Abstract
Plants produce biomass and then allocate some of this biomass to reproduction. The pattern of reproductive
allocation is an important aspect of a plant’s reproductive strategy in nature and is closely linked
to yield and Harvest Index in cereal crops. Recent research has concluded that reproductive allocation
should be analyzed and interpreted allometrically because ratios or fractions such as Reproductive Effort
or Harvest Index are size dependent. We investigated reproductive allocation of individuals in 6 varieties
of Triticum (wheat) grown at a wide range of densities. We harvested leaves, stems, spikes and grains of
individual plants and analyzed the relationship between grain mass and vegetative mass allometrically.
The large variation in density created large variation in plant mass and reproductive output. Most of
the variation in individual yield (grain mass) was due to variation in plant size. There were significant
differences among the varieties in the allometric exponent (slope of log–log relationship) of grain versus
vegetative mass, such that some varieties produced higher yield (and therefore had a higher Harvest
Index) than others when plants were small, while others had higher yield at larger sizes. Thus, the Harvest
Index and its rank among varieties changed with plant size, which puts into question the practice of
selecting for Harvest Index when crop performance varies greatly among individuals, years or environments.
Selection for a high Harvest Index when individuals are large may mean unintentional selection
for a lower Harvest Index when individuals are smaller. We conclude that cereal breeders should focus
on reproductive allometry when interpreting Harvest Index, and select for allometric patterns that are
most advantageous in a given agronomic context, especially when there is large variation in productivity
among individuals, locations or years.
allocation is an important aspect of a plant’s reproductive strategy in nature and is closely linked
to yield and Harvest Index in cereal crops. Recent research has concluded that reproductive allocation
should be analyzed and interpreted allometrically because ratios or fractions such as Reproductive Effort
or Harvest Index are size dependent. We investigated reproductive allocation of individuals in 6 varieties
of Triticum (wheat) grown at a wide range of densities. We harvested leaves, stems, spikes and grains of
individual plants and analyzed the relationship between grain mass and vegetative mass allometrically.
The large variation in density created large variation in plant mass and reproductive output. Most of
the variation in individual yield (grain mass) was due to variation in plant size. There were significant
differences among the varieties in the allometric exponent (slope of log–log relationship) of grain versus
vegetative mass, such that some varieties produced higher yield (and therefore had a higher Harvest
Index) than others when plants were small, while others had higher yield at larger sizes. Thus, the Harvest
Index and its rank among varieties changed with plant size, which puts into question the practice of
selecting for Harvest Index when crop performance varies greatly among individuals, years or environments.
Selection for a high Harvest Index when individuals are large may mean unintentional selection
for a lower Harvest Index when individuals are smaller. We conclude that cereal breeders should focus
on reproductive allometry when interpreting Harvest Index, and select for allometric patterns that are
most advantageous in a given agronomic context, especially when there is large variation in productivity
among individuals, locations or years.
| Original language | English |
|---|---|
| Journal | Field Crops Research |
| Volume | 144 |
| Pages (from-to) | 162–166 |
| Number of pages | 5 |
| ISSN | 0378-4290 |
| DOIs | |
| Publication status | Published - Mar 2013 |