A genetic plant type is defined as a genetically conditioned association of morphophysiological traits. Two axes of genetic variation in plant type were obtained from principal component analysis of genetic correlations. The genetic plant-type variations were found to be correlated with yielding potential.
A new rice variety "Reimei" was obtained by gamma-ray irradiation of seed of "Fujiminori", a leading variety with long culm in north-eastern district of Japan. This new mutant variety has a characteristic of short culm, reduced by approximately 15cm as compared with the original variety.
Three hundred and thirty-nine rice varieties and strains from various origins were tested for resistance to stripe disease by the "seedling test method." All the Japanese paddy varieties tested were susceptible, while the Japanese upland varieties were highly resistant with a few exceptions. Among foreign varieties, all of the Japonica type were susceptible, and most of the Indica type were resistant. Some Japanese upland strains, which were derived from the hybrids between Japanese paddy and upland rice varieties, were recognized as suitable parents for transferring stripe resistance to the Japanese paddy rice.
performed. These varieties were found to carry two dominant genes for resistance, Pi-a and Pi-z. The latter gene is on a locus independent of or distant from the genes, Pi-a, Pi-k and Pi-ta, and is linked with the gene, Pi-i.
Cytogenetical studies using crosses with species of known genome constitutions such as Mentha rotundifolia, M. spicata, and M. spicata var. crispa led to the conclusion that the genome constitutions of M. arvensis var. agrestis and M. arvensis var. piperascens are RaRaSSJJ and RaRaSSJJAA, respectively.
Variances of general and specific combining ability, reciprocal effect and their interactions with year were estimated on some traits of Renge. The variances of g.c.a. were larger than those of s.c.a. for all characters except forage yield. NO relation could be detected between the magnitude of g.c.a. or s.c.a. variance and that of interaction variance.
Germination of tulip seeds was completed in 45 days at 5°C. Optimum temperature for growth of seedlings was maintained at about 13°C, and 70 days after germination tops began to turn yellow. Plants that were moved to a 23°C environment at this stage turned to yellow rapidly and bulbs dormant. The thermoperiodicity may be expressed as follows ; 45L+70M+20H in the seedling phase, where L is 5°, M 13°, H is 23°C and the total period of growth from sowing to production of bulbs was about 135 days.
Devclopmental processes and the remains of starch grains in the seeds were observed to vary greatly in an indeterminate soybean, because the variety has a longer flowering period than determinate ones. The indeterminate type soybean seemed to be consistently inferior in the uniformity of seeds due to the growth habit.
Heterosis and combining ability analysis computed on a modified complete diallel cross of six inbred sorghum varieties in the F1 generations. The results suggested that F1 hybrids between dwarf male-sterile lines and Sudangrass would be full of promise for forage production.
Considerable dormancy or delayed germination was found to be induced, when the rice seeds matured at relatively low temperature in the early stage of maturation and at high temperature (about 30°C. or more) in the latter half of that period. In contrast to this fact, the germination speed was accelerated by the high temperature 5 or 10 days after ear emergence. These facts were observed equally in three varieties differentiating each other in germination habit.