II.29. A new type of cultivar, Mitake, with very few in number, but thick and stiff culms.
Shunji Nonaka. Tochigi Agricultural Experiment Station, Minamikawachi Division, Minamikawachi, Tochigi, Japan.
Mitake is a new variety selected among a bulk hybrid population of a cross between Chikurin-Ibaragi 2 and Miho Hadaka at Central Agricultural Experiment Station at Konosu, Saitama-ken. As seen in Figure 1, this is characterized by very few in number, but thick and stiff culms, and hence is highly resistant to lodging. In many other characters, however, this variety resembles Sekitori, a leading cultivar prevalent in Kanto districts. It is noteworthy that, despite its inferior ability of tillering, this variety generally outyields Sekitori when given appropriate cultural treatments, such as dense seeding, application of sufficient quantity of manures, etc.
Figure 1. Mitake (A) Sekitori-sai No. l (B)
Inheritance and linkage studies of the main characters of Mitake were made using crosses with several tester stocks of the normal type having more tillers than Mitake. Since the reduced number of tillers in Mitake was found to be inherited as simple recessive to normal, the gene for the character was tentatively designated rnt. As shown in Table 1, rnt is linked with uz on chromosome 3 with 31.8% recombination value. Independent inheritance of rnt with the following markers was also confirmed by F2 segregation in these crosses: n (chromosome 1), V (2), K (4), B (5), o (6) and s (7), where the numeral in parenthesis is the number of the respective chromosome.
Table l. Linkage between rnt and uz.
The location of rnt on chromosome 3 was further studied in F2 of a cross made between Mitake and Russian 82 which is characterized by albino lemma (al). Table 2 shows the results, which clearly indicate that the order of arrangement of three genes tested is rnt - uz - al, namely, rnt is located on the opposite side of al in relation to uz. Thus, it was noted that rnt is located rather close to als involved in absent lower laterals which is also characterized by reduced number of tillers, so a test of allelism between als and rnt was performed further. The result has indicated that these two are different loci.
