Breeding for Resistance to Biotic Stresses in Crops: Conventional to Genome Editing

Abstract

Biotic stress is caused by fungi, bacteria, viruses, insects, nematodes as well weeds and it significantly reduces crop yield globally. For instance, the outbreak of a new strain of stripe rust in wheat worldwide, the emergence of white scale insect affecting mango in Ethiopia, the newly emerged Maize Lethal Necrosis viral disease in maize, and invasive fall armyworm insect are devastating maize crop and causing yield loss in Africa. To reduce the yield losses due to biotic stresses, the development of resistant variety and integrated insect pest approach is the way forward for managing disease and insects at respective agroecologies. Thus, this review paper discussed on conventional breeding methods and molecular-assisted selection for breeding resistance to foliar disease in major cereal crops. Wide array of germplasm such as landraces, recombinant inbred lines, pure lines, Double haploid lines, elite lines, multi-parent population, mutant lines, introgressed lines, hybrids, open population variety and wild relative can be used as source germplasm and should be screened under artificial inoculation and or at hotspot areas to develop disease resistance variety. Many maize inbred lines and hybrids showed resistance to turcicum leaf blight, grey leaf spot and common rust diseases and indicating that these genotypes have carrying genes/favorable alleles for multiple disease resistance and it is possible to develop variety resistance to fungi foliar disease in maize. Similarly, several advanced lines and some varieties showed resistance to strip and leaf rust in wheat. However, host plant resistance could be broken down due to new emerging race pathogens. Thus, conventional breeding and molecular screening should be integrated for resistant variety development. Indeed, Marker-assisted selection through backcrossing, gene pyramiding, combined Genome-Wide Association, and transcriptome approach is useful to identify candidate genes and resistant parents in crops. .......