Figure 1.
Composite figure outlining the evolutionary relationship between Microlaena stipoides and cultivated rice (Oryza sativa).
Nodal numbers reflect the estimated million years since each bifurcation [4]–[6]. Although O. sativa and M. stipoides shared their last common ancestor approximately 34 million years ago they retain the same base chromosome number, n = 12, similar individual genome sizes [3], endosperm morphology and characteristics [8] and genetic homology [7].
Figure 2.
An overview of experimental flow identifying initial optimisation of appropriate EMS treatment (A) and development of the control and mutant populations for reverse genetic screening for SNP discovery and validation.
Note, mutant generational nomenclature is as per McCallum et al 2000, where d denotes dosage trial, M indicates EMS treated seed and S indicates the selfed control line.
Figure 3.
Examples of mutant plant phenotypes with differing doses of EMS and developmental stages.
A. 145 mM EMS treated chlorophyll aberration, only observed in M2 145 mM population, and not observed across all sibling M2 seedlings B. 130 mM treated mutant seedling C. 115 mM EMS treated mature plants showing root variation within pot trial D. 145 mM treated dwarf, no seed produced E. control F–I. 145 mM mature plants showing mutant phenotypes not seen in control populations; variations to plant architecture, leaf width, length and color, plant vigor, panicle shape, seed production and synchrony of maturity, and inter-nodal span length I. Individuals with this plant architecture did not produce seed. Other novel phenotypes observed in the mutant population included rhizome production, crooked nodes, non-surviving dwarfs, and sectoring as variegated leaves.
Figure 4.
Panicle shattering habit and awn length variations observed in Microlaena stipoides.
A. wild-type shattering habit with individual grains dehiscing as they reach maturity, and lodging seed heads B. Typical wild-type seed head showing empty panicle (↓) by the time the lower seeds have reached maturity C. Non-shattering panicle with all seeds retained at maturity (→) D. Short versus long awned grains. Short awned varieties are highly desirable as they minimise difficulties associated with handling, processing and mechanisation of the production system.
Table 1.
Total Microlaena stipoides population numbers and treatment distribution in final field site compared with top 50 mutant phenotypes selected for their amenability to domestication and the component phenotypes observed in these groups.
Figure 5.
Venn diagram identifying the number of SNP identified in each of the three pools: C109 pool containing 109 wild-type individuals, M109 pool containing 109 145 mM EMS treated mutants and M754 pool containing 754 145 mM EMS treated individuals.
The number of putatively EMS induced SNP (rare G/A or C/T polymorphism only found in mutant pools) is in square brackets. Full descriptions of SNPs are available in Table S2 in File S1.