from this study will inform the crossing strategy for the subtropical soybean breeding programs. Innovation strategies for improving genetic variability in the germplasm collection, such as investments in pre-breeding, increasing the geographic sources of introductions and exploitation of mutation breeding would be recommended to enhance genetic gain

Selection of wheat genotypes for biomass allocation to improve drought tolerance and carbon sequestration into soils

The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements such as carbon, water and nutrients with, for instance, the greatest allocations to roots fostering the transfer of atmospheric carbon to soils through photosynthesis. Several studies have investigated the root to shoot ratio (R:S) biomass of existing crops but variation within a crop species constitutes an important information gap for selecting genotypes aiming for increasing soil carbon stocks for climate change mitigation and food security. The objectives of this study were to evaluate agronomic performance and quantify biomass production and allocation between roots and shoots, in response to different soil water levels to select promising genotypes for breeding. Field and greenhouse experiments were carried out using 100 genotypes including wheat and Triticale under drought-stressed and non-stressed conditions. The experiments were set-up using a 10 x 10 alpha lattice design with two replications under water stress and non-stress conditions. The following phenotypic traits were collected: number of days to heading (DTH), number of productive tillers per plant (NPT), plant height (PH), days to maturity (DTM), spike length (SL), kernels per spike (KPS), thousand kernel weight (TKW), root biomass (RB), shoot biomass (SB), root to shoot ratio (R:S) and grain yield (GY). There was significant (p < 0.05) variation for grain yield and biomass production because of genotypic variation. The highest grain yield of 247.3 g/m(2) was recorded in the genotype LM52 and the least was in genotype Sossognon with 30 g/m(2). Shoot biomass ranged from 830 g/m(2) (genotype Arenza) to 437 g/m(2) (LM57), whilst root biomass ranged between 603 g/m(2) for Triticale and 140 g/m(2) for LM15 across testing sites and water regimes. Triticale also recorded the highest R:S of 1.2, whilst the least was 0.30 for wheat genotype LM18. Overall, drought stress reduced total biomass production by 35% and R:S by 14%. Genotypic variation existed for all measured traits useful for improving drought tolerance, whilst the calculated R:S values can improve accuracy in estimating C sequestration potential of wheat. Wheat genotypes LM26, LM47, BW140, LM70, LM48, BW152, LM75, BW162, LM71 and BW141 were selected for further development based on their high total biomass production, grain yield potential and genetic diversity under drought stress