Kin discrimination in allelopathy and consequences for
agriculture.
Niels P. R. Anten1,* & Bin J. W.
Chen2
1 Centre for Crop Systems Analysis, Wageningen
University, Wageningen, the Netherlands
2 College of Biology and the Environment, Nanjing
Forestry University, Nanjing, China
*Correspondence author: Centre for Crop Systems Analysis, Wageningen
University, Droevendaalsesteeg 1, 6708PB Wageningen, the Netherlands
Recent research has shown that plants can distinguish
genetically-related individuals from strangers (kin recognition) and
exhibit more cooperative behaviours towards these more related
individuals (kin discrimination). The first evidence for this was found
when Cakile edentula plants growing with half-sibs allocated
relatively less biomass to roots than plants growing with unrelated
individuals, indicating that kin recognition can reduce the intensity of
competition (Dudley & File, 2007). Since then, kin discrimination has
been shown to result in reduced competition for soil resources
(Semchenko, Saar, & Lepik, 2014), light (Crepy & Casal, 2015) and
pollinators (Torices, Gómez, & Pannell, 2018). On the other hand,
allelopathy, plants producing chemical compounds that negatively affect
performance of neighbour plants, has also been widely documented
(Inderjit & Duke, 2003) and shown to profoundly affect local species
coexistence and plant community structure (Meiners, Kong, Ladwig,
Pisula, & Lang, 2012). In crops allelopathy can also be beneficial in
suppressing weeds (Macías, Mejías, & Molinillo, 2019). In the current
issue, Xu, Cheng, Kong, and Meiners (2021) published the first study to
show that kin discrimination can also affect the balance between direct
competition for resources and allelopathy, and this together may lead to
improved weed suppression in rice.
Xu et al. grew target plants of two rice cultivars known to be both
allelopathic and capable of kin recognition, with four different
neighbour-plant treatments in order of decreasing relatedness:
neighbours being of the same cultivar, a genetically closely-related
cultivar, a genetically more distant cultivar but of the same ecotype
(‘indica’) or of a different type (‘japonica’). They explored: root
allocation, allelopathy, weed suppression and biomass production of
target plants in these treatments. They found that plants grown with
neighbouring rice plants of the same cultivar or a closely-related
cultivar allocated their roots less towards neighbouring rice plants but
more towards weeds, with a consequence of greater suppression of the
weeds. This showed that kin interaction could lead to reduced
intraspecific and more effective interspecific competition, consistent
with results from wild plants Semchenko et al. (2014). However, results
for allelopathy were less clear. Rice plants produced less
allelochemicals when growing with neighbours of a closely-related
cultivar than when growing with less related ones, but produced the
highest level when growing with neighbours of the same cultivar. This
indicates that the pattern through which kin recognition may affect
allopathy is still unclear. Moreover, despite of the differences in root
allocation, allelochemical production and weed suppression among
treatments, there was no clear pattern in grain production of rice
plants across treatments. This could imply that weed suppression did not
contribute to yields. It could also be that more related individuals
being phenotypically more similar competed more intensively for e.g.
light, a phenomenon known as kin competition (Platt & Bever, 2009), so
that positive kin cooperative effects and negative kin competitive
effects compensated each other in their effects on yield (Anten & Chen,
2021).