| The pea aphid,Acyrthosiphon pisum(Harris)(Hemiptera: Aphidiidae),is an important pest on legume crops,and a model organism for the study of ecological speciation and molecular biology.We design a set of the experiment to assess the effect of high temperatures on population parameters of A.pisum,on various cultivars of pea,with different temperatures of 27°C,30°C,33°C,36°C,and 39°C.For the living nymphs,the development period(from birth to adulthood)was highest at 27°C and lowest at 39°C.At all temperatures,the nymphs developed rapidly,whereas as at 39°C,the development period recorded was slow.The immature rate of development from 27°C to an optimum 36°C increased fast,and after that declined to 37% at 39°C.The adult aphid longevity was 9.0,9.1,8.8,and 6.9 days,offspring number usually produced was 37,30,16,11,and 0,at temperatures of 27°C,30°C,33°C,36°C,and 39°C,respectively.Furthermore,the intrinsic rate of increase significantly high from 27 to 36°C.These results were reflected in the population growth of A.pisum,on broad bean increased with increasing temperatures between 27°C and 36°C,and declining after that.In the second experiment,the results showed that the response of A.pisum population parameters to selected high temperatures(27,30,33,36,39°C)on 5 cultivars of a pea,Pisum sativum L.,was determined in laboratory testing.Of the 5 pea cultivars and 5 temperature levels included in our study,the highest values of the population parameters of net reproductive rate,intrinsic rate increase,finite rate increase,generation time,and fecundity of A.pisum was observed at 27°C,regardless of pea cultivar.In general,these values decreased as temperature increased at and above 30°C for each cultivar.Furthermore,differences among cultivars were detected at 27°C and 30°C,but not at higher temperatures.In a further study,the results indicate that the shortest nymph development period of A.pisum(5.75 ± 0.31 days)was recorded on cv.Feizai-3 at 39°C and longest development period of A.pisum(9.38 ± 0.34 days)were noted on cv.Nenzao at 30°C.The shortest adult development period of A.pisum(4.16±0.20 days)was recorded on cv.Hanyi-401 at 39°C and the most prolonged adult development period of A.pisum(5.72 ± 0.33 days)were noted on cv.Hanyi-401 at 30°C.The shortest longevity period of A.pisum(5.43 ± 0.72 days)was recorded on cv.Feizai-3 at 39°C and longest longevity period of A.pisum(11.83 ± 0.72 days)were noted on cv.Hanyi-401 at 30°C.The shortest reproduction period of A.pisum(3.61±0.32 a days)was recorded on cv.Hanyi-401 at 33°C and longest longevity period of A.pisum(4.58 ± 0.33 a days)were noted on cv.Nenzao at 27°C.The maximum fecundity was determined on cv.Hanyi-401(27.70 ± 2.77)at 27°C and minimum fecundity was observed on cv.Hanyi-401(10.08 ± 0.44)at 36°C.The maximum total pre-reproduction period was determined on cv.Nenzao(9.38 ± 0.34 days)at 30°C and minimum total pre-reproduction period were observed on cv.Feizai-3(5.75 ± 0.31)at 39°C According to the DMRT test,there was a non-significant difference in all parameters between the cultivars in all temperature regimes.Numerically,the highest values of net reproductive rate,intrinsic rate of increase,finite rate of growth,generation time and fecundity of A.pisum was observed at 27°C in all five pea cultivars,and the values of above-studied parameters were decreased gradually by increasing the temperature beyond 30 to 39°C.Statistically,there was a nonsignificant difference in all studied parameters among the cultivars in the temperature regimes higher than 33°C.This study will help understand aphid host selection and sets a stage to study the attractant-based integrated aphid management programs further. |
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