Variety susceptibility
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https://doi.org/ 10.1590/S0031-10492012001000001 |
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persistent identifier |
https://treatment.plazi.org/id/03F887CC-F80F-FFFA-3CC6-2AF7FC78F960 |
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treatment provided by |
Felipe |
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scientific name |
Variety susceptibility |
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Variety susceptibility to O. afrasiaticus
Comparison of seasonal fluctuation of selected date palm varieties showed significant and quantifiable differences in susceptibility to O. afrasiaticus feeding activity ( Fig. 2 View FIGURE 2 ). In fact, Deglet Noor variety appeared to be the most sensitive to O. afrasiaticus attacks; on this variety mite populations were detected on field between early July and September. However, for the other present varieties colonization by this mite may occur late on the second week of July and the stress caused to the plant by this infestation can be judged as intermediate on Alig, Bessr and Kentichi varieties which were qualified as more resistant.
Maximum of O. afrasiaticus motile forms on Deglet Noor dates were approximately 1.7 and 7.5 times more abundant than on Bessr and Kentichi, respectively. The period spent by the mite on fruit dates varied from a variety to another in fact it was of 8 weeks on Deglet Noor variety, 2 to 5 weeks on Alig, 2 to 4 weeks on Kentichi dates for and 2 to 4 weeks on Bessr dates. Previously findings revealed that performance of O. afrasiaticus varied greatly depending on chemical composition of date variety ( Ben Chaaban & Chermiti, 2009).
Different degrees in susceptibility of date palm varieties to O. afrasiaticus , have been reported from several areas. In Gulf area, Hussain (1974) indicated that the Iraqi variety ‘Sayer’ was relatively resistant to mite attacks. In the Kingdom of Saudi Arabia, date fruit cultivars ‘Sokary’ and ‘Rothan’ appeared as highly susceptible to O. afrasiaticus contrary to ‘Cebiky’ cultivar that seems to be resistant, and to the ‘Khodary’ cultivar that appeared to be moderately resistant to attacks by this mite’s specie ( Aldosari & Ali, 2007). In Oman the cultivars ‘Hilali’, ‘Gibri’ and ‘Khanazani’ were infested by O. afrasiaticus during the month of April, whereas other cultivars were attacked later in the season ( Elwan, 2000). In the Middle East ( Israel), Palevsky et al. (2005) reported that the ‘Deglet Noor’ cultivar was more targeted than ‘Medjool’ and ‘Barhi’ cultivars. In north Africa and specifically in Libya, the varieties ‘Asabir’, ‘Aurig’, ‘Bestian’, ‘Apel’ and ‘Talise’ were found to be more attractant and susceptible to this mite than ‘Tafsirt’ which was found to be less susceptible ( Edongali et al., 1988).
Mite development and life table construction
Immature development
The total developmental time (egg-adult) of O. afrasiaticus females showed significant differences between host plants (Sheffe test, P <0.01; Table 1 View TABLE 1 ), indeed on sorghum leaves and Deglet Noor fruits, mites spent respectively 10.9 and 11.1 days to reach adulthood, while on Alig fruits development was approximately two days slower. For males developmental duration, statistical analysis showed significant differences among host plants (Sheffe test, P <0.01; Table 1 View TABLE 1 ), the highest means on the development period were registered on Deglet Noor pinnae (11.1), Kentichi (11.1) and Alig (11) against the lowest one registered on sorghum leaves (9.6). The total development duration was significantly longer for females than for males on all host plants (Sheffe test, P <0.01; Table 1 View TABLE 1 ). Van de Vrie et al. (1972) emphasised the occurrence of the differences between males and females as to development rate. Previous studies had demonstrated cultivar effects on life cycle and population increase of a variety of tetranychid species. For example, the life cycle of O. punicae differed among grape cultivars with an average values ranging between 8.2 days on Tucupita leaves and 9.1 days on Sirah ( Vásquez et al., 2008). Another example is the developmental time of Amphitetranychus viennensis (Zacher) , which was found to be lower when reared on apple cultivars ‘Starkrimson Delicious’ and ‘Golden Delicious’ (10.7 days) than on ‘Amasya’ and ‘Starking Delicious’ (11.7 days) ( Kasap, 2003).
In this study, the rate of immature survival ( Table 1 View TABLE 1 ) ranged from 81to 94% with the highest registered rate on Deglet Noor fruits (94%). However, for other species like Oligonychus perseae survival was significantly different across three avocado cultivars ( Kerguelen & Hoddle, 2000).
Adult female longevity
Periods of pre-oviposition, oviposition and post-oviposition for O. afrasiaticus females varied in accordance with alimentary supports. In this study, the longest pre-oviposition and post-oviposition periods were registered respectively, for the Kentichi fruits (2.8 days) and Alig dates (3.2 days); while on others fruits pre and post-oviposition periods ranged from 0.9 to 2 and 1.4 to 2.6 days, respectively ( Table 2 View TABLE 2 ). The oviposition period was longer on Deglet Noor fruits than on other supports (Sheffe test, P <0.01; Table 2 View TABLE 2 ). Add to these results, this study showed that the longevity of female of O. afrasiaticus was highly affected by the nature of the host plant, in fact the longest period was registered on Deglet Noor fruits (13.4 days) and the shortest period on sorghum leaves (7.5 days) ( Table 2 View TABLE 2 ).
Vásquez et al. (2008) founded that mean longevity of O. punicae was affected by grape cultivar: females lived longest on ‘Sauvignon’ (17.5 days) and shortest on ‘Villanueva’ (8.1 days). The mean female O. perseae longevity increased by 100% from 12 days in May to 24 days in July in the susceptible avocado cultivar ‘Hass’, while in more resistant cultivars, ‘Pinkerton’ and ‘Lamb Hass’, longevity dropped by 30% over the same period ( Kerguelen & Hoddle, 2000).
Fecundity and hatchability
The total number of eggs laid per female was highest on Deglet Noor fruits and lowest on Bessr fruits (Sheffe test, P <0.01; Table 3 View TABLE 3 ). Daily egg production obtained on Alig, Kentichi, and Bessr fruits also on Deglet Noor pinnae were less than one egg per female, while it reached 2 eggs /female on sorghum leaves. The peak of this parameter is reached on day 18 (1.36 eggs/female/day), 16 (1.66 eggs/female/ day), 18 (2.4 eggs/female/day), 20 (1.7 eggs/female/ day), 16 (1.8 eggs/female/day) and 17 (3.2 eggs/female/day) respectively, on Alig, Bessr, Deglet Noor, Kentichi, Deglet Noor pinnae and sorghum leaves, and thereafter decreased gradually ( Fig. 3 View FIGURE 3 ).
Host plants N Female Development duration Male Immature survival (%) Deglet Noor 100 11.1 ± 0.9 (
64) a 9.9 ± 0.7 (30) a
94 Alig 100 13 ± 1 (58) c 11 ± 0.7 (28) b 86 Kentichi 100 11.9 ± 1.2 ( 62) b 11.1 ± 1.1 (19) b 81 Bessr 100 11.9 ± 0.7 ( 65) b 9.7 ± 0.8 (18) a 83 Deglet Noor pinnae 100 12.1 ± 0.6 ( 59) b 11.1 ± 0.7 (22) b 81 Sorghum leaves 100 10.9 ± 0.8 ( 67) a 9.6 ± 0.7 (19) a 86
In general, there was no distinct mx peak, egg production on all tested varieties was distributed over a relatively long time period, and survival declined gradually after an extended oviposition period. No significant difference in hatchability was observed between the different plant-based food resources. The lowest hatchability was observed with Kentichi dates (92.8%) ( Table 3 View TABLE 3 ). In fact of host plant on reproduction has been established for several Tetranychid species (e.g., Ribeiro et al., 1988; Krisp et al., 1998; Kerguelen & Hoddle, 2000; Hilker & Meiner, 2002; Vásquez et al., 2008; Razmjou et al., 2009).
Sex ratio
There were no significant effects of plant-based foods on sex ratio of the descendant of O. afrasiaticus (λ 2, P> 0.05; Table 3 View TABLE 3 ). The sex ratio is always female biased.
Calculated life table parameters are given in the Table 4. The longest mean generation time ( T) occurred on Kentichi (19.2 days), followed by Alig. Whereas the shortest mean generation time was determined on sorghum leaves (15.8 days). Net reproductive rate (Ro) was highest on Deglet Noor fruits (20.1 female/female). Concurrently with the tendency observed for lowest duration of development and with the observed higher rates of oviposition, the mites reared on the Deglet Noor fruits and sorghum leaves present the highest values of the intrinsic rate of natural increase successively rm = 0.166 day -1 and rm = 0.171 day -1, while mites on Alig had the lowest intrinsic rate of increase (rm) (0.103). Consequently, feeding on sorghum leaves engenders the shortest doubling time (Dt = 4.1 days) of mites.
The intrinsic rate of natural increase (rm) is an important parameter to describe population growth potential under specific climatic and food conditions because it reflects the overall effects of temperature and food on development, reproduction and survival ( Southwood, 1978). The rm- values of Oligonychus mites range from 0.178 to 0.290 day -1 at near 25°C ( Perring et al., 1984; Saito, 1979). Oligonychus punicae (Hirst) Biology, were studied on six grapevine cultivars at 27 ± 2°C, demonstrated that Intrinsic rate of increase (rm) varied between 0.292 and 0.135 ( Vásquez et al., 2008).
These differences may be associated with impediments to feeding such as host plant texture, nutritional value of the host plant, host physiology ( Bengston, 1970; Archer et al., 1986; Kielkiewicz & Van de Vrie, 1990; Kerguelen & Hoddle, 2000; Kasap, 2003; Ragusa & Ferragut, 2005; Kafil et al., 2007; Vásquez et al., 2008). Tetranychids pierce the parenchyma tissue of leaves with their stylets and siphon out the cells’ contents ( Jeppson et al., 1975; Van der Geest, 1985). Consequently, mite nutrition is directly affected by the chemical composition of ingested fluids.
Population dynamics
The finite rate of increase (λ), ranged from 1.11 to 1.19 mites/day. The multiplication of population per unit of time is represented by the equation: Nt = λ N0 (Nt: population density at the time t, λ: the finite rate of increase, N0: population density at initial time). The logarithmic transformation of this equation permits to illustrate the variation of population in time ( Fig. 4 View FIGURE 4 ). So, an important difference between the six plant based food resources is observed. After two generations (19, 19, 18, 17, 17 and 16 days successively for Kentichi, Alig, Deglet Noor, Bessr, Deglet Noor pinnae, and sorghum leaves), populations of O. afrasiaticus reared on Deglet Noor fruits and sorghum leaves would be in theory more abundant than on other food sources.
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Tavera, Department of Geology and Geophysics |
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