Molecular Breeding for Striga Resistance in Sorghum - Translational Genomics for Crop Breeding: Biotic Stress - page 77

Chapter 6

Molecular Breeding for Striga Resistance
in Sorghum

SantoshP.Deshpande,AbdallaMohamed,and CharlesThomasHash,Jr.

Abstract

Among the biotic stresses affecting dryland cereals, especially sorghum, Striga hermonthica is the
most damaging obligate parasite, and is an important bottleneck to yield increases by smallholder farm-
ers, yet it has been neglected by research in recent years. Integrated Striga management packages have
been designed, but these will continue to require new cultural and chemical treatments, resistant vari-
eties, and integrated approaches to manage both Striga and soil fertility. This review attempts to assess
recent advances in bioassay development that are specific to resistance mechanisms, genomics such as
New Generation Sequencing tools, RNA interference (RNAi) technologies in advancing knowledge of
resistance and susceptibility to Striga including diversity in striga populations, and molecular marker
technology in accelerating the development of Striga -resistant cultivars of sorghum. Recent advances
in developing effective bioassays involving several modifications of rhizotrons and sand-packed titer
plate assay will help dissect resistance mechanisms into component traits and increased understanding
of the specific resistance mechanisms, which will directly help in efficient introgression and selection
of several striga resistance mechanisms in breeding population. The current studies for identification of
parasite genes specifically involved in haustorigenesis through transcriptomic and/or proteomic stud-
ies and more recently RNAseq studies will help understand susceptibility or resistance genes in striga.
Release of improved version of cultivars resistant to striga developed by marker-assisted backcrossing
of several striga resistance QTLs in Sudan had shown the power of integrating genomics and molecular
breeding tools/techniques into routine breeding for tackling the complex constraint such as striga. Ap-
plication and utilization of advance techniques in genomics and molecular breeding appropriately can
further enhance the efficiency of integrated striga management practices, and thus crop productivity.

of Asia and in the United States. These para-
sitic weeds have become the greatest biological
constraint to cereal food production in resource-
limited agricultural areas (Ejeta and Butler 1993;
Gressel et al. 2004) as nearly 50 million hectares

Introduction

Witchweeds ( Striga spp.) are important pests of
agricultural crops in much of Africa, especially
East Africa, and had been a problem in parts