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

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

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

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

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

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

The 19 fungal strains isolated from the soil of the Qinghai-Tibet plateau and Gansu Corridor.

<p>The 19 fungal strains isolated from the soil of the Qinghai-Tibet plateau and Gansu Corridor.</p

Mortality of 2^nd B-biotype whitefly nymphs infected by fungal isolates after 13 days of treatment.

<p>The letters on the columns indicated statistical significance (LSD, P<0.05).</p