|Title:||荔技果實炭疸病與褐變原因之探討||Other Titles:||Litchi fruit anthracnose and the cause of black skin||Authors:||安寶貞
|Keywords:||荔枝病害;炭疽病;果實褐變;Litchi chinensis;anthracnose;litchi skin browning;atent infection||Issue Date:||Dec-2004||Publisher:||中華民國植物病理學會||Journal Volume:||13||Journal Issue:||4||Start page/Pages:||299-308||Source:||植物病理學會刊||Abstract:||
自1980-2003年進行荔枝果實病害之研究，發現荔枝果實開始轉色後，少數果實出現水浸狀褐色小斑點，而後發展成直徑0.2-0.4cm的圓形黑褐色斑點，每果病斑數目約為l-2個，發病果實率約為0.1-10%，病果不會提早掉落，但在採收後病斑會開始擴大，最後全果褐變腐敗。此外，亦有果實出現水浸狀褐色小斑點後，病斑繼續擴大成直徑0.5-1.5cm的黑褐色圓形大病斑，發病果實率為0-5%，病果會腐敗並提早掉落。兩種罹病果實之果皮組織均可分離到炭疽病菌Colletotrichum gloeosporioides。將分離之菌株接種經套袋處理過之無病徵果實後，亦可誘發果實出現黑褐色斑點，證實炭疽病菌為引起田間荔枝出現黑斑與腐敗之主因。荔枝炭疽病菌在馬鈴薯葡萄糖瓊脂培養基(PDA)上之可生長溫度為8-32℃，最適溫度為28℃；菌株在PDA上可形成大量分生孢子，孢子無色透明，短桿狀，一端鈍圓、一端稍尖，大小平均為12.3-15.2-18.2 4.65-5.63-6.75 µm。部份菌株同時亦產生有性世代，子囊殼(pelithecia)囊狀，子囊長筒狀，子囊抱子透明無色、新月形（擲菱狀）、兩端鈍圓，大小為12.1-14.3-17.5 3.5-4.7-5.5 µm。除果實外，炭疽病菌亦可自無病徵之荔枝花穗、幼果及發育期果實上分離得到，顯示炭疽病菌危害荔枝為潛伏感染。生育期間噴方鬱辛錳乃浦可濕性粉劑，可顯著降低採收時與採收後果實腐敗情形。炭疽病菌危害其他荔枝品種果實亦可於田間發現，病徵相仿，惟危害桂味品種果實時，尚可出現為密佈之黑褐色針尖狀小點。999-2001年，許多荔枝園之果實於轉色時出現直徑1.0cm以上之黑褐色不規則病斑與大量落果現象，分離真菌之出現率依序為炭疽病菌40-80% 、Fusarium spp. 20-60 %、Pestalotia spp. 0-30 %、Botryodiplodia sp. 0-20 %、Penicillium spp. 0-20%及Alternaria spp. 0-5%，但接種炭疽病菌並不誘發接種果實出現相同病徵，而改善田間管理與施肥可遏止果實褐變病害發生。
Litchi (Litchi chinensis) fruit diseases related to anthracnose have been studied since 1980. Two types of disease symptoms were found on Black leaf variety in the fields. Most diseased fruits first showed symptoms as 1-2 water-soaked spots at the near mature stage and developed into a diameter of 0.2-0.4 m small black spots (BS) before harvesting. The small black spots expanded rapidly on the post-harvest fruit and covered the whole skin eventually. Some other diseased fruit appeared symptoms as small black spots at the early stage, but the spots grew continually to a diameter of 0.5-1.5 m black rot (BR) resulting in premature fruit drop. Generally, the disease fruit for black spot and black rot were 0.1-10% and 0-5%,
respectively, in different investigated orchards. Colletotrichum gloeosporioides was consistently isolated from both types of diseased fruit and pathogenicity test proved that the isolated fungus could induce severe skin rot on the health detached-fruit of black leaf variety. The same fungus was reisolated from the inoculated diseased fruit. All of the tested isolates could grow on potato dextrose agar from 8-32 with the optimum growth at 28 . They produced abundant conidia on PDA plates at 24. Conidia were hyaline, short rod, and mean ranged 12.3-(15.2)-18.2 4.65-(5.63)-6.75 m. In addition to asexual reproduction, some isolates formed sexual stage by producing perithecia and ascospores on agar medium. The perithecia were dark brown, obpyriform or subglobose and asci were hyaline, clavated, and 8 spored. Ascospores were hyaline and slightly symmetrical curved, with sizes of ranging 42.5-(53.5)-65.0 27.5-(32.1)-35 m. The conidial isolates were mostly isolated from fruit with BS symptoms whereas the perithecial isolates were from BR fruit. The same pathogen was also frequently isolated from symptomless litchi tissues, including flower, flower stem and green fruit in different growing stages, indicating the anthracnose pathogen attacking litchi fruit through latent infection. Anthracnose symptoms on the fruit of other litchi varieties were similar to those on Black leaf, except of Kwai-mi fruit with numerous flecks. Recently, a serious fruit disease, with symptoms as skin irregular browning combing with heavy premature fruit drop, was found in many orchards in the central Taiwan in 1999-2001. Colletotrichum sp. and many other fungi were isolated, but none of them induced similar symptoms in pathogenicity test, indicating non-infectious causes might involve in the disease development. Many diseased orchards recovered after adequate use of pesticides and fertilizers for 1-2 years. It is thought that the incorrect use of chemicals might weaken and damage the fruit, resulting in infection by weak pathogens as well as earlier appearance of latent infection diseases.
|Appears in Collections:||植物病理組|
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