桉树枝瘿姬小蜂虫瘿解剖特征与寄主叶片生理指标的变化

Physiological responses of Eucalyptus trees to infestation of Leptocybe invasa Fisher & La Salle

采用人工接蜂、桉树组织石蜡切片和生化组分测定等方法研究了桉树受桉树枝瘿姬小蜂诱导后的生理生化响应机制。结果表明:DH201-2叶柄角质层厚度和油囊数量均较GL-UG9的厚、多,且差异均达到极显著水平(P角质层厚度=0.00001<0.01,P油囊数量=0.00209<0.01),但是GL-UG9叶柄表皮细胞厚度和维管束数量均较DH201-2厚、多,差异分别达到显著水平(P=0.015215<0.05)和极显著水平(P=0.002375<0.01),DH201-2茎皮层薄壁细胞厚度、油囊直径、维管束数量较GL-UG9厚、多,差异分别为显著(P皮层薄壁细胞厚度=0.04071<0.05)、极显著(P油囊直径=000016<0.05)、极显著(P维管束数量=0.00000<0.01)。而GL-UG9茎角质层和表皮细胞厚度均较DH201-2厚,差异达到了极显著水平(P角质层厚度=0.00167,P表皮细胞厚度=0.00000<0.01);桉树枝瘿姬小蜂虫瘿为组织瘿,由内到外可以分为:营养组织层、薄/厚壁组织层、维管束层、皮层、表皮等结构;接种桉树枝瘿姬小蜂成虫后,桉树叶片可溶性总糖、游离氨基酸、叶绿素含量均升高,差异达到了极显著水平(P<0.01),但是蛋白质、pH值、类黄酮、总酚的变化没有达到显著水平(P>0.05);吲哚乙酸氧化酶、过氧化物、过氧化氢酶活力均有不同程度的升高。研究显示桉树枝瘿姬小蜂入侵诱导了桉树一系列的生理生化变化,实验结果为抗桉树枝瘿姬小蜂桉树无性系的选育技术体系构建提供了理论基础。

The gall wasp Leptocybe invasa Fisher ＆ La Salle is a significant pest to eucalyptus. The physiological responses of eucalyptus clones （ DH201-2 and GL-UG9 ） infested by L. invasa were investigated using artificial inoculation at different wasp densities, microtome sectioning, microscopic observation, and chemical analysis. The results indicated that the stem and petiole cross-sections of DH201-2 and GL-UG9 had similar structures that were typical of dicotyledonous plants. The tissues were clearly divided into an outer epidermis, cortex, vascular bundles, and medullary structure, However, the petiole epidermal cells of DH201-2 had significantly more oil capsules than GL-UG9 （P = 0. 00209 ）, and the DH201-2petiole cutin layer was thicker than that of GL-UG9 （P= 0. 00001 ）. However the petiole epidermal cells of GL-UG9 were significantly thicker than those of DH201- 2 （ P = 0. 015215 ）, and GL-UG9 had significantly more vascular bundles than DH201-2 （P = 0. 002375 ）. In addition, in DH201-2, the stem cortex parenchyma cells were thicker （P= 0. 04071 ）, the oil capsule diameter was greater （ P = 000016）, and there were more vascular bundles （P = 0. 00000） than in GL-UG9, while in GL-UG9, the stem corneous layer was thicker （P = 0. 00167 ） and there were more epidermal cells （P = 0. 00000） than in DH201-2. Each gall contained about 10 insect larvae. The anatomical structure of the gall tissue, from inside to outside, was ： nutritive tissue, thin/sclerenchyma layer, vascular bundle layer, cortex, epidermis. When the adult wasps were not dense, they formed small galls only in petioles, while leaves occasionally had calluses. As adult wasp density increased, females laid eggs in the veins of stems to form stem-petiole-vein galls. Early in gall formation, the larvae had not hatched, but the plant tissue organization had begun to differentiate, the normal vascular structure had been destroyed, and the vascular bundle layer structure had deformed. As the eggs hatched into larvae, a cortex vascular bundle formed outside the approximately spherical internal space. Further structural analysis of the L. invasa gall structure indicated that the gall was divided into several distinct layers that could be roughly classified, from inside to outside, into： nutrition organization layer （21.84_＋0.42） Ixm, parenchyma layer （13.34_＋0. 19） I^m, sclerenchyma layer （18.68_＋1.13） Ixm, vascular bundle layer, cortex, and epidermis. The development of the gall destroyed the original plant internal organization, forming many internal chambers for larvae. Each internal chamber had a radius of about （211.61_＋5.12） ~m. The center of the gall was different from the eucalyptus oil capsule structure. In the middle of the thin/sclerenchyma layer was a crystal layer approximately 7.92 I^mx 4.92 ~m in size ; the crystals were disorganized and colorless. The average length of a mature gall was （16.10_＋8.81） mm its average diameter was （3.05_＋1.73） mm. After inoculation with L. invasa, the total sugar, soluble free amino acid, and chlorophyll contents of the eucalyptus leaves increased significantly （ P〈0.01 ）, but the pH and protein, flavonoid, and total phenol contents increased only slightly （P 〉 0.05 ）. Moreover, the indole acetic acid oxidase, peroxide, and hydrogen peroxide enzyme activities increased at different rates. In conclusion, a series of physiological and biochemical changes in eucalyptus were induced by L. invasa galls. This study provided a theoretical basis to establish an improved breeding system for eucalyptus to minimize gall wasp damage