Cytological and Genetical Studies on Male Sterile Sugi (Cryptomeria japonica D. Don), Shindai 1 and Shindai 5

Abstract

Male sterile sugi (Cryptomeria japonica D. Don) trees, “Shindai 1,” “Shindai 5,” were found in Niigata Prefecture, Japan. There were no significant differences in the appearances of male flowers and needles between these trees and the common wild type. We investigated the cyiological characteristics and inheritance of the male sterility trait in Shindai 1 and Shindai 5. We also determined the differences between Shindai 1, Shindai 5 and another male sterile tree, “Toyama MS”. Microsporogenesis in Shindai 1 and Shindai 5 produced normal microspores, but the microspores began to contract and clump. In the pollen dispersal season, the microspores agglomerated. Degeneration of microspores in Shindai 1 and Shindai 5 are different each others and also differ from that in Toyama MS in which microspores collapsed after expansion. All F₁ seedlings obtained from Shindai 1 and Shindai 5 produced pollen in male flowers, but F₂ seedlings segregated into 75% fertile and 25% sterile seedlings. Backcrossed seedlings obtained from Shindai 1 segragated into 50% fertile and 50% sterile seedlings. Moreover, seedlings obtained from a cross of Shindai 1 and Toyama MS F₁, Shindai 5 and Toyama MS F₁, Shindai 5 and Shindai 1 F₁ had only fertile male flowers. The male sterility trait in Shindai 1 and Shindai 5 are nuclear sterility controlled by a pair of recessive genes, and the male sterility in Shindai 1 and Shindai 5 are controlled by a different genetic mechanism than in Toyama MS.