Contributing traits for nitrogen use efficiency in selected wheat genotypes and corollary between screening methodologies

ABSTRACT

Nitrogen uptake being part of nitrogen use efficiency (NUE) is largely decided by root traits. Root traits variability has hardly been explored by breeders mainly because of difficulties in scoring. The hydroponic system requiring lesser space for precise phenotyping of large numbers of genotypes independently of the growing season can be a suitable alternative. However, the effectiveness of hydroponic screening methods needs to be verified under the soil condition of the field or pot. In the present study, root traits and NUE were investigated in 19 genotypes under two conditions (hydroponic and pipe filled with soil). Both environments revealed large variability for root traits and NUE under high and low N conditions establishing the absence of any direct selection for these traits in the past. Under both sets of experimentation, NUpE was largely responsible for improved nitrogen efficiency mainly because of higher root biomass. The significant association between the two screening methods i.e. hydroponic and pot filled with soil under both low and high N condition support large scale screening for root traits under hydroponic condition.     

Peste des petits ruminants has been widely present in southern India since, if not before, the late 1980s

Because previous authorities had suggested that small ruminants were playing a part in the dissemination of rinderpest, and a rinderpest-eradication campaign was about to begin, it was necessary to make precise virus identifications from a number of small-ruminant “rinderpest” outbreaks. When this was done using a database created from passive disease reports, we found that epidemics—reportedly due to rinderpest—were in fact due to peste des petits ruminants (PPRs). Although such cases had been common in India for a number of years, earlier clinical and laboratory reports no longer should be regarded as definitive. PPR outbreaks have been frequent in recent years. Further, we suggest that PPR is not a recent invader of India.     

Clinical exercise testing in the normal Thoroughbred racehorse

To evaluate normal cardiorespiratory and metabolic responses of Thoroughbred horses to a standardised treadmill exercise test, we examined 28 horses ranging in age from 1 to 4 years. The group consisted of eight yearlings, eight 2-year-olds and twelve 3 and 4-year-olds. All horses except the yearlings were in training, and either racing or ready to race, at the time of examination. None of the horses had histories of performance problems. On the first day the horses received a full physical examination, resting electrocardiogram, upper respiratory tract endoscopy and either one or two acclimatisation runs on the treadmill. The following day they were given an exercise test on a treadmill inclined at 6 degrees (+10% slope). The test consisted of 3 min at 4 m/sec, 90 sec at 6 m/sec and 60 sec intervals at 8, 10, 11, 12 and 13 m/sec. During the last 15 sec of each step, blood samples were collected for plasma lactate determination, expired respiratory gases were obtained using an open flow mask system for measurement of oxygen uptake, and heart rate was measured using telemetry electrocardiogram. From these measurements, various derived values were calculated, which have been used by others as indices of exercise capacity. These values included: V200 (speed at HR of 200 bpm), VHRmax (speed at which horses reached maximum HR), VO2-200 (oxygen uptake at a HR of 200 bpm), VO2max (maximum oxygen uptake), VLA4 (speed at which horses reached a plasma lactate of 4 mmol/l) and HRLA4 (HR at which horses reached a plasma lactate of 4 mmol/l). The yearlings had significantly lower values than the older age groups for most of the derived values.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genes Lr48 and Lr49 for hypersensitive adult plant leaf rust resistance in wheat (Triticum aestivum L.)

The genetic bases of leaf rust resistance in wheat (Triticum aestivum L.) line CSP44, selected from the Australian cultivar Condor, and Indian cultivar VL404, were studied. The reaction patterns of CSP44 and VL404 against Indian races 12, 77, 77-1, 77-2, 77-3, 77-4, 77-5 and 108 were different from reaction patterns shown by near-isogenic lines with known adult plant resistance (APR) genes, viz. Lr12, Lr13, Lr22b and Lr34. Although the reaction patterns of CSP44 and VL404 were similar to the near-isogenic line Tc+Lr22a, tests of allelism indicated absence of Lr22a in both CSP44 and VL404. On the basis of genetic studies, their resistances in field tests against race 77-5, the most virulent race from the Indian sub-continent, were each ascribed to two genes. One of the two genes in each wheat was identified to be the non-hypersensitive APR gene Lr34. The second APR genes in CSP44 and VL404 gave hypersensitive reaction types and were recessive and dominant, respectively. The gene in CSP44 was designated Lr48and the gene in VL404, Lr49. This revised version was published online in August 2006 with corrections to the Cover Date.     

Amplification of Bovine Viral Diarrhoea Virus Introduced into an In Vitro Embryo Production System Via Oocytes from Persistently Infected Cattle

The purpose of this study was to determine whether or not embryos derived from in vitro fertilization of oocytes from persistently infected (PI) cattle would contain infectious virus. Three in vitro embryo production treatment groups were assessed: 1) oocytes and uterine tubal cells (UTC) free of bovine viral diarrhoea virus (BVDV) (negative control), 2) oocytes free of BVDV fertilized and cultured in media containing UTC obtained from PI heifers, and 3) oocytes from PI heifers fertilized and cultured in media containing UTC free of BVDV. The developmental media, UTC and embryos (individual or groups of five) were assayed for virus. Virus was not isolated from any samples in treatment group 1. As shown in previous studies, a proportion of embryo samples were positive for BVDV in treatment group 2. In treatment group 3, the virus associated with the oocytes contaminated the developmental media and infected susceptible co-culture cells used during fertilization and culture. In addition, 65% (11/17) of the degenerated ova from treatment group 3 had infectious virus associated with them. While none of the ova developed into transferable embryos, the study did confirm that use of oocytes from PI cows could lead to amplification of BVDV and cross contamination during in vitro embryo production.     

Stability analysis over seasons and locations of multilines of wheat (Triticum aestivum L.)

Summary Three multilines each of Kalyansona and PV 18 varieties of wheat were compared for their stability of yield and agronomic characters and disease resistance against the respective recurrent parents. The experiments were conducted for four years at nine locations.The multilines had more tillers and bolder seeds than the recurrent parents. There were, however, no differences for plant height, ear length and number of spikelets per spike.The genotypes x years x locations interaction was much more important than genotypes x years or genotypes x locations interaction as well as the main effects for genotypes. It is suggested that the number of test locations should be increased while decreasing the number of years.The stability parameters indicated that the multilines had a higher mean yield in the case of Kalyansona multilines whereas the yield of multilines of PV 18 was not significantly inferior to that of the recurrent parent. The regression coefficients were very close to unity except for KSML 3 (b=1.132). The deviations from regression were much larger for the multilines than for the recurrent parents.For rust resistance the multilines were superior over the varieties Kalyansona and PV 18.This is publication No. 9 of the series Studies on multilines in wheat (Triticum aestivum L.)