Toward haplotype studies in polyploid plants to assist breeding

THE IMPORTANCE OF POLYPLOIDS Polyploids are typically classified as either autopolyploids or allo-polyploids(Figure 1).Autopolyploids result from whole-genome duplication within the same species,while allopolyploids derive from the hybridization of different species followed by chromo-some doubling.Taxonomically,plant allopolyploids are thought to be the most common polyploids,although autopolyploid plants and allopolyploid plants might be at parity in numbers(Barker et al.,2016).During speciation,polyploidization allows plants to adapt to different environments(Soltis et al.,2009).Mutation and hybridization increase the heterozygosity of the genome,while genome rearrangements during polyploidization lead to the formation of new chromosomes and new chromosome rearrangements,which complicate polyploid genomes and the following studies.

A Statistical Growth Property of Plant Root Architectures

Numerous types of biological branching networks,with varying shapes and sizes,are used to acquire and distribute resources.Here,we show that plant root and shoot architectures share a fundamental design property.We studied the spatial density function of plant architectures,which specifies the probability of finding a branch at each location in the 3-dimensional volume occupied by the plant.We analyzed 1645 root architectures from four species and discovered that the spatial density functions of all architectures are population-similar.This means that despite their apparent visual diversity,all of the roots studied share the same basic shape,aside from stretching and compression along orthogonal directions.Moreover,the spatial density of all architectures can be described as variations on a single underlying function:a Gaussian density truncated at a boundary of roughly three standard deviations.Thus,the root density of any architecture requires only four parameters to specify:the total mass of the architecture and the standard deviations of the Gaussian in the threeðx,y,zÞgrowth directions.Plant shoot architectures also follow this design form,suggesting that two basic plant transport systems may use similar growth strategies.