Infestation Of Seeds Research Articles

Acacia tortilis subsp. raddiana in the North African arid zone: the obstacles to natural regeneration

The main objective of this study is to determine the possible reasons for regeneration failure of Acacia tortilis subsp. raddiana (Fabaceae). We conducted some laboratory experiments, simulating natural conditions. We estimated rate of infestation of seeds by Bruchidius raddianae and B. aurivillil and tested the autotoxicity effect of leaf extracts (different concentrations) of A. tortilis in the laboratory at 30 °C (optimum germination temperature). Results show that the inhibitory effect on germination increase with the increased leaf extract concentration. At 100% concentration, a significant reduction of germination rate was found compared to other concentrations. On the other hand, the study also revealed a high infestation rate of seeds by B. raddianae and B. aurivillil which reduces the possibility in inhibits natural regeneration in A. tortilis.

Pesticidal seed coats based on azadirachtin‐A: release kinetics, storage life and performance

Infestation of seeds by pests during storage leads to deterioration in quality. Seed coating is an effective option to overcome the menace. Unlike synthetic fungicidal seed coats, little is known of those based on botanicals. This study aims at developing azadirachtin-A-based pesticidal seed coats to maintain seed quality during storage. Polymer- and clay-based coats containing azadirachtin-A were prepared and evaluated for quality maintenance of soybean seed during storage. Gum acacia, gum tragacanth, rosin, ethyl cellulose, hydroxyethyl cellulose, polyethyl methacrylate, methyl cellulose, polyethylene glycol, polyvinyl chloride, polyvinyl acetate, polyvinyl pyrrolidone and Agrimer VA 6 polymers and the clay bentonite were used as carriers. The time for 50% release (t(1/2)) of azadirachtin-A into water from the seeds coated with the different coats ranged from 8.02 to 21.36 h. The half-life (T(1/2)) of azadirachtin-A in the coats on seed ranged from 4.37 to 11.22 months, as compared with 3.45 months in azadirachtin-A WP, showing an increase by a factor of nearly 1.3-3.3 over the latter. The coats apparently acted as a barrier to moisture to reduce azadirachtin-A degradation and prevented proliferation of storage fungi. Polyethyl methacrylate, polyvinyl acetate and polyvinyl pyrrolidone were significantly superior to the other polymers. Azadirachtin-A showed a significant positive correlation with seed germination and vigour, and negative correlation with moisture content. Effective polymeric carriers for seed coats based on azadirachtin-A are reported. These checked seed deterioration during storage by acting as a barrier to moisture and reduced the degradation of azadirachtin-A.

Survival and Scatterhoarding of Frugivores‐Dispersed Seeds as a Function of Forest Disturbance

ABSTRACTThe effect of forest disturbance on survival and secondary dispersal of an artificial seed shadow (N= 800) was studied at Brownsberg Natural Park, Suriname, South America. We scattered single seeds of the frugivore‐dispersed tree Virola kwatae (Myristicaceae), simulating loose dispersal by frugivores, in undisturbed and disturbed secondary forest habitats. Seed survival rate aboveground was high (69%) within 2 wk and was negatively correlated with scatterhoarding rate by rodents, the latter being significantly lower in the undisturbed forest (9%) than in the disturbed forest (20%). Postdispersal seed predation by vertebrates was low (3%) and infestation of seeds by invertebrates was almost zero in all instances. Therefore, secondary seed dispersal by rodents in forest is not as critical for recruitment as observed among other bruchid‐infested large‐seeded species. Secondary seed dispersal by rodents may, however, facilitate seedling recruitment whether cached seeds experience greater survival than seeds remaining above ground surface.

Colonization of Female Watermelon Blossoms by Acidovorax avenae ssp. citrulli and the Relationship between Blossom Inoculum Dosage and Seed Infestation

AbstractThe aim of this work was to investigate the ability of Acidovorax avenae ssp. citrulli, the causal agent of bacterial fruit blotch of cucurbits (BFB), to colonize female watermelon blossoms, and to explore the relationship between blossom inoculum dosage and seed infestation. Under greenhouse conditions A. avenae ssp. citrulli colonized stigmas and styles of female watermelon blossoms reaching populations of ≈107 to 108 colony‐forming units (CFU) per blossom for 96 h after inoculation. Acidovorax avenae ssp. citrulli growth on stigmas was slower than that of Pseudomonas syringae Cit7, a non‐pathogenic, foliar epiphyte of tomato. While pollination reduced growth of A. avenae ssp. citrulli, but P. syringae Cit7 was unaffected. Both bacteria colonized style tissues but bacterial growth in the style was significantly less than the stigma. Blossom inoculation with ≈1 × 103A. avenae ssp. citrulli CFU/blossom led to 36–55% infested seedlots within symptomless fruits. On average 14% of the seedlings produced from these seedlots displayed BFB symptoms. There was a strong positive correlation between A. avenae ssp. citrulli inoculum concentration applied to blossoms and the percentage of infested seedlots, as determined by the seedling grow‐out assay (R2 = 0.94). However, this relationship was weaker when seedlot infestation was determined by a polymerase chain reaction‐based assay (R2 = 0.34). There was also a strong positive linear relationship between A. avenae ssp. citrulli blossom inoculum dose and the mean percentage of BFB‐infected seedlings (R2 = 0.99) produced in seedling grow‐out assays. These data support the hypothesis that blossom colonization might be involved in seed infestation under field conditions.

Frequency of Alternaria brassicicola in commercial cabbage seeds in Japan

Plug seedlings, widely used in cabbage cultivation in Japan, are often infected by seed-borne pathogens, especially the serious pathogen Alternaria brassicicola. Because information on seed infestation is scant in Japan, we investigated fungal infestation in commercial batches of cabbage seeds produced between 1984 and 2001. A total of 123 lots were divided into six groups by production period (1984–1989, 1994–1998, and 2001) and by use or nonuse of fungicide. One hundred seeds from each lot were incubated separately on agar at 25°C to isolate the predominant fungus. Alternaria brassicicola was isolated most frequently, 0%–94% of the seeds depending on seed lot or 6%–21% of the seeds grouped by production period and fungicide treatment. Thus, the pathogen was isolated even from seeds refrigerated for 17 years. Alternaria brassicicola accounted for 57%–95% of all isolated fungi by the group and was higher on older or fungicide-treated seeds. Seeds that were not treated with fungicide in lots grouped by production districts in western Japan were infested with A. brassicicola at a rate of over 12%, higher than that in the eastern region (<4%). Infestation was higher in the warmer areas of Japan. Eighty-five isolates, other than A. brassicicola, produced spots on cabbage cotyledons, although they were not isolated as frequently: less than 5% of seeds by group separated by production period and fungicide treatment. Most of these isolates were Alternaria alternata. This is the first report on the frequency of fungal infestation of commercial cabbage seeds in Japan.

Reproductive phenology and pre‐dispersal seed‐feeding in Protium tovarense (Burseraceae), with a description of the first known phytophagous “Bracon” species (Hymenoptera: Braconidae: Braconinae)

The reproductive phenology of the cloud forest tree Protium tovarense (Burseraceae) is analysed for one population in northern Venezuela. Reproductive phenophases were monitored using both long‐term(21 years) and detailed short‐term (4 years) surveys of flower and fruit set. The reproductive phenology of this tree varies, with periods in which the species behaves as a supra‐annual reproducer, and other periods in which it reproduces annually, at the end of the rainy season. Marked spatial variation in reproductive condition was also observed, with subpopulations separated by less than 2 km showing contrasting phenological stages. Larval infestation of seeds by a braconid wasp was observed for a period of 1 year and is described. This wasp, the first obligately phytophagous species of Braconinae, is described as Bracon phytophagus Quicke sp. n. Percentage fruit infestation by this wasp was relatively high (50–60%) during the entire period (∼10 months) of fruit development. The larval stages are described and illustrated, and compared with those of other phytophagous Ichneumonoidea. DNA sequencing of wasp colour variants provided no indication that multiple species were involved. Two related braconine species described in the genus Iphiaulax are transferred to Bracon, hence, B. flavipalpisimus replacement name (Szépligeti) ( = Iphiaulax flavipalpis Szépligeti, 1901 not B. flavipalpis Thomson, 1892) and B. glabrescens (Szépligeti) n. comb. ( = Iphiaulax glabrescens Szépligeti, 1901). Evolutionary routes to phytophagy in braconid wasps and hypothetical scenarios in which this plant–seed predator interaction can be maintained are discussed.

Pitch canker ratings of longleaf pine clones correlate with Fusarium circinatum infestation of seeds and seedling mortality in containers

SummaryThe incidence and severity of pitch canker was rated among 16 clones of mature longleaf pine (Pinus palustris) in a seed orchard and cones were collected from five of those clones across the range of pitch canker disease ratings. Seed were extracted and commercially processed by clone and the percentages contaminated with Fusarium circinatum determined. Seed from each clone were sown either without treatment or with one of three fungicide treatments in a soil‐less mix at a commercial container nursery to evaluate the effects of F. circinatum (syn. F. subglutinans) on seed and seedling survival. The percent of seed with F. circinatum correlated with the pitch canker ratings in the orchard for the year of collection (r = 0.88, p = 0.05) and, when sown without fungicide treatment, with the number of seedlings produced (r = −0.94, p = 0.01) and with seedling mortality after germination (r = 0.92, p = 0.02). The same orchard clones were more symptomatic of pitch canker through three annual surveys. Fusarium circinatum was isolated from a higher percent of seed from more symptomatic clones and a lower percent of their seed produced plantable seedlings. We propose that removing such clones from seed collections should reduce seedling mortality at the nursery.

Fruit infestation of Acacia tortilis (Forsk) hyne by Bruchidius andrewesi Pic. (Coleoptera: Bruchidae) in the Thar desert

Bruchidius andrewesi Pic. has been recorded as a serious pest of pods and seeds of Acacia tortilis in the Thar desert of India. Pest infestation on developing pods and its relationship with morphological traits is reported. Pod infestation varied from 5 to 19% with 5–29% infestation of seeds. Infestation of pods is directly related to infestation of seed ( r = 0.72 ∗∗ ), and both pod and seed infestation are also directly correlated with loss in seed biomass ( r = 0.79 ∗∗ and r = 0.88 ∗∗ ). The infestation of pods starts in November and increases steady until harvest. Seeds kept in the laboratory for further studies were found to be 100% infested with B. andrewesi, as the insect multiplied faster under these conditions. The heavy infestation is damaging not only to A. tortilis but also to other leguminous trees of the desert. Bruchidius andrewesi has also been found on pods and seeds of Prosopis cineraria, an important indigenous tree of the region.

The fate of mature African Acacia pods and seeds during their passage from the tree to the soil

ABSTRACTThe fate of mature Acacia tortilis pods on the tree and ground and A. nilotica pods on the ground were investigated at a site in South Africa. Pods on Acacia trees were browsed only by giraffe whereas pods on the ground were browsed by kudu, impala, steenbok and duiker. In the absence of giraffe most A. tortilis pods fell from the tree to the ground. When giraffe were present they consumed most A. tortilis pods at tree level. Bruchids infested 21.6–54.0% of seeds within pods on the tree. Once fallen, in the absence of browsing ungulates, A. tortilis and A. nilotica pod and seed disappearance could be attributed to burial by termites and ants, seed consumption by rodents and to decomposition; when browsing ungulates were present they consumed most pods on the ground. Between 20.0–47.6% of A. tortilis and 31.0–58.0% of A. nilotica seeds on the ground were infested by bruchids. Ungulate browsing had no effect on bruchid infestation of seeds. This study exemplifies the importance of browsing ungulates as consumers of Acacia pods. Although survival of A. tortilis and A. nilotica seeds was greatest in the absence of browsing ungulates the survival of seeds following pod consumption by ungulates is unknown.

Effect of level of seed infestation on mortality of larvae and pupae of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in some controlled atmospheres

Blackeye cowpea seeds of fairly uniform weight were infested with Callosobruchus maculatus (F.). Seeds containing 10–12 larvae or pupae per seed (high infestation) and those containing 1–2 larvae or pupae per seed (low infestation) were exposed to 70% CO 2 in air, 30% CO 2 in air, 1% O 2 in N 2 and 4% O 2 in N 2 atmospheres respectively at 27 ± 2°C and 70 ± 5% r.h. In the different atmospheres, larval and pupal mortality was generally higher in seeds with low infestation than in seeds with high infestation. Insect mortality was not significantly different between treatments involving 70% CO 2 in air and 1% O 2 in N 2; and between treatments involving 30% CO 2 in air and 4% O 2 in N 2, irrespective of level of insect infestation in seeds. The results are discussed in relation to practical application of controlled atmospheres for stored-products protection.

Reduction of Bacterial Blight Infestation of Cotton Seeds by Treatment with Sodium Hypochlorite

AbstractThe efficacy of sodium hypochlorite (NaOCl) for restraining cotton seed infestation by Xanthomonas campestris pv. malvacearum was studied. Seeds of three cotton cultivars were artificially inoculated by soaking in suspensions (ca. 5.10 8 CFU/ml) of different strains of Xcm. Twelve h after soaking (at 30°C) various dilutions of NaOCl were added to the soaking suspensions and incubated for another 12 h. The infestation rate of cotyledons and effect on germination were determined 14 and 21 days after treatment under the standardized conditions of a growth chamber (12 h 20,000 Lux at plant height, 30/20 °C day/night, ca. 100 % relative humidity). Cbncentrations below 0.15 % of active chlorine in the soaking‐water had no marked effect on reduction of the disease. Goncentrations between 0.45 % to 0.60 % appeared to be most effective without reducing germination rate. Seed germination was affected, however, by concentration of active chlorine above 0.6 %. Seed quality during sodium hypochlorite treatment obviously influenced the effectivity of this measure.

Carry over of bruchid,Caryedon serratus(Olivier) (Coleoptera) from field to stores through seeds ofAcacia nilotica(L.) Willd. in India

Abstract A percentage pod damage of 6.8% in Acacia nilotica (L.) Willd. by the bruchid, Caryedon serratus (Olivier) in the field was recorded by examining exit holes on the pods. The mean number of females and males that emerged from 50 pods kept in laboratory were 1.3 and 1.2 respectively. The pods of A. nilotica gathered from the field for seed purposes were found to be infested in small numbers but the bruchid population increased during storage. The infestation of seeds and carry over to stores is not only a danger to uninfested seeds of A. nilotica and other plants, important in social forestry, but the tree also acts as secondary host for the population build‐up of C. serratus which spreads to its primary host, the groundnut, Arachis hypogea (L).

Fungal infestation of seeds from seven populations of wild oats (Avena fatuaL.) with different dormancy and viability characteristics

SummarySeeds from seven genetically inbred pure lines of wild oats (Avena fatuaL.) with different levels of dormancy and viability were analysed for seed‐borne fungi. All lines had fungi on the seeds. The predominating fungi wereAlternaria alternataandCladosporium herbarum, of which the latter was non‐pathogenic and the former only weakly pathogenic on seedlings of wild oats.Drechslera avenacea, Cochliobulus sativusandFusariumspp., frequently isolated, were pathogenic onA. fatua.OnlyD. avenaceawas host specific toA. fatuaand cultivated oatsAvena sativa. Cochliobolus sativusandFusariumspp, were equal or more pathogenic on seedlings of wheat (Triticum aestivumL.), barley (Hordeum vulgareL.), oats and rye (Secale cerealeL.) than on seedlings ofA. fatua. Drechslera avenaceaoccurred on a significantly higher percentage of seeds fromA. fatualines, AN 51 and AN 474, than from the other lines. Other fungi isolated occurred randomly on allA. fatualines. There was no relationship between low viability of seeds and fungi carried on the seeds.

Tests of a Spun Polyester Row Cover as a Barrier Against Seedcorn Maggot (Diptera: Anthomyiidae) and Cabbage Pest Infestations

Reemay, a spun polyester row-cover material, was tested as a barrier to insect pest infestations in two different systems. The row cover was ineffective in preventing infestation of seeds by seedcorn maggot, Delia platura (Meigen), suggesting that eggs or larvae were already present in the field at time of planting. The row cover dramatically reduced populations of cabbage insect pests (lepidopterous larvae, flea beetles, cabbage maggots, and aphids) as well as numbers of insect-damaged cabbage heads in both 1984 and 1986. In 1986, numbers of heads produced were lower under the row cover, probably because of bacterial rot due to excessive humidity. Marketable yields were still substantially higher under the row covers.

Sunflower Seed Midge1: Effects of Larval Infestation on Pericarp Development in Sunflower2

Helianthus annum L. seeds infested by larvae of the sunflower seed midge, Neolasioptera helianthi (= murtfeldtiana) (Felt), develop an abnormally colored and soft pericarp. Larvae are accompanied by an unidentified fungus in infested seeds. Normal-appearing seeds are dark, hard, and contain neither larvae nor fungus. It appears that successful infestation of seeds by the sunflower seed midge depends upon the accompanying fungus infection. Microscopic observations indicate that midge larval penetration and fungal infection of seeds occur at an early stage of differentiation and maturation of the pericarp. Seeds harboring larvae and fungi experience <50% reduction in sclerification of the sclerenchyma and incomplete filling of hypodermal cells. Also, the inner pericarp wall of infested-infected seeds are penetrated by fungal mycelium, where hyphae obliterate phloem cells in the vascular bundles.

Detection and Estimation of Internal Pest Infestation in Seeds by the Application of X‐ray Techniques

AbstractIn quarantine inspection it is particularly important to use reliable and rapid testing methods for revealing internal infestation of seeds. Generally, it is impossible to diagnose correctly hidden infestation, at a low level, by means of traditional inspection test methods. The X‐ray technique, however, has considerable merit in the rapid and objective detection of insects living inside seeds. This radiographic process, most appropriate to quarantine practice, is presented. Optimal exposures were determined for seeds of 46 plant species. The reliability of radiographic counts of infestation was controlled by a model‐experiment, in which a very high correlation (r =−0.986) was found between the rate of infestation in the samples and the number of seeds to be tested from the sample. On a certain level by the regression equation (y = 7691–2468 log. x) it is possible to determine the number of seeds which have to be tested in order to obtain the real value of infestation.