Potato production from true potato seed (TPS) is highly promising, and may put remarkable contribution to potato production for marginal farmers of developing countries. But the farmers often face serious problems for the utilization of TPS technology. On this aspect, some agronomic management practices and promotional activities of TPS technology were conducted during 1993 to 2003 to find out the appropriate method of utilization of TPS and to make TPS more attractive to the potato farmers. Thirty one hybrid TPS progenies were evaluated in nursery beds followed by normal planting in field. In nursery beds, among the 31 TPS progenies, the yields of seedling tubers were exceptionally high in P-364 X TPS-67 (73.4 t ha^-1). In the following year, the seedling tubers were planted in the field to observe their performance in second generation. Both in nursery bed and field, 3 progenies, TS-7 X TPS-67, MF-II X TPS-67, and P-364 X TPS-67 showed superior performance in respect of tuber uniformity, virus infection, and tuber yield.

　An experiment was conducted in order to determine the optimum plant spacing of TPS to obtain the highest seedling tubers yield with maximum economic return. Four TPS progenies were sown at 4 different spacings. Among the TPS progenies and spacings, P-364 X TPS-67 and 25 x 4 cm produced the highest yields (73.8 and 71.9 t ha^-1, respectively). For all crop production operations, a plant spacing of 25 x 4 cm was found to be the most economic for the production of seedling tubers.

　Ten TPS progenies were evaluated in 3 consecutive years. An average yields of the10 TPS progenies, obtained in the first, second, and third generations were 65.9, 29.5, and 26.4 t ha^-1, respectively. Significant variations were observed among the progenies in respect of yield and other characters providing a basis for selection of superior progenies.

　Field performance of 5 different TPS progenies were investigated in their 3 successive generations. The first year crops derived from the TPS were free from virus and bacterial wilt and yielded 48.5 t ha^-1. In the second and third year, the yield decreased to 31.2 and 27.9 t ha^-1, respectively, while disease incidence increased. Total tuber yield of BARI TPS 1 and P-364 X TPS-67 in the second and third year were similar to the commercial cultivar 'Diamant' and significantly higher than other TPS progenies. Virus infection of MF-I X TS-15 and MF-II X TS-15 were significantly lower than 'Diamant', especially in the third year.

　Storability of tubers obtained from 9 hybrid TPS progenies were compared with that of 'Diamant' under ambient conditions. Among the progenies, P-364 X TPS-67 and P-364 X TS-9 showed better storage performance than 'Diamant'.

　Two hybrid TPS progenies, MF-II X TPS-67 and TS-7 X TPS-67, were evaluated at a farmer's field. Both progenies had good seedling tubers yield (about 50 t ha^-1) which produced 30 to 35 t ha^-1 in the following year. Moreover, the use of these TPS progenies resulted in higher yield than that of seed potatoes.

　Nutrient conditions in the potato mother plants directly affect the production of quality TPS. Therefore, experiments were conducted during 2004-2007 to examine the effects of combinations of different levels of nitrogen (N), phosphorus (P), and potassium (K) on yield and quality of TPS using crosses of ♀MF-II and ♂TPS-67. Four levels of each of N (0. 150, 225, and 300 kg ha^-1) and P (0, 60, 120, and 180 kg ha^-1) were applied to MF-II for obtaining better flowering, berry setting, and TPS production. Out of the 16 treatment combinations, the highest 100-TPS weight (84.1 mg) was obtained with 300 kg N and 120 kg P ha^-1, while the highest TPS yield (136.1 kg ha^-1) was obtained with 225 kg N and 120 kg P ha^-1. Considering the findings of the previous study, 2 levels of N (225 and 300 kg ha^-1) and a fixed value of P (120 kg ha^-1) were selected as promising for TPS production. Twelve combinations of 3 N (0, 225, and 300 kg ha^-1, respectively) and 4 K (0, 125, 175, and 225 kg ha^-1, respectively) levels were also applied to MF-II to investigate the effects of yield components of TPS. The weight of 100-TPS increased with increasing N rate but decreased with increasing K rate. The highest 100-TPS weight (83.8 mg) and maximum quantity (113.0 kg ha^-1 ) of quality (> 1.18 mm) TPS were obtained with the application of 300 kg N and 125 kg K ha^-1, while 225 kg N and 125 kg K ha^-1 produced the highest TPS yield (145.3 kg ha^-1).

　TPS that was produced from above mentioned 12 different fertilizer combinations were then used for nutritional analysis, germination tests in vitro, and growth performance in nursery beds. Large size TPS (>1.18 mm) produced from 300 kg N and 125 kg K ha^-1 gave the highest emergence rate (94%), seedling vigor (4.8), and dry matter content (10.5%) of seedling in nursery beds. Considering the present results together with those of the previous studies, it can be concluded that the combination of 300 kg N, 120 kg P and 125 kg K ha^-1 was the most suitable for the production of high quality TPS.

　A field experiment was also carried out to evaluate the relative economic return as influenced by supplemental N (0-250 kg ha^-1) and planting density (8-16 haulms m^-2) in MF-II. Most parameters showed maximum values when 0 to 150 kg N ha^-1 was applied, but the values decreased thereafter as supplemental N application increased. Although only the weight of 100-TPS showed a maximum value at 250 kg N ha^-1, the value was similar to that at 200 kg N ha^-1. A positive effect of higher planting density was detected only in the number of berries plant^-1 and yield of TPS. The combination effect of supplemental N and planting density on the yield of berries and TPS was significant. Although the total yield of TPS was the highest at the combination of 150 N kg ha^-1 and 16 stems m^-2, the yield of high quality TPS, was the highest at the combination of 200 N kg ha^-1 and 12 stems m^-2. The benefit cost ratio also showed that the combination of 200 kg supplemental N ha^-1 and 12 stems m^-2 was the optimal growth conditions to harvest high quality TPS. Therefore, in the commercial aspect, 200 kg N ha^-1 of supplemental application in 7 separate installments at 7 day intervals starting from 27 DAP along with basal application (150-120-125-120-12-6 kg ha^-1, N-P-K-Gypsum-ZnSO4-Borax, and 10 t ha^-1 farm yard manure) and 12 stems m^-2 is the most suitable combination to produce high quality TPS from ♀MF-II X ♂TPS-67.

（和訳）

　真性種子（TPS）によるジャガイモ生産は，特に発展途上国における多くの農民のジャガイモ生産に大きく貢献できる可能性を持つが， 一般農民にとってTPSの実用化には様々な障害がある． そこで本研究では，1993～1997年にかけて，適切なTSP利用技術を開発し， ジャガイモ生産農家にとってより魅力のあるTPS技術を提供する目的から，実用化試験を実施した． 31種の雑種TSPを供試した結果，収量性ではP-364×TSP-67（73.4 t/ha）が最大であった． 翌年，種いもを圃場に植付け，第2世代の生産性を見たところ，育苗ベッド， 圃場ともTS-7×TPS-67，MF-II×TPS-67，P-364×TSP-67の3種の交配組み合わせが塊茎の大きさ， ウイルス抵抗性，収量とも最も良い成績を収めた．

　最大収量を得られる植付け幅及びその経済性について調べたところ，品種はP-364×TPS-67（73.8 t/ha）を， 植え幅は25×4 cm（71.9 t/ha）の時に最大収量が得られ，経済性についても，25×4 cmが最も収益性が高かった．

　5品種のTPSの品質を3世代に渡り追跡調査した． その結果，初年度ではどの品種も細菌およびウイルス感染症はなく，48.5 t/haの収量を得た． 第2，第3世代では収量はそれぞれ31.2，27.9 t/haに低下し，病害抵抗性も低下した． しかし，Bari TSP1とP-364×TPS-67では，第2，第3世代における収量性は，供試した他のTPS品種より優れ， 市販の栄養繁殖性品種'Diamant'と同程度であった． また，MF-I×TS-15とMF-II×TS-15では第3世代におけるウイルス抵抗性が'Diamant'より高かった．

　9種の雑種TPSを用いて常温下における塊茎の貯蔵性を調べたところ，P-364×TPS-67，P-364×TX-9が'Diamant'より優れた貯蔵性を示した．

　MF-II×TPS-67，TS-7×TPS-67の圃場試験を実施したところ，初年度は共に約50 t/haの，翌年はそれぞれ30，35 t/haの収量が得られ， この結果は栄養繁殖系を用いた場合より高い値であった．

　種子親の栄養状態はTPSの品質に大きく影響することから，MF-II（♀），TPS-67（♂）を供試し， 2004～2007年にかけてN，P，Kの3施肥量を変えた実験を行った． N量を0，150，225，300 kg/ha，P量を0，60，120，180 kg/haの計16処理区で栽培実験を行ったところ， 100粒重（84.1 mg）は300 N-120 P kg/haで，TPS収量（136.1 kg/ha）は225 N-120 P kg/haで最大となった． こうした結果から，225～300 N kg/ha，120 P kg/haの組み合わせが最も良いと判断した． そこで，N量を0，225，300 kg/ha，P量を120 kg/haとし，K量を0，125，175，225 kg/haの計12処理区で MF-IIに対する栽培実験を行ったところ，300 N-125 K kg/haの時に100粒重（83.8 mg）， 高品質（>1.18 mm）TPS収量（113.0 kg/ha）が最大となり，225 N-125 K kg/haの時に粗TPS収量（145.3 kg/ha）が最大となった． 更に，上記の12処理区から得られたTPSの栄養分析，in vitroでの発芽試験，圃場で発芽後の生長解析を行ったところ， 300 N-125 K kg/haの組み合わせから収穫した1.18 mm以上のTPSは，発芽率（94%），苗の成長活性（4.8），乾物重（10.5%）が最も高くなった． 本結果と前述した施肥試験の結果を総合し，N-P-Kは300-120-125 kg/haの組み合わせが高品質TPSを得る上で最も望ましいと結論付けた．

　最後に，追肥条件とTPS生産の経済性を調べるため，追肥N量を0～250 kg/ha， 栽植密度を8～16本/m2の組み合わせでMF-IIの栽培実験を行ったところ， ほとんどのパラメーターが0～150 N kg/haの際に最大値を示し，追肥N量がそれ以上に増えると低下した． 唯一100粒重のみが250 N kg/haで最大値を示したが，200 N kg/haの時とほぼ同じ値であった． 栽植密度に関しては，株当りの果実数，TPS収量のみが正の相関を示した． また，果実およびTPS収量については，追肥N量と栽植密度の相乗効果が認められた． 150 N kg/ha・栽植密度16本/m2の際に全TPS収量が最大となったが， 高品質TPS収量は200 N kg/ha・栽植密度12本/m2で最大となり，経済収益性について調べた結果も同様であった． これらの結果を総合し，経済性をも考慮した場合，MF-II（♀）とTPS-67（♂）から高品質のTPSを得るためには， 基肥としてN-P-K-石こう-硫化亜鉛-ホウ砂を150-120-125-120-12-6 kg/ha， 厩肥を10 t/ha，追肥として，定植27日後から7日間隔で7回の追肥N量が計200 kg/haとなるように施肥し， 12株/m2の栽植密度で育てた場合に，最も高品質のTPSを生産できる．