Genetic relationship among selected heat and drought tolerant bread wheat genotypes using SSR markers,agronomic traits and grain protein content

ABSTRACT

Assessing the genetic variation and relationships present in crop germplasm is a pre-requisite for parental selection and breeding. The objective of this study was to determine the genetic relationships present among selected heat and drought tolerant wheat genotypes using simple sequence repeat (SSR) markers, agronomic traits and grain quality parameters to select desirable parents for breeding. Twenty-four agronomically selected wheat genotypes sourced from the International Maize and Wheat Improvement Centre (CIMMYT)’s heat and drought tolerance nursery and four local check varieties were genotyped using 12 selected polymorphic SSR markers. The test genotypes were phenotyped using yield and yield-component traits, and grain protein content (GPC) under non-stressed (NS) and drought-stressed (DS) conditions. Expected heterozygosity mean value of 0.58 indicated moderate genetic diversity for breeding. The studied wheat genotypes were delineated into six genetic groups using cluster analysis. Significant genotypic differences were observed for agronomic traits and GPC under NS and DS conditions. Genetically unrelated breeding parents including LM02, LM13, LM23, LM41, LM44, LM71, LM73 and LM75 were selected for population development and breeding for enhanced grain yield and protein content under heat and drought-stressed environments.     

Progeny testing of maize (Zea mays) genotypes for grain yield and yield components,Striga resistance and Fusarium oxysporum f.sp. strigae compatibility

Maize cultivars with resistance to Striga spp. and compatible to Fusarium oxysporum f.sp. strigae (FOS) are an economical, sustainable and environmentally Striga control option. This study's objective was to determine the type and magnitude of gene action controlling grain yield and yield-related components, Striga resistance, FOS compatibility and to select promising maize genotypes for an integrated Striga management approach. Ninety-nine experimental hybrids, generated by a North Carolina mating design II, were evaluated with and without FOS treatment at three Striga-infested sites in western Tanzania. The general (GCA), and specific combining ability (SCA) effects were significant (P < .05) for all the assessed traits with and without FOS except, Striga damage ratings eight (SDR8), and 10 (SDR10) weeks after planting with FOS treatment. FOS-treated progenies had fewer emerged Striga plants than untreated controls. Parental genotypes such as SITUKA M1, TZA4010, TZA4016, TZA4203, JL01, JL05, JL13 and JL17 showed negative GCA effects for all Striga parameters and positive GCA effects for grain yield. The new progenies and selected parents are recommended for Striga resistance breeding.     

Resistance breeding and biocontrol of Striga asiatica (L.) Kuntze in maize: a review

Purpose: The aims of this article are to highlight pre-breeding procedures for identifying primary sources of Striga-resistance genes and to summarize complimentary breeding techniques that enhance partial resistance of maize varieties against Striga species.

Materials and methods: The paper presented a comprehensive account of Striga screening and controlling techniques and highlighted the potential of integrating partial resistance with FOS to boost maize production and productivity in SSA.

Results: Striga infestation is a major constraint to maize production and productivity in Sub-Saharan Africa (SSA). A lack of Striga-resistant maize varieties and the limited adoption of other control methods hinder effective and integrated control of the parasitic weed in maize and related cereal crops globally. Genetic resistance of maize should be complemented with the use of Fusarium oxysporum f.sp. strigea (FOS), a biocontrol agent known to suppress Striga.

Conclusions: A combined use of genetic resistance and FOS has remained largely unutilized in controlling Striga in Africa. A combination of conventional and molecular Striga-resistance breeding tools as well as the use of FOS are promising methods to effectively control Striga in SSA.