臺灣博碩士論文加值系統

台灣之香蕉萎縮病毒(BBTV),依病徵表現可分為強烈型(S)、中間型(I)、
輕微型(M)及潛伏型(L)四種病毒系統。強烈型系統引起嚴重之典型病徵,
包括植株萎縮、葉片細小萎黃、葉片叢集於株頂、葉脈透化,葉柄出現綠
條紋。中間型系統引起輕度矮化及葉片萎縮,葉脈透化清楚。輕微型系統
感染蕉株不呈現顯著病徵,惟有引起輕微之斷續狀葉脈透化。潛伏型系統
不引起任何病徵,外觀與健株相似。田間病株往往受不同病毒系統之複合
感染(strain complex),經蕉蚜(Pentalonia nigronervosa)媒介,可由複
合感染株分離為單純系統分離株(isolate)。單元抗體2H6與此四系統均可
反應,但不

能區分系統間之差異。利用三對引子對系列(C1-CR、S-CR、SR-CR)進行聚
合酵素鏈鎖反應(PCR),可將四種病毒系統分離株鑑別分為六種基因型(
PCR genotype)。國外強烈型系統之基因型,多半與台灣之強烈型分離株
S-3相同,均屬於基因型Ⅱ,對三對引子對增幅反應為+/+/-。惟有來自馬來
西亞之分離株S-My-3不與2H6單元抗體之反應,PCR增幅型為-/+/-,獨立成
為基因型Ⅲ。台灣之強烈型分離株,其聚合酵素鏈鎖反應之基因型,
Ⅰ(+/+/+)與Ⅱ各佔一半。蕉園附近之非蕉屬蕉蚜寄主(野薑花,美人蕉及
月桃)可以酵素連結抗體法及聚合酵素鏈鎖反應測得病毒存在,並可以蕉蚜
為媒介,將病毒在

香蕉與非蕉屬寄主間互相傳染。無論是在蕉株或中間寄主,病毒於病株不
同部位之分佈不均勻,都以靠近心葉之幼葉序中病毒量較高,尤其以葉柄及
中肋中含量最高。接種植物株高(株齡)會影響發病潛伏期之長短,接種植
物愈高,潛伏期愈長,組織培養苗株高在10至50公分,潛伏期在1至5個月之
間,株高超過70公分以上,往往潛伏期長達一個世代, 至吸芽始出現病徵。
強烈型系統之蕉蚜傳播率高達100%,中間型、輕微型只佔40~44%。

田間蕉株受香蕉萎縮病毒與香蕉嵌紋病毒(CMV)複合感染率頗高。二病毒
在同一蕉株中之交互作用,影響病毒複製及病徵表現,香蕉萎縮病毒略佔優
勢,有抑制嵌紋病毒表現病徵之現象。香蕉萎縮病毒與香蕉條紋病毒(
banana streak badnavirus)同時接種於同一蕉株,條紋病徵會先出現,但
各病毒複製彼此間並不會互相抑制,兩者病徵相繼出現,到後萎縮病徵佔優
勢。若香蕉萎縮病罹病株接種條紋病毒,條紋病毒不會在蕉株中增殖感染
。若條紋病罹病株接種萎縮病毒,萎縮病毒能侵入感染複製,於接種後二個
月內會使條紋病罹病株之葉片併發萎縮病徵。

The banana bunchy top virus (BBTV) was differentiated into such
four strains as severe (S), intermediate (I), mild (M) and
latent (L) strains according to symptom expression in Taiwan. S
strain induced severe typical symptoms including dwarfing,
slender atrophy leaf with marginal chlorosis, bunchy top, vein
clearing and green streaks on petioles. I strain caused mild
stunt, slight leaf atrophy and distinct vein clearing. M strain-
infected banana plants produced no distinct symptoms except
dash-like vein
clearing scarcely. No visible symptoms were developed in L
strain-infected plants which were looked like healthy plants.
The banana plants were frequently infected with strain complex
of different strains. Single pure isolates of different BBTV
strains were obtained through transmission by vector aphid
(Pentalonia nigronervosa). Monoclonal antibody, 2H6 reacted
with the all strains, however did not differentiate the strains
of Taiwan. The four strains were differentiated into six
genotypes by polymerase
chain reaction (PCR) amplification with 3 primer pairs (C1-CR,
S-CR, and SR-CR) followed by electrophoresis analysis. The
foreign isolates of severe strain were mainly identical with
Taiwan severe S-3 isolate belonging to PCR genotype II showing
amplification pattern, +/+/- with the 3 primer pairs. Only the
S-My-3 isolate of Malaysian severe strain was found as distinct
as no reaction with 2H6 monoclonal antibody, and PCR
amplification pattern of genotype Ⅲ (-/+/-). The isolates of
Taiwan severe strain
belonged to each half of genotype I and Ⅱ. BBTV was detected
in such non-Mussa hosts of vector aphid as garland flower
(Hedychium coronarium), Canna spp. and Alpinia formosana by
ELISA and PCR assays. The virus was transmitted by aphid
between banana plants and alternative host plants reciprocally.
The virus distributed quite unevenly in different portions of
bananas and alternative host plants. The virus titer was higher
in the leaves near by spindle leaf and lower toward outer older
leaves. The highest
content of virus titer was detected in the petioles and
midribes. The incubation periods (lp) of BBTV infecting tissue
culture (TC) plantlets of 10 to 50 ㎝ height, were about 1 to 5
months after infection. It was over a lifespan in banana plants
over 70 ㎝ high during infection, which developed BT symptoms
in the following suckers from the mother plants. The severe
strain was transmitted at highest rate of aphid transmission
(100%), which the intermediate and mild strains showed 40 to
44% of transmission
rates. The banana plants in the field were commonly mix-
infected by BBTV and CMV causing banana mosaic. The interaction
between the two viruses in a banana plant, affected virus
replication and symptom expression. BBTV usually dominated CMV
by suppressing development of mosaic symptom. The streak
symptoms appeared ahead the bunchy-top symptoms in a same plant
inoculates with BBTV and banana streak badnavirus (BSV)
simultaneously. Each of the two viruses replicated without
counter interaction between the
two viruses. Consequently, the symptoms of the two viruses
appeared later on, and the BT symptoms dominated finally. The
BSV could not be inoculated into a plant infected with BBTV
ahead. However, BBTV was able to be inoculated into BSV-
infected plants, and replicated normally. The BT symptoms were
developed well along with the BS symptoms in the mix-infected
plants.