Impacts of coffee agroforestry management on tropical bee communities

Though it is undoubted that tropical bees are influenced by habitat composition, few studies have investigated the relative importance of both local and landscape-level habitat parameters in supporting large and diverse bee communities. The conservation of native bee communities within agroforestry landscapes is particularly urgent given the importance of pollination services within these systems. In this study, we examined tropical bee communities within a largely deforested shade coffee-growing region in Chiapas, Mexico. We used regression tree modeling to examine the response of bee functional groups to local and landscape-level habitat management. Our models revealed that the most predictive factors for bee abundance and species richness were the number of tree species, the number of tree species in flower, and the canopy cover of the local agroforestry landscape. Solitary bees were most abundant in habitats with high canopy cover, while social bees were most abundant in habitats with greater tree species richness. Cavity-nesting and wood-nesting bee abundance was positively affected by the amount of canopy cover in the farm, while ground-nesting bees were most abundant in habitats with a large number of tree species in flower. Our results demonstrate that across bee sociality groups, nesting guilds, and tribes, the most critical factor impacting native bee communities was within-farm local vegetation management. These results reveal the important role that agroforestry managers can have on biodiversity conservation, and the potential contribution they can make by creating resource-rich agricultural matrices. Specifically, our findings highlight the importance of diverse overstory tree management in supporting native bee communities within tropical agroforestry systems.     

Temperature induced changes in wheat (Triticum aestivum) growth and yield under salt affected environment of Indo-Gangetic Plains

An attempt has been made in the field conditions to evaluate the effect of atmospheric temperature rise on yield, ionic ratio (Na:K), and accumulation of antioxidative pigments in wheat in different growth stages under different soils. Five planting windows (PW) were classified, based on date of wheat sowing where the average temperature difference between a particular PW and PW-I varied from 1.33–4.24°C. Plant leaf area and root length density showed decreasing trend with increasing temperature. A low flag leaf water potential (?1.14?MPa) in sodic soil and high solute potential (?1.34?MPa) in saline-sodic soil was observed under PW-V, where high temperature difference (4.24°C) was recorded. The Na:K ratio was found to be highest in both straw and grain which were 1.802 and 1.126%, respectively, under saline-sodic conditions in PW-V. Proline and malondialdehyde concentration was highest under sodic conditions which varied between 2.82–2.95?mg?g^?1 fresh weight (FW) and 18.38–30.18 nmol g^?1 FW, respectively, under maximum temperature difference. An increase in temperature (>1°C) significantly reduced grain yield (>10%) that was negatively correlated with Na⁺ (r?=??0.78) but positively with K⁺ (r?=?+0.62) concentrations under saline-sodic conditions, however under sodic conditions, it was positively correlated with K⁺ (r?=?+0.63) concentration. Therefore, looking in to the climate change scenario, shifting planting window of wheat sowing may be helpful in mitigating the negative effects of heat and salt stress on wheat crop.     

Molecular characterization of <Emphasis Type="Italic">Triticum militinae</Emphasis> derived introgression lines carrying leaf rust resistance

Triticum militinae Zhuk. et Migusch. belongs to timopheevii [Triticum timopheevii (Zhuk.) Zhuk.] group of wheats with 2n = 4x = 28 chromosomes and genome formula A^tA^tGG. Triticum militinae Zhuk. et Migusch. is known to carry resistance to fungal diseases including rusts and powdery mildew. Genes from timopheevii wheat can be incorporated into cultivated wheat by either direct hybridization or through development of amphiploids. Three T. militinae derived introgression lines (ILs) Triticum Militinae Derivative (TMD) 6-4, TMD7-5 and TMD11-5 were selected for the current study based on cytological stability. All three ILs showed resistance against wide spectrum of Indian pathotypes of leaf rust. More than 1200 SSR markers were used for genotyping of ILs and parental lines. The ILs showed variable and multiple introgressions in different chromosomes of A, B and D genome of wheat. The introgression points were distributed mostly in the distal regions though significant introgressions were also observed in proximal regions of some chromosomes. The extent of introgression in ILs TMD6-4, TMD7-5 and TMD11-5 was 2.8, 8.3 and 8.6% respectively. The set of ‘informative markers’ in the Molecularly Tagged Chromosome Regions (MTCR) of T. militinae origin can also be used in future for tagging of genes associated with traits of economic importance apart from leaf rust resistance. The transferability of Triticum aestivum L. SSR markers to T. militinae was 96.4% for A genome, 95.8% for B genome and 84.3% for D genome. Transferability of wheat SSR markers to T. militinae can be used in preparing genetic maps in timopheevii group of wheats.