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Effects of Bemisia tabaci (Gennadius) infestation and squash silverleaf disorder on Cucurbita pepo L. leaf

Zhang, Jialei, Wang, Lanlan, Zheng, Yueping, Feng, Jie, Ruan, Yongming, Diao, Shuo, Chen, Shaoning, Jiang, Bo, Shen, Zonggen, Lu, Hongfei
Scientia horticulturae 2017 v.217 pp. 8-16
Bemisia tabaci, Cucurbita pepo, air, chlorophyll, environmental factors, etiology, fluorescence, insect pests, leaves, malondialdehyde, mesophyll, proteins, squashes, sugars
The aetiology of squash silverleaf (SSL) induced by the infestation of Bemisia tabaci (Gennadius) ‘biotype’ B (B. tabaci-B) is poorly understood. To help to find out how B. tabaci destroys Cucurbita pepo L. and induces SSL, changes induced by SSL and responses of C. pepo to B. tabaci-B infestation were studied by comparing chlorophyll fluorescence parameters and biochemical, morphological and anatomical aspects of grade 0–4 SSL leaves. The results showed that chlorophyll contents decreased and the chlorophyll a/b ratio increased with the increase of silvered leaf, which indicated that the decrease of chlorophyll contents led to silvered leaf. Anatomical observation showed that B. tabaci-B infestation changed the shape and arrangement of lower epidermis cells and spongy mesophyll cells. Moreover, air spaces appeared between upper epidermis and palisade tissue and in spongy tissue, which might be the cause of the increase in leaf thickness. Additionally, the altering of former spaces light reflection was another reason for leaf silvering. As response to B. tabaci-B infestation, the content of soluble proteins and soluble sugar decreased, and the content of Malondialdehyde (MDA) increased. Pearson correlation showed a significant correlation between fluorescence parameters (except α) and the other parameters measured in this study. The result also suggested that chlorophyll fluorescence can be widely used in field studies as an early diagnostic measure of stress in plant caused by adverse environmental conditions, especially by insect pests.