To elucidate the effects of vernalization response genes on the growth and yield of wheat (Triticum aestivum L.), near-isogenic lines (NILs) carrying different vernalization response genes were developed in the genetic background of Abukumawase, a cultivar with extremely early maturity. Spring type NILs carrying either of the Vrn-A1, Vrn-B1, Vrn-D1 or Vrn-D5 gene, and winter type NIL without dominant Vrn gene were used for the experiment. These NILs were planted at two sites, Ibaraki and Fukuoka, and were observed over a period of two years. The results showed that stem elongation and ear development were early in the NILs carrying Vrn-A1, Vrn-D5, Vrn-D1 and Vrn-B1, in that order, while in winter type NIL they were the latest. The stem of the NIL carrying Vrn-A1 or Vrn-D5 elongated earlier than that of the other NILs and was prone to damage by frost, causing unstabilty growth. Since the NIL with Vrn-B1 was late heading, the subsequent grain filling period became shorter and the grain yield was reduced at Fukuoka. On the other hand, at Ibaraki, the grain yield of the NIL with Vrn-B1 was the highest among spring type NILs. Compared with the spring type NILs, the winter type NIL headed later but the maturity time was almost identical. Winter type NIL was superior due to its avoidance of frost damage and stablity of heading time and grain yield. The growth and developmental rates of the NIL with Vrn-D1 were intermediate in various aspects. Therefore, it was considered that, under the genetic background of wheat cultivars with extremely early heading, the adaptability of wheat and the stability of grain yield could be enhanced by the introduction of the winter growth habit or Vrn-B1.

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