Quantifying benefits of kinship dependent variation in allelopathy
Plants produce a wide variety of allelopathic compounds which can have negative effects on con-specific plants or negative effects on hetero-specific plants, the former also being called autotoxicity. Autotoxicity has been documented in a wide variety of plants and is thought as a mechanism to avoid local intraspecific competition and thus ensure a greater spatial and temporal seed dispersal (Singh, Batish, & Kohli, 1999). It is also well documented in several crops including rice (Singh et al., 1999) and is believed as an important cause of yield reductions in continuous mono-cropping (i.e., growing the same crop on a field year after year, Chi et al., 2013). Xu et al.’s finding of reduced allelopathic activities in rice plants only interacting with closely-related-cultivar neighbours may suggest this reduction to reflect a kinship-selected cooperative strategy avoiding auto-toxic effects on kin. However, this raises the question why the highest allelopathic activities were found in plants interacting with neighbours of the same cultivar (i.e., the treatment with the greatest degree of neighbour relatedness).Recent research has shown for wheat that plants may produce allelochemicals in response to exudates produced by neighbours, particularly loliolide and jasmonic acid (Kong et al., 2018). It is possible that such signalling also occurs in rice and that it differs between cultivars, independently of relatedness, and that the two focal cultivars in Xu et al. (2021) may have happened to be active producers of such signalling compounds. Clearly, more research is needed to better understand the possible connection between kin recognition and allopathy.