varies among genotypes for different phytophagous insects. A
high number of genotypes and replicates will reduce losses due
to the effect of biotic agents.
8. Field experiments can be directly started from seeds sown in the
field site, or with seedlings previously produced in greenhouses
or growth chambers, and moved or transplanted to the field
site. Starting from seeds allows measurements of germination
and seedling survival under natural conditions, which are crucial life cycle stages for evaluating the effects of natural selection
[31, 39]. Starting from seedlings reduces risks of germination
failure or seedling mortality due to unfavorable weather
conditions.
9. The seed sowing date will strongly determine the life cycle and
phenology of plants grown in the field experiment [25, 39]. It
is advisable to choose sowing dates according to the germination behavior of natural populations of annual plants in the
neighborhood and/or the climate of the site. Overall, natural
Arabidopsis populations will germinate with the first period of
rain occurring at the end of summer or during fall (producing
the so-called winter cohort). However, in temperate or Mediterranean climates, later cohorts of germination will often
occur during the rain periods that take place at the end of
winter (so-called spring cohort). If needed, winter and spring
germinating cohorts can be differentiated by tagging seedlings
or rosettes with stainless steel pins in the middle of the winter,
when winter cohorts are established and spring cohorts have
not appeared yet [62].
10. Starting field experiments from seedlings previously grown in a
greenhouse requires synchronization of the phenology of these
seedlings with the expected phenology of Arabidopsis natural
populations in the experimental site location (see Note 9).
Seedlings can be directly transferred to the field site on the
starting date [27, 63].
11. Field experiments should be done in agreement with the local
legislations and rules for growing non-native plant material,
because they will mostly include wild accessions or genetic
materials derived from nonlocal natural or mutagenized populations. In addition, it is advisable to periodically check out the
experimental facility for Arabidopsis plants growing out of the
pots/trays. Although Arabidopsis is a poor competitor in natural conditions, the genetic materials used in field conditions
must be kept under strict control even after the end of the
experiment.
12. Field experiments can be set in very different sites, such as
natural areas, agricultural fields near research institutes, or
gardens outside the laboratory buildings, and preparation will
Analyses of Natural Variation
101
high number of genotypes and replicates will reduce losses due
to the effect of biotic agents.
8. Field experiments can be directly started from seeds sown in the
field site, or with seedlings previously produced in greenhouses
or growth chambers, and moved or transplanted to the field
site. Starting from seeds allows measurements of germination
and seedling survival under natural conditions, which are crucial life cycle stages for evaluating the effects of natural selection
[31, 39]. Starting from seedlings reduces risks of germination
failure or seedling mortality due to unfavorable weather
conditions.
9. The seed sowing date will strongly determine the life cycle and
phenology of plants grown in the field experiment [25, 39]. It
is advisable to choose sowing dates according to the germination behavior of natural populations of annual plants in the
neighborhood and/or the climate of the site. Overall, natural
Arabidopsis populations will germinate with the first period of
rain occurring at the end of summer or during fall (producing
the so-called winter cohort). However, in temperate or Mediterranean climates, later cohorts of germination will often
occur during the rain periods that take place at the end of
winter (so-called spring cohort). If needed, winter and spring
germinating cohorts can be differentiated by tagging seedlings
or rosettes with stainless steel pins in the middle of the winter,
when winter cohorts are established and spring cohorts have
not appeared yet [62].
10. Starting field experiments from seedlings previously grown in a
greenhouse requires synchronization of the phenology of these
seedlings with the expected phenology of Arabidopsis natural
populations in the experimental site location (see Note 9).
Seedlings can be directly transferred to the field site on the
starting date [27, 63].
11. Field experiments should be done in agreement with the local
legislations and rules for growing non-native plant material,
because they will mostly include wild accessions or genetic
materials derived from nonlocal natural or mutagenized populations. In addition, it is advisable to periodically check out the
experimental facility for Arabidopsis plants growing out of the
pots/trays. Although Arabidopsis is a poor competitor in natural conditions, the genetic materials used in field conditions
must be kept under strict control even after the end of the
experiment.
12. Field experiments can be set in very different sites, such as
natural areas, agricultural fields near research institutes, or
gardens outside the laboratory buildings, and preparation will
Analyses of Natural Variation
101