Carbon allocation and partitioning in Vigna radiata (L.) Wilczek as affected by additional carbon gain

Carbon allocation to the source leaf, export and partitioning to the sink were studied in mungbean supplied by additional carbon from the source leaves subjected to high CO2 concentrations (600 and 900 cm3 m-3) in three metabolic and functional source-sink combinations. The plants were pruned to a source-path-sink system. With CO2 enrichment there was an appreciable increase in net photosynthetic CO2 uptake in earlier formed and physiologically younger leaves. Most of the carbon fixed as a result of enrichment was translocated out of the source leaf within one diurnal cycle. The carbon remaining in the source leaf was unchanged. Partitioning of extra carbon into starch or sugar depended upon the amount of extra carbon synthesized. The unloading of the extra carbon into sinks depended on whether it was used for growth or stored. Under increased carbon content, the leaf as a sink was able to reorganize its metabolic reactions more rapidly to maintain the required gradient for unloading than the pod acting as the sink.     

Genetic variability,character association and divergence studies in <Emphasis Type="Italic">Jatropha curcas</Emphasis> for improvement in oil yield

Key message

Variability in traits of 15, diverse 6-year-old candidate plus trees of Jatropha curcas was determined to identify the best gain heritable traits correlating with oil yield for Jatropha improvement.

Abstract

Study was carried out on 15 6-year-old candidate plus trees of Jatropha curcas adapted on semi-arid wasteland with an objective to assess variation in morphological, physiological and oil quality characters. Heritable and non-heritable components of the total variability of the characters were determined by genotypic (GCV) and phenotypic (PCV) co-efficient of variation, heritability and genetic advance (GA) and the best gain traits for Jatropha improvement through selection and breeding were assessed. Further, association among the traits were assessed and germplasm were separated into different clusters. Significant variation was found among the different genotypes for all the characters. The photosynthetic and transpiration rate correlated with oil content, seed and oil yield. The chlorophyll pigments correlated positively with the photosynthetic rate and oil content. The seed oil content varied considerably from 27.68 % (JCN01) to 37.49 % (JCN14) and had high heritability, but it had low PCV and GCV and moderate GA. The oil yield plant^?1 had high genetic variability and varied significantly from 0.07 (JCN15) to 0.47 kg plant^?1 (JCN09/IC 565733). Though the different fatty acids differed significantly with different germplasm and also had high heritability, they had low PCV, GCV and GA. Seed weight, fruit weight, seed weight fruit^?1 and seed yield plant^?1 strongly correlated with oil yield and had moderate to high GCV, PCV, coupled with high heritability and GA. Germplasm were separated into four distinct clusters with a maximum inter distance found between cluster II and IV, and minimum between cluster I and III. The study helped to identify the superior germplasm among diverse genotypes of J. curcas that can serve as parents with desirable characters like high oil yield, low stomatal conductance and high water use efficiency for further breeding purposes.

     

Marker-assisted introgression of the major bacterial blight resistance gene, <Emphasis Type="Italic">Xa21</Emphasis> and blast resistance gene, <Emphasis Type="Italic">Pi54</Emphasis> into RPHR-1005, the restorer line of the popular rice hybrid,DRRH3

The elite Indian rice hybrid, DRRH3 is highly susceptible to two major diseases, bacterial blight (BB) and blast, which limit its productivity significantly. In the present study, we have introgressed two major genes, viz., Xa21 and Pi54 conferring resistance against BB and blast, respectively into RPHR-1005, the male parent of DRRH3 through marker-assisted backcross breeding (MABB) and analyzed the backcross derived plants for their resistance against BB and blast. RPBio Patho-2 was used as a donor for both the resistance genes. Gene-specific markers were used for the foreground selection of Xa21 and Pi54 at each stage of backcrossing and markers specific for the major fertility restorer genes, Rf3 and Rf4 were used only at BC₁F₁ generation for foreground selection. Background selection was done using 62 polymorphic SSR markers and marker-assisted backcrossing was continued till BC₃ generation. At BC₃F₄, through intensive phenotype-based selections 15 promising lines (ABLs) possessing high level of resistance against BB and blast, high yield, fine-grain type, complete fertility restoration along with better panicle exsertion and taller plant type as compared to RPHR-1005 were identified and test crossed with APMS 6 A, the female parent of DRRH3. The newly derived hybrids (i.e. improved versions of DRRH3) were observed to possess high level of resistance against BB and blast along with medium-slender grain type and yield level better than or equivalent to that of DRRH3. Our study exemplifies the utility of MABB for targeted improvement of multiple traits in hybrid rice.     

Dosimetric characteristics of a MOSFET dosimeter for clinical electron beams

The fundamental dosimetric characteristics of commercially available metal oxide semiconductor field effect transistor (MOSFET) detectors were studied for clinical electron beam irradiations. MOSFET showed excellent linearity against doses measured using an ion chamber in the dose range of 20–630 cGy. MOSFET reproducibility is better at high doses compared to low doses. The output factors measured with the MOSFET were within ±3% when compared with those measured with a parallel plate chamber. From 4 to 12 MeV, MOSFETs showed a large angular dependence in the tilt directions and less in the axial directions. MOSFETs do not show any dose-rate dependence between 100 and 600 MU/min. However, MOSFETs have shown under-response when the dose per pulse of the beam is decreased. No measurable effect in MOSFET response was observed in the temperature range of 23–40 °C. The energy dependence of a MOSFET dosimeter was within ±3.0% for 6–18 MeV electron beams and 5.5% for 4 MeV ones. This study shows that MOSFET detectors are suitable for dosimetry of electron beams in the energy range of 4–18 MeV.     

The impact of naturally occurring entomopathogenic nematodes on false codling moth,Thaumatotibia leucotreta (Lepidoptera: Tortricidae), in citrus orchards

The impact of naturally occurring entomopathogenic nematodes (EPNs) on Thaumatotibia leucotreta was studied in a citrus orchard in Nelspruit, South Africa. Fruit infestation by T. leucotreta was 58.6% lower (P < 0.05) in an orchard block where EPN was conserved compared to a block where EPN was suppressed by nematicide (cadusafos) application.