Cactus Plants Research Articles

"Cactus Plant Resources and Utilization" edited by Tian Guohang and Zhao Tianbang. 2011. [book review

"Cactus Plant Resources and Utilization" edited by Tian Guohang and Zhao Tianbang. 2011. [book review

The form of sexual selection arising from male–male competition depends on the presence of females in the social environment

Sexual selection arises from social interactions, and if social environments vary so too should sexual selection. For example, male-male competition often occurs either in the presence or in the absence of females, and such changes in the social environment could affect the form and strength of sexual selection. Here we examine how the presence of a female influences selection arising from male-male competition in a leaf-footed cactus bug, Narnia femorata, which has a resource defence mating system. Males compete for territories on cacti because females lay eggs on the cactus plants. Females are not always present when this competition first occurs; however, the presence or absence of the female matters. We found that both the form and strength of selection on male traits, those traits that influenced success in intrasexual competition, depended on the social context. When a female was not present, male size and the area of the sexually dimorphic hind legs was only marginally important to winning a contest. However, males with larger overall size and leg area were more likely to win in the presence of a female. There was also positive quadratic selection on these traits when a female was present with both the largest and the smallest males winning. The implication is unexpected alternative strategies when females are present. Our results support the notion that sexual selection should be studied under all relevant social contexts.

Bacterial community structure in the rhizosphere of three cactus species from semi-arid highlands in central Mexico

The nature reserve of Tehuacan-Cuicatlan in central Mexico is known for its diversity and endemism mainly in cactus plants. Although the xerophytic flora is reasonably documented, the bacterial communities associated with these species have been largely neglected. We assessed the diversity and composition of bacterial communities in bulk (non-rhizospheric) soil and the rhizosphere of three cactus plant species: Mammillaria carnea, Opuntia pilifera and Stenocereus stellatus, approached using cultivation and molecular techniques, considering the possible effect of dry and rainy seasons. Cultivation-dependent methods were focused on putative N(2)-fixers and heterotrophic aerobic bacteria, in the two media tested the values obtained for dry season samples grouped together regardless of the sample type (rhizospheric or non-rhizospheric), these groups also included the non-rhizospheric sample for rainy season, on each medium. These CFU values were smaller and significantly different from those obtained on rhizospheric samples from rainy season. Genera composition among isolates of the rhizospheric samples was very similar for each season, the most abundant taxa being α-Proteobacteria, Actinobacteria and Firmicutes. Interestingly, the genus Ochrobactrum was highly represented among rhizospheric samples, when cultured in N-free medium. The structure of the bacterial communities was approached with molecular techniques targeting partial 16SrRNA sequences such as denaturing gradient gel electrophoresis and serial analysis of ribosomal sequence tags. Under these approaches, the most represented bacterial phyla were Actinobacteria, Proteobacteria and Acidobacteria. The first two were also highly represented when using isolation techniques.

Characterization and comparison of Serratia marcescens isolated from edible cactus and from silkworm for virulence potential and chitosan susceptibility

Representative strains of Serratia marcescens from an edible cactus plant and silkworms were characterized and a comparison based on their cellular fatty acid composition, 16S rRNA and groE gene sequence analysis as well as silkworm virulence and chitosan susceptibility was carried out. Results from this study indicate that there are no significant differences between the phenotypic and molecular characterization, virulence and chitosan susceptibility of the S. marcescens strains from the cactus plant and silkworms. Silkworms inoculated with S. marcescens from either plant or silkworm resulted in nearly 100% mortality. Chitosan solution exhibited strong antibacterial activity against S. marcescens. This activity increased with the increase of chitosan concentration and incubation time regardless of the strain source. Also, the results indicate that the plant associated S. marcescens maybe plays a possible role in the contamination of humans and animals, in particular silkworms, while chitosan showed a potential to control the contamination caused by S. marcescens.

Variability of Seed Traits in Interspecific and Intergeneric Combinations between Different Genotypes of Cactaceae

Based on aesthetic consideration of cacti plants and germination capacity of the pollen grains (more than 30%), 19 genotypes of cacti (including Aylostera narvaecensis, A. buiningiana, Rebutia kupperiana var. spiniflorum, R. donaldiana) have been used in cyclic cross-pollination pattern. Fruits and seeds obtained from 24 interspecific and intergeneric combinations were analyzed by studying their main traits. The highest weight was registered for fruit belonging to R. pseudodeminuta var. schumaniana x R. senilis (23.3 mg) and A. buiningiana x A. vallegardensis (20.4 mg). Coefficient of variability for fruit weight had large amplitude, between 12.3% (A. spinosissima x A. albiflora) and 98.4% (A. favistyla x A. archibuinigiana). The fruits belonging to A. muscula x A. vallegardensis were registered with the highest value of number of seeds/fruit (93.2). In the cross between genera, the greatest value of fruits weights mean was registered on R. senilis x A. archibuinigiana (29.2 mg) and R. cajasensis x A. muscula (23.1 mg). Peculiarities of the fruits and seeds resulted from intergeneric combinations presented closer connections than interspecific ones. The phenotypic traits of fruits and seeds did not influence the seeds germination, but germination was clearly influenced by compatibility between genitors.

The natural history of Caenorhabditis elegans

Summary In the laboratory, the nematode Caenorhabditis elegans lives on the surface of nutrient agar in Petri dishes, feeding on a lawn of the uracil auxotroph strain OP50, an Escherichia coli mutant strain. This sentence sums up the fundamentals of C. elegans ecology, as most of us know it. While over 15,000 articles on diverse biological aspects of C. elegans attest to the worm's undisputable virtues as a major model organism, its biology in the wild remains mysterious. To properly interpret and fully understand the available wealth of genetic, molecular and other biological observations made in the laboratory, it will be important to know its natural history and to place the species in its ecological and evolutionary context. With the aim of connecting the discoveries that have been made about C. elegans biology to its ‘real life', we shall discuss recent studies on the worm's natural habitat and population biology, and outline key issues in attaining a modern natural history of C. elegans.

Microtesla MRI with dynamic nuclear polarization

Magnetic resonance imaging at microtesla fields is a promising imaging method that combines the pre-polarization technique and broadband signal reception by superconducting quantum interference device (SQUID) sensors to enable in vivo MRI at microtesla-range magnetic fields similar in strength to the Earth magnetic field. Despite significant advances in recent years, the potential of microtesla MRI for biomedical imaging is limited by its insufficient signal-to-noise ratio due to a relatively low sample polarization. Dynamic nuclear polarization (DNP) is a widely used approach that allows polarization enhancement by 2–4 orders of magnitude without an increase in the polarizing field strength. In this work, the first implementation of microtesla MRI with Overhauser DNP and SQUID signal detection is described. The first measurements of carbon-13 NMR spectra at microtesla fields are also reported. The experiments were performed at the measurement field of 96μT, corresponding to Larmor frequency of 4kHz for protons and 1kHz for carbon-13. The Overhauser DNP was carried out at 3.5–5.7mT fields using rf irradiation at 120MHz. Objects for imaging included water phantoms and a cactus plant. Aqueous solutions of metabolically relevant sodium bicarbonate, pyruvate, alanine, and lactate, labeled with carbon-13, were used for NMR studies. All the samples were doped with TEMPO free radicals. The Overhauser DNP enabled nuclear polarization enhancement by factor as large as −95 for protons and as large as −200 for carbon-13, corresponding to thermal polarizations at 0.33T and 1.1T fields, respectively. These results demonstrate that SQUID-based microtesla MRI can be naturally combined with Overhauser DNP in one system, and that its signal-to-noise performance is greatly improved in this case. They also suggest that microtesla MRI can become an efficient tool for in vivo imaging of hyperpolarized carbon-13, produced by low-temperature dissolution DNP.

Effects of agave nectar versus sucrose on weight gain, adiposity, blood glucose, insulin and lipid responses in mice

Agave nectar is a liquid sweetener derived from a cactus plant and is often promoted as a low glycemic alternative to refined sugar. However, little scientific research has been conducted in animals or humans to determine its metabolic and/or health effects. The aim of this study was to explore the influence of agave nectar versus sucrose on weight gain, adiposity, fasting plasma blood glucose, insulin and lipid levels. Twelve male ICR mice (33.8 ± 1.6g), were equally divided by weight into two groups (n=6) and provided free access to one of two diets of equal energy densities differing only in a portion of the carbohydrate provided. Diets contained 20% carbohydrate (by weight of total diet) from either raw agave nectar or sucrose. After 34 days, epididymal fat pads were excised and blood was collected. Weight gain (4.3 ± 2.2 vs 8.6 ± 4.2 g), fat pad weights (0.95 ± 0.54 vs 1.75 ± 0.68 g), plasma glucose (77.8 ± 12.2 vs 111.0 ± 27.9 mg/dl) and insulin (0.61 ± 0.29 vs 1.46 ± 0.81 ng/ml) were significantly lower (p≤0.05) for agave nectar‐fed mice compared to sucrose‐fed mice, respectively. No significant differences in total cholesterol, triglycerides or HDL‐C were detected. These results suggest that in comparison to sucrose, agave nectar may have a positive influence on weight gain and glucose control. However, more research with a larger sample of animals and/or with human subjects is warranted.Sponsored by American Heart Association

First Report of Ashy stem blight caused by Macrophomina phaseolina on Aeonium canariense in Egypt

Cactus plants Aeonium canariense L. (Webb & Berthelot) showing symptoms of ashy stem blight disease, collected from some ornamental nurseries, resulted in isolation of the causal organism Macrophomina phaseolina (Tassi) Goid . The in vitro optimum temperature for fungal growth was recorded at 30 0 C. Topsin-M showed high inhibitory effect on the fungal growth in vitro. Complete growth inhibition of M. phaseolina was observed at concentration of 4ppm, while the growth of the bioagent Trichoderma harzianum inhibited completely at 10ppm. Antagonistic ability of T. harzianum against M. phaseolina increased gradually in the presence of the fungicide in growth medium to cause complete reduction in pathogenic fungal growth at 2ppm of Topsin-M. Under greenhouse conditions application of integrated treatment of T. harzianum and Topsin-M had superior effect for suppressing the disease incidence of cactus plants Aeonium canariense L . by 100% comparing with each individual treatment of either fungicide (86.67%) or the bioagent (73.33%). It could be suggested that application of biological and fungicidal integrated treatment might be used as successful control measure for ashy stem blight of cactus plants Aeonium canariense L . cactus plants Aeonium canariense L. To the best of our knowledge this is the first report for M. phaseolina caused infection to cactus A. canariense in Egypt.

Phenology and Egg Production of the Cactus Moth (Lepidoptera: Pyralidae): Comparison of Field Census Data and Life Stage Development in the Field

Natural phenology and development of the cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), was studied under field conditions in St. Marks National Wildlife Refuge, St. Marks, FL, from July 2006 to September 2007. Pads of cactus (Opuntia stricta Haw. [Cactaceae]) were visually surveyed weekly for presence of moth immature stages. Adult male C. cactorum populations were surveyed using a pheromone lure and wing style sticky traps. The field census data identified 3 generations per year which generally occurred in August to September, October to April, and May to July. Numbers of eggsticks peaked in midAugust, midOctober and midApril. High numbers of early larval immatures (1st to 3rd instars) were recorded in October 2006, May 2007 and September 2007. High numbers of late-stage larvae (4th to 5th instar) were recorded in September to October 2006, December to January 2006, June to July 2007. Peak numbers of Cactoblastis male adults occurred approximately in midOctober 2006, April to May 2007, and July to August 2007. Pupae were cryptic and difficult to sample. Development in field cages was studied by introducing cohorts of moth eggs on potted cactus plants (Opuntia ficus-indica (L.) Mill.) into the field at approximately the same times they were found to occur naturally. During the course of each generation, the potted plants were returned to the laboratory for determination of moth lifestage. Body weights and lengths also were recorded. In the field cages, 3 generations were observed and these coincided with the populations that were observed in the open field. However, the generations were more clearly defined because eggs were introduced as cohorts and most insects were recovered. Measurements of larval head capsules and body lengths show that development in the winter generation is slower than that of the summer and fall generations, although peak measurements are approximately identical in all 3 generations. Female pupae weighed 225.25 (± 4.8 SE) mg which was significantly heavier than males weighing 138.01 (± 5.5) mg. Pupal weights differed according to generation, but there was no effect on adult weight. Female adults weighed 130.3 (± 11.3) mg, compared with males, which weighed 60.81 (± 2.4) mg. Adult sex ratio was approximately 1:1. Male adults appeared to have emerged earlier than females in the fall generation.

Androgenesis in the vine cacti Selenicereus and Hylocereus (Cactaceae)

Anther culture techniques were applied to develop a methodology for producing haploid vine cactus plants. Anthers with most microspores in the middle uninucleate developmental stage from the tetraploid species Selenicereus megalanthus and the diploid species Hylocereus polyrhizus and H. undatus were cultured on basal MS medium supplemented with picloram and 6-benzyladenine (BA). H. polyrhizus and H. undatus anthers were also cultured on MS medium containing either thidiazuron (TDZ) or 2,4-dichlorophenoxyacetic acid (2,4-D). Pro-embryo development started after three days of culture. A direct androgenic embryo response was achieved in S. megalanthus with and without picloram/BA, while H. polyrhizus exhibited non-regenerative callus formation. Only a single direct androgenic embryo was obtained in H. polyrhizus (with 0.1 mg/l TDZ). H. undatus required a cold pre-treatment of 4°C for 24 h in 0.3 M D-mannitol to produce a response, but only calluses were obtained and they did not regenerate. S. megalanthus and H. polyrhizus embryos converted into plantlets after transfer to MS medium in the light. Rooted plants were acclimatized successfully, and most plants showed normal phenotypes. Flow cytometry and cytological studies revealed monoploid, haploid, dihaploid, and mixoploid plants. This study showed that androgenesis is strongly species- and culture-medium-dependent, thus revealing new perspectives in the genetics and breeding of vine cactus species. To the best of our knowledge, this is the first report on the production of monoploid, haploid and dihaploid plants in Cactaceae.

Penetrating cactus spine injury to the mediastinum of a child

Injuries from contact with cactus plants are not uncommon in the southwestern United States and other arid landscapes. Most often, accidental encounters with sharp spines and barbs result in little more than mechanical damage to the skin and soft tissues with minor pain and irritation. Although cactus spine penetration into the skin has been reported to be a stimulus for cutaneous granuloma formation, our review of the published literature did not reveal any potentially life-threatening injuries from such insults. We present a unique case of a penetrating cactus spine to the anterior mediastinum in a child which required surgical extraction.

Genetic diversity among phytoplasmas infecting Opuntia species: virtual RFLP analysis identifies new subgroups in the peanut witches'-broom phytoplasma group

Phytoplasmas were detected in cactus (Opuntia species) plants exhibiting witches'-broom disease symptoms in Yunnan Province, south-western China. Comparative and phylogenetic analyses of 16S rRNA gene sequences indicated that an overwhelming majority of the cactus-infecting phytoplasmas under study belonged to the peanut witches'-broom phytoplasma group (16SrII). Genotyping through use of computer-simulated restriction fragment length polymorphism (RFLP) analysis of 16S rRNA genes revealed a remarkable genetic diversity among these cactus-infecting phytoplasma strains. Based on calculated coefficients of RFLP pattern similarities, seven new 16SrII subgroups were recognized, bringing the total of described group 16SrII subgroups to 12 worldwide. Geographical areas differed from one another in the extent of genetic diversity among cactus-infecting phytoplasma strains. The findings have implications for relationships between ecosystem distribution and the emergence of group 16SrII subgroup diversity.

Succulent cactus plant from Mexico

Succulent cactus plant from Mexico

First Report of a Natural Infection of Opuntia sp. by a 'Candidatus Phytoplasma asteris'-Related Phytoplasma in China.

Cacti (Opuntia spp.) are perennial, evergreen, succulent plants native to arid areas of the Americas. Because of their aesthetic appearance, many cacti have been cultivated and introduced to other parts of the world as ornamentals. Cacti are susceptible to phytoplasma infections and develop witches'-broom (WB) disease. Currently, all reported cactus WB cases are associated with infections by phytoplasmas in the peanut witches'-broom group (16SrII) (1,2,4). During a phytoplasma diversity survey carried out during 2004 in Yunnan, China, we collected 29 malformed and 14 healthy-looking naturally occurring cactus plants from 14 locations representing five geographical regions. Each of the 29 malformed plants exhibited stunted growth and possessed clusters of highly proliferating cladodia, typical symptoms of cactus WB disease. Nested-PCR was carried out on the DNA samples extracted from young cladodia of these plants using phytoplasma-universal 16S rDNA primers P1A/P7A and R16F2n/R16R2 (3). Results revealed that all 29 diseased plants that were examined were infected by phytoplasmas, whereas all 14 healthy-looking plants were negative for phytoplasmas. Subsequent restriction fragment length polymorphism (RFLP) analysis of the PCR-amplified 1.25-kb 16S rDNA fragments indicated that 28 diseased plants were infected by a phytoplasma of group 16SrII, whereas one plant (from Suan Village) was infected by a 'Candidatus Phytoplasma asteris'-related (group 16SrI) phytoplasma designated as strain YN26. Nucleotide sequence analysis of the strain YN26 partial rRNA operon (GenBank Accession No. EF190970), covering a near full-length 16S rRNA gene, a 16S-23S rRNA intergenic spacer, a tRNA-Ile gene, and a partial 23S rRNA gene, suggested that this phytoplasma is most closely related to an ash witches'-broom phytoplasma (GenBank Accession No. AY566302, 99.7% identity) and an epilobium phyllody phytoplasma (GenBank Accession No. AY101386, 99.7% identity), both members of subgroup16SrI-B. This YN26-infected cactus plant was transferred to a greenhouse and maintained for more than 2 years, during which time DNA samples were extracted and tested two additional times. The same 16S rDNA RFLP pattern type was consistently obtained in these tests, confirming that the plant remained infected by the 16SrI phytoplasma. To our knowledge, this is the first report of a natural infection of a cactus species by a group 16SrI phytoplasma. Since this 16SrI-cactus WB phytoplasma was found in the same geographical location where 16SrII-cactus WB phytoplasma was detected both in this and a previous study (1), the findings raised the question whether 16SrI- and 16SrII-cactus WB phytoplasmas have overlapping geo- and bioecological niches.

Isolation of alkaline phosphatase enzyme from cactus plant Aloe Vera and study its properties

The research was concerned with isolation of alkaline phosphatase (ALP) from the aqueous extract of Aloe Vera using gel filtration technique. It was shown that, using gel filtration chromatography on Sephadex G-100, the solution of the proteinous precipitate produced by ammonium sulphate saturation, contained two proteinous peaks. The two peaks possessed a variable activity of alkaline phosphatase, where maximum specific activity was obtained in the first peak with higher molecular weight which showed (28) folds of purification. Furthermore, the comparative molecular weight of the partially purified alkaline phosphatase (first proteinous peak) using gel filtration was found to be (147353) Dalton. The research was also concerned with finding the optimum conditions of alkaline phosphatase. Maximum activity was obtained using sodium carbonate- bicarbonate buffer (100 mM) at pH ( 9.7 ), (50ºC) and (30 mM) of di-sodium phenyl phosphate as a substrate. Using linweaver-Burk plot, it was found that the Vmax and Km have the values of (185.18 enzyme unit/dl of proteinous solution) and (3.9mM) respectively. The results also predicted that the activity of alkaline phosphatase decreased gradually and reached 76% and 50% from the original value when stored at 4ºC and at room temperature (33-40ºC) respectively for 30 days.

Tamaño de Neobuxbaumia tetezo y longitud de sus espinas apicales en un gradiente de luz bajo Mimosa luisana, un arbusto nodriza

Las condiciones ambientales y los recursos bajo el dosel de un arbusto nodriza no son uniformes y afectan las tasas de crecimiento y de supervivencia de las plantas que lo usan como refugio, así como algunas características morfológicas. En el Valle de Zapotitlán Salinas, Puebla, se estudió el efecto que tiene la radiación fotosintéticamente activa (RFA) en función de su distancia al centro de Mimosa luisana sobre dos características morfométricas de Neobuxbaumia tetetzo: (1) la longitud de las espinas apicales y (2) el tamaño de los individuos. Se encontraron correlaciones significativas y positivas entre la longitud máxima de las espinas apicales y su distancia al centro del arbusto, así como entre el tamaño de N. tetetzo y la longitud de las espinas apicales. Del mismo modo, el tamaño de N. tetetzo y su distancia al centro de la nodriza guardan una correlación significativa y positiva. Un análisis de regresión múltiple mostró que el largo de las espinas apicales de N. tetetzo se vincula con el tamaño del individuo, pero no de su distancia al arbusto. Por su parte, el tamaño de N. tetetzo es una característica dependiente de su distancia a la nodriza. Se discute el hecho de que cuando N. tetetzo se establece cerca de la periferia de M. luisana existe una baja probabilidad de reclutamiento debida a la incidencia de altos niveles de radiación, los cuales también pueden afectar negativamente el crecimiento de N. tetetzo, debido a las altas temperaturas asociadas que afectan negativamente sus tasas fotosintéticas.

Molecular analysis and pathogenicity of the Cladophialophora carrionii complex, with the description of a novel species.

Cladophialophora carrionii is one of the four major etiologic agents of human chromoblastomycosis in semi-arid climates. This species was studied using sequence data of the internal transcribed spacer region of rDNA, the partial β-tubulin gene and an intron in the translation elongation factor 1-alpha gene, in addition to morphology. With all genes a clear bipartition was observed, which corresponded with minute differences in conidiophore morphology. A new species, C. yegresii, was introduced, which appeared to be, in contrast to C. carrionii, associated with living cactus plants. All strains from humans, and a few isolates from dead cactus debris, belonged to C. carrionii, for which a lectotype was designated. Artificial inoculation of cactus plants grown from seeds in the greenhouse showed that both fungi are able to persist in cactus tissue. When reaching the spines they produce cells that morphologically resemble the muriform cells known as the “invasive form” in chromoblastomycosis. The tested clinical strain of C. carrionii proved to be more virulent in cactus than the environmental strain of C. yegresii that originated from the same species of cactus, Stenocereus griseus. The muriform cell expressed in cactus spines can be regarded as the extremotolerant survival phase, and is likely to play an essential role in the natural life cycle of these organisms.

ENHANCED REGENERATIVE CAPACITY IN RHIPSALIDOPSIS AND SCHLUMBERGERA EXPLANTS BY IN VITRO MANIPULATIONS

Several plant species are recalcitrant when considering regeneration through adventitious organs. Establishment of regeneration systems for the plants of interest is a pre-requisite for further work such as genetic transformation and induced mutation. The cactus plants belonging to species Schlumbergera and Rhipsalidopsis were found to be recalcitrant. In addition to this problem, they were very slow to grow. However, it was possible to achieve high regenerative ability in explants of in vitro cultures of these cacti. The initial phylloclade explants established from adult plants grown in greenhouse were found to be recalcitrant. These explants produced only axillary shoots from the pre-formed shoot primodia when treated with exogenous plant hormones, but they failed to produce any adventitious shoots. There was a significant improvement in adventitious shoot formation in phylloclade explants, more particularly, of Rhipsalidopsis in long-term cultures. After the first subculture, sporadic adventitious shoot formation began, and after the third subculture 87% explants of one of the cultiyars of Rhipsalidopsis produced adventitious shoots. There was an increase in the regenerative capacity in the explants of Schlumbergera, however, the efficiency was not to the same extent as for the other species. Callus cultures were found to be more regenerative compared to the phylloclade explants. The results clearly indicated that the in vitro manipulations helped in increasing the capacity to regenerate.

The effect of spent mushroom sawdust compost mixes, calcium cyanamide and solarization on basal stem rot of the cactus Hylocereus trigonus caused by Fusarium oxysporum

A severe epidemic of basal stem rot of the cactus Hylocereus trigonus occurred in 2001, in greenhouses of Goyang City, South Korea, possibly due to continuous cultivation in soil beds. Fusarium oxysporum was isolated and its pathogenicity was demonstrated. Inoculation of mycelial plugs on stem disks of cactus showed brown discoloration. Inoculation of a spore suspension of F. oxysporum (1.40×10 4 or 1.24×10 8 spores ml −1) on the underground basal stems of cactus plants, followed by incubation at 28 °C in a growth chamber, led to the development of brown spots identical to the original symptoms after 3 months. The effect of amendment with spent mushroom sawdust, calcium cyanamide, straw and solarization on the development of the disease was studied. In a greenhouse study, amendment with spent mushroom sawdust compost to the disease-conducive soil reduced the disease incidence to 3–12%, as compared to 44–59% with the unamended disease-conducive soil. Autoclaved spent mushroom sawdust compost did not reduce the disease incidence. The bacterial (1.95×10 11 cfu g −1) and fungal population (9.50×10 7 cfu g −1) of spent mushroom sawdust was significantly higher than those (2.0×10 9 cfu g −1 and 0.13×10 5 g −1 for bacteria and fungi, respectively) of disease-conducive soil. Also, disease-suppressive soil had a higher fungal population (1.25×10 5 cfu g −1) compared to disease-conducive soil (0.13×10 5 cfu g −1). This trend was repeated in the second experiment. Solarization with and without calcium cyanamide of disease-conducive soil reduced effectively pathogen population and disease development, resulting in 16–53% disease incidence, as compared to 81% in the untreated control. Rice straw as an organic amendment did not have synergistic effect on disease control when it was used along with calcium cyanamide for solarization. The results indicate that the control of basal stem rot with spent mushroom sawdust compost may be due to biological activity, and that solarization with calcium cyanamide is a highly effective tool for controlling basal stem rot.