The genetic diversity and relationships among 127 Japanese apricot (Prunus mume Siebold et Zucc.) germplasms, including 56 fruiting and 55 flower-ornamental cultivars derived from Japan, 8 germplasms from China, 7 germplasms from Taiwan and 1 germplasm from Thailand were assessed by SSR markers. Thirtynine out of 58 SSR markers developed from peach and apricot could produce one or two amplified fragments in Japanese apricot, suggesting transferability across species. Fourteen SSR markers showing clear amplification and high polymorphisms were chosen for further analysis. A total of 155 putative alleles were observed in Japanese apricot for 14 SSR loci with an average value of 11.1. The values of observed heterozygosity (H O ) and expected heterozygosity (H E ) ranged from 0.29 to 0.88 (mean value of 0.61) and 0.32 to 0.92 (mean value of 0.68), respectively. A phenogram for 127 Japanese apricot and 3 apricot germplasms showed 3 major clusters, 1) Bungo group of Japanese apricot and apricot, 2) germplasms from Taiwan and Thailand, 3) fruiting and flower-ornamental germplasms derived from Japan and China. In the present study, definite genetic differences were not found between fruiting and flower-ornamental groups, which supported the hypothesis that fruiting cultivars have been selected from flower-ornamentals.

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Control effect of bactericides on bacterial shot hole disease caused by Xanthomonas campestris pv. pruni in peach in relation to severity of infection SummaryWe investigated the control effect of bactericides, mainly antibiotics, on bacterial shot hole disease caused by Xantho monas campestris pv. pruni in peach from 1998 to 2005 in relation to the severity of infection. The antibiotic streptomycin was effective giving a protective value of 6367 in the untreated plots when the percentage of infected fruit was 5.59.8%. At a higher rate of infection, however, the protective value decreased. Streptomycin was as effective as the other bacteriocides (oxytetracycline, validamycin and dithianon) when the rate of infection in the untreated plot was low. The efficacy of strepto mycin was not improved by combined administration with ziramthiram compounds.aÌR §_ÑYZpZ^[Ê÷±ê©«Eàà¤E aÌR §_AEåwZE aÌR §_ÑYZpZ^[Ê

白紋羽病の病原である Rosellinia necatrix Prillieux は広 範囲の農作物を犯し 5) ，特に永年性作物である果樹では 発病により枯死に至るため被害が大きく，重要病害と なっている。 和歌山県のウメは栽培面積 5620 ha，生産量 68800 t 11) で，いずれも全国１位であり，県内の果樹ではカンキツ に次ぐ重要な位置を占めている。本県においてウメ白紋 羽病は1980年代前半から急増し，当時の発生園率は10％ 以上と推定された 10) 。現在も慢性的に発生がみられ，発 病樹はほ場内に散在する場合が多い。 本病は土壌病害であるため発病樹の防除が困難なこと に加え，発病跡地にウメ苗を定植しても再発するため， 改植を阻害する重大な要因となっている。 発病樹の治療， 跡地消毒は主にフルアジナム水和剤の土壌潅注により行 われている。しかし，処理に労力を要し，500倍液を１ 樹当たり50～100リットル潅注するため，経済的負担が 大きい。 一方，露地 4) ，施設 6) において，夏期の地表面被覆に よる太陽熱土壌消毒法が開発され，野菜，花き等で土壌 病害の有効な防除法として広く用いられている。白紋羽 病に対する本法を用いた防除については，海外において リンゴ，アボカドで検討されている 3,8,9) 。しかし，国内 の果樹での試験事例はほとんどなく，ウメでの検討はこ れまで行われていなかった。本法をウメ白紋羽病の改植 時の跡地消毒に適用することができれば， 防除の軽労化， 低コスト化が期待される。 そこで，ほ場での防除効果の実証に先立ち，高地温土 壌における白紋羽病菌の死滅条件を検討した。また，本 県ウメほ場においては白紋羽病が樹単位で散発的に発生 Summary White root rot fungus, (Rosellinia necatrix ( ( Prillieux) was eliminated from both naturally infected root segments and inoculated shoot segments buried in non-sterilized soil when the soil temperature was maintained at 35°C for 12 hours per day for 4 days. At a soil temperature of 32°C, 7 days were required for the elimination of the fungus from shoot segments. In a Japanese apricot orchard located in the southern area of Wakayama Prefecture, Minabe-cho, Hidaka-gun, Japan, the effects of solarization on the eradication of R. necatrix in mulched soil on vinyl sheets (3×3 m) were evaluated for 2 months from late July in 2006, 2007, and 2008. The pathogen, which was inoculated into shoot segments buried at depths of up to 80 cm at the center of the site and at depths of up to 60 cm at a distance of 110 cm from the center of the site was eliminated after 2 months of solarization,although the rate of elimination was lower at the edge of the site. The depth of shoots in the soil almost eliminated the pathogen when soil temperature above 32°C was recorded for at least 7 consecutive days. In contrast, the pathogen was not eliminated when the temperature of the soil was observed to be not above 32°C for at least 7 consecutive days; thus, the integration time of the soil temperature can estimate the success of elimination of the pathogen. Therefore, in areas that, in summer, show weather conditions similar to those of the orchard in which this field experiment was performed, soil solarization may be effective in the eradication of white root rot fungus in soil at the plot from which the affected Japanese apricot tree was removed.