Calophyllum inophyllum: recalcitrant or intermediate seed?

We studied seed storage behaviour of a multipurpose tree Calophyllum inophyllum (Clusiaseae). Seeds were collected at Roslyn bay (23°7′60″ S, 150°43’60″ E) Central Queensland. Seed drying and desiccation tolerance tests were carried out according to International Seed Testing Association (ISTA) rules. We found C. inophyllum seeds to be recalcitrant and vulnerable to chilling injury, hence, unsuited for cold storage. C. inophyllum seeds maintained their viability for an appreciable period (> 8 months) if stored in warmer environments.     

Cold acclimation induced accumulation of phenolic compounds and freezing tolerance in Ammopiptanthus mongolicus

Ammopiptanthus mongolicus, the only freezing tolerant evergreen broad-leaved shrub, local species of the Alashan desert, northwest sand area of China, can survive -30°C or even lower temperature in winter. In the present study, the secondary products phenolics in A. mongolicus cotyledons were determined to study the effects of phenolics on cold tolerance. Cytochemical localization of phenolics in cotyledon cells was observed by electron microscopy and the content of phenolic compounds was assayed by spec-trophotometric measurement. The results showed that the freezing tolerance of A. mongolicus seedlings increased after acclimation at 2-6°C for 14 days, which accompanied the increase of the content of phenolic compounds in cotyledons. Cytochemical observation showed that phenolic deposits were mainly localized in vacuoles and in close proximity to tonoplast, and also in the cytoplasm. The amount and the size of phenolics droplets increased obviously in cytoplasm and vacuoles after cold acclimation, predominantly ag-gregated along membranes of vacuoles and tonoplast. No phenolic deposits were found in cell walls. As hydrogen-or elec-tron-donating agents, phenolics may protect plant cells against reactive oxygen species formed during chilling or freezing stress and improve the freezing tolerance of cold-acclimated A. mongolicus seedlings.     

Growth rate and shoot: Root allometry in Pseudotsuga menziesii (Mirb.) Franco and Pinus contorta Dougl. Seedlings raised under two photoperiodic regimes

Six provenances of both Pseudotsuga menziesii (Mirb.) Franco and Pinus contorta Dougl. from a range of locations in the interior of British Columbia between latitudes 49° and 58° were grown for 80 days in controlled environment chambers programmed to provide daylengths comparable with those at either latitude 48°, or latitude 58°, during the period from mid‐June to early September. Neither shoot : root ratio nor whole plant dry weight of P. menziesii were affected by photoperiod. However, P. contorta seedlings, which unlike P. menziesii set bud during the experiment, had a greater dry weight and a higher shoot:root ratio (p<0.05) under longer daylengths. The results appear relevant to the interpretation of effects of cross‐latitudinal provenance transfer on plantation productivity.     

Mountain pine beetle-associated blue-stain fungi are differentially adapted to boreal temperatures

Mountain pine beetles (MPB) are the most serious pest of lodgepole pine in Canada and are likely to invade boreal jack pine forests. MPB vector three blue-stain fungi, Grosmannia clavigera, Ophiostoma montium and Leptographium longiclavatum, which contribute to beetle success. Fungal survival at extreme boreal temperatures will contribute to their success in jack pine. Growth, sporulation and survival of the three fungi at −20 to 37°C were tested in vitro. Overwintering survival of G. clavigera and O. montium was assessed in vivo. All species grew at 5–30°C, with optimal growth at 20–25°C. Grosmannia clavigera and L. longiclavatum survived at −20°C, but O. montium died. Growth of G. clavigera and L. longiclavatum was inhibited at 30°C, but O. montium grew well. Grosmannia clavigera and O. montium overwintered in living pines. These results suggest that G. clavigera and L. longiclavatum were adapted to cold boreal winters but not hot summers, with the converse true for O. montium. Temperature tolerance varied among G. clavigera isolates. British Columbian and Californian isolates grew faster at 25°C than Albertan isolates. Isolates from Alberta and Idaho/Montana grew optimally at 20°C, while British Columbian and Californian isolates grew optimally at 25°C.     

Agronomic evaluation of Leucaena. Part 1. Adaptation to environmental challenges in multi-environment trials

A multi-environment trial was conducted to evaluate the performance of high yielding accessions from most taxa of Leucaena, for broad and specific adaptation to growth-limiting environments, and to develop an understanding of environmental parameters limiting growth of this important multipurpose tropical tree-legume genus. Eighteen sites were selected to include environments known to constrain the growth of L. leucocephala. Accessions were planted in replicated line plots, with 10 trees/plot, spaced 50 cm apart, and with rows spaced 3 m apart. Environmental parameters measured were maximum and minimum temperatures, rainfall and psyllid pressure. Soil fertility and acidity indices were derived from soil analyses. A KX2 F1 hybrid accession proved broadly adapted with high yield rankings in all environments, and with yield advantage greatest at low temperature and high psyllid pressure sites. Specific adaptation to low temperature environments was identified in L. trichandra OFI53/88, and to a lesser extent in L. pallida CQ3439. No accessions were specifically adapted to acid-infertile soils. Highest dry matter production was achieved in fertile, hot, humid, low psyllid environments. Very low growth rates were achieved in acid-infertile and low temperature environments. Yield was strongly reduced by mean monthly minimum temperatures of 22 °C, mean monthly maximum temperatures of 29 °C, psyllid pressure of >2.5 (1–9 scale of increasing pressure based on damage to young leaves), acidity index of 6 (1–7 scale of decreasing acidity based on soil and Al saturation) and fertility index of 9 (1–12 scale of increasing fertility based on critical soil nutrient levels). This revised version was published online in June 2006 with corrections to the Cover Date.     

Respiration rate determinations suggest Heterobasidion parviporum subpopulations have potential to adapt to global warming

Trees are known to have adapted to local climatic conditions, but the adaptation of their pathogenic associates is poorly understood. Heterobasidion parviporum causes root and butt rot in spruce. In this work, the respiration of H. parviporum subpopulations from climatically diverse environments was examined at various temperatures. Isolates were obtained from three areas in Europe (southern Finland, Denmark and northern Italy) and from two locations in Central Siberia (Krasnoyarsk and Irkutsk). Respiration rates were measured in gas tight vials at eight temperatures from 0 to 33°C, using spruce saw dust as the sole substrate. Strains from Siberian locations with cold winters had higher activity at low temperatures (2–15°C) than strains from European locations with mild winters. Respiration rates of Siberian subpopulations increased more than those of European strains when the temperature rose from 0 to 6°C, but the increase was greater with the European subpopulations when the temperature increased further from 6 to 20°C. Only small differences were found among European as well as Siberian subpopulations. Variation in respiration rates between subpopulations was low compared to variation within subpopulations. Using strains isolated 2–18 years ago and thereafter stored at 5°C, we found lower respiration rates at 20°C in older isolates, independent of geographical origin, suggesting phenotypic plasticity of H. parviporum in regard to responses to temperature. Based on these findings, we propose that subpopulations of H. parviporum have the potential to adapt to global warming.     

Variation in spring and autumn frost tolerance among provenances of Russian larches (Larix Mill.)

Abstract

Spring and autumn frost tolerance was measured using material from a range-wide (50–67° N, 38–158° E) provenance trial of four Russian larch species (Larix sukaczewii Dyl., L. sibirica Ledeb., L. gmelinii Rupr. and L. cajanderi Mayr.) growing in northern Sweden. Shoots were collected in early May and late September and frozen at ?8, ?12, ?16 and ?20°C. Cambial damage was assessed visually after development under ideal conditions for 2 weeks. Differences in frost damage among provenances were highly significant in both spring and autumn. Autumn frost damage was significantly correlated with provenance latitude and longitude and spring frost damage was significantly correlated with provenance longitude but not latitude. Frost damage was not correlated with provenance elevation. North-western provenances showed the least damage and far-eastern provenances the greatest damage in both spring and autumn. A possible explanation for less spring frost damage to north-western provenances is adaptation to maritime conditions in proximity to the Barents Sea, which is often ice free in late winter. This would counteract early loss of frost tolerance and bud flushing if warm spells occurred in late winter. North-eastern Siberian provenances did not show similar adaptation and may exhibit increased spring frost damage if global warming eventually results in the Arctic Ocean north of Siberia becoming ice free in late winter.     

Marker trait association for autumn cold acclimation and growth rhythm in pinus sylvestris

The main objective of this study was to identify quantitative trait loci (QTLs) involved in the genetic control of growth rhythm and autumn cold acclimation in Pinus sylvestris L. Eighteen full‐sib families of P. sylvestris with parental origins between latitudes 62 and 67° N in Sweden were assessed for autumn cold acclimation (frost injury measured from artificial freeze testing) and growth rhythm during the first two growing seasons. One family north × south with 108 individuals was used for the construction of one linkage map for the male and one for the female parent using 286 markers from random amplification of polymorphic DNA. Marker trait associations (QTLs) for shoot elongation, growth cessation and cold acclimation were found on both maps. Some QTLs were verified in two additional north × south families. Proportions of the additive genetic variance explained by the markers (R ²/_G) indicated that genetic factors of large effect were involved in all investigated traits. Single or multiple markers accounted for between 16 and 47% of the additive variance in annual shoot elongation, between 42 and 79% of the additive variance in growth termination, and between 7 and 31% of the additive variation in autumn cold acclimation. The study confirms that there are major QTL regions on different linkage groups controlling a large part of the variation for growth rhythm and autumn cold acclimation in P. sylvestris.     

Longevity of <Emphasis Type="Italic">Juniperus procera</Emphasis> seed lots under different storage conditions: implications for ex situ conservation in seed banks

Juniperus procera Endl. is economically important timber species, but its populations are extremely small and fragmented in its natural habitat, thus, calling for immediate ex situ conservation. Here we examined the effects of seed sources and storage temperature on the longevity of Juniperus procera seed lots through collection and preservation of seeds in seed banks. Seeds were collected from nine sites across the species natural distribution in Ethiopia and stored in four warehouses: modern cold room (5℃), mud house (15℃), concrete block house (17℃ or corrugated iron house (20℃) for 42 months. Every three months, a random sample of stored seeds were drawn and tested for germination. A highly significant variation (p < 0.01) in germination of stored seeds was observed among different storage environments, seed lots, and duration of storage. Over the storage period, seeds stored in the cold room had the highest mean percentage germination, followed by the mud house, corrugated house and blocket house. The cold room (41%) and the mud house (38%) maintained the same level of germination as the intitial germination of the seedlotds (42%). The variation in longevity of stored seeds was significnatly correlated with the initial germination of seed lots (r > 0.80; p < 0.01). Cold storage also resulted in enhancement of germination through its stratification effect that terminated the non-deepphysiological dormancy of juniper seeds. In conclusion, seed lots with good initial germination can be effectively stored in cold room (5℃) up to four years. In the absence of modern cold stores, mud houses can be used as a good alternative to store seeds at local level.     

The effect of cold stress on endogenous hormones and CBF 1 homolog in four contrasting bamboo species

An unusually severe snow disaster in southern China in 2008 exposed variation among different species of bamboo: some species were highly tolerant to low-temperature damage, but some suffered extensive damage or death. Therefore, this study was conducted to determine the effects of cold stress on endogenous hormones and the expression of homologs of CBF ₁ in four bamboo species differing in their tolerance to cold. All four bamboo species were subjected to cold stress with a temperature gradient (10, 5, 0, −5, and −10°C), and each low temperature treatment was maintained for 48 h. Results showed that ABA, GA₁, and GA₄ were significantly affected by cold stress: ABA increased with cold stress in all species, while GA₁ and GA₄ reduced with cold stress. ABA levels and the ratio of ABA/(GA₁ + GA₄) in leaves of Neosinocalamus affinis and Bambusa rigida were both higher than those of hybrid bamboo (Bambusa pervariabilis × Dendrocalamopsis grandis) and Dendrocalamus latiflorus for all treatments, while GA₁ and GA₄ were conversely lower as compared to the hybrid variety and D. latiflorus. Moreover, CBF ₁ homolog was up-regulated during cold stress, with higher expression levels in the leaves of cold-tolerant species than cold-sensitive ones. Results revealed that high levels of ABA and CBF ₁ , as well as the ABA/GA_s balance, are important in increased plant resistance to cold stress.     

Relationship between salt tolerance and proline accumulation in Australian acacia species

 The effects of salinity on the seedlings of five acacia species, Acacia ampliceps, A. salicina, A. ligulata, A. holosericea, and A. mangium were studied with respect to mortality, growth, and proline accumulation. There was marked variation among the species in their response to salinity. A. ampliceps showed the highest level of salt tolerance among the five acacia species. In contrast, A. holosericea and A. mangium were classified as the least tolerant. The concentration which caused 100% mortality in 2-week-old seedlings during 1 week of treatment was 2.5% (w/v) and 1.5% NaCl for A. ampliceps and A. holosericea, respectively. The dry weights of whole plant of two acacia species decreased markedly under the above salt stress conditions. Proline accumulation was found in leaves and roots after NaCl treatment. The maximum level of proline accumulation in A. holosericea was about twice as great as that in A. ampliceps throughout the stress period. Thus, the level of proline accumulation was not related to the degree of salt tolerance in these acacia species, although a positive correlation between the extent of salt stress and the accumulation of proline was found. Received: July 18, 2002 / Accepted: October 10, 2002 Acknowledgments The author thanks Dr. Kiyoshi Tazaki for his technical advice on the quantitative analysis of proline and Toshiro Sumizono for use of the phytotron. He is also grateful to Dr. Kenji Shinohara for reviewing the language. This work was supported by a grant from the Science and Technology Agency of Japan to the Forestry and Forest Products Research Institute (Encouragement of Basic Biology).     

植物抗寒性的生理生态学机制研究进展

综述植物在冷驯化过程中发生的一系列生理生化变化.环境对植物抗寒性的影响主要与光诱导、温湿度以及气候的变化有关.植物表面形成冰层会引起植物的无氧呼吸,导致植物受害;光抑制诱导活性氧的产生,从而导致植物光合系统的退化,抗寒能力下降,而短日照诱导植物休眠,有利于植物抗寒.光敏色素则被认为是启动冷驯化的光受体;植物通过冷驯化增加碳水化合物的积累及病原体相关蛋白的合成,以增强对低温病原体的抵抗能力;气候的变化使植物遭受了更大的冷伤害风险.微管最初遇冷时部分的解体可以有效诱导植物抗寒性;抗氧化酶活性增强,植物体内糖、脯氨酸、多胺等内含物含量上升.植物休眠状态中的生理变化(种子的休眠、芽的休眠)与ABA敏感性的差异有关.对植物抗寒性分子机制的研究表明:COR基因的表达对于植物抗寒性和冷驯化是十分关键的;与气候梯度有关的基因梯度的分布说明寒冷地区的树种更为抗寒;多表型性状的数量性状分析,为重要的农艺性状标记辅助选择(MAS)提供基础.对植物抗寒过程中的信号转导进行研究发现,Ca2 是低温下参与调节冷驯化应答机制中信号转导途径的重要的第二信使.未来植物抗寒领域的研究热点为信号转导和基因调节,低温抗性的遗传学和遗传应用及代谢组学,气候变化对于植物抗寒的影响等方面.     

Biocontrol of decay in seasoning utility poles. I. Growth rate and colonizing ability of bluestain and decay fungi in vivo and in vitro

Seasoning (air drying) of utility poles for 6–12 months is essential before preservative treatment can be achieved. However, during seasoning, pine sapwood is often colonized by decay fungi, thereby compromising the performance and service life of the poles. This study investigated the potential of bluestain fungi to act as short‐term biocontrol agents against decay during seasoning. An important attribute for biocontrol is rapid growth, so growth rates of common bluestain (Ceratocystis coerulescens, Ophiostoma minus, Ophiostoma piceae, Ophiostoma piliferum, Sphaeropsis sapinea) and decay fungi (Heterobasidion annosum, Phlebiopsis gigantea, Stereum sanguinolentum) were compared on agar medium and pine in logs at various temperatures. On agar, the growth temperature optimum of most bluestain fungi and all the decay fungi was ～25°C, with little growth at ≤5°C or above 32.5°C. Overall, the fastest growing were S. sapinea and O. minus. In logs, the most effective colonizers were S. sapinea and O. minus with pathogenic abilities that made them well fitted to colonize the sapwood of freshly felled pine. Within these species, certain isolates produced much larger lesions in phloem and the sapwood tangential plane than all the decay fungi. Notably, there was significant variation in colonizing ability between different isolates within a species, emphasizing the need for testing a range of isolates when selecting a potential biocontrol agent.     

Short-term responses to salinity of seabuckthorn (Hippophae rhamnoides L.) seedlings in the extremely cold and saline Qinghai region of China

The investigation of the mechanisms of plant adaptation to stressor action is one of the leading directions of current biological studies. To understand the mechanism of salt tolerance of seabuckthorn (Hippophae rhamnoides L.) and identify its ability to cope with the salinity effect in the saline and extremely cold region of Qinghai, China, a test was conducted with two-year-old seedlings subjected to 0, 200, 400 and 600 mmol·L–1 NaCl solutions for 30 d. The results show that with an increase in salinity, the biomass of H. rhamnoides seedlings clearly decreased. Leaf water potential (Ψw) and relative water content (RWC) were significantly reduced under salinity, with severe water shortages appearing in leaves. At the same time, the total chlorophyll content declined markedly. When salinity increased and stress time prolonged, the net CO2 assimilation rate (A) significantly declined. Intercellular CO2 concentration (Ci) declined at first and was then followed by an increase over the stress time. We conclude that H. rhamnoides grown in the extremely cold and saline region of Qinghai has a certain resistance to salt, which can be planted at appropriate salinity levels.     

Field performance potential of a somatic interior spruce seedlot

This study defined the field performance potential for 34 genotypes that composed a somatic seedlot of interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex. Engelm.) crosses, white spruce (P. glauca (Moench) Voss) crosses, or a mixture. Each genotype was measured for morphological attributes: height, diameter, shoot dry weight, root dry weight, shoot-to-root ratio, height-to-diameter ratio at time of lifting. Each genotype was also measured for physiological attributes of cuticular transpiration (TFD_cut), osmotic potential at turgor loss point (Ψ_tlp) and freezing tolerance (index of injury at −6°C and −4°C; II_@−6 & II_@−4) during inactive and active shoot growth phases. Shoot growth potential (SGP = length of new leader elongation) and root growth potential (RGP) were conducted under four environmental regimes: nutrient-rich/well-watered, nutrient-poor/well-watered, low root temperature, and planting stress conditions. The somatic seedlot met target height, diameter and RGP standards for a plantable seedling crop in British Columbia, Canada, though genotypes differed in morphology at time of lifting. These genotypes also differed in their measured physiological attributes (TFD_cut, Ψ_tlp, II_@−6 and II_@−4) at time of lifting and during active shoot growth. Genotypic differences were also found for SGP and RGP under different testing environments. A stock quality assessment program describing elite genotypes within a seedlot can aid foresters in applying benefits of clonal forestry. Raymund S. Folk is now self employed.     

Expression of a carrot 36 kD antifreeze protein gene improves cold stress tolerance in transgenic tobacco

Antifreeze proteins （AFPs） enable organisms to survive under cold conditions, and have great potential in improving cold tolerance of cold-sensitive plants, In order to determine whether expression of the carrot 36 kD antifreeze protein gene confers improved cold-resistant properties to plant tissues, we tried to obtain transgenic tobacco plants which expressed the antifreeze protein. Cold, salt, and drought induced promoter Prd29A was cloned using PCR from Arabidopsis. Two plant expression vectors based on pBI121 were constructed with CaMV35S：AFP and Prd29A：AFP. Tobacco plantlets were transformed by Agrobacterium-medicated transformation. PCR and Southern blotting demonstrated that the carrot 36 kD afp gene was successfully integrated into the genomes of transformed plantlets. The expression of the afp gene in transgenic plants led to improved tolerance to cold stress. However, the use of the strong constitutive 35S cauliflower mosaic virus （CaMV） promoter to drive expression of afp also resulted in growth retardation under normal growing conditions. In contrast, the expression of afp driven by the stress-inducible Prd29A promoter from Arabidopsis gave rise to minimal effects on plant growth while providing an increased tolerance to cold stress condition （2℃）. The results demonstrated the prospect of using Prd29A-AFP transgenic plants in cold-stressed conditions that will in turn benefit agriculture.     

Effects of Cold Acclimation on Several Enzyme Activities in Euonymus radicans ‘Emorald & Gold’ and Its Relation to Semi-lethal Temperature

The changes in activities of superoxide dismutase (SOD), peroxidase (POD) and ATPase in the leaves of Euonymus radicans were studied when seedlings were cold-acclimated (at 4℃) for 1 week, 2 weeks, 3 weeks and then treated for 1d under low temperature stress (at-5℃).The semi-lethal temperatures of acclimated and unacclimated seedlings were also investigated.The results indicated that the activities of the three enzymes in the leaves of the seedlings treated at 4℃ for 1, 2 and 3 weeks were all higher than those of unacclimated seedings (treated at 22℃ as controls). The activities of SOD and POD increased continuously with the prolongation of the time of cold acclimation, but stepped up to summits then down to the levels of the controls. The activities of SOD culminated at the first week, and the activities of POD at the second week. When acclimated and unacclimated seedlings were both treated at -5℃ for 1d, the activities of the three enzymes in the leaves of acclimated seedlings were a little lower than those before stress, but higher than those of the controls. Moreover, the decrease rate of enzyme activities was greatly lower than that of the controls. The results showed that cold acclimation could enhance the stability of the three enzymes in the leaves of seedlings under low temperature stress; the semi-lethal temperature was -19.1℃ when the seedlings were treated at 4℃ for 3 weeks, but it was -5.4℃ when the seedlings were treated at 22℃. The decline of the semi-lethal temperature caused by the adaptive changes of enzyme activities was one of the foundations of enhancing the cold tolerance.     

Differences between provenances of pinus contort a var. latifolia in resistance to attack by gremmeniella abietina

A provenance trial of lodgepole pine (Pinus contorta var. latifolia) planted in 1969 at Matrand, Eidskog, Norway was apparently attacked by Gremmeniella abietina in 1984/85. In late autumn the damage was recorded separately on the lower and upper halves of the trees. The material ranged in latitude from 40.25°N to 56.28°N, and in altitude from 2 850 to 450 m a.s.l., highest in interior western United States and lowest in western Canada. The most heavily attacked sources were those from southern latitudes and from high elevations. The attack frequency changed gradually from south to north. In order to avoid attack by G. abietina, only well‐adapted provenances should be used.     

Chemical characteristics of woods from several Chilean native forest species and their relationship with nanomechanical cell properties

The objective of this research was to study the chemical and nanomechanical characteristics of native woods grown in southern Chile region. The species analysed were Drimys winteri, Laureliopsis philippiana, Aextoxicon puctatum, Nothofagus alpina, Nothofagus dombeyi, Laurelia sempervirens, Austrocedrus chilensis and Fitzroya cupressoides. The samples were collected from the regions of Biobío (37° S, 73° W), Araucanía (37° S, 71° W) and Los Lagos (40° S, 73° W). Chemical analysis reported that glucan content of native woods was between 39% and 44% and lignin content between 28% and 35%. The nanomechanical properties analysed in the secondary cell wall (S2 layer) and middle lamella (ML) were elastic modulus (E), hardness (H) and ductility ratio (E/H). Values for E_S2 were between 12.0 and 15.4 GPa and for E_ML between 4.3 and 6.6 GPa. Hardness values were similar in ML and S2 (≈0.3 GPa). The compilation of results showed high correlations between E_S2 and carbohydrate content (r = 0.80), between E_S2 and hemicellulose content (r = 0.89), and between H_S2 and lignin content (r = 0.88).     

Fitness of heat and desiccation tolerant hybrid strains of <Emphasis Type="Italic">Heterorhabditis</Emphasis> <Emphasis Type="Italic">bacteriophora</Emphasis> (Rhabditidomorpha: Heterorhabditidae)

Entomopathogenic nematodes of the genus Heterorhabditis are a suitable alternative to chemical insecticides because of their high control effect against insects in cryptic environments and their environmental safety. The availability of H. bacteriophora hybrid strains with increased tolerance to environmental extremes could be a driving force for a more widespread use of nematode-based plant protection products. However, increase in heat and desiccation tolerance of hybrid strains could compromise their fitness regarding virulence, host penetration and reproductive capacity. The fitness of heat and desiccation tolerant hybrid strains was compared to the commercial strain EN 01. Only the heat tolerant strains were superior or similar in fitness to strain EN 01. The strains with increased desiccation tolerance were usually less fit, a possible result of a trade-off effect of selection for desiccation tolerance. Hybrid strains selected for enhanced tolerance after an adaptation to stress were generally better in fitness ranking compared to those for which adaptation prior to stress exposure was excluded. This might be a result of pleitropy. Host penetration and virulence was not correlated. The commercial strain had the highest reproduction per mean number of nematodes penetrating the host insect, which is a result of automatic selection of inbred lines with high reproduction potential during the commercial production process in liquid culture.