Nature of Sweet Potato Resistance to Meloidogyne incognita and the Effects of Temperature on Parasitism

Penetration, rate of development, and total population of Meloidogyne incognita in roots of susceptible ''Allgold'' and resistant ''Nemagold'' sweet potatoes increased with temperature 24-32 C. Rate of larval penetration in ''Allgold'' was significantly higher than in ''Nemagold'' after 48 hr of root exposure at 24, 28, and 32 C. At 24, 28, and 32 C (16 hr) day and 20 C (8 hr) night temperature the life cycle of M. incognita required 42, 32, and 28 days in ''Allgold'', and 44, 33, and 31 days in ''Nemagold''; mature females in the first generation were 40, 40, 40, and 10, 22, 20 respectively. The correlation between the length of time roots were allowed to grow in the soil prior to inoculation and number of larvae recovered from the roots after inoculation was positive for ''Allgold'' and negative for ''Nemagold''. Therefore, a root exudate repellent to M. incognita larvae is proposed as a hypothetical basis for resistance to M. incognita in sweet potatoes.     

Development of Meloidogyne chitwoodi on Wheat

Postinfection development of Meloidogyne chitwoodi from second-stage juveniles (J2) to mature females and egg deposition on ''Nugaines'' winter wheat required 105, 51, 36, and 21 days at 10, 15, 20, and 25 C. At 25 C, the J2 induced cavities and hyperplasia in the cortex and apical meristem of root tips with hypertrophy of cortical and apical meristem cell nuclei, 2 and 5 days after inoculation. Giant cells induced by late J2 were observed in the stele 10 days after inoculation. Clusters of egg-laying females were common on wheat root galls 25 days after inoculation. Juveniles penetrated wheat roots at 4 C and above, but not at 2 C, when inoculum was obtained from cultures grown at 20 C, but no penetration occurred at 4 C when inoculum was stored for 12 hours at 4 C before inoculation. In northern Utah, J2 penetrated Nugaines wheat roots in the field in mid-May, about 5 months after seedling emergence. M. chitwoodi eggs were first observed on wheat roots in mid-July when plants were in blossom. Only 40% of overwintered M. chitwoodi eggs hatched at 25 C.     

Pathogenicity of Meloidogyne hapla to Lettuce as Affected by Inoculum Level, Plant Age at Inoculation and Temperature

Pathogenicity of Meloidogyne hapla to lettuce was influenced by inoculum level, age of plant at inoculation and temperature. Top weight of ''Minetto'' lettuce was reduced 32% when 2-week-old lettuce plants were each inoculated with five egg masses. Higher inoculum levels did not further decrease top weight significantly. Inoculation at seeding reduced top growth more than inoculation of 1-, 2- or 3-week-old seedlings. M. hapla reduced growth more at the intermediate (21.1 C night and 26.7 C day), than at the low (15.5 C night and 21.1 C day) or high (26.7 C night and 32.2 C day), temperature regimes.     

Effect of Soil Temperature on Infectivity and Development of Rotylenchulus reniformis on Resistant and Susceptible Soybeans,Glycine max

The effect o f soil temperature on parasitism and development of Rotylenchulus reniformis on resistant (''Peking'' and ''Custer'') and susceptible (''Hood'' and ''Lee'') soybean (Glycine max) cultivars was studied. Soil temperatures of 15, 21.5, 25, 29.5 and 36 C ± 1 C were maintained in temperature tanks in a greenhouse. R. reniformis developed best at 25 and 29.5 C. The female life cycle can be completed within 19 days after inoculation under favorable conditions at 29.5 C. Plant root growth was best at 21.5 C. During a 27-day period, no egg masses were present on nematodes feeding on roots grown at 15 and 36 C. Egg masses developed on Hood but not on Lee when nematodes were introduced into soil and maintained at 29.5 C for 2 days before raising the temperature to 36 C.     

Pathogenicity of the Lesion Nematode,Pratylenchus brachyurus,on Six Soybean Cultivars

Pathogenicity tests of Pratylenchus brachyurus on selected greenhouse-grown soybean cultivars indicated the nematode reduced seed yield of ''Hood'' but not that of ''Custer'', ''Bragg'', ''Dyer'', or ''Pickett''. Root weights of all cultivars were reduced. Damage and numbers of nematodes within soybean roots growing at 13, 21, and 29 C were greater at higher temperatures. At 29 C, root pruning was prominent in ''Hood'' and ''Pickett'' but limited in ''Custer'' and ''Hill''. Root pruning was not observed at 13 C and only ''Pickett'' showed pruning at 21 C. Plant height and foliage weight were not affected. P. brachyurus had no effect on the emergence of ''Pickett'' or ''Bragg'' soybeans. Nematode counts from roots of ''Pickett'' at intervals after inoculation indicated that hatching of second generation second-stage larvae occurred about 15 days after egg laying. An average of 68% of the initial inoculum penetrated the roots within five days of inoculation, the highest observed was 81% in five days. Details of structural damage in penetrated tissues were studied in sectioned roots. In soybean roots infected by P. brachyurus and/or Rhizoctonia solani greater damage occurred with nematode and fungus combined than with either acting alone.     

Temperature effects on essential oil composition of citronella selections

Four citronella [Cymbopogon nardus (L.) Rendle] selections indigenous to Sri Lanka were grown for 90 days at 27/21° or 32/27°C daylnight temperatures in controlled environments. Leaves were harvested and oil extracted by steam distillation. Analysis for chemical constituents was carried out by gas liquid chromatography. Growing temperatures affected oil composition with the response to temperature differing among selections. The commercially desired constituent. citronellal, was higher at 27/21°C than at 32/27°C in all selections, whereas the commercially undesirable constituent borneol was higher at 32/27°C than at 27/ 21°C. The production of total monoterpene hydrocarbons was enhanced at 27/ 21°C in selections C-4 and C-8 compared to 32/27°C. The level of methyl isoeugenol differed among selections.     

Life Cycle and Mating Behavior of Belonolaimus longicaudatus in Gnotobiotic Culture

The life cycle of Belonolaimus longicaudatus was observed in vitro on excised roots of Zea mays. Roots were cultured on Gamborg''s B5 medium in petri dishes with 1.5% agar adjusted to pH 5.8 and incubated at 28 °C in darkness. Second-stage juveniles (J2) fed on the roots and started the second molt (M2) to the third-stage juveniles 2 days after inoculation (DAI). The third molt (M3) to the fourth-stage juveniles occurred 7 DAI, followed by the fourth molt (M4) to males 13 DAI or to females 14 DAI. Nematode gender differences were observed by the end of the fourth molt. The first male appeared 15 DAI and the first female 17 DAI, after which mating occurred. Males were attracted to females, and mating was observed. Mating was required for reproduction. Fertilized females began to lay eggs 19 DAI and continued egg laying without the further presence of males during a 90-day observation. All of the eggs hatched. Unfertilized females rarely laid eggs, and none of the eggs were able to hatch. Feeding took place between each molt and before egg deposition occurred. The first-stage juveniles molted in the eggs 4 days after deposition, and J2 hatched from eggs 5 days after egg deposition. The life cycle from J2 to J2 was completed in 24 days.     

Pathogenicity ofBeauveria bassiana for adults ofTribolium castaneum (Col.: Tenebrionidae) in stored grains

Conidia ofBeauveria bassiana were evaluated for activity against adults ofTribolium castaneum, under laboratory conditions closely resembling the stored-grain conditions. Three doses of the fungus were applied in the treatments: 0.1 g, 0.5 g and 1 g per 20 insects/dose/flask. Treated insects and untreated were incubated in broken wheat. There were 5 replications for each test. A total of 1600 treated and control insects used were kept in a climatic chamber (70±5% and 27±2°C) for 45 days. Observations were performed daily and the recording of infected cadavers began when the percentage of mortality exceeded 50%. The evaluation of the efficiency of each dose ofB. bassiana was made 14, 21, 28 and 45 days after inoculation. Mortality of adults that were exposed to the beetles treated with 0.5 g and 1 g of conidia ofB. bassiana / 20 adults was 87 and 85% respectively, within 21 days of exposure. Onset of mortality was further delayed at lower dosage of the fungus; 55% after 21 days. After 28 days there were no difference in mortality between the 0.5 g and 1 g dosages ofB. bassiana. The most efficient treatment was 0.5 g/20 insects, which resulted in a control higher than 50% 14 days post treatment.     

A cotyledon double inoculation technique for evaluating resistance to anthracnose (Colletotrichum orbiculare) and scab (Cladosporium cucumerinum) in cucumber

A technique for simultaneous inoculation of cucumber cotyledons with Colletotrichum orbiculare race 1 and Cladosporium cucumerinum has been developed. The procedure permitted both resistant and susceptible plants to be recovered. Seedlings were grown at 20°C and inoculated 24 h after emergence with Colletotrichum orbiculare (200 spores in 2 μ1 of water) and Cladosporium cucumerinum (1000 spores in 5 μ1 of water) followed by 48 h of incubation in the dark at 20°C and 100% r.h., and 48 h in a 20°C lighted growth chamber. Seedlings were then moved to a growth chamber at 21°C at night and at 26°C during the day for 4 days and plants were rated as resistant or susceptible 8 days after inoculation. No interference in the expression of resistance or susceptibility of cultivars to either pathogen was detected in simultaneous inoculations.     

In Vitro Culture and Feeding Behavior of Belonolaimus longicaudatus on Excised Zea mays Roots

A greenhouse population of the sting nematode, Belonolaimus longicaudatus, obtained from an infested golf course in California''s Coachella Valley, was surface-decontaminated and cuhured on excised roots of Zea mays supported by Gamborg''s B5 medium. At 26-27 °C the females laid eggs, and newly emerged juveniles of the second generation completed three molts within 29 days after egg deposition. Sixty days after inoculation with 60 females and 40 males, an average of 529 nematodes and 83 eggs were recovered from the culture. The feeding process consisted of probing, stylet penetration, ingestion, and stylet retraction. Feeding seemed to be necessary before egg deposition or molting occurred. The sting nematode was observed feeding exclusively as an ectoparasite and preferably at the region of cell division and elongation. Vigorous feeding by many nematodes usually caused discoloration of root tips and termination of growth.     

The reproductive response to the male effect of 7- or 10-month-old female goats is improved when photostimulated males are used

The exposure of adult, female, Mediterranean goats during anoestrus to males with induced sexual activity via photostimulation, induces a very high percentage of ovulations. The present work examines the ability of photostimulated bucks to improve the male effect-induced reproductive response of young does over that induced by non-stimulated bucks. A 2×2 factorial experiment was designed, consisting of doe age and buck photoperiod treatments. During seasonal anoestrus, 41 does aged 7 (n=19) or 10 (n=22) months were subjected to the male effect on 10 April; half of each group was exposed to males rendered sexually active by prior exposure to 3 months of long days (16 h of light/day) from 31 October (PHOTO bucks), and half to males maintained under the natural photoperiod (CONTROL bucks). Oestrous activity was recorded daily by direct visual observation of the marks left by male-worn marking harnesses over the 32 days following the bringing of the sexes together (introduction). Doe body weight and body condition were determined weekly. Ovulation was detected by measuring plasma progesterone concentrations twice per week over the 3 weeks after introduction. The ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. The interaction doe age × buck photoperiod treatment had no effect on any outcome. The percentage of females showing ovulation or oestrus was higher in the does exposed to PHOTO bucks (85% v. 43% for those exposed to CONTROL bucks) they also showed higher fertility (75% v. 43%) and productivity (1.05±0.17 v. 0.57±0.16 kids born per doe serviced) (all P values at least P<0.05). The 10-month-old group showed higher percentage of females showing ovulation, oestrus, fertility and productivity than the 7-month-old does after the male effect (females showing ovulation: 82% v. 42%; showing oestrus: 73% v. 42%; fertility: 73% v. 42% and productivity: 1.09±0.17 v. 0.47±0.14 goat kids born per doe serviced; respectively, all P values at least P<0.05). The present results show that the use of photostimulated males improves the reproductive performance of 7- and 10-month-old does, and may contribute towards increasing their productivity and lifetime reproductive performance.     

Penetration and Development of Meloidogyne hapla in Resistant and Susceptible Alfalfa Under Differing Temperatures

Studies were conducted to examine under differing temperatures (12, 16, 20, 24, 28, and 32 C) the penetration anti development of Meloidogyne hapla in resistant lines ''298'' and ''Nev. Syn XX'', and susceptible ''Lahontan'' and ''Ranger'' hardy-type alfalfas. The results indicated that resistance to M. hapla was similar to that previously described for M. incognita in nonhardy alfalfa. Although initial penetration in resistant seedlings was similar to that of susceptible seedlings, nematode larvae failed to establish and develop in root tissues and nematode numbers subsequently declined. In susceptible seedlings, nematode development proceeded rapidly, and egg production began after 5 weeks. Temperature had little influence on the nematode development except to slow the response at the lower temperatures. Other studies were conducted to verify a previously reported immune (no penetration) reaction to M. hapla by the ''Vernal'' selection ''M-4''. When compared to the resistant (penetration without nematode development) Vernal selection ''M-9'' under differing temperatures (20, 24, 28, and 32 C), each selection was equally penetrated by M. hapla but at a lower level than in susceptible Ranger cuttings. Generally, no root galling was observed in either M-4 or M-9; however, very slight galling was found 35 days after inoculation on about 50% of these cuttings when grown at 32 C.     

Effect of diet upon singly established Hymenolepis diminuta in rats

The onset and course of the elimination of eggs in the feces of rats of singly-established Hymenolepis diminuta has been studied. In both male and female hosts, eggs of this tapeworm first appeared about 18 to 20 days after inoculation, and the daily output gradually increased to a fairly stable level which was higher in males (average about 205,000) than in females (average about 167,000). Egg outputs were maintained at these levels for at least 150 days.In male rats on a complete diet the average number of eggs per proglottid was about 2100. Approximately 7.6 cm of strobila was shed daily which is equivalent to about 8% of the worm's length.In female rats on deficient diet there was a drop in egg output to about 50,000 eggs/24 hours in about 30 days whereas in male hosts on deficient diet a comparable drop occurred only after a period of approximately 3 months.In normal male rats on deficient diet there was very little stunting of worm growth. In females on complete diet worm-size approximately equaled that in male rats, but on deficient diet the worms were significantly smaller.Vitamin B₁₂ failed to raise the egg output in two normal female rats on deficient diet.An increase in egg output was associated with administration of male dog bile in both male and female hosts which continued in males until termination of the experiment, but which failed in females and resulted in a subsequent decrease in elimination of eggs. In both sexes there were unusually large fluctuations in egg output from day to day.     

The fungicide methyl 2-benzimidazole carbamate causes infertility in male Sprague-Dawley rats

A serial breeding technique was used to evaluate the fertility of male Sprague-Dawley rats after exposure to the fungicide carbendazim (methyl 2-benzimidazole carbamate). Proven-fertile male rats (90 days old) received 10 daily doses of corn oil or carbendazim (400 mg/kg/day) peroral. Each male was bred with a new female each week; breeding began on the third day of treatment and continued for 32 wk after the last day of chemical exposure. Twelve days after each breeding period, the females were killed, their uteri were examined for resorptions, and the number of dead and viable fetuses was determined. All males were killed 35 wk post exposure, and testicular tissue was prepared for histopathological examination by vascular perfusion. Fertility (percent fertile as indicated by pregnant females) of males in the carbendazim-treated group was depressed the first post-exposure week; 10 of the 24 treated males failed to produce a pregnant female as compared with no failures in the control group. By the fifth post-exposure week, 16 of the 24 carbendazim-treated males were infertile. Of these 16 males, 4 recovered fertility after a failure to produce a pregnant female for 5-11 consecutive breeding periods. However, 12 of the males did not recover fertility during the remainder of the 32-wk post-exposure period. Histological examinations of testicular sections 245 days post exposure revealed that exposure to carbendazim caused severe seminiferous tubular atrophy (greater than 85% of tubules were atrophic) in those carbendazim-treated males that failed to recover fertility.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pathogenicity of a nuclear polyhedrosis virus of the almond moth, Cadra cautella

Tests were conducted with neonate Cadra cautella larvae to determine the pathogenicity of a nuclear polyhedrosis virus. A bioassay on an agar base diet showed that concentrations of 0.25, 0.50, 2.00, and 4.00 polyhedra/mm² killed 27, 55, 87, and 92% of the test larvae, respectively. A study of the time of death showed that most larvae died on the 9th or 10th day after exposure to 4 polyhedra/mm² at 27°C. When larvae were exposed to 8, 16, 32, and 64 × 10³ polyhedra/g of bran diet, recorded mortalities were 18, 22, 48, and 80%, respectively. All the samples of virus in bran diet which were incubated at various temperatures for 7, 14, and 28 days remained stable at all test conditions except the sample incubated at 42°C for 14 days, and those held at 37° and 42° for 28 days. Larvae of C. cautella, Plodia interpunctella, Ephestia elutella, and Paramyelois transitella placed on a diet with 40 × 10³ polyhedra/g had mortalities of 75, 59, 16, and 4%, respectively. Light and electron microscopical examination of P. interpunctella cadavers showed that they were infected with a multiply occluded nuclear polyhedrosis virus.     

Pathogenic Potential of Tylenchorhynchus dubius on Selected Turfgrass

Tylenchorhynchus dubius was observed to feed on ''Toronto'' creeping bentgrass and ''Merion'' Kentucky bluegrass, and was a key participant in reducing the vegetative growth of both grass species. The severity of foliar and root macrosymptoms incited by T. dubius to ''Toronto'' bentgrass was greater on plants grown at 16 C than on plants maintained at 21, 27 and 32 C. These parasitized plants exhibited a suppression of secondary stolon formation, shortened internodes and premature inflorescence initiation. Initial inoculum densities of 500 and 1000 nematodes/test pot produced similar pathogenic effects on the host. Feeding was primarily on root hairs and epidermal cells immediately behind the meristematic region. No necrotic lesions or other diagnostic symptoms were visible at the feeding sites. Nematodes were not observed inside the roots.     

Production of sexual morphs by apterous virginoparae of Myzus persicae (Hemiptera: Aphididae) in relation to pre- and postnatal exposure to short day conditions

The production of males and females by apterae of a holocyclic clone of Myzus persicae (Sulzer) was studied in the laboratory by transferring apterous virginoparae from long day to short day conditions at different stages of their pre- and post-natal development. Prenatal exposure was also examined in nine additional clones coming from different regions of Greece. By increasing the number of short day cycles at 17 degrees C, the aphids switched to male production earlier and produced more males. The highest mean number of male progeny was observed in apterae that were transferred to short day conditions 13-14 days prenatally. Apterae that were transferred to short day conditions after the fourth nymphal instar produced only females. Apterous virginoparae were produced by aphids that were transferred to short day conditions 0-1 days prenatally or postnatally. Aphids, given short days prenatally or in the first instar, produced alate female progeny that were all gynoparae. The later the instar aphids were transferred to short day conditions the fewer the gynoparae produced among their female progeny. A reduction in the total number of progeny and embryos per ovariole was observed as aphids were transferred to short day conditions in earlier stages of their development. The increase in male production, which follows the increase in the duration of long night exposure, was also observed in the additional eight out of nine examined clones.     

Diapause termination in two species of damselflies

Larvae of two species of damselflies, Enallagma hageni and E. aspersum, were collected in southwestern North Carolina and subjected to different combinations of daylength (SD, 11 hr day; LD, 14 hr day) and temperature to determine the factor critical in the termination of diapause. Diapausing larvae were collected in September, and 15 comparable groups of each species were given pretreatments (SD, 10°C; LD, 10°C; or SD, 21°C) for 2, 4, or 8 weeks and then transferred to SD, 21°C or LD, 21°C until emergence. Control groups were maintained under both photoperiods at 21°C.Response times (days from collection to emergence) for both species showed that rapid development required transfer to LD, 21°C regardless of the type of pretreatment or length of exposure. Larvae transferred to LD, 21°C after exposure to any of the three types of pretreatment for equal lengths of time developed at similar rates. Pretreatments at 10°C, which were equally effective with SD or LD, stimulated subsequent rapid development at LD, 21°C to a greater extent than continuous exposure to LD, 21°C conditions, and the longer the exposure to 10°C, the faster the subsequent response. Pretreatments at SD, 21°C also resulted in rapid development, similar to that of larvae exposed to 10°C, upon transfer to LD, 21°C conditions. Long daylengths administered only during pretreatments did not effect rapid development, since all larvae responded slowly when transferred to SD, 21°C. Diapause termination, therefore, was effected by LD, 21°C conditions preceded by exposure to either low temperatures, during which the photoperiod was not important, or short daylengths at 21°C.     

Effect of Temperature on Susceptibility of the Primary Leaves ofPhaseolus vulgaris L. to Red Clover Mottle Virus

Red clover mottle virus isolated in Czechoslovakia was studied in relation to its reaction to varying temperature on primary French bean leaves (Phaseolus vulgaris L.) on which it forms local necrotic lesions. The plants were kept 24 or 48 h before, or 24 or 48 h after inoculation at the temperatures 23, 25, 27, 30, 33 and 36°C. After such exposures the French beans were kept at a constant temperature of 25°C. The lesions were counted at various intervals. In the experiment the optimal temperature for the maximum number of lesions seems to be 36°C 48 h before inoculation. The temperature above 25°C applied 24 h after inoculation seems to have a decreasing effect upon the number of lesions formed by RCMV on primary leaves of French beans and the lesions appeared several hours later, especially at 30, 33 and 36°C. The temperatures 27, 30 and 33°C applied 48 h after inoculation have a further decreasing effect on the number of lesions. The temperature of 36°C applied 48 h after inoculation has an inactivating effect upon RCMV inoculated on French bean leaves and no lesions appeared 5 days after inoculation.     

Sperm precedence in the dragonfly Erythemis simplicicollis

Females of the dragonfly Erythemis simplicicollis (Say) (Odonata, Libellulidae) store enough sperm to fertilize 6–13 clutches of eggs laid on consecutive days. Nonetheless, they usually mate one or more times per day. Males wait for females at ponds containing surface vegetation on which the females lay eggs. Some males defend vegetation while other act as satellites. After mating, both types of males attempt to guard females against takeover by other males. Sperm precedence by male E. simplicicollis was studied using sterility produced by gamma irradiation to label sperm. After a dose-response analysis, males receiving a dose of 25 kiloroentgens (>99.9% sterile) were returned to their home pond as territory residents and satellites. Both types of males fertilized an average of 99.5% (range 97.3–100%) of the female's remaining clutch. After mating with a sterile male, females were isolated in a large cage, and eggs collected for several consecutive days. These clutches revealed that sperm mixing in the bursa of the females is essentially complete after 24 to 48 h and that the last male to mate had replaced an average of more than 57–75% of the sperm stored by female from previous matings. Thus, the last sperm in is the first sperm out fertilizing essentially all of the eggs laid soon (5–6 min) after the mating. Sperm from the most recent mating competes for fertilizations with sperm stored from previous matings only if the female oviposits on the following day without remating.