Symptoms of Abnormally Early Ripening in a Wheat Cultivar “Minaminokaori” Grown in Kumamoto Prefecture and the Causative Factors

Abstract

Abnormally early ripening, locally called “Kareure”, induces early senescence of leaves and poor grain filling. The objectives of this study were to find the cause of Kareure. Kareure occurred in trial fields in 2001/12 and 2012/13 where mineral or nitrogen fertilizers or both were additionally applied. Thousand grain weight in the trail fields was 15% and 30% lower in 2011/12 and 2012/13, respectively, than in fields where plants ripened normally (control). The mineral fertilizers rich in silicate, calcium and iron did not influence the thousand grain weight. In 2012/13, omitting of the top-dressed nitrogen made the symptoms worse and increase of top-dressed nitrogen after heading did not influence the symptoms. However, increase of basal nitrogen reduced the symptoms in 2012/13. Excision of spikes significantly alleviated early fall in greenness and relative water content of flag leaves. Cultivars that have been evaluated as susceptible to Kareure in other regions were also susceptible in this region. We discussed the possibility that Kareure might be induced by nitrogen deficiency that might also induce early decline of water uptake and senescence during grain filling.