六种植物叶片中葫芦素B对美洲斑潜蝇寄主选择性的影响

Effect of cucurbitacin B in leaves from six plants species on plant selectivity of the leafminer, Liriomyza sativae

在网室条件下 ,测定了美洲斑潜蝇对豇豆、苦瓜、黄瓜、白瓜、节瓜和丝瓜的寄主选择性。结果表明 ,美洲斑潜蝇在 6种不同植物叶片上的幼虫数、虫道数和为害程度具有明显的差异。从幼虫数和为害程度综合分析 ,美洲斑潜蝇在豇豆和丝瓜上的幼虫数、为害程度最高 ,分别是 0 .183头 / cm2 ,13.4 7%和 0 .0 99头 / cm2 ,2 3.4 2 % ,表明该虫对豇豆和丝瓜的选择性最强。在苦瓜上没有美洲斑潜蝇的幼虫寄生及取食虫道。该虫对其它 3种植物的选择性依次为节瓜、白瓜和黄瓜。在此基础上 ,进一步研究了不同植物叶片甲醇提取物中葫芦素 B的含量与美洲斑潜蝇寄主选择性的关系。经高效液相色谱 (HPL C)测定 ,苦瓜中的葫芦素 B含量最高 (2 3.8μg/ ml) ,其次是黄瓜 (9.6 μg/ ml)、白瓜 (4 .3μg/ ml)、豇豆 (2 .7μg/ ml)和节瓜 (2 .5 μg/ m l) ,丝瓜中含量最少 ,仅为1.3μg/ ml。分析结果证实不同植物叶中的葫芦素 B含量与其幼虫数呈负相关 (r1 =- 0 .82 0 6 ,r0 .0 5=0 .811) ;将不同植物叶中的葫芦素 B含量和美洲斑潜蝇的为害程度分别转换成对数后进行相关性分析 ,二者之间的相关性呈极显著的负相关(r2 =- 0 .980 4 ,r0 .0 1 =0 .917)。说明随着寄主植物叶片中葫芦素 B含量的增加 。

The selectivity of six plants species by Liriomyza sativae Blanchard was evaluated using choice tests in a net-house (2.5m×2m×1.5m). The six plant species were grown together in rectangular plastic pots (100cm×50cm×30cm) and 6 pots were used in the experiment. At the 4～5 leaf stage, one leaf was sampled from each of six plants from each host plant species. Leaves from each species were pooled and 1g of fresh tissue cut into 0.2～0.3 cm pieces and soaked in 10 mL methanol for 30h at 25℃. The extract was filtered and the filtrate immediately analyzed by HPLC to determine cucurbitacin B levels. After leaf sampling, 500 one-day-old L. sativae adults leafminer were released into the net-house. Adults were hatched in the laboratory from L. sativae pupae collected from a Vigna sesquipedlis field at the South China Agricultural University. After 5d, the number of larvae, feeding tunnels and damaged plants were recorded on 6 plants of each species in each of 6 pots. The number of larvae and degree of damage of L. sativae differed significantly between the six host species tested with the mean number of larvae per cm^2 being 0.183,0.116,0.102,0.099,0.043 and 0.0 respectively for Vigna sesquipedalis, Cucumis melo var. conomon f. albus, Benincasa hispida var. chieh-qua, Luffa cylindrical, Cucumis sativus and Monordica charantia. The average degree of larval damage was 23.42%, 13.47%, 8.78%, 5.83%, and 1.63% on L. cylindrical, V. sesquipedalis, B. hispida var. chieh-qua, C. melo var. conomon f. albus and C. sativus, respectively. There were no larvae or feeding tunnels on M. charantia. The selectivity of L. sativae to the six plants species indicated the order of host plant suitability was L. cylindrical, V. sesquipedalis, B.hispida var. chieh-qua, C. melo var. conomon f. albus and C. sativus while M. charantia was not a host plant of L. sativae. The relationship between leafminer selectivity and levels of cucurbitacin B from host plant leaf samples was investigated. Mean cucurbitacin B content was 23.8μg/ml,9.6μg/ml, 4.3μg/ml, 2.7μg/ml, 2.5μg/ml and 1.3μg/ml for M. charantia, C. sativus, C. melo var. conomon f. albus, V. sesquipedalis, B. hispida var. chieh-qua and L.cylindrical, respectively, and there was a significant negative correlation (r_1=-0.8206 ,r_(0.05)=0.811) between the number of L. sativae larvae and cucurbitacin B content. There was a very significant negative correlation (r_2=-0.9804, r_(0.01)=0.917) between the degree of L. sativae damage on host plants and the content of cucurbitacin B. Results demonstrate that cucurbitacin B is an important factors influencing host selectivity of L. sativae.