2. If a phenotype has not been previously analyzed under natural
conditions, it is advisable to run a small preliminary field
experiment.
3. Field experiments involving the comparison of specific treatments applied by the researchers, such as water availability,
pesticide treatment, or soil type [27], should be designed
carefully to avoid increasing differences between treatments
due to other external environmental factors (e.g., use mock
treatments for control plants when infecting or adding chemical compounds).
4. Field experiments involving gene expression analyses will
require substantially larger amounts of plants to obtain enough
tissue because plants grown under natural conditions are often
very small (Fig. 1d, h, l). This amount should be even larger for
expression analyses at early vegetative stages [33].
5. General rules for the experimental design in field sites are
similar to those for plant phenotyping under controlled conditions (greenhouses or growth chambers) or for agricultural
fields [61], but taking into account that fewer Arabidopsis
seedlings and adult plants will survive under natural conditions
[31, 35]. Depending on the goal, the unit for phenotyping in
field experiments can be a pot with 50–100 seeds; a pot with
one or several previously grown seedlings; or a tray with an
admixture of seeds from the same or different genotypes. The
final size of the experiment quantified as the total number of
seeds/plants, the number of pots/trays, and the area of the
experimental setting will depend on the number of genotypes
or lines, the number of blocks, the number of replicates per
block, and the number of plants per replicate/pot.
6. Overall, larger environmental and phenotypic variability is
observed between blocks (or replicates) in field sites than in
greenhouses or growth chambers. The heterogeneity of the
facility (e.g., sunny and shady zones within the facility) to
conduct field experiments will strongly determine the amount
of phenotypic variability observed, although not all genotypes
respond in the same manner to such environmental heterogeneity. Therefore, it is convenient to have at least 6–10 blocks
and/or replicates per block of all genotypes, with sufficient
number of plants per genotype and replicate, to cover the
heterogeneity of the facility. As a rule of thumb, the greater
the environmental heterogeneity of the experimental facility is,
the greater the number of replications will be needed.
7. Diseases and all sort of insects (e.g., aphids, caterpillars) can
reduce plant survival and fecundity. In the worst case, they can
wipe out a large portion of the experiment, but normally some
genotypes are more affected than others as palatability strongly
100
Carlos Alonso-Blanco et al.
conditions, it is advisable to run a small preliminary field
experiment.
3. Field experiments involving the comparison of specific treatments applied by the researchers, such as water availability,
pesticide treatment, or soil type [27], should be designed
carefully to avoid increasing differences between treatments
due to other external environmental factors (e.g., use mock
treatments for control plants when infecting or adding chemical compounds).
4. Field experiments involving gene expression analyses will
require substantially larger amounts of plants to obtain enough
tissue because plants grown under natural conditions are often
very small (Fig. 1d, h, l). This amount should be even larger for
expression analyses at early vegetative stages [33].
5. General rules for the experimental design in field sites are
similar to those for plant phenotyping under controlled conditions (greenhouses or growth chambers) or for agricultural
fields [61], but taking into account that fewer Arabidopsis
seedlings and adult plants will survive under natural conditions
[31, 35]. Depending on the goal, the unit for phenotyping in
field experiments can be a pot with 50–100 seeds; a pot with
one or several previously grown seedlings; or a tray with an
admixture of seeds from the same or different genotypes. The
final size of the experiment quantified as the total number of
seeds/plants, the number of pots/trays, and the area of the
experimental setting will depend on the number of genotypes
or lines, the number of blocks, the number of replicates per
block, and the number of plants per replicate/pot.
6. Overall, larger environmental and phenotypic variability is
observed between blocks (or replicates) in field sites than in
greenhouses or growth chambers. The heterogeneity of the
facility (e.g., sunny and shady zones within the facility) to
conduct field experiments will strongly determine the amount
of phenotypic variability observed, although not all genotypes
respond in the same manner to such environmental heterogeneity. Therefore, it is convenient to have at least 6–10 blocks
and/or replicates per block of all genotypes, with sufficient
number of plants per genotype and replicate, to cover the
heterogeneity of the facility. As a rule of thumb, the greater
the environmental heterogeneity of the experimental facility is,
the greater the number of replications will be needed.
7. Diseases and all sort of insects (e.g., aphids, caterpillars) can
reduce plant survival and fecundity. In the worst case, they can
wipe out a large portion of the experiment, but normally some
genotypes are more affected than others as palatability strongly
100
Carlos Alonso-Blanco et al.