Effects of <i>Isaria fumosorosea</i> on <i>TYLCV</i> (<i>Tomato Yellow Leaf Curl Virus</i>) Accumulation and Transmitting Capacity of <i>Bemisia tabaci</i>

<div><p><i>Tomato yellow leaf curl virus</i> (<i>TYLCV</i>) is transmitted by the <i>Bemisia tabaci</i> pest Middle East-Asia Minor 1 (MEAM1) in China. <i>Isaria fumosorosea</i> is a fungal pathogen of <i>B</i>. <i>tabaci</i>. However, the effects of fungal infection on <i>TYLCV</i> expression and transmission by MEAM1 are unclear. In this study, potted tomatoes containing second instar nymphs of MEAM1 were treated with <i>I</i>. <i>fumosorosea</i> IfB01 strain and the relationship between fungal infection in MEAM1 and its <i>TYLCV</i> transmission capacity was investigated. The results indicated that a significantly (p < 0.05) decreased incidence of transmission of <i>TYLCV</i>-infected plants (ITYPs) transmitted by second instar nymphs of MEAM1 infected with fungus. Further, we found a negative correlation between fungal conidial concentrations and eclosion rates of MEAM1, and a positive correlation between ITYPs and eclosion. In addition, when each plant was exposed to three adults treated with fungus, a significantly decreased transmission of <i>TYLCV</i> (TYTE) was observed in the infected group. However, the incidence of <i>TYLCV</i>-carrying MEAM1 adults (ITYAs) was not significantly different in the infected and control groups (p < 0.05). Nevertheless, a significant decrease in viral accumulation using <i>TYLCV AC2</i> gene as a marker was observed in the fungus-infected MEAM1. In conclusion, the results suggested that <i>I</i>. <i>fumosorosea</i> infection decreases <i>TYLCV</i> accumulation in MEAM1 and subsequently reduces its transmission. Our study provides new insights into the relationship between host plant, plant virus, insect vector, and entomopathogenic fungus.</p></div

ANOVA of eclosion rates of MEAM1.

<p>ANOVA of eclosion rates of MEAM1.</p

Effects of IfB01 strain on MEAM1 eclosion rate (fungal treatment experiment 1).

<p>Effects of IfB01 strain on MEAM1 eclosion rate (fungal treatment experiment 1).</p

Arrangement of tomato plants in cages in the fungal experiment 1.

<p>A: 3 TY-plants (yellow) and 3 normal plants (green) (3/3 cage), B: 2 TY-plants and 6 normal plants (2/6 cage), C: 1 TY-plant and 5 normal plants (1/5 cage).</p

ANOVA of the incidence of TY-plants (ITYP).

<p>ANOVA of the incidence of TY-plants (ITYP).</p

Relative expression of <i>TYLCV AC2</i> gene in the adults tested in fungal treatment experiment 2.

<p>The expression of the <i>AC2</i> (322 bp) in <i>TYLCV</i> of each TY-adult on post-eclosion day 3 was detected by qPCR. Treatment group comprised 2^nd instar nymphs of MEAM1 on TY-plant in cage treated with a conidial suspension of 10×10⁶ spores/mL from IfB01 strain of <i>I</i>. <i>fumosorosea</i>. The control group was treated only with 0.02% Tween 80 solution. Thirty adults were detected.</p

<i>TYLCV</i> transmission efficiency of each MEAM1 adult in the fungal treatment experiment 1.

<p>T/N 3/3-C100: TY-plants/ Normal plants = 3/3 with fungal conidia 100.0×10⁶ spores/mL; others were designated similarly.</p

Effects of IfB01 strain on ITYP in fungal treatment experiment 1.

<p>Effects of IfB01 strain on ITYP in fungal treatment experiment 1.</p

Map of the soil sample collection sites.

<p>Fungi were successfully isolated from locations labeled in green. Fungi could not be isolated from areas labeled in pink. The map was downloaded from“Map World of Public Platform of National Geographic Information of China (<a href="http://www.tianditu.com/" target="_blank">http://www.tianditu.com/</a>). The south Tibet line: Xigaze, RB (Renbu), JZ (Jiangzhi, Ggangze), YZYC (Yangzhuoyongcuo, Langkazi,), QS (Qushui), Lhasa, Dazi, Mila (Mila Mountain, Mozhugongka), GBJD (Gongbujiangda), BSC (Basongcuo, Nyingchi), NYH (Niyang river, Nyingchi), LL (LuLang, Nyingchi), BGC (Brahmaputra grand canyon, Nyingchi). The Gansu corridor line: HY (Huangyuan, Qinghai), Datong (Datong, Qinghai), CHH (Chahanhe, Qinghai), MY (Menyuan, Qinghai), JYL (Jingyangling, Qinghai), Lanzhou (Yongdeng, Gansu), Jintai (Jintai, Gansu), Qilian (Qilian, Qinghai), Gonghe (Gonghe, Qinghai), Tianzhu (Tianzhu, Gansu), Wuwei (Wuwei, Gansu), YCH (Yongchang,Gansu), Zhangye (Zhangye, Gansu), Jiayuguan (Jiayuguan, Gansu), Yumen (Yumen, Gansu), Guazhou (Guazhou, Gansu), Dunhuang (Dunhuang, Gansu), YMG ((Yumenguan, Dunhuang, Gansu), Yadan (Dunhuang, Gansu).</p

Isolation and Classification of Fungal Whitefly Entomopathogens from Soils of Qinghai-Tibet Plateau and Gansu Corridor in China

<div><p>Qinghai-Tibet Plateau and Gansu Corridor of China with distinct geographic and climatic conditions are remote and less disturbed by humans, in which are likely to find some new strains of fungal entomopathogens against B-biotype whiteflies that is a very important invading pest worldwide. In this research, nineteen strains among six species of entomogenous fungi were isolated from the soil samples collected from 32 locations in Qinghai-Tibet Plateau and Gansu Corridor. From the data of isolation rates, it was indicated that the good biodiversity of entomogenous fungi was found in the soil covered good vegetations. On the contrary, no strains were isolated from the desert areas. In addition, the dominant species, <i>Isaria fumosorosea</i> and <i>Metarhizium anisopliae</i> var. <i>anisopliae</i> in the Qinghai-Tibet Plateau are different from the strains of other places based on ITS genetic homology analysis. It was verified that the Qinghai-Tibet Plateau area was less disturbed by human, and the fungi in this place exchanged less compared with other regional species. All of these strains showed the pathogenicity against the B-biotype whitefly with the mortality of more than 30%. However, a few strains of <i>Paecilomyces lilacinus</i>, <i>Lecanicillium psalliotae</i>, <i>Aspergillus ustus</i>, <i>I</i>. <i>fumosorosea</i> and <i>M</i>. <i>anisopliae</i> var. <i>anisopliae</i> had better virulence with LC₅₀s of 0.36–26.44×10⁶ spores/mL on post-treatment day 6–7. Especially, the <i>L</i>. <i>psalliotae</i> strain LpTS01 was the greatest virulence with LC₅₀ of 0.36×10⁶spores/mL and LT₅₀ of 4.23d. Our research thus presents some new insights to discover new entomopathogenic fungal strains used for B-biotype whitefly biocontrol.</p></div