Muhammad Atiq

Relationship of Collembola population with different abiotic factors in an agricultural ecosystem of Faisalabad, Punjab, Pakistan.

Soil is one of the most essential and diverse natural habitat of biodiversity on earth. Soil fauna constitute 23% of the total diversity of living organisms (Decaens et al., 2006). Among these soil fauna, Collembola is reported to dominate in most kinds of soils (Brahmam et al., 2010; Zhu et al., 2010; Abbas, 2012). Their high abundance makes them significant contributors to several processes of soil, such as material and energy cycles, and formation of soil (Vu and Nguyen, 2000). Collembola are also particularly sensitive to environmental changes, and therefore thought to be an excellent bioindicator (Hopkin, 1997; Jucevica and Melecis, 2006; Xu et al., 2009). Environmental changes such as variation in the soil moisture, precipitation, drought, global warming, soil pH and soil temperature are likely to cause changes in the density, diversity, survival, behaviour, activity and reproduction of Collembola (Loring, 1981; Bauer and Christian, 1993; Wolters, 1998; Pflug and Wolters, 1998; Choi et al., 2002, Ke et al., 2004). Several studies indicated the effects of abiotic factors on the abundance, distribution and activity of Collembola in sitespecific ecosystems. Many of these studies included effects of combinations of edaphic and meteorological factors such as soil moisture (Choi et al., 2002; Choi et al., 2006; Schultz et al., 2006; Abbas and Parwez, 2012), soil temperature (Frampton et al., 2001; Karoline et al., 2010; Kardol et al., 2011; Begum et al., 2011), soil organic matter (Mussury et al., 2002; Muturi et al., 2009; Karoline et al., 2010), relative humidity (Loring, 1981; Gope and Ray, 2012), soil pH (Ke et al., 2004; Begum et al., 2014), rainfall (Ferguson and Joly, 2002; Lensing et al., 2005), vegetation cover (Hansen, 2000; Bandyopadhyaya et al., 2002; Abbas, 2012) and crop type (Kanal, 2004) on Collembola. These studies also suggest that there is ample scope of investigation on these abiotic factors in context of Collembola to envisage the challenges of climatic changes. Variation in the abundance of Collembola in response to different abiotic factors although have been documented in grassland, pastures, forest and desert but their abundance / density and dynamics in an agricultural ecosystem have not been studied extensively. The low soil pH, high soil moisture, rainfall, high organic matter had positive influence on the abundance of Collembola in a mixture of different clovers (Trifolium angustifolium, T. strictum, T. repens, T. glomeratum and T. campestre), rice, wheat and vegetables (Sousa et al., 2004; Zhimomi et al., 2009; Muturi et al., 2009; Begum et al., 2014). The density of Collembola in a forest and agroecosystem significantly increased with soil temperature. However, soil pH had a negative impact on the Pak. J. Agri. Sci., Vol. 53(1), 201-208; 2016 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/16.4179 http://www.pakjas.com.pk

Pathogenic aspects of Pantoea agglomerans in relation to cotton boll age and Dysdercus cingulatus (Fabricius) transmitting seed and boll rot in cotton germplasm

Bacterial seed and boll rot is a newly emerging cotton disease in Pakistan. Twenty-one cotton varieties were screened to find resistance source against the disease. None of these was found to be resistant. Five cotton varieties (CIM-595, MK2, BT-986, BT-986 & SG-1) having 700–1400 Area under disease progress curve (AUDPC) units were found to be moderately resistant to the disease. SLH-317, FH-942, BT-222, BT-666, MNH-457 ranging from 1401–1700 AUDPC units were moderately susceptible while MNH-456, SLH-336, 9811, FH-942, MNH-886 susceptible to boll rot. Seven varieties (FH-114, FH-113, BT-7, BT-212, SLH-BT-4, BT-212 and FH-941) were highly susceptible to bacterial seed and boll rot indicated by 2001–2300 AUDPC units. Biochemical tests identified bacterial isolates as Pantoea agglomerans. Different inoculation techniques were assessed for bacterial pathogenicity and symptoms of boll rot were only observed in needle punctured bolls. One, two and three weeks old bolls were mechanically inoculated by injecting bacterial suspension to evaluate the boll’s age impact on disease severity. Maximum severity was observed in two weeks old bolls. Red cotton bugs (Dysdercus cingulatus) were fed on artificially inoculated diseased bolls and then transferred on healthy bolls. Diseased symptoms were noticed on healthy cotton bolls. Bacterial colonies were recovered and red cotton bug was confirmed as the disease-transmitting vector.

The increasing carbon dioxide (CO2) due to global climate change strengthens the plants and inhibits pathogenic infection

Climate change is a threatening global issue that has entirely changed the crops’ growing pattern. The continuous change in climate has occurred due to dreadful human activities such as burning of fossil fuels (Batley and Edwards 2016), agricultural debris, plastic/polythene bags, and contaminated hospital syringes, surgical instruments, gloves etc. Similarly, emission of dangerous gases from factories, vehicles, and refrigerator is also polluting the environment and playing pivotal role to raise the temperature and consequently disturbing the climate (Thompson et al. 2017). Likewise, the emission of greenhouse gases (CO2, CH4 and N2O) (IPCC 2007) has also increased the CO2 concentration from 300 to 398 μmol mol . According to the Inter-government Panel on Climate Change (IPCC-2013), the increase in CO2 will ultimately enhance the air temperature from 0.3–1.7 °C during 2081–2100; whereas under high CO2 emission, the predicted rise in temperature will be 2.6–4.8 °C (Thinh et al. 2017). It is a matter of fact that the emission of dreadful gases is themajor cause among other numerous factors of climate change (Tans and Keeling 2016). Several new virulent races/ biotypes including PI-296341 of Fusarium oxysporum f. sp. niveum, Plectosphaerella cucumerina of Tomato wilt, and Pseudomonas putida of mustard rot of plant pathogens have appeared due to abrupt fluctuation in the environment. These virulent races/ biotypes under favorable growth conditions disrupt the planting density, cause huge losses in various crops, and resultantly diminish the total production and yield. However, only carbon dioxide (CO2) among these dangerous gases plays a significant role through stimulating biochemical and physiological defense in plants against diseases (Agrios 2005). Carbon dioxide is the most imperative component of photosynthesis in plants. Thus, increase in CO2 level directly enhances the rate of photosynthesis and consequently stimulates the plants vegetative growth, total biomass, leaves per plant, more photorespiration, carboxylation, and transpiration. The increase in photosynthesis is mainly due to increase in ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) activity (Makino and Mae 1999). RuBisCo, RuBPCase, or RuBPco is an enzyme that activates/initiate an imperative step of carbon fixation. Carbon fixation is a process in which plants and other photosynthetic organisms converts atmospheric carbon dioxide to energy-rich molecules such as glucose. The abundant availability of photosynthetic products (glucose as well as phosphoglyceraldehyde in C3 plants and oxaloacetate in C4 plants) also increases the rate of Kreb’s or tricarboxylic acid cycle, transcription and translation, and production of protein molecules as well as availability of more ATPs (adenosine triphosphate). The increase in photosynthesis owing to CO2 results in an increase in production and activation of phenolic compounds (chlorogenic acid, caffeic acid, and ferulic acid), manufacturing of more carbohydrates production such as glucose, sucrose, and fructose as well as alters nitrogen and carbon metabolism in plants (Garavaglia et al. 2010a, b). Glucose stimulates different signaling enzymes such as hexokinase, SnRk1, and KIN10. Similarly, different other signaling molecules, i.e., salicylic acid, jasmonic acid, ethylene, and nitric oxide, are also induced in healthy plants after the attack of pathogen. The healthier plants retard hyphal growth and sporulation due to incompatibility in host pathogen interaction (Selvaraj and Bourlaye 2012). The minimum availability of CO2 reduces the photosynthesis that causes necrosis and chlorosis. The plants become weak and vulnerable to aggressive virulent races of pathogens due to these physiological Responsible editor: Philippe Garrigues

Prediction of cotton leaf curl virus disease and its management through resistant germplasm and bio-products

Abstract Cotton leaf curl virus disease reduces the cotton yield significantly every year and is transmitted by Bemisia tabaci. The study was designed to evaluate 15 varieties/lines against the disease. Multiple regression analysis was performed based on a-biotic environmental variables (maximum air temperature, minimum air temperature, relative humidity and rainfall) to predict disease incidence and its vector (Bemisia tabaci). Two bio-products were evaluated against the whitefly population to control the disease. Out of 15 cotton varieties/lines, no one was found highly resistant against the disease. Five varieties/lines (BT BT-980, BT-457, KIRAN, BT-666 and SLH-BT-6) exhibited moderately resistant response. Maximum air temperature (34–35.5 °C), minimum temperature (25.75–26.25 °C), relative humidity (64.14–66%), rainfall (1–2 mm) and wind speed (5.50–5.75 Kmh−1) favoured the disease development. Maximum whitefly population was favoured by maximum air temperature from 34–35.5 °C, 25.8–26.2 °C minimum air temperature, 64.14–66% relative humidity, 1–2 mm from rainfall and 5.50–5.75 Kmh−1 wind speed. Datura stramonium was found more effective as compared to Aviara (Homoeopathic) but not from the positive control (Acetamiprid).

Effect of Different Inoculum Levels of Ascochyta lentis on Growth and Yield Attributes of Lentil Plant

Effect of different inoculums levels (103, 5x103, 104, 5x104 spores/ml) of A. lentis was studied on growth and yield parameters of four lines of lentil. Results showed that among these lines one (ILL-358) showed microsperma resistant, one (ILL-4605) macrosperma resistant, one (ILL-5580) microsperma susceptible and the remaining one (ILL-6002) macrosperma susceptible response over control. Plant height was the minimum in case of all the four lentil lines are at 5spores/ml. Similarly no. of leaflets, no. of pods/ plant, no. of grains/pod and 100 grain weight were reduced with increased level of spores concentration from 103 spore/ml to 5x104 spore/ml. Size and frequency of lesions/pods showed positive correlation with increasing spore concentrations.

APPRAISAL OF RESISTANT GENES AND GENE PYRAMID LINES OF RICE AGAINST INDIGENOUS PATHOTYPES OF Xanthomonas oryzae pv. oryzae IN PUNJAB, PAKISTAN

The Bacterial Leaf Blight (BLB) disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the main reasons limiting production of rice in Asia ensuing to an average of 20 to 30% and in some Asian countries, up to 50% rice yield losses .The disease, when occurs in severe condition on susceptible cultivars, causes 74 to 81% yield losses (Srinivasan and Gnanamanickam, 2005). It was reported that yield losses can be 100% in Basmati rice at tillering stage (Mannan et al., 2009). Cultural practices, chemical control or resistant varieties are optional strategies for the control of plant diseases. The chemical control of BLB is impractical in the monsoon climatic conditions of Asia (Agrawal et al., 2005). Furthermore, no effective bactericide is commercially available for disease control. Therefore, the preferred strategy for disease management is through varietal resistance (Naveed et al., 2010). The manipulation of host resistance has been shown to be the only and most reliable method to manage this disease. Globally, to date, 39 Xa genes (28 dominant and 11 recessive) conferring resistance against Xoo have been identified (Chen et al., 2011; Zhang et al., 2014). These identified genes were evaluated in different countries against their indigenous Xoo populations to deploy in local germplasm for BLB resistance. The response of 23 lines like 10 NILs and 13 pyramids was evaluated against BLB under field conditions in Vietnam. The resistance gene xa13 and Xa14 were susceptible, Xa4 and xa5 were moderately susceptible and the rest were moderately resistant to BLB. Among the pyramids, Xa4+xa5+xa13+Xa21, Xa4+Xa7+Xa21 and xa5+Xa7+xa13 had short lesion length and low diseased leaf area (Loan et al., 2006). Three gene pyramid (xa5+xa13+Xa21) in variety Sawarna was transferred to Jalmagna, a popular deep-water variety in India, which exhibited a high level of resistance against BLB (Pradhan et al., 2015). However, the durability of resistance depends upon the prevalence of pathogen races in time and space. A lot of research has been done on the evaluation of rice genotype (Khan et al., 2009), virulence reaction of local Xoo isolates (Mannan et al., 2009), molecular screening of local germplasm against a specific R gene (Abbasi et al., 2011) and evaluation of resistance genes in rice against local isolates of Xoo (Khan et al., 2012) in Pakistan. But for the development of durable resistant cultivar, it is of prime importance to screen all available resistant genes either single or in combination against all prevailing 29 pathotypes of Xoo Pak. J. Agri. Sci., Vol. 53(2), 365-370; 2016 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/16.5357 http://www.pakjas.com.pk

Exploitation of Nematicidal Potential of Paecilomyces lilacinus against Root Knot Nematode on Eggplant

ABSTRACT Root knot nematodes cause severe losses in vegetables throughout the world because its management is difficult due to its wide host range. The nematicidal potential of Paecilomyces lilacinus (Thom.) Samson was evaluated against root knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood, on eggplant (Solanum melongena L.) under greenhouse conditions. Inoculation with M. incognita and P. lilacinus was carried out individually, in combination, and sequentially. Inoculation of 1000 juveniles (J2) of M. incognita reduced plant growth. The sequential application of P. lilacinus 7 days prior to M. incognita was more effectual than sequential application of M. incognita 7 days prior to P. lilacinus. Our findings concluded that P. lilacinus has the aptitude to adjust the nematode population and may serve as an alternative to nematicide.

Prediction of citrus canker epidemics generated through different inoculation methods

Citrus canker epidemics were generated with 108 cfu/ml of Xanthomonas axonopodis pv. citri (ex Hasse) on Citrus limonia cv. China lemon, Citrus reticulate cv. kinnow, Citrus jambhiri, Citrus reticulate cv. Feutral’s early and Citrus limettioides using four inoculation techniques. Natural inoculum was also relied upon for infection. Overall, the injection infiltration method led to maximum disease generation followed by spray, pinprick and smear inoculation methods. Citrus canker incidence along with environmental data were recorded and subjected to stepwise regression analysis. Except relative humidity, the relationship of weekly air temperature (maximum and minimum), rainfall and wind speed with citrus canker disease development in all citrus cultivars was positively correlated and best explained by linear regression. Overall, two environmental variable model containing maximum and minimum air temperature fit the data well explaining 93% variability in disease development. The observed citrus canker incidence values and those predicted by the model were close in most of citrus cultivars. This two environmental variable model can be used to issue advance warning forecasts for the timely management of the citrus canker in Pakistan.