Dengue Fever: A Continuous Threat

Dengue fever is a vector borne disease and is caused by DEN Virus. This virus has four different serotypes. The vectors are two mosquitoes known as Aedesaegypti (the yellow fever mosquito) and Aedesalbopictus(the Asian tiger mosquito).  First case of dengue fever was reported back in 1994 in Karachi. A complete outbreak of this epidemic shook the whole nation in 2012. Uptill now, Lahore a city full of culture, witnessed about 16,580 confirmed cases and 257 deaths. About 5000 confirmed cases with 60 deaths were reported from the rest of the provinces. Under guidelines of WHO, Government has made efforts to combat this epidemic. Although the overall efforts have minimized the outbreak on controllable levels but dengue fever is a continuous threat. Since no permanent cure is available, the transmission of DEN virus is controlled indirectly. So the prime focus is to control mosquito population and decrease the possible hot spots i.e. Mosquito breeding sites in human habitations. Every year, the country witnesses monsoon season which brings vast areas full of clear standing waters providing breeding sites for mosquitoes which ultimately leads to increased number of patients suffering from dengue fever. Efforts have been made to fight against dengue including formation of dengue wards in hospitals, vector surveillance, community education, reactive vector control etc. A study has shown prevalence of four mosquito genera in Pakistan including Aedes, Culex, Armigeresand Anopheles. All of the above mentioned genera are associated with disease transmissions as they are the vectors of different viruses and parasites. It is the need of hour to do a collaborative effort stressing the community mobilization and management in war against dengue.

Genetic Basic of Various Morpho-Physiological Traits in Zea Mays L. under Heat Stress

Fifty inbreds of maize from diverse origin were screened in the growth-chamber and glass-house for seedling parameters under both normal and high temperature regimes. Six parental lines were earmarked on the basis of various agro- physiological seedling traits under high temperature stress. The parental lines were sown in the field using diallel mating design to make all possible cross combinations. The parents, F1’s and their reciprocals were sown in the field in two sets using a triplicate RCBD. Normal irrigations were applied to both sets of experiment. Normal experiment was sown on Feb. 8th, whereas stress experiment was sown on March 8th. Data pertaining to various morpho-physiological parameters were recorded at different crop growth stages and subjected to statistical analysis. Significant mean square values for all the parameters under normal and heat stress environments revealed considerable genetic variability. Scaling tests were performed to check adequacy of data for analyzing additive-dominance model. Under both temperature regeims, all traits except RCI (fully inadequate) were fully adequate to additive-dominance model. Inheritance of all agro-physiological parameters was influenced by overdominant type of genetic effects as male × female interaction was also found significant for all parameters under both temperature regimes. Significant mean square values were observed for GCA & SCA effects under optimal and stress conditions in maize. Existence of highly significant GCA and SCA effects revealed that trait inheritance was controlled by additive, dominance and over-dominance type of genetic attributes under optimal and high temperature regimes. Reciprocal effects were highly significant for DTS, OP, PH, DTM, GDDs to 50 % silking and GDDs to 50 % maturity under optimal environmental conditions, while under stress environment significant reciprocal attributes were expressed by DTS, ELA, OP, PH, GDDs to 50 % silking and GDDs to 50 % maturity, depicting that inheritance of these traits is influenced by maternal or cytoplasmic contents. Magnitude of SCA variance was higher than GCA variance for all studied traits under both temperature regimes, due to which GCA/SCA variance ratio was less than unity indicating that all parameters were controlled by non-additive (dominance & over-dominance) type of genetic effects except leaf osmotic potential, whose inheritance was influenced by partial dominance type of genetic attributes under high temperature. Inbred lines D-103, NCIL-20-4 and NCIL-10-5 were best suited early maturing inbreds under both environments. Inbred lines NCIL-10-5, D-135 and NCIL-20-4 earmarked as high yielding parents under both temperature regimes. Three F1 crosses D-103 × NCIL-30-5, NCIL-20-4 × NCIL-10-5 and NCIL-10-5 × NCIL-30-5 were tagged as best combiners for most of the physiological, grain yield and yield related parameters under both environmental conditions. Heterotic estimates were studied for all traits under normal and high temperature. Under normal and heat stress environment, cross combinations D-103 × NCIL-30-5, NCIL-20-4 × NCIL-10-5 (its reciprocal) and NCIL-20-4 × WA3748 expressed maximal HP heterosis estimates for grain yield. Pioneer hybrid P-1543 used as commercial check to estimate standard heterosis for GPE, 100-KW and grain yield per plant under both environmental conditions. Results revealed cross combinations NCIL-20-4 × NCIL-10-5, its reciprocal and NCIL-10-5 × NCIL-30-5 as best F1’s due to their high performance over commercial hybrid. Under both temperature regimes, all seedling parameters were significantly interrelated with each other except root-shoot ratio. Under optimal and heat stress growth conditions in the field, agronomic parameters showed significant correlation with grain yield except days to 50 % tasseling, days to 50 % silking, ASI and days to 50 % maturity. All physiological parameters showed significant interrelation with grain yield except GDDs to tasseling, silking, GDDs between anthesis-silking and maturity.