番石榴立枯病接種方法之探討及其抗病篩選

Abstract

番石榴立枯病(Myxosporium wilt)乃病原菌Nalanthamala psidii (Sawada et Kurosawa) Schroers & M. J. Wingf. (≡Myxosporium psidii Sawada et Kurosawa)所造成的一種系統性真菌病害(systemical fungal disease)。自1970年代以來，由於番石榴多以修剪方式進行產期調節，植株常因修剪產生大量傷口，致病原菌入侵的機會大為提高，使該病成為臺灣番石榴栽培最嚴重、破壞性最大的病害。此病目前尚無法藉由藥劑防治，植株一旦發病要防治其蔓延，除將其焚燒與清除外別無他法。因此，進行抗病育種是必要的。 本研究之目的為：（1）番石榴實生苗接種方法之研究（2）實生苗之抗病篩選（3）菌株培養濾液(culture filtrate)對實生苗致病性之測試。本試驗中，摘心及剪根處理時強度過強，過度傷害實生苗，造成植株大量死亡，無法比較其接種效果，因此目前尚無法確定傷口製造法、苗齡及接種濃度對接種番石榴立枯病菌的影響。4品種共2760株實生苗在兩年內接種三次後，選拔出132擬抗病株。其中50% 為‘白拔’開放授粉實生苗後代。‘白拔’雜交後代及其他品系開放授粉實生苗經菌株Mp-02培養基塊接種至枝條傷口後，多數植株之枯萎病徵僅限於接種位置上方。由於目前僅為接種後2個月，尚無法確立其抗感病性。依據結果，目前菌株培養濾液對實生苗的致病性仍無法判定。

Myxosporium wilt, caused by the pathogen Nalanthamala psidii (Sawada et Kurosawa) Schroers & M. J. Wingf. (≡Myxosporium psidii Sawada et Kurosawa), belongs to one of systemical fungal diseases. This disease has been the most severe and destructive disease of guava (Psidium guajava) cultivation in Taiwan since the 1970s due to the development of pruning techniques for nonseasonal production. The pruning techniques result in numerous wounded sites and increase chances for the invasion of this pathogen. No chemical could prevent or cure this disease and no other solution is available except to burn and remove infected trees from the orchards immediately as the symptoms ocurred. Therefore, breeding for disease resistance is requied. The objectives for the present studies were to: (1) study the effectiveness of inoculation methods for guava seedlings; (2) screening seedlings for N. psidii resistance; (3) evaluate the pathogenicity of N. psidii culture filtrate to seedlings. In the present study, pitiching and root trimming severely injured seedlings and caused a lot portion of seedlings died. Therefore, the effectiveness of the two inoculation methods could not be compared; and thus, the effects of wounding method, seedling stage and inoculum concentration on inoculation of N. psidii could not be determined. Among 2760 seedlings we screened after 3 inoculations within 2 years, 132 puataive resistant plants were obtained. Half of them were ‘Pei-pa’ open-pollinated (OP) progenies. After wounding branches of ‘Pei-pa’ hybrid and OP seedlings of other lines were inoculated with agar plugs of N. psidii Mp-02 isolate, wilting symptoms of most plants only occurred above the wounds. The observation period, 2 months, was not long enough to determine their resistance/susceptibility. However, pathogenicity of N. psidii culture filtrate to guava seedlings could not be confirmed.