ABSTRACT
Maize (Zea mays L.) being the highest yielding cereal crop in the world is of significant importance for countries like India, where rapidly increasing population already out stripped the available food supplies. Maize crop possesses great genetic diversity. Maize Plant is attacked by 140 species of insects causing varying degree of damage causing an annual loss of over 1 billion in the Semi Arid Tropics (ICRISAT, 1992). Out of these, only 10 species cause serious damage from sowing till storage, of which the stemborer Chilo partellus (Swinhoe) is the major one (Hiremath et al., 1988). The larvae of C.partellus after hatching feed on soft surface of the leaves and then enter the stem through whorl of feeding on the pith of the stem. The growth of the plants becomes shunted and resulting in dead hearts when attacked by C.partellus at their initial stages. The larvae transferred from other plants enter the stem through lower nodes by making the holes. Stem borers pupate inside the stem. They make holes before pupation for the emergence of adults. Since host plant resistance is the back bone of Insect Pest Management; hence the present investigation was initiated. Present studies were designed to identify maize genotype resistance against stem borer in order to minimize pesticide use, improve natural balance, and enhance the activity of bio control agents, and to increase crop production. The investigations were carried out on the screening of Maize genotypes against Maize stem borer Chilo partellus in kharif season were conducted on the agricultural farm of the institute of Agricultural Sciences, Banaras Hindu University, Varanasi during kharif season of 2010-2011 to screen the relative resistance /susceptibility of 19 genotypes of maize to the insect pest, maize stem borer (Chilo partellus). In order to screen the relative susceptibility of different maize genotypes to maize stem borer the following genotypes were screened under field conditions. The symbols T1 to T19 have been used to represent the following cultivars of maize. HUZM 217, HUZM 185, HUZM 227, HUZM 186, AH 411, NMH 9858, HUM 152, CM 119, QPM 466, QPM 467, QPM 169, QPM 193, QPM 163, HUZQPM 240, HUZQPM 241, HUZQPM 242, HUZQPM 243, HUZQPM 246, HUZQPM 247. The maize varieties were grown in plots having 19 rows, plot size 13x2.5 m². The plant spacing between rows and plants were maintained 70 cm and 20 cm, respectively. The crop was grown as per the normal agronomic practices during the kharif season of 2010-2011. The effect of natural infestation was studied. The crop was sown on 22nd July 2010 and harvested on 10th November 2010. Entire screening was based on leaf damage, dead heart formation, no. of exit holes. No. of larvae and pupae population and mean tunnel length. Dead heart formations were higher in more susceptible genotypes than least susceptible genotypes. There were no sign of dead heart was found in cultivar HUZQPM 242, HUZQPM 246, QPM 193, CM 119, AH 411, HUM 152, NMH 9858, HUZM 185, HUZM 217. Maximum occurrences of dead heart were in cultivar HUZM 227, QPM 169. Leaf damage was measured on visual rating scale. In context of leaf injury rating mean was 2.6 to 6.6. Maximum leaf damage was reported on cultivar QPM 169.Average plant height was mean of length from root to flag leaf. Mean tunnel length was divided into three categories-Least susceptible (0-5cm), moderately susceptible (5-10cm), highly susceptible (>10 cm) and respected genotypes also have been identified.
ABSTRACT
This study aimed to evaluate the variability in the fecal egg count (FEC) and the parasitic burden of naive hair sheep after grazing in nematode infected paddocks. The research was carried out in Tabasco, Mexico, during two periods (August and December). In each period 32 lambs were grazed for one month on African star grass (Cynodon plectostachyus) contaminated with gastrointestinal parasitic nematodes. FEC, packed cell volume (PCV) and body weight (BW) were recorded. Gastrointestinal worms were recovered at necropsy. Data were analyzed with the MIXED procedure of SAS using a model of repeated measurements over time. A higher number of Haemonchus contortus worms was found in December (2814±838) than in August (1166±305). The opposite occurred with Cooperia curticei (2167±393 and 3638±441, respectively). The FEC and correlation coefficient in respect to the worm burden were higher in December (6516 ± 1599, r=0.83, respectively) than in August (4364±771, r=0.44, respectively). A high variability in resistance-susceptibility to gastrointestinal nematodes (GIN) occurred in Katahdin × Pelibuey lambs after grazing.