Biplot Analysis to Detect Synergism between Genotypes of Different Species

This chapter exemplifies biplot analysis of synergism between genotypes of different species using two datasets. The first dataset is about host-by-rhizobium interaction for nitrogen fixation, and the second is about wheat–maize interaction for wheat haploid embryo formation. Both represent a wide range of research interest in plant breeding and biological research.

In contrast to the host-by-pathogen relationship, in which pathogens have harmful effects on their hosts, symbiosis is an inter-species relationship in which two different species live together and benefit each other. A well-known example is the relationship between legume species and nitrogen-fixing rhizobial species. The first part of this chapter exemplifies biplot analysis of interactions between host genotype-by-nitrogen-fixing rhizobial strains using a dataset of four Casuarina host species inoculated with four Frankia strains (Mansour and Baker, 1994). Casuarina is a tropical plant used in agroforestry, and Frankia is a nitrogen-fixing rhizobial species.

The second part of this chapter discusses a wheat-by-maize hybridization dataset and demonstrates the application of biplots in identifying the best wheat and maize genotypes for wheat doubled-haploid production. In recent years, wheat breeding via doubled-haploids produced by pollinating wheat F₁ plants with maize pollen has become a common practice in some wheat breeding programs (O’Donoughue and Bennett, 1994; Laurie et al., 1990; Sadasivaiah et al., 1999). Cherkaoui et al. (2000) provided data on the interactions between ten wheat genotypes and eight maize genotypes for haploid wheat embryo formation (Table 11.2). Although maize–wheat interaction does not belong to the category of genotype-by-strain interaction, they share exactly the same data structure and nature of interaction.