| Bemisia tabaci (Gennadius) is phloem-feeding insects. Our long-term field survey revealed that the Cardinium infection rate in Bemisia tabaci Q population was low in Shandong, China over the past few years. From this phenomenon, we hypothesize that: the Cardinium-infected (C+) B. tabaci Q population cannot efficiently compete with the Cardinium-uninfected (C) B. tabaci Q population; no reproductive isolation may have occurred between C+ and C-; the C population has higher fitness than the C+ population.To reveal the differences in competitive ability and fitness between the two introduced populations (C+ and C-). We conducted that: Through the competition between C+ and C- was examined over ten generations to Comparative competitive ability; The reproductive isolation between C+ and C- was studied by crossing C+ with C- individuals; The fitnesses of C+ and C- populations were compared using a two-sex life table method; Using Illumina sequencing technology to analyze the genome-wide transcriptomes of two whitefly populations. The results included:1. In the competition between C+ and C- populations was examined over ten generations. The mixed cohort began with 50% C+ and 50% C- individuals. The relative ratio of C individuals reached 76% after 75 days and increased steadily over time, reaching 93% after 310 days. By contrast, the relative ratio of C+ individuals decreased from the initial 50% to 24% after 75 days and remained between 7% and 20% thereafter, Thus the C+ population did not have advantaged in the competition experiments.2. No significant differences(P> 0.05, ANOVA)were observed in the sex ratio of the F1 generation among the four possible crosses between C+ and C- populations (♀C+×♂C+,♀C+×♂C-,♀C-×♂C+, ♀C-×♂C-).These results suggest that no reproductive isolation or reproductive abnormalities occurred between C+ and C populations. We did not found the offsprings decrease appeared in the ♀C-×♂C+ combination, so the Cardinium did not induce cytoplasmic incompatibility in the Bemisia tabaci Q. 3. Based on the two-sex life table method, the intrinsic rate of increase (r), net reproductive rate (Ro), and finite rate of increase (λ) of the C population (0.09192 d-1,29.06 offspring, and 1.096 d-1, respectively) were significantly higher than that of the C+ population (0.07561 d-1,17.82 offspring, and 1.078 d-1, respectively). The mean generation time (T) of the C+ population (38.09 d) was significantly longer than that of C- population (36.67 d). This data show that the C- population has higher fitness than C+ population.4. We analyzed the genome wide transcriptomes of the two whitefly populations, using Illumina sequencing technology. Using BLAST searches against eight public databases (NCBI nr, Swiss-Prot, TrEMBL, CDD, Pfam, KEGG, KOG, and GO) and with an E-value threshold of 10’5. We identified 892 significantly differentially expressed genes between the two whitefly populations, among which the expression levels of 625 genes (70.07%) were higher and 267 genes (29.93%) were lower in C+ than in C-samples. Among them, we annotated 290 genes (32.51%) that were involved in metabolism (106 genes) and immunity (20 genes. Compared with C-,62 of the 71 genes involved in metabolism in C+ were up-regulated.17 of the 20 genes involved in immunity in C+ were up-regulated. These data suggest that the performance differences between the two whitefly populations result primarily from physiological costs.The competitive ability and fitness differences of two populations may explain why C- whitefly populations have been dominant during the past few years in Shandong, China. This research studied on whitefly transcriptome of bioinformatics to supplement the fundamental theory. And the genes related gene related in metabolism and immunity were identified, which will provide the theory basis for the future research on prevention and control management of whitefly. |
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