نشریه تحقیقات نوین در گیاه پزشکی
پیاپی 1 (بهار 1388)

Benthic macroinvertebrate species are differentially sensitive to many biotic and abiotic factors in their environment. The field biotic index is based on family level identification of water arthropods. An interest in environmental quality is one of the major reasons for the study of aquatic insects. The idea of using the aquatic insect community to “indicate” the degree of purity or pollution of a body of water is over half a century old. It is based on the concept of indicator organisms and tolerance levels. During October, November and Dececember 2008 studies were carried out on the field biotic index of Kor river in Marvdasht region (Fars province) using aquatic insects fauna. A total of 16 families were collected and identified in 14 habitat codes of Kor river. In this survey, biotic index of KorRiver was 7.2 and evaluation of the water quality based on the biotic index was calculated. Water quality of Kor river was fairly poor (significant organic pollution) during this survey.

Feeding behaviour of the Scolothrips longicornis Priesner preying on Tetranychus turkestani (Ugarov & Nikolski) was investigated by leaf - island method under laboratory conditions (26±1°C, 60±5% RH and photoperiod of L16: D8 hours). One starved female thrips consumed a mite’s egg, a first instar larva and a protonymph, a deutonymph and an adult female mite in 1.52, 2.63, 3.13, 7.93 and 15.5 minute respectively. The first instar larva of the thrips ate 10.1 eggs or 1.2 female mites, the second instar larva consumed 34.5 eggs or 4.7 female mites and the adult female ate 49.1 eggs or 11.7 adult females per day. The mated female with a prey consumption of 11.7 female mites had the highest appetite. The unmated females and males by daily consumption of respectively 7.3 and 6.2 females had no significant difference in their voracity. The daily mean voracity increased from 0.3 to 17.1 female mites per female thrips by increasing temperature from 5 to 40°C. The rate of feeding severely decreased at 45°C and it was almost equal to rate of feeding at 26°C. Switching behavior of the thrips by using Murdach model, in different proportion of two prey, T. turkestani and E. orientalis shown negative switching and more number of T. turkestani was consumed when the proportion increased. The results indicated that S. longicornis may be a suitable biological agent for suppression of the Tetranychidae mites.

The predator bugs (Heteroptera) are one of the powerful natural enemies in almost agro-ecosystems which have important role in biological control programs. In attention to presence of diverse pests in rice fields and importance of this crop as the main food in Northern Iran, species diversity and population fluctuation of predator bugs were studied in rice fields of Mazandaran province through 2005 - 2006. In a total, 20 species of predator bugs were collected and identified from rice fields of Mazandaran province. Of the collected species, eight species including, Oncocephalus pilicornis Reuter, Oncocephalus plumicornis (Germar), Reduvius pallipes Klug, Rhynocoris iracundus (Poda) and Coranus cf. niger Rambur of family Reduviidae, Stenodema calcaratum (Fieb.), Orthotylus flavosparsus (C.Sahlb.) of family Miridae, and Brachynema puncticornis Rt. of family Pentatomidae are newly recorded from Iran. The results of population fluctuation indicated that the density of predator bugs increases through the crop season gradually, but application of insecticides causes damage to the density population severely. Also, the population density of predator bugs was varied through a day; the most abundant of population was obtained in hours 10 and 18, because of moderate climate. These beneficial insects rest beyond the rice seedlings and among the weeds around the fields through the hours 12 - 16, because of high temperature and humidity in rice fields. The results of population density of predator bugs on three rice varieties including, Fajr, Khazar, and Nemat indicated that highest density was obtained from Fajr and there was not significant difference between the two other varieties. Since the Fajr is a sensitive variety to C. suppressalis and the pest population density on it is higher than other studied varieties, there is higher density of heteropteran predators on this variety than the two others.

Sugarcane white leaf (SCWL) is among the most important and economical diseases of sugarcane in Asia. SCWL is reported from Khuzestan province as an emerging phytoplasmal disease of sugarcane. In addition to SCWL, Bermuda grass white leaf (BGWL) the other monocot phytoplasmal disease also is reported from this province. Rabbit has been used for rising of antiserum by injection of partially purified SCWL at 40g of infected tissue. This antiserum exhibited specificity for its homologous phytoplasma antigen in Plate- Trapped Antigen enzyme-linked immunosorbent assay (PTA-ELISA) dot immunoblotting assay (DIBA) and tissue print immuno assay (TPIA). No cross-reactions were observed in reciprocal tests between this antiserum and other tested phytoplasmas.

In order to study cause and effect of seed yield with some agronomical traits in bean genotypes, two experiments were conducted under field conditions. Twenty five common bean genotypes were sown in 2 separate RCB design with three replications under non-infected and infected conditions. First, phenotypic correlation coefficient of traits with each other was counted. At non-infected conditions number of secondary stem, harvest index, reproduction period and under infected conditions number of seeds in plant, number of seeds in pod and harvest index showed significant correlation with seed yield at 0.05 & 0.01 probability levels. Stepwise regression and then path analysis were used to determine the traits that were effective on seed yield. In stepwise regression analysis seed yield was the dependent and other traits were as independent variables. At non-infected conditions number of secondary stem, harvest index and main stem length were entered in regression model respectively and explained 84% of seed yield variations. In this manner, under infected conditions, harvest index, plant weight and number of seeds in pod justified 93% of seed yield variations. On the basis of achieved results, harvest index was introduced as profitable selection index at non-infected and infected conditions. In order to results of path analysis after harvest index at non-infected conditions number of secondary stem and at infected conditions number of seeds in pod were introduced as suitable indices.

Antagonistic mechanisms of three isolates of Trichodermaharzianum (THJ1, THJ2 & THB), one isolates of T.virens and one isolates of T.viride were studied against wet root rot agent of Iranian chickpea, Rhizoctoniasolani. In dual culture, all isolates of Trichoderma were able to affect the mycelial growth of R. solani. The isolate THJ2 had the highest percent of growth inhibition (72.77, 94.72 and 94.05 %) at three times interval. On the base of microscopic study R. solani was affected by Trichoderma through hyphal contact, hyphal penetration, hyphal coiling and hyphal fragmentation. The effect of Non Volatile Metabolites (NVM) of Trichoderma isolates on mycelial growth of R. solani indicated that the NVM of THJ2 inhibited the growth of pathogen more than other isolates at three times of measurement, using 5ml (62.34, 73.83 and 70.97 %) and 10 ml (68.04, 72.59 and 80.52 %). Volatile Metabolites (VM) of all Trichoderma isolates inhibited mycelial growth wherease T. harzianum (THB) had the highest effect at three times of measurement (68.02, 73.32 and 73.54 %).

In order to investigate the effects of seed heteroblasty on germination and seedling vigor in wild radish (Raphanus raphanistrum L.) this study was conducted in Agricultural College of Darab in 2007. In laboratory and greenhouse, germination and seedling growth studies were conducted on seed harvested from different seed positions and heights of mother plant of wild radish by factorial in completely randomized design using four replications. Treatments consisted of three heights of mother plant (40-60, 60-80, 80-100 cm) and three seed positions within the inflorescence including: 1- Seeds in low part of inflorescence (seeds of the first to fifth siliceous in inflorescence), 2- Seeds in middle part of inflorescence (seeds of the sixth to tenth siliceous in inflorescence), 3- Seeds in upper part of inflorescence (seeds of the eleventh to fifteenth siliceous in inflorescence). The results in laboratory showed that among three heights of mother plant, the seeds of the sixth to tenth siliceous in inflorescence had the maximum germination percentage and produced the tallest length of radicle. Also, in height of 60-80 cm of mother plant, the seeds of sixth to tenth and first to fifth siliceous in inflorescence produced the tallest length of primary shoot. In greenhouse experiments, the seeds of sixth to tenth siliceous of inflorescence in height of 60-80 cm of mother plant produced the maximum number of plants and the seeds that harvested from sixth to tenth siliceous of inflorescence in height of 80-100 cm of mother plant had the maximum height of wild radish.

Anagrus atomus (L.) (Hymenoptera: Mymaridae) is an egg parasitoid and an important mortality factor for the grape leafhopper, Arboridia kermanshah Dlabola (Hemiptera: Cicadellidae) populations in Isfahan vineyards. A study was conducted to characterize the plants in which A. atomus overwinters, dispersal of the parasitoid, and the level of parasitism of grape leafhopper eggs in two vineyards through 2000-2001. A. atomus overwinters in leafhopper eggs on rose, sweetbriar and blackberry. In a vineyard, with nearby overwintering refuges, the parasitoid emerged by mid-March from alternate hosts. It completed one generation on these alternate hosts, and then arrived in vineyard by late April, synchronized with grape leafhopper oviposition. The pattern of wasp colonization and parasitism indicated that parasitoids were more abundant in the vineyard with refuges close to it. In early spring, density of A. atomus was more than twice in this vineyard compared with vineyard with no refuges close to it. By mid season (July), A. atomus parasitism of A. kermanshah was significantly greater in the vineyard associated with refuges. Cumulative egg parasitism demonstrated that enhanced early season parasitism resulted in a better season-long increase in the mortality imposed by A. atomus on A. kermanshah eggs.

The efficacy of four fungal bioagents viz., Trichoderma hamatum, Trichoderma harzianum, Trichoderma viride, Gliocladium virens and two bacterial bioagents namely Pseudomonas fluorescens and Bacillus subtilis were evaluated against the chickpea vascular wilt pathogen, Fusarium oxysporum f.sp. ciceri in vitro condition using Dual Culture Technique. Among the fungal bioagents, T. harzianum produced the maximum inhibition zone of 17 mm compared to the minimum of 7 mm by T. hamatum. There was no significant difference between the inhibition zones produced by P. fluorescens and B. subtilis. Soil application of talc- based formulation of T. harzianum, P. fluorescens and G. virens effectively controlled the vascular wilt of chickpea under field condition.