Impact Of Host Plant Xylem Fluid On Xylella Fastidiosa Multiplication ...

Adult longevity was comparable for males (47 d) and females (52 d). For both males and females, no mortality occurred
until 20 d after adult emergence. There was a 5 d pre-oviposition period (3 - 9 d) and a 3 d post-oviposition period (0 - 7 d).
A high proportion of females (88%) deposited eggs, with a mean total of 194 eggs per female. The eggs were deposited in
clusters under the epidermis layer of cowpea leaves and were mostly in even numbers (93%). Most of the eggs incubated
(92.6%) were fertile, and took from 5 to 8 d, with a mean value of 7.1 d, to emerge at 27 ºC.
Life table statistics of GWSS on cowpea are presented on Table 2. Populations of GWSS could multiply at a rate of 33.6
times per generation on cowpea, thus doubling in 15.6 d. Analysis of natality pattern of GWSS revealed that the number of
offspring per female was independent of female age, suggesting that food availability might determine the fecundity potential
of females.
The successful completion of GWSS life cycle on cowpea suggests that the xylem fluid of this plant has a nutrient profile
suitable for both immature and adult stages. The rearing approach used here is quite sample and allowed us to follow each
individual GWSS during its development.
Biometric analysis
Values of the three biometric parameters, BDL, HTL, and HCW, varied significantly with the developmental stage (Table 1).
Only the grouping for the HCW did not overlap between nymphal stages as indicated by the mean comparison and the
distribution of frequency analysis (Table 1, Figure 2). Thus, the HCW could be used as a reliable parameter for
distinguishing the five nymphal stages of GWSS.
Survivorship of H. coagulata
1.0
0.8
0.6
0.4
0.2
instar 1
instar 2
instar 3
instar 4
instar 5
Adults emerged
0.0
0 10 20 30 40 50 60
Days
Figure 1. Survival of H. coagulata nymphal stages on excised cowpea leaves maintained at 27 °C.
- 121 -