Mycoherbicidal potential of Alternaria alternata for management of Chenopodium album under field condition

A field experiment was conducted to evaluate the mycoherbicidal potential of Alternaria alternata to control Chenopodium album L., a problematic weed of wheat. Two wheat cultivars viz. Inqalab 91 and Punjab 96 were co-cultivated with C. album in 1:1 crop-weed ratio. Mycoherbicidal formulation was prepared in 20% canola oil emulsion with 107 conidia mL-1 of A. alternata. The mycoherbicidal formulation was sprayed at 2 - 3 and then at 4 - 5 leaf stage of the weed. Application of mycoherbicide significantly reduced the biomass of the target weed species up to 90%. Mycoherbicidal application significantly enhanced number of fertile tillers and 100 grains weight in both wheat cultivars. As a result of mycoherbicidal application, root and shoot biomass was significantly increased in cv. Inqalab 91 but not in cv. Punjab 96. The present study concludes that application of A. alternata in 20% canola oil can reduced growth of C. album resulting in enhanced growth and yield of wheat.Key words: Alternaria alternata, canola oil emulsion, Chenopodium album, mycoherbicide

Assessment of genetic diversity among different indigenous Xanthomonas isolates via RAPD and ISSR

The genetic diversity among seven Xanthomonas isolates representing four species was assessed using RAPD and ISSR PCR-based techniques. Both techniques revealed high degrees of polymorphisms among the studied isolates. A cluster dendrogram based on the combined data of RAPD and ISSR showed that genetic diversity exists in local isolates of Xanthomonas. In terms of percentage similarity values, the genomic variation was found to be in the range of 29.29% - 100% among the isolates. X. campestris (Mangifera indica) remained unclustered in cluster dendrogram and revealed a unique genomic profile compared to other isolates used in this study

Antifungal Activity of Allelopathic Plant Extracts III. Growth response of some pathogenic fungi to aqueous extract of Parthenium hysterophorus

The present investigations were designed to evaluate the potential of aqueous extracts of allelopathic weed, Parthenium hysterophorus, against three pathogenic fungi viz., Drechslera tetramera, Aspergillus niger and Phoma glomerata. The test fungal species were grown in 100 ml liquid malt extract medium containing 20 ml of each of 0, 10, 20, 30, 50, 60 and 70 % w/v shoot extract of Parthenium hysterophorus. Fungal growth was monitored periodically after 5, 10 and 15 days of incubation. A highly contrasting response was exhibited by the test pathogens to employed extract treatments. The lower concentrations of 10, 20 and 30% extract exhibited antifungal activity resulting in a pronounced decrease in fungal biomass production. The response to extract was species-specific. Drechslera tetramera was the most susceptible while Phoma glomerata was found to be least susceptible to the applied aqueous extracts. The higher concentrations of 50, 60 and 70 % extract markedly enhanced the fungal biomass production at all the harvest intervals.&nbsp

Endogonaceous spore flora of Pakistan. IX. Frequency of occurrence of VAM fungi in wheat fields around Punjab University Campus area

For the screening of Endogonaceous spore types the rhizosphere soil was sampled randomly from three adjacent wheat fields around new University campus. Spore extraction was done following wet sieving and decanting technique and direct soil paste method. Decaying root pieces and sheathing leaf bases on decaying wheat stumps were also studied after staining. A total of forty spore types were recorded from soil samples and decaying plant debris. Species of Glomus predominated the samples. There were twenty-eight species of Glomus recorded in the soil samples. One Glomus species i.e., Glomus monosporum formed sporocarps in the decaying sheathing leaf bases of left over wheat stumps after the crop was harvested. Four species of Acaulospora, three species of Sclerocystis, two species each of Gigaspora and Scutellospora were recorded. Among highly abundant species were Glomus fasciculatum, G. mosseae, G. constrictum, G. aggregatum, and G. microaggregatum.&nbsp

Effect of leaf rust infection on mycorrhizal colonization of weeds

Abstract The present study reports the effect of leaf rusts Puccinia punctiformis (Str.) Röhl., Melampsora euphorbiae (Schub.) Cast. and Uromyces rumicis (Schum.) Winter, on arbuscular mycorrhizal (AM) colonization of host weeds namely Cirsium arvense (L.) Scop., Euphorbia helioscopia L. and Rumex dentatus L., respectively. Healthy, moderately infected and severely infected plants of these test species were collected at flowering stage. Mycelial colonization was recorded in terms of percentage on the bases of presence and absence of these structures. Arbuscular and vesicular colonization were quantified by counting these structures per centimeter of root length on an average. Mycelial colonization was not significantly affected by disease in any of the three test species. There was very heavy colonization ranging from 90-100% in different healthy and diseased root samples. Response of arbuscular colonization to rust infection was variable with respect to host species. In both C. arvense and E. helioscopia effect of moderate rust infection was insignificant. Heavy disease infection significantly suppressed the number of arbuscules in C. ravens and increased in E. helioscopia. Conversely, in R. dentatus moderate rust infection significantly enhanced the number of arbuscules while heavy infection completely arrested the formation of these structures. Vesicular colonization was significantly enhanced by heavy infection in C. arvense while in E. helioscopia both moderate and heavy infections significantly reduced the number of arbuscules. In R. dentatus vesicular colonization was entirely lacking

In vitro biological control of Fusarium solani – cause of wilt in Dalbergia sissoo Roxb.

Five species of Trichoderma viz. Trichoderma viride Pers. Ex Gray, T. harzianum Rifai, T. koningii Oudem, T. aureoviride Rifai and T. pseudokoningii Rifai, and three species of Aspergillus viz. Aspergillus fumigatus Fresenius, A. glaucus Link and A. oryzae (Ahlb.) Cohn were evaluated for their in vitro antagonistic potential against Fusarium solani (Mart.) Sacc., the cause of wilt disease in Shisham (Dalbergia sissoo Roxb.). Among the Trichoderma species T. harzianum showed the best performance followed by T. viride, T. aureoviride, T. koningii and T. pseudokoningii, respectively, resulting in 52.4, 24,13.7, 9 and 2% reduction in colony growth of the test pathogenic fungus. Similarly there was 23, 20 and 7.5% reduction in colony growth of F. solani due to antagonistic effects of A. fumigatus, A. glaucus and A. oryzae, respectively

Isolation of Mesophyll Protoplasts from Leaves of Dalbergia sissoo Roxb

Dalbergia sissoo is an important timber tree facing mysterious die back and wilting problem. In case of die back, Dalbergia is facing the threat of destruction in its natural habitats due to lack of potential pathogenicity test which is the major bottleneck in pathogen assessment and tree improvement programmes. Isolation of protoplasts was attempted to produce an effective source for the pathogenicity test. This study described a procedure for the rapid isolation, in high yield, of photosynthetically active mesophyll protoplasts from young leaves of D. sissoo. The present study reports the isolation of protoplasts from leaf mesophyll of D. sissoo. Leaf strips were suspended in the enzyme solution for the isolation of protoplast. Different concentrations of enzymes were used to optimize the suitable combination for the protoplast isolation. Enzyme solution turned green after a gentle swirling motion, which indicates the release of protoplasts. Release of protoplast was checked in the solution under the microscope. A combination of filtration, centrifugation and washing was used to purify the protoplasts. The optimum combination of enzymes for protoplast isolation was 1.5% cellulase R-10+ 0.5 % pectinase R-1 after incubation for 6 hr at 28\ub0 C. The isolated protoplasts were round and filled with chloroplasts. The size of protoplasts was 20~35 \ub5m. The protoplast yield was 2 7 105 per g of leaf tissue. The protoplast viability as assessed by 0.01% Phenosaphranine staining was 77%

Tree dieback in Punjab, Pakistan

Survey of 10 districts of Punjab viz. Sialkot, Gujranwala, Lahore, Faisalabad, Sheikhupura, Gujrat, Jehlem, Rawalpindi, Sargodha, and Hafizabad were undertaken from March 2003 to March 2004 to study the present status of tree dieback incidence in these areas. A total of 21 tree species were found victim of the dieback disease. The disease incidence, however, varied in different tree species. Furthermore, there was also difference in disease severity in different surveyed districts of the province. Dalbergia sissoo Roxb. and Acacia nilotica (Lam) Willd. ex Delile., were found to be the most affected species in all the districts. Among the commonly grown trees Mangifera indica L., Eucalyptus citriodora Hook., E. camal-dulensis Dehnh., Populus hybrida M. Bieb., Ficus religiosa L., F. bengalensis L., Bombax ceiba L., Syzygium cumini (L.) Skeels., Psidum guajava L., and Albizia lebbeck Benth. were found affected with dieback. The less commonly cultivated species like Toona ciliata (Roxb.) M. Roemer, Heterophragma adenophyllum Seem. ex Benth. & Hook., Ficus glomerata Roxb., Mimosup elengi, Terminalia arjuna Wight & Arn., Grevillea robusta Cunn., Ehretia acuminata R. Br., Platanus  orientalis L. and Barringtonia acutangula (L.) Gaertn. were also found victims of the dieback.  Termites and fungi were found to be the most common biotic factors responsible for the disease. Among the abiotic factors generally drought and environmental pollution seemed to be the main causes for dieback initiation and severity

Role of VAM in alleviating allelopathic stress of Parthenium hysterophorus on maize (Zea mays L.)

Experiments were conducted to evaluate the impact of allelopathic potential of Parthenium hysterophorus on germination, growth and yield of maize (Zea mays L.) as well as the role of Vesicular Arbuscular Mycorrhizae (VAM) in alleviating allelopathic stress. In the first experiment germination and seedling growth response of maize to 5, 10, 15, 25 and 50 % w/v aqueous extract of P. hysterophorus was studied in petri dishes. Higher concentrations of 25 and 50% aqueous extract of Parthenium significantly reduced the germination of maize grains. Root and shoot growths of seedlings were also similarly affected. In the other experiment, shoot material of P. hysterophorus was cut into very small pieces and mixed in the heat sterilized pot soil @ 0, 5 and 10 % w/w, half the pots were inoculated with VAM. The results regarding the various vegetative and reproductive growth parameters revealed that the maize crop was not susceptible to applied rates of P. hysterophorus Mulch, the maize growth was considerably enhanced in 5 % treatment while in 10 % mulch treatment crop growth was as good as in control while plants inoculated with VAM showed markedly enhanced the crop growth both in control as well as Parthenium mixed treatments. Mycorrhizal colonization was markedly suppressed by mixing shoot material of P. hysterophorus at vegetative growth stage especially in 10 % treatment.&nbsp

Dieback Resistance Potential in Different Varieties of Shisham (Dalbergia sissoo Roxb.)

Nine phenotypically different varieties of Shisham (Dalbergia sissoo Roxb.) were identified from Punjab University, Quaid-e-Azam Lahore, Pakistan and adjacent areas, on the basis of physical appearance of the plant, branching pattern, pod characters, leaf and leaflet size and shape, branching and leaf density and stem surface characteristics. On the basis of their relative resistance to dieback disease, the different varieties were named as Resistant 1, Susceptible 1‑4, Unspecified 1‑4. The Resistant 1 variety is characterized with dense, and long branches, which grow outward and downward forming a canopy. Generally plants do not attain much height. Leaves are large up to 16 cm in length, with four or five leaflets per leaf. Leaflets broad, globose or subglobose, young leaflets glaucous, mature leaflets glabrous, leaflet apex apiculate. Pods small, generally one rarely two seeded. Susceptible 1 and Susceptible 2 varieties were found to be highly susceptible to dieback showing 20% or more dieback incidence. These two varieties have been commonly cultivated in Punjab. Susceptible 3 and Susceptible 4 varieties were least susceptible showing dieback incidence not more than 2 %. The unspecified varieties 1 – 4 were named so because they did not show any disease symptoms but number of plants of these varieties was not large enough to decide their resistant potential. Shisham forestation can be revived by planting Resistant 1 and less susceptible varieties viz., Susceptible 3 and Susceptible 4 on suitable, well-drained sandy loam soils