Abstract
Early maturing which enables harvesting before the rainy season is a desirable trait for wheat, in Japan. The objective of this study was to assess the length of developmental phases in 6 wheat cultivars which were sown in a field at 20 planting date-year combinations. The time at each developmental stage varied with the cultivar, planting date, and year. The variation was larger in early stages (e.g., double ridge) and smaller in late stages (e.g., maturity). After the double ridge stage, the lengths of each developmental phase was negatively correlated with the time of the beginning of the phase. These negative correlations indicate that hastening of planting date and double ridge stage does not result in earlier maturity. These correlations also make it difficult to screen for the developmental phase lengths in the field condition. The length of each developmental phases was always negatively correlated with the mean temperature, but, we could not confirm which climatic factor directly influenced the phase length, because there were high correlations between the factors. Additional experiments were conducted under controlled environments (phytotron) to screen for the cultivars with shorter heading-to-maturity phase lengths. T. spelta cultivars (e.g., 'Khapli' and ' France-62') had significantly shorter anthesis-to-maturity phase length than the control cultivar 'Shirasagi-komugi'. T. compactum cultivars had a shorter heading-to-anthesis phase length than the control cultivar, but the length from flag-leaf expansion to anthesis did not differ significantly among cultivars.
