Varietal difference in the effects of low temperature on tassel development in hybrid maize

In 2003, severe barrenness due to low temperatures in hybrid maize (Zea mays L.) cultivar occurred in the Konsen region, one of the coldest areas in Japan. Varietal difference in grain set, and abnormal flowering habits and tassel growth were observed in the field in 2003. For the cultivar 39B29, which was affected severely, anthesis occurred several days after silking, and tassel size was reduced. For the cultivar Papirika, which was not affected by low temperature, anthesis began 0–1 d before silking, and tassel size was similar to that in previous years. In a 2011–2013 experiment, three varieties, Papirika, 39B29, and Kwiss were treated at 10 °C for 7 d at 6- to 9-leaf stage. Following the treatment, anthesis was delayed, and tassel length was reduced, in 39B29 and Kwiss, but not in Papirika. The relative tassel length (RTL, ratio of tassel length of experimental plants to that of untreated control plants) was around 60 in 39B29, 80 in Papirika, and 30 in Kwiss on average over 3 years. Based on field observations in 2003 and the pot experiment in 2011–2013, a cultivar whose RTL was 60 or less was deemed sensitive, and a cultivar whose RTL was 80 or more was deemed less sensitive to low-temperature stress during the tassel development stage.