The influence of vermicomposting on photosynthetic activity and productivity of maize (Zea mays L.) crop under semi-arid climate.

Food production and waste recycling are the two major issues faced globally with rapidly increasing population. Recycling organic wastes to crop amendments could be a possible solution to these issues. Earthworms transfer organic waste to compost, which is used to grow crops and increase crop productivity. This study assessed the impact of vermicompost produced from the residues of six desert plant species, i.e., (Ziziphus mauritiana, Aerva javanica, Calligonum comosum, Sacchrum benghalens, Calligonum polygonoides and Prosopis cineraria) combined with farmyard manure (5 t ha-1) on growth, yield and photosynthetic activity of maize crop. Earthworm species Eisenia fetida (Savigny, 1826) was used to prepare vermicomposting of all tested plant species. The desert species were collected from natural habitats, chopped, dried, mixed with FYM and then earthworms were released to prepare the vermicompost. The earthworms were excluded twenty days after release and resultant was considered as compost and used in the experiment. Results revealed that application of P. cineraria vermicompost resulted in the highest plant height (75.33 cm), stem diameter (22.66 mm), cob length (17.66 cm), number of grains/cob (374.67), 1000-grain weight (260.41 g) and grains yield (3.20 t/ha). Application of P. cineraria vermicompost resulted in the highest uptake of macronutrients, i.e., N (91.01%), P (22.07%), K (80.41%), micronutrients, i.e., Fe (19.07 ppm), Zn (40.05 ppm), and phenolic contents (150). Application of P. cineraria vermicompost also resulted in the highest quantum photosynthetic yield (0.42 mole C/mole of photon), chlorophyll florescence (355.18 moles of photon m-2s-1) and electron transport rate (310.18 micro mole m-2s-1). It is concluded that vermicomposting has the potential to improve growth and yield of maize crop. Particularly, application of vermicompost obtained from P. cineraria can be used to improve the growth and yield of maize crop. Nonetheless, field trials are necessary for a wide scale recommendation.

Occurrence of Leaf Spot Caused by Alternaria alternata on Eggplant (Solanum melongena) in Pakistan.

Eggplant (Solanum melongena L.) is a popular vegetable that is grown in both tropical and subtropical regions all year long. The crop is cultivated on small family farms and is a good source of income for resource-limited farmers in Pakistan. In early May 2019, leaf spots on eggplant (cv. Bemisaal) were observed in an experimental field (31°26'14.0"N 73°04'23.4"E) at the University of Agriculture, Faisalabad, Pakistan. Early symptoms were small, circular, brown, necrotic spots uniformly distributed on leaves. The spots gradually enlarged and coalesced into large, nearly circular or irregularly shaped spots that could be up to 3 cm in length. The center of the spots was light tan, surrounded by a dark brown ring, a chlorotic halo, and tended to split in the later developmental stages. Disease incidence was approximately 35% in the infected field. The causal agent of this disease was isolated consistently by plating surface sterilized (1% NaOCl) sections of symptomatic leaf tissue onto potato dextrose agar (PDA). After 6 days incubation at 25°C with a 12-h photoperiod, fungal colonies had round margins and the cottony mycelia were dark olivaceous with a mean diameter of 7.5 cm. For conidial production, the fungus was grown on potato carrot agar (PCA) and V8 agar media under a 16-h/8-h light/ dark photoperiod at 25°C. Conidiophores were septate, light to olive golden brown with a conidial scar, from which conidia were produced. Conidia were borne singly or in short chains and were obpyriform to obclavate, measured 29 ± 4.8 × 13.25 ± 2.78 µm (n=30) with zero to three longitudinal and two to six transversal septa. The morphological characters matched those of Alternaria alternata (Fr.) Keisel (Simmons et al. 2007). DNA was extracted using the DNAzol reagent (Thermo Fisher Scientific MA, USA). For molecular identification, internal transcribed spacer (ITS) region between ITS1 and ITS2, actin gene (ß-Actin), translation elongation factor (TEF-1α) gene, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene of two representative isolates (JLUAF1 and JLUAF2) were amplified with primers ITS1/ITS4 (White et al. 1990), ß-Actin 512 F/783 R, EF1-728F/-986R (Carbone et al. 1999), and gpd1/gpd2 (Berbee et al. 1999), respectively. The sequences were deposited in GenBank (accession nos. MT228734.1 and MT228735.1 for ITS; MT260151.1 and MT260152.1 for ß-Actin, MT260163.1 and MT260164.1, for TEF-1a, and MT260157.1 and MT260158.1 for GAPDH). BLASTn analysis of these sequences showed 100% identity with the sequences of A. alternata for ITS rDNA, ß-Actin, TEF-1α, and GAPDH, respectively. Based on the morphological characters and DNA sequences, the leaf spot isolates of eggplant were identified as A. alternata. To confirm the pathogenicity on eggplant, six-week old healthy potted eggplants of cv. Bemisaal were sprayed at the true leaf stage with conidial suspensions of A. alternata (106 conidia/ml; obtained from 1-week-old cultures) amended with 0.1% (vol/vol) of Tween 20 until runoff (1.5 to 2 ml per plant) using an atomizer in the greenhouse. Three plants were inoculated with each of the two isolates (JLUAF1 and JLUAF2), whereas three control plants were sprayed with sterile distilled water amended with 0.1% Tween 20. The plants were incubated at 25 ± 2°C in a greenhouse, and the experiment was conducted twice. After 10 days of inoculation, each isolate induced leaf spots which were similar to typical spots observed in the field, whereas the control plants remained symptomless. The fungus was re-isolated from symptomatic tissues. Re-isolated fungal cultures were morphologically and molecularly identical to A. alternata, thus fulfilling Koch's postulates. Previously, A. alternata has been reported to cause leaf spots on eggplant in India (Raina et al. 2018). To our knowledge, this is the first report of A. alternata causing leaf spot on eggplant in Pakistan. The disease could represent a threat for eggplant crops due to its increasing cultivation. It is important to develop disease management strategies for Alternaria alternata causing leaf spot of Eggplant in Pakistan.

Comparative analysis of resistance gene analogues encoding NBS-LRR domains in cotton.

BACKGROUND: Plant production is severely affected by biotic and abiotic stresses R-genes exhibit resistance against a range of diseases and pathogens in plants. The nucleotide binding site and leucine rich repeat (NBS-LRR) class of R-genes is the most comprehensively studied in terms of sequence evolution and genome distribution. The differential response for resistance against biotic and abiotic stress has been observed in cultivated and wild relatives of the genus Gossypium. RESULTS: Efforts have been made to address the recent evolution of NBS-LRR sequences within Gossypium hirsutum and resistance gene analogue (RGA) sequences derived from G. arboreum and G. raimondii. The % identity and phylogenetic analysis of NBS-LRR-encoded RGAs from tetraploid New World cotton and its diploid ancestors G. raimondii and G. arboreum suggest that the evolution of NBS-LRR-encoding sequences in G. hirsutum occurred by gradual accumulation of mutants that led to positive selection and a slow rate of divergence within distinct R-gene families. CONCLUSION: The allotetraploid genome of cotton, after separating from its diploid parents, experienced polyploidisation, natural and artificial selection, hybrid necrosis, duplication and recombination which became the reason to shed off and evolve new genes for its survival. These driving forces influenced the development of genomic architecture that make it susceptible to diseases and pathogens as compared to donor parents.

Effects of genetic changes to the begomovirus/betasatellite complex causing cotton leaf curl disease in South Asia post-resistance breaking.

Cotton leaf curl disease (CLCuD) has been a problem for cotton production across Pakistan and north-eastern India since the early 1990s. The appearance of the disease has been attributed to the introduction, and near monoculture of highly susceptible cotton varieties. During the intervening period the genetic make-up of the virus(es) causing the disease has changed dramatically. The most prominent of these changes has been in response to the introduction of CLCuD-resistant cotton varieties in the late 1990s, which provided a brief respite from the losses due to the disease. During the 1990s the disease was shown to be caused by multiple begomoviruses and a single, disease-specific betasatellite. Post-resistance breaking the complex encompassed only a single begomovirus, Cotton leaf curl Burewala virus (CLCuBuV), and a recombinant version of the betasatellite. Surprisingly CLCuBuV lacks an intact transcriptional-activator protein (TrAP) gene. The TrAP gene is found in all begomoviruses and encodes a product of ∼134 amino acids that is important in virus-host interactions; being a suppressor of post-transcriptional gene silencing (host defence) and a transcription factor that modulates host gene expression, including microRNA genes. Recent studies have highlighted the differences between CLCuBuV and the earlier viruses that are part of on-going efforts to define the molecular basis for resistance breaking in cotton.

Cotton leaf curl disease in resistant cotton is associated with a single begomovirus that lacks an intact transcriptional activator protein.

Cotton leaf curl disease (CLCuD) is the major limitation to cotton production across Pakistan and northwestern India. The disease first appeared in epidemic form in the 1980s and was shown to be caused by monopartite begomoviruses (seven distinct species have thus far been shown to be involved), frequently as multiple infections. Additionally, the viruses are associated with a specific satellite, the CLCuD betasatellite Cotton leaf curl Multan betasatellite (CLCuMB), which is responsible for the distinctive disease symptoms, and a satellite-like molecule (termed an alphasatellite), the function of which is unclear. During the late 1990s, cotton varieties with conventional resistance were introduced, alleviating losses to cotton production. However, during 2001 a resistance breaking strain of CLCuD (known as the "Burewala" strain) appeared which spread across most cotton producing areas of Pakistan. We have conducted an analysis of the Burewala strain and show that, contrary to the earlier (Multan) strain, it consists of a single begomovirus. The virus is associated with a recombinant betasatellite, derived from the Multan strain, but we were unable to detect the presence of an alphasatellite. Sequence comparisons show the virus to be a new recombinant species, consisting of sequences derived from two of the viruses associated with the first epidemic, for which we propose the name Cotton leaf curl Burewala virus (CLCuBuV). Surprisingly the virus lacks an intact C2 gene, encoding the transcriptional activator protein, which is invariably present in begomoviruses. The possible mechanisms for the selection of a "defective" begomovirus are discussed.

Cotton leaf curl disease in Sindh province of Pakistan is associated with recombinant begomovirus components.

Cotton leaf curl disease (CLCuD) is a devastating disease of cotton causing severe losses to cotton across the Punjab province of Pakistan and northeastern India. Although the disease has been reported as occurring sporadically in Sindh province, Pakistan, this has not caused significant losses. However, in the last few years the disease has become more significant in Sindh province. CLCuD is caused by begomoviruses in association with a disease-specific symptom determining satellite (Cotton leaf curl Multan betasaellite [CLCuMB]) and, in some cases, a non-essential alphasatellite (the function of which remains unclear). These components were cloned from six samples collected in Sindh. Analysis of the full-length sequences of six begomovirus clones showed one to be an isolate of Cotton leaf curl Kokhran virus (CLCuKV), a virus previously shown to be associated with CLCuD in the Punjab, whereas the other five clones showed less than approximately 90% nucleotide sequence identity to several known begomoviruses associated with CLCuD. We take this to indicate that these are isolates of a newly identified begomovirus, for which we propose the name Cotton leaf curl Shahdadpur virus (CLCuShV). Closer inspection of the sequence of CLCuShV showed it to have a recombinant origin. For only two of the cotton samples was the presence of an alphasatellite detected. The sequences of clones of these alphasatellites indicate them to be newly identified species. A betasatellite was shown to be present in all six plants examined and sequence analysis of seven full-length clones indicated that two types of CLCuMB are present in Sindh and both are recombinant. These results indicate that the virus complex causing CLCuD in Sindh is distinct from that in the adjacent Punjab province. Possible reasons for these differences are discussed.

The hypersensitive response induced by the V2 protein of a monopartite begomovirus is countered by the C2 protein.

A functional analysis of the V2 protein of two monopartite begomoviruses, Papaya leaf curl virus (PaLCuV) and Cotton leaf curl Kokhran virus (CLCuKoV), has been performed. Expression of the V2 gene from a Potato virus X (PVX) vector resulted in severe leaf curling followed by a hypersensitive response (HR) in Nicotiana benthamiana and N. tabacum, demonstrating that the V2 protein is a pathogenicity determinant and a target of host defence responses. Agroinfiltration of a PVX vector expressing the V2 protein resulted in cell death in the infiltrated area. Subsequently, a systemic HR developed that was associated with the long-distance spread of the virus and led to the death of the plant. V2 amino acid sequences encompassing a conserved putative protein kinase C (PKC) phosphorylation motif were shown to be essential for the elicitation of cell death. In co-inoculation experiments, the transient expression of the C2 protein of PaLCuV or Cotton leaf curl Multan virus under the control of the Cauliflower mosaic virus 35S promoter inhibited the HR induced by V2 in the agroinfiltrated area. These findings demonstrate that the V2 protein of monopartite begomoviruses is a pathogenicity determinant and induces an HR that can be suppressed by the C2 protein. The induction and suppression of HR have been demonstrated previously in bipartite begomoviruses and our results extend this to monopartite begomoviruses.