Seasonal changes have a great impact on
plant development and crop production. For warm season grasses like switchgrass
(Panicum virgatum), the transition
from a long-day, hot summer to a short-day cold winter will induce a phenomenon
called winter dormancy. Like most perennial warm season species, switchgrass
undergoes growth suspension in winter as a surviving strategy in temperate
climates to protect their meristems from cold injuries and dehydration, while
storage organs below ground drive spring regrowth when conditions become
favourable.
In this paper, the
authors described a reliable phenotyping method for winter dormancy in
switchgrass using various traits including regrowth height after clipping in
early fall (FRH), senescence percentage, date of spring regrowth (SRD), and
flowering date (FD). A diverse panel of switchgrass germplasm was used to
evaluate the phenotyping approaches. The panel consisted of 36 accessions that
included 14 uplands, 17 lowlands, and 5 intermediate ecotypes, in addition to
the parents of the mapping populations AP13 × VS16. Dormancy phenotypic data
evaluated consisted of 1) Level of senescence (senescence %) and plant regrowth
height after clipping in the fall (FRH), 2) Date of spring regrowth initiation
(SRD), 3) Date of flowering (FD), and 4) Dry biomass weight.
Fall regrowth height data showed a normal distribution with a slight
left skewness, signifying a high proportion of lower FRH values in the
population. Senescence % distribution was also normal but skewed to the right,
indicating a high proportion of higher senescence values in the population.
This is expected because most of the upland and intermediate genotypes enter
dormancy and senesce much earlier than lowland accessions. The data
distribution for SRD was normal but with some outliers in both tails. For FD,
the distribution was less bell-shaped and left skewed, suggesting a wide window
of flowering and a large variation of flowering dates in the population.
In conclusion, combining
the variables FRH, senescence, and SRD in a selection index may provide a
reliable tool to phenotype winter dormancy in switchgrass. The strong
correlation of these variables with biomass yield makes them useful candidates
for the manipulation of the duration of dormancy to increase the growing season
and consequently improving biomass production.
Article by Rasyidah
Mohamad Razar and Ali Missaoui, from University of Georgia, Athens, GA, USA.
Full access: http://mrw.so/2JLiAB
Photo credit: Matt Lavin on
Visualhunt/CC BY-SA.
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