Modern maize hybrids in Northeast China exhibit increased yield potential and resource use efficiency despite adverse climate change

The impact of global changes on food security is of serious concern. Breeding novel crop cultivars adaptable to climate change is one potential solution, but this approach requires an understanding of complex adaptive traits for climate‐change conditions. In this study, plant growth, nitrogen (N) uptake, and yield in relation to climatic resource use efficiency of nine representative maize cultivars released between 1973 and 2000 in China were investigated in a 2‐year field experiment under three N applications. The Hybrid‐Maize model was used to simulate maize yield potential in the period from 1973 to 2011. During the past four decades, the total thermal time (growing degree days) increased whereas the total precipitation and sunshine hours decreased. This climate change led to a reduction of maize potential yield by an average of 12.9% across different hybrids. However, the potential yield of individual hybrids increased by 118.5 kg ha^?1 yr^?1 with increasing year of release. From 1973 to 2000, the use efficiency of sunshine hours, thermal time, and precipitation resources increased by 37%, 40%, and 41%, respectively. The late developed hybrids showed less reduction in yield potential in current climate conditions than old cultivars, indicating some adaptation to new conditions. Since the mid‐1990s, however, the yield impact of climate change exhibited little change, and even a slight worsening for new cultivars. Modern breeding increased ear fertility and grain‐filling rate, and delayed leaf senescence without modification in net photosynthetic rate. The trade‐off associated with delayed leaf senescence was decreased grain N concentration rather than increased plant N uptake, therefore N agronomic efficiency increased simultaneously. It is concluded that modern maize hybrids tolerate the climatic changes mainly by constitutively optimizing plant productivity. Maize breeding programs in the future should pay more attention to cope with the limiting climate factors specifically.     

Development of Dactylaria eudermata Drechsler a predaceous fungi in Meloidogyne incognita

Dactylaria eudermata Drechsler is one of the important predaceous fungi occurring widely in different soils. The fungus produces hyphal bails and network compound in which nematodes are entangled. This hyphal nets as trapping structure which may be single dimensional to two or three dimensional and are formed through repeated hyphal anastomosis, which capture nematodes either through the adhesive material present on the surface of hyphal nets or due to physical entanglement. In the experiment it was observed that inflation of hyphal bails takes 30 to 50 minutes and capturing and killing the nematode by a single conidia in water takes 35–55 hours, were as time required for inflation of hyphal bails and real trapping and killing of a nematode in maize meal (MMA: water (1:10) medium) takes one minute and 30–50 hours respectively.     

Efficacy of intercropping and harvest time modification for reducing field infestation of maize by Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Most management practices of Sitophilus zeamais Motschulsky, a field-to-post-harvest insect pest of cereals, have focused on post harvest control methods. This experiment was designed to investigate the potential of cropping system and modification of time of harvest to control S. zeamais. Intercropping and harvest time modification had significant (P < 0.05) effect on the number of S. zeamais emerging 42 days post-harvest. For the early harvest (15 weeks after planting (WAP)), the mean number of S. zeamais recorded from a maize monoculture (7.39) was significantly (P < 0.05) higher than the mean numbers of weevils emerging from a maize–soybean intercrop (2.31), but not significantly higher than the number recorded in maize–groundnut (3.87) intercrop. For the late harvest (18 WAP), the mean number of emerged adult observed in the maize–soybean intercrop (6.13) was significantly lower than the mean number of adult emerging from the monocrop maize (13.24). Maize–groundnut intercrop did not significantly reduce field infestation of S. zeamais compared with monocrop maize. Percentage weight loss observed in early harvested maize was significantly (P < 0.0001) lower than what was observed in late-harvested maize. Percentage weight loss was highest in stored maize harvested from monocrop maize plots for the early harvest, whereas intercropping maize with soybean reduced percentage weight loss when harvest was delayed.     

Sources of resistance against post-flowering stalk rots of maize

The post-flowering stalk rots (PFSR) are a complex disease, which are widely distributed in almost all the maize growing regions across the globe. A number of fungi are involved in causing decay of the pith resulting in pre-mature wilting of the plants. Most of the commercially grown cultivars have shown a high level of disease incidence at the grain filling stage. A systematic breeding programme on PFSR was initiated in India in collaboration with Asian Regional Maize Program of CIMMYT. Under this programme, germplasm screening was carried out at four ‘hot spot’ locations in India for different diseases: Hyderabad (Cephalosporium maydis), Udaipur (Fusarium moniliforme), Ludhiana and Delhi (Macrophomina phaseolina). Across the locations, promising maize genotypes were artificially inoculated using the toothpick method, year after year; resistant plants were selfed to derive resistant inbreds. After extensive screening, three resistant lines, namely PFSR-13-5, JCY2-2-4-1-1-1-1 and JCY3-7-1-2-1-b-1, were identified. In addition, the resistance level of five pools/populations; (PFSR (Y)-C1, PFSR (white), Extra-early (White), P-100, P-300 and P-345) was upgraded to an acceptable level. These genotypes may prove useful for utilisation in breeding cultivars for resistance to PFSR.     

Integration of Glomus mosseae with Chromolaena odorata powder for suppression of Meloidogyne incognita on maize (Zea mays L.)

Meloidogyne incognita infestation on maize results in heavy yield loss in farmers’ field. Most of the varieties adopted by subsistence farmers in Nigeria are susceptible to M. incognita. Beside these, the cost of control exceeding the profit from the crop using nematicides and the pollution risk they pose to the environment has necessitated the need for alternatives. Pot and field experiments were, therefore, conducted to investigate the effects of Chromolaena odorata powder and Glomus mosseae (a mycorrhizal fungus) on M. incognita pathogenicity on maize. Hybrid Oba super II improved maize variety adopted by local farmers was selected for the study. Maize plants were grown with G. mosseae (5 spores/g of soil) and soil amended with C. odorata powder (1% w/w) singly and in combination. Two weeks after emergence, Test plants were inoculated with 5000 M. incognita eggs. Sixty days after planting, destructive samples were assessed for root gall symptom and severity, and nematode population. Results show that G. mosseae and C. odorata powder were effective in controlling the population of M. incognita and the root knot nematode symptom and gave the highest yield parameters in combination. Single application of G. mosseae and C. odorata powder was similar in the effect on M. incognita and maize yield. Combination of G. mosseae and C. odorata powder may become a viable alternative to nematicide in managing M. incognita pathogenicity on maize as C. odorata powder may serve as a carrier medium for G. mosseae.     

The effects of disinfectant foam on microbial biofilms

This investigation examined the effects of common aqueous biocides and disinfectant foams derived from them on Pseudomonas aeruginosa biofilms. Biofilms were grown on stainless steel coupons under standardised conditions in a reactor supplemented with low concentrations of organic matter to simulate conditions prevalent in industrial systems. Five-day-old biofilms formed under ambient conditions with continuous agitation demonstrated a low coefficient of variation (5.809%) amongst viable biofilm bacteria from independent trials. Scanning electron microscopy revealed biofilms on coupons with viable biofilm bacteria observed by confocal microscopy. An aqueous solution of a common foaming agent amine oxide (AO) produced negligible effects on bacterial viability in biofilms (p?>?0.05). However, significant biofilm inactivation was noted with aqueous solutions of common biocides (peracetic acid, sodium hypochlorite, sodium ethylenediaminetetraacetic acid) with or without AO (p?<?0.05). Aereation of a mixture of AO with each of these common biocides resulted in significant reductions in the viability of biofilm bacteria (p?<?0.05). In contrast, limited effects were noted by foam devoid of biocides. A relationship between microbial inactivation and the concentration of biocide in foam (ranging from 0.1?–?0.5%) and exposure period were noted (p?<?0.05). Although, lower numbers of viable biofilm bacteria were recovered after treatment with the disinfectant foam than by the cognate aqueous biocide, significant differences between these treatments were not evident (p?>?0.05). In summary, the studies revealed significant biofilm inactivation by biocidal foam prepared with common biocides. Validation of foam disinfectants in controlled trials at manufacturing sites may facilitate developments for clean in place applications. Advantages of foam disinfectants include reductions in the volumes of biocides for industrial disinfection and in their disposal after use.     

Macrophage lipoprotein lipase modulates the development of atherosclerosis but not adiposity

The role of macrophage lipoprotein lipase (LpL) in the development of atherosclerosis and adiposity was examined in macrophage LpL knockout (MLpLKO) mice. MLpLKO mice were generated using cre-loxP gene targeting. Loss of LpL in macrophages did not alter plasma LpL activity or lipoprotein levels. Incubation of apolipoprotein E (ApoE)-deficient β-VLDL with peritoneal macrophages from ApoE knockout mice lacking macrophage LpL (MLpLKO/ApoEKO) led to less cholesteryl ester formation than that found with ApoEKO macrophages. MLpLKO/ApoEKO macrophages had reduced intracellular triglyceride levels, with decreased CD36 and carnitine palmitoyltransferase-1 mRNA levels compared with ApoEKO macrophages, when incubated with VLDL. Although both MLpLKO/ApoEKO and ApoEKO mice developed comparable hypercholesterolemia in response to feeding with a Western-type diet for 12 weeks, atherosclerosis was less in MLpLKO/ApoEKO mice. Epididymal fat mass and gene expression levels associated with inflammation did not differ between the two groups. In conclusion, macrophage LpL plays an important role in the development of atherosclerosis but not adiposity.     

Genomic Resources for Gene Discovery,Functional Genome Annotation,and Evolutionary Studies of Maize and Its Close Relatives

Maize is one of the most important food crops and a key model for genetics and developmental biology. A genetically anchored and high-quality draft genome sequence of maize inbred B73 has been obtained to serve as a reference sequence. To facilitate evolutionary studies in maize and its close relatives, much like the Oryza Map Alignment Project (OMAP) (www.OMAP.org) bacterial artificial chromosome (BAC) resource did for the rice community, we constructed BAC libraries for maize inbred lines Zheng58, Chang7-2, and Mo17 and maize wild relatives Zea mays ssp. parviglumis and Tripsacum dactyloides. Furthermore, to extend functional genomic studies to maize and sorghum, we also constructed binary BAC (BIBAC) libraries for the maize inbred B73 and the sorghum landrace Nengsi-1. The BAC/BIBAC vectors facilitate transfer of large intact DNA inserts from BAC clones to the BIBAC vector and functional complementation of large DNA fragments. These seven Zea Map Alignment Project (ZMAP) BAC/BIBAC libraries have average insert sizes ranging from 92 to 148 kb, organellar DNA from 0.17 to 2.3%, empty vector rates between 0.35 and 5.56%, and genome equivalents of 4.7- to 8.4-fold. The usefulness of the Parviglumis and Tripsacum BAC libraries was demonstrated by mapping clones to the reference genome. Novel genes and alleles present in these ZMAP libraries can now be used for functional complementation studies and positional or homology-based cloning of genes for translational genomics.