Agriculture Reference
In-Depth Information
had a preliminary AM study carried out with 99 individuals. Chickpea
has a well-studied core collection, which could be reduced in size to a
reference collection or association mapping panel. LD studies in several
other grain legumes (Faba beans, Lupines, Peas, and Pigeonpeas) are still
pending to have a better understanding of the precision with which AM
can be carried out in these legumes. This is especially important given
the inbreeding system that is typical of most food legumes (other than
Faba bean and Pigeon pea, which are mainly outcrossing species).
Outcrossing species of legumes are also typical in the forages; how-
ever, bottlenecks can also increase the amount of LD as was found in case
of alfalfa by Sakiroglu et al. (2011). Despite this bottleneck, stem com-
position traits and biomass were loosely associated with four lignin
biosynthesis candidate genes markers used in that study. Other forages
such as clovers have not used AM studies, but could bene
t from use of
association genetics.
In the model legume,
Medicago truncatula
, the AM approach has been
slow to take off due to lack of germplasm collections that vary in traits
and morphology. Soybean also has few AM studies to date considering
the crop
s importance. However, two pioneering studies looked at iron
chlorosis de
'
ciency and chlorophyll content, respectively, using a
moderate number of SNP markers (up to 1536) and different technolo-
gies for detection (Mamidi et al. 2011; Hao et al. 2012). Interestingly iron
chlorosis de
ciency was treated as a more oligogenic trait and was
studied with candidate genes at 15 different loci, while the chlorophyll
study was a GWA study.
One key factor noted for all the AM studies in legumes was the
importance of creating diverse germplasm panels for each species.
The concept of core or mini core collections is valuable for AM. These
collections would be made up of diverse genotypes representing most of
the crop diversity but that can be grown together in one environment
with common agronomic practices (Glaszmann et al. 2010; Upadhyaya
et al. 2011). So far the number of markers has been a limitation in
association studies with legumes. However, there are more markers
available from a recent project for most crops as well as for soybean,
which has long been a leader in SNP and SSR development among the
legumes, even more so in the private sector than in the public sector. In
some cases, such as cultivated peanuts and commercial soybean, lack of
diversity may be limiting for AM studies.
Root and tuber crops are the next group of dicotyledenous plants of
interest. Potato is one of the most important noncereal crops in the
world. Potato is a stem tuber crop that is propagated clonally. Other root
crops of great importance in tropical regions of the world are cassava,
