Fecundity,reproductive rate,longevity, and intrinsic rate of increase of an aphidiid parasitoidLysiphlebia mirzai

A life-table was constructed for a little known aphidiid waspLysiphlebia mirzai, a parasitoid of cereal aphid,Rhopalosiphum maidis. The female parasitoid survived 6.4 ± 1.17 (SD) days and oviposited intensively 4.0 ± 0.47 days. The total fecundity rate, R_t, was 169.2 ± 6.94 mummies/female and net reproductive rate, R_o, was 92.70 female offspring/female. The intrinsic total fecundity rate, r_t, and intrinsic rate of natural increase, r_m, the finite rate of total fecundity, λ^t, and finite rate of increase, λ^m, was 0.27048, 0.24155, 1.31059 and 1.27322 respectively. The mean generation time (18.75 days) and doubling time of the population (2.87 days) was slightly higher than other aphidiids studied so far. The proportion of female progenies decreased significantly on the successive oviposition days.      

The role of predators and parasites in controlling populations ofEarias insulana,heliothis armigera andBemisia tabaci on cotton in the Syrian Arab Republic

Studies on the relationship between insect pests and their predators and parasites were conducted in the Syrian cotton agro-ecosystem from 1980 up to 1983.Earias insulana (Boisduval) was found to be the most damaging pest, whileHeliothis armigera (Hübner) was not an annual returning problem. Among the entomophagous insects found, coccinellids were most numerous during the months June and July and the hemipterous predators were more abundant during August and September. When predator numbers were reduced with insecticide applications, a significant increase in the bollworm populations occurred, resulting in significant reductions in seed cotton yields. Parasites were relatively not important for the control of lepidopterous pests on cotton. Egg and larva populations ofE. insulana andH. armigera were parasitized byTrichogramma spp. andHabrobracon brevicornis Wesmael respectively. Populations ofBemisia tabaci (Gennadius) were heavily parasitized byEretmocerus mundus Mercet.      

A new species ofAphidius [Hymenoptera] attacking the pea aphid,Acyrthosiphon pisum

Aphidius staryi Chen & Luhman n. sp. is described. The species was collected and introduced into California from Israel and Turkey byD. González. The new species is morphologically most similar toAphidius smithi, and keys toEady's urticae group.     

水分胁迫对棉花叶片中IAA从含量、IAA氧化酶和过氧化物酶活性的影响

整株干旱降低盐棉46号叶片中的IAA总量,叶龄愈小下降愈多。幼叶中IAA总量的下降主要是结合态IAA减少的结果。气干和-1.7MPa PEG溶液渗透胁迫处理也降低离体成熟叶片的IAA总量,其变化与叶片含水量呈直线相关(r=0.905)。整株干旱处理提高各叶片的过氧化物酶活性,叶龄愈小提高愈多,但IAA氧化酶活性无显著变化。离体和整株干旱时IAA总量的下降,可能是过氧化物酶活性增加所致。     

Alkaloid level in narrow-leafed lupin, Lupinus angustifolius, influences green peach aphid reproductive performance

Two viviparous parthenogenetic clones of the green peach aphid, Myzus persicae (Sulzer), one collected from Rydalmere, New South Wales (NSW), and the other from South Perth (SP), Western Australia, were reared on radish, Raphanus sativus L. cv. Scarlet Globe, under controlled conditions. The NSW clone was fed on simple artificial diets containing alkaloid extracted from narrow-leafed lupin, Lupinus angustifolius L. cv. Fest., and its reproductive performance monitored over 112 h. Forty (40) h into the experiment and thereafter, aphids on the control diet (sucrose solution) produced significantly more offspring (P<0.05) than those on diets containing alkaloid. In a separate experiment, apterae of each clone were caged on three lines (cv. Yorrel, cv. Danja and 84L:441) of narrow-leafed lupin, and allowed to reproduce. The first three offspring were retained, and all developed to 3rd or 4th instar stage. Two nymphs were removed, and the remaining nymph reared through. All three lines produced adults. The number of young produced were counted over 11 days. Fecundity of the SP clone was lower on line 84L:441, but there was no difference in the fecundity of the NSW clone. Phloem exudate and green tissue was concomitantly collected from all lines, and analysed by GC-MS for the alkaloids lupanine and 13-hydroxylupanine. Line 84L:441 contained the highest level of total alkaloids in both phloem and tissue. All experiments indicate that alkaloid level may suppress fecundity of green peach aphids.     

Temporal changes in host adaptation in the pea aphid, Acyrthosiphon pisum

Abstract.

• 1 Temporal changes in host adaptation were followed in a local population of the pea aphid, Acyrthosiphon pisum. Aphid clones were collected in one alfalfa and one clover field at three different times. In the spring, first-generation females were collected. Later, in the autumn, females belonging to the last parthenogenetic generation were collected. Lastly, sexual females were collected after mating in autumn and allowed to produce eggs which were hatched. The performance was evaluated on alfalfa and clover. The spring-collected individuals were also assessed on peas.
• 2 On the overwintering hosts clover and alfalfa, the clones performed best on the plant of origin, i.e. negative correlations in performance. Correlations between performance on the temporary summer host, pea, and that on clover/alfalfa were weak or nonsignificant.
• 3 Significant variation in host performance was found within both host fields at spring, which is a prerequisite for changes in clone composition due to selection/migration.
• 4 The clones from alfalfa showed an increase in mean performance on alfalfa between spring and autumn, whereas no changes among the clones from the clover field were observed. This difference in seasonal response between the two fields could have been the result of larger variation in performance among the alfalfa clones and/or a differential tendency to migrate among clones in both fields.
• 5 After sexual recombination in the autumn, mean performance in the alfalfa field returned to the spring level, probably as a result of emergence of new genetic combinations. In the clover field, mean performance did not change significantly over time.

     

华北棉区夏播棉田害虫发生特点分析

分析和比较了华北棉区夏季播种与春季播种的棉田主要害虫（棉铃虫与棉蚜）的发生特点,探讨了它们的管理对策。     

Structural characterization of genes corresponding to cotton fiber mRNA, E6: reduced E6 protein in transgenic plants by antisense gene

Two genes, each corresponding to fiber mRNA E6, were isolated from cotton cultivars Coker 312 (Gossypium hirsutum L.) and Sea Island (G. barbadense L.). E6 is one of the predominant fiber-specific mRNAs present during early fiber development. The distinguishing feature of the nucleotide-derived E6 protein is the presence of a motif where a dimer, Ser-Gly, is repeated several times. Two of the Sea Island genes contained a pentameric motif, Ser-Gly, while one of the Coker genes had one and the other had four motifs each. cDNA clones containing one or five Ser-Gly motifs were also identified. Thus, it appears that the strict conservation of this motif may not be critical to E6 protein function. Sequence characterizations of the genes and cDNAs showed that multiple members of the E6 family are transcribed in fiber and may result in proteins 238 to 246 amino acids long. The 3 ends of the genes and cDNAs showed considerable heterology among them. Transgenic plants containing antisense genes were generated to decipher E6 function. Transgenic cotton with reduced E6 protein levels in the range of 60 to 98% were identified. However, no discernible phenotypic changes in fiber development or properties were apparent. This result leads to the conclusion that E6 is not critical to the normal development or structural integrity of cotton fibers.     

Mepiquat chloride (PIX)-induced changes in photosynthesis and growth of cotton

Mepiquat chloride (N, N-dimethylpiperidinium chloride), well known as PIX, is a potential systemic plant growth regulator. The effects of PIX on plant height, stem elongation, leaf area, net photosynthetic rates, chlorophyll content, sucrose and starch levels, and RuBP carboxylase activity in cotton (Gossypium hirsutum L. cv. DES 119) plants were measured. PIX was sprayed (0, 7.65, 15.3, 30.6 or 61.2 g active ingredient ha^–1) on the plants at first square (25 days after emergence) and measurements were made at frequent intervals. Plant height was clearly reduced by PIX. The total length of vegetative branches and fruiting branches was 40% and 50% less than the control. Total leaf area in PIX treated plants was 16% less than the control. Net photosynthetic rates were 25% less in PIX-treated leaves. PIX treated leaves had more chlorophyll content. The activity of RuBP carboxylase was decreased in PIX treated plants. Starch accumulation was noticed in PIX treated leaves while sucrose content was not changed. The data reported here suggest that reduced growth responses induced by PIX results in partial loss of photosynthetic capacity in cotton at least up to 20 days after application of the growth regulator.     

Alfalfa mosaic and cucumber mosaic virus infection in chickpea and lentil: incidence and seed transmission

Samples collected in 1994 and 1995 from commercial crops of chickpeas and lentils growing in the agricultural region of south-west Western Australia were tested for infection with alfalfa mosaic (AMV) and cucumber mosaic (CMV) viruses, and for members of the family Potyviridae using enzyme-linked immunosorbent assay (ELISA). In 1994 no virus was detected in the 21 chickpea crops tested but in 1995, out of 42 crops, AMV was found in two and CMV in seven. With lentils, AMV and/or CMV was found in three out of 14 crops in 1994 and 4 out of 13 in 1995, both viruses being detected in two crops in each year. Similar tests on samples from chickpea and lentil crops and plots growing at experimental sites, revealed more frequent infection with both viruses. No potyvirus infection was found in chickpeas or lentils in agricultural areas either in commercial crops or at experimental sites. However, bean yellow mosaic virus (BYMV) was detected along with AMV and CMV in irrigated plots of chickpeas and lentils at a site in Perth. When samples of seed from infected crops or plots of chickpeas and lentils were germinated and leaves or roots of seedlings tested for virus infection by ELISA, AMV and CMV were found to be seed-borne in both while BYMV was seed-borne in lentils. The rates of transmission found through seed of chickpea to seedlings were 0.1–1% with AMV and 0.1–2% with CMV. Seed transmission rates with lentil were 0.1–5% for AMV, 0.1–1% for CMV and 0.8% for BYMV. Individual seed samples of lentil and chickpea sometimes contained both AMV and CMV. With both species, infection with AMV and CMV was sometimes found in commercial seed stocks or seed stocks from multiplication crops of advanced selections nearing release as new cultivars. Seed-borne virus infection has important practical implications, as virus sources can be re-introduced every year to chickpea and lentil crops or plots through sowing infected seed stocks leading to spread of infection by aphid vectors, losses in grain yield and further contamination of seed stocks.