Inability of tobacco callus to express resistance against avirulent race of Phytophthora parasitica var. nicotianae and various non-pathogenic fungi (Agriculture)

タバコの羅病性品種(Burley-21)の茎は, その病原菌であるPhytophthora parasitica var. nicotianaeによって侵入を受けたが抵抗性品種(L-8)は侵入を受けなかった。しかしながら, 両タバコ品種より誘導されたカルス組織は本病原菌により同程度によく侵入を受けた。ホルモン濃度, 光, また温度を変化することによりカルスの培養条件を変化させても侵入の程度に差異は認められなかった。また, カルス組織は本来タバコ植物に病原性をもたない多くの非病原菌によってもよく侵入を受けた。これらカルス組織における非特異的な抵抗性消失は, カルス組織より誘導したタバコ植物が再び抵抗性を獲得するので, 抵抗性遺伝子がカルス細胞に欠除したためであるとは考え難く, むしろ抵抗性遺伝子の発現が何らかの作用により抑制されていると考えられる。タバコの葉も羅病性ならびに抵抗性品種に関係なくP. parasitica var. nicotianaeによってよく侵入を受けたが, 数種の非病原菌に対しては抵抗性を示した。このようにタバコはその組織の違いにより, 感受性を著しく異にする。Tobacco calluses derived from stem pith of either the resistant (L-8) or the susceptible (Burley-21) cultivar were equally colonized by race 0 of Phytophthora parasitica var. nicotianae. Several attempts by changing the cultural conditions of callus such as modifications of the hormonal regime, light, and temperature failed to obtain differential colonization rates by the fungus. A wide variety of the non-pathogenic fungi, which could not normally attack stem of intact tobacco plant, did also colonized on callus. Since the plant stems derived from callus regained the resistance not only to avirulent race of P. parasitica var. nicotianae but also to the nonpathogenic fungi, it was concluded that the mechanism for loss of resistance in callus is due to other than the deletion of genes governing resistance from genome of callus cells, and presumably being due to repression of the resistance gene expression. Leaves of the resistant and susceptible cultivar were equally attacked by P. parasitica var. nicotianae, but resisted to certain non-pathogenic fungi. The results, thus, revealed differential degrees of susceptibility among tobacco tissues

植物培養細胞に対する mutagens の効果に関する研究 II : 菜豆カルスの放射線感受性(農学部門)

菜豆(Phaseolus vulgaris L. cv. Kentucky Wonder)のカルス, 幼苗および種子に対するγ線照射の影響を比較した。照射カルスの生長は線量の増加に伴って有意な減少を示したが抑制程度は一様ではなく, 初期から生長が認められた2.5∿5KR, 生長遅延を示したが生長を続けた6.25∿8.75KRおよびほとんど生長が認められなかった10KR以上のほぼ3群に大別された。照射カルスの継代能力は12.5KR以上ではほとんど認められなかった。カルスは線量の増加に伴って褐色の度合およびもろさの程度が増加した。一方, 幼苗照射における生長抑制は, 1KRでは約50%で頂端分裂組織も正常であったが, 2KRでは顕著な抑制と頂端分裂組織の脱落が認められ, 5KR以上では枯死した。また, 種子照射においては, 10KRまでは約30%の抑制であったが, 20KR以上ではほとんど生長が認められなかった。以上の結果から, 生長抑制でみた菜豆のカルス, 幼苗および種子の放射線感受性には顕著な差異が認められた。すなわち, 幼苗が最も感受性で, 種子が抵抗性であり, カルスはほぼその中間であった。A comparative study on the effects of ^(Co) gamma radiation was carried out on callus tissue, seedlings and seeds of Phaseolus vulgaris L. cv. Kentucky Wonder. Callus was obtained from the hypocotyl pieces grown on an agar-solidified, modified Linsmaier and Skoog\u27s medium supplemented with 2,4-D (5mg/1), kinetin (5mg/1) and yeast extract (1,000mg/1). Subculture was conducted on the same medium in the dark at 28±1℃. Callus was exposed to various doses (2.5-15KR) of gamma radiation at 20KR/hr. Fresh and dry weight, potency of growth in subculture of irradiated callus, color and friability were measured. As compared with control, irradiated callus growth showed a significant decrease with increasing doses. Callus growth was classified into three types, i.e. callus began to grow from the early stage of culture at 5KR and below, from 6.25-8.75KR there was a delayed growth, at 10KR and over there was little visual sign of growth. The potency of growth in subculture for 28 days of irradiated- and 24-day-cultured callus was recognized at 10KR and below. With increasing doses, color of callus darkened, and the degree of friability increased. While 10-day-old seedlings were irradiated, striking inhibition of growth occurred at 2KR, followed by degradation of the apical meristem and growth ceased completely at 5KR. Severe inhibition of growth of irradiated seeds occurred at 20KR and over. A remarkable difference in radiosensitivity was observed among callus tissue, seedlings and seeds, i.e. seedlings were most sensitive, followed by callus tissue, and seeds were most resistant