The aim of the work was to specifically differentiate S. typhimurium from other closely related Salmonella serovars by monoplex or multiplex PCR and to detect it from water and food samples. Genes targeted were invA, iroB, STM4497, STM2755, fliC, fljB and rfbJ and evaluated on 58 Salmonella standard serovars/strains including 9 S. typhimurium strains, 7 suspected Salmonella isolates and 8 other organisms as negative controls. Both invA and iroB showed a uniform amplification with all serovars of S. enterica group. STM2755 and STM4497 gene based PCR's specifically exhibited amplification in all the nine confirmed S. typhimurium strains. The rfbJ PCR produced amplification with confirmed S. typhimurium strains, in addition showed reaction with S. abony. Both STM4497, STM2755 PCR's and rfbJ could identify two of the seven biochemically suspected Salmonella isolates that were later confirmed to be S. typhimurium on the basis of sequence data. PCR for fliC genes had amplification exhibited by a large number of serovars of the S. enterica group, including S. typhimurium strains but not to S. brunei, S. newporti, S. abony and S. weltevreden. fljB was detected in all strains of S. enterica and E. coli with the exception of S. typhi. fljB and fliC were amplified in 6/7 and 5/7 presumptive Salmonella isolates. The same PCR's were converted into two multiplex formats for simultaneous identification of the Salmonella genus, S. enterica group and S. typhimurium as a species. The first multiplex set comprised on invA, iroB, STM4497, STM2755 and the IAC. The second multiplex set comprised of invA, iroB, fljB, fliC, rfbJ along with IAC. The detection limit for S. typhimurium in the two multiplex PCR sets was in the range of 350-400 cfu/PCR reaction and that of DNA around 2 pg. The multiplex PCR (format 1) was first evaluated on spiked water, chicken and mutton samples and the detection limit for S. typhimurium was in the range of 100 cfu/100 ml, \60 and \50 cfu/gm, respectively. Further evaluation of multiplex PCR (format 1) was undertaken on 50 natural samples of chicken, eggs, litter, soil etc. and the comparison done with conventional culture isolation and identification procedure. The multiplex PCR could identify the presence of Salmonellla in three samples and the same three samples also yielded Salmonella by the conventional method. Therefore, the presently described multiplex PCR can serve as an alternative to the tedious time-consuming procedure of Salmonella culture and identification in food safety laboratories.

No abstract

Larviposition by the Tachinid fly, Sturmiopsis inferens Tns. on sugarcane shoot borer larvae was studied. One adult female laid on an average 285 maggots (range 126-521). More than 90% of the maggots extruded were free of the enveloping chorion. Less than 4% were found to be unfertilized and undeveloped. The mean number of maggots laid per host was 1.21 and more than 70% were laid at the bore hole, the remaining being larviposited near the bore hole. Larviposition began on the sixth day after emergence of the female and mating, reached its peak during seventh to eleventh days and declined thereafter. Over 90% of the total number of maggots were deposited by the thirteenth day. Some maggots (9.52%) were not extruded but remained in the fly's uterus. The number of maggots laid at a bore hole varied from one to nine, but in more than 50% of the shoots only a single maggot was deposited. The flies preferred third, fourth and fifth instar larvae and shoots having only wet frass for larviposition, although larviposition did occur in shoots having second instar larvae and freshly formed pupae.

Field experiments were carried out at Coimbatore, Tamil Nadu State, India, for four consecutive years , to monitor the seasonal activity of Cotesiciflavipes Cameron (Hymenoptera: Braconidae), a larval parasitoid of gramineous borers, including the sugarcane shoot borer (Chilo infuscatellits Snellen), sugarcane internode borer (Chilo sacchariphagus indicus (Kapur) and sorghum stemborer (Chilo partellus Swinhoe) (all Lepidoptera: Crambidae). The highest levels of parasitism (0.0-17.9%) were recorded on Ch. partellus followed by Ch. sacchariphagus indicus (0.0-8.3%) and Ch. infuscatellus (0.0-1.1%). The parasitoid was collected in Ch. partellus and Ch. saccharipliagus indicus in all the four study years, whereas it was not observed in Ch. infuscatellus during 1993-94. Parasitism rates in Ch. partellus were positively correlated with minimum temperature and afternoon RH. In Ch. sacchariphagus indicus, parasitism levels showed significant negative correlation with minimum temperature. Parasitism rates in Ch. sacchariphagus indidus larvae collected during harvest from seven sugar factory areas of Tamil Nadu State were lower in 1992-93 (0.0-1.8%) and higher in 1993-94 (0.0-3.2%) than those recorded at Coimbatore in the corresponding period (December-March). Cotesia flavipes was the only larval parasitoid recorded from the borers both at Coimbatore and the seven sugar factory areas surveyed in Tamil Nadu.

The influence of constant temperatures of 27, 29, 31 and 33oC and alternating temperature of 31/33oC (18/6 h) on Sturrniopsis inferens TOWNSEND was studied during 12 successive generations. The larval and pupal periods for male parasites were 13.5 + 0.5 and 11.0 _+ 0.3 days respectively and for female 12.8 _+ 0.5 and 11.1 + 0.3 days respectively in the 1 st generation at 27 ~ C. It decreased progressively with increase in temperature. Survival of females, fertility and fecundity were adversely affected at higher temperatures. A temperature range of 27-29 ~ C appeared to be optimum for mass rearing of the parasite in the laboratory. The high~ premature mortality observed at a constant 33oC was not observed at temperatures fluctuating between 31/33oC, Presumably under field conditions, where temperature is constantly fluctuating, the flies will be able to withstand a comparatively higher temperature. TOWNSEND (Dip. : Tachinidae) is an important larval parasite of sugarcane shoot borers, Child infuscatellus SNELLEN (anon., 1971 ; KALRA & DUTTA, 1971) and C. auricilius DUDGEON (SINGH & YADAV, 1 979) in certain parts of India in recent years. The attempts made to breed it in the laboratory (DAVID et ai., 1980) and to colonize it in a new area (our unpubl, data) have given encouraging results. The success of a natural enemy in biological pest suppression depends mainly on its ability to survive in the environment. Environmental factors that influence the success of a natural enemy are weather, food, resource other than food (i. e. a particular place to live) and other organisms of the same and different species (SoLoMON, 1949). Among these factors, temperature plays a key role and affects the survival and activity of the parasite. In this laboratory study, an attempt was made to study the influence of temperature on S. inferens and to establish the optimum temperature for mass-rearing the parasite in the laboratory for field colonization. Sturmiopsis inferens MATERIALS AND METHODSA culture of S. inferens was started with puparia collected from cane fields around Coimbatore on larvae of the shoot borer, C. infuscatellus. One hundred freshly formed