Effects of Different Exogenous Substances on Seed Germination of Isatis indigotica Under Drought Stress and Chemical Composition of Isatis indigotica leaves

This study was to investigate the effects of three exogenous substances on chemical constituents of Isatis indigotica leavesand their efficacy in alleviating drought stress, and explore the methods of applying exogenous substances to efficient cultivationof Isatis indigotica. Polyethylene glycol (PEG) was used to simulate drought stress to deal with seeds of Isatis indigotica at thegermination stage (concentration: 0, 10%, 15%, and 20%). Simultaneous operation of exogenous growth regulators [microbialinoculum (MI), γ-aminobutyric acid (GABA) and salicylic acid (SA)] and PEG were implemented in seeds of Isatis indigotica.The effects of drought stress and the mitigation of exogenous substances were observed by statistics of seed germination potential,germination rate, hypocotyl length, and radicle length of each treatment. The effects of exogenous substances on the content ofalkaloids, crude protein and free amino acids in the leaves of Isatis indigotica grown in a greenhouse were determined after sprayingexogenous substances on the plants. The differences of germination potential, germination rate, hypocotyl length, and radicle lengthamong 15% PEG stress treatment, 10% PEG stress treatment and the control were significant (P<0.05). According to the predesignedgermination standard, the seeds did not germinate under 20% PEG stress treatment. When the PEG concentration was 15%, the resultsof seed germination potential and germination rate after adding MI were significantly different from those under stress alone (P<0.05).When exposed to 10% PEG stress, the supplementation of GABA led to a notable increase in radicle length of Isatis indigotica seeds,showing significant differences compared to other three treatments. The application of MI and GABA under 15% PEG stress resultedin a significant increase in the radicle and hypocotyl length of Isatis indigotica seeds compared to other two treatments. The contentof the total alkaloids in leaves of Isatis indigotica was significantly increased after spraying GABA. Meanwhile, the contents of crudeprotein and the total free amino acids were kept constant after spraying exogenous substances. Application of MI and GABA couldalleviate drought stress of Isatis indigotica. The content of the total alkaloids in leaves of Isatis indigotica could significantly increaseafter spraying GABA.

Genetic Analysis and Preliminary Mapping of a Highly Male-Sterile Gene in Foxtail Millet(Setaria italica L.Beauv.) Using SSR Markers

Breeding of male-sterile lines has become the mainstream for the heterosis utilization in foxtail millet,but the genetic basis of most male-sterile lines used for the hybrid is still an area to be elucidated.In this study,a highly male-sterile line Gao146A was investigated.Genetic analysis indicated that the highly male-sterile phenotype was controlled by a single recessive gene a single recessive gene.Using F 2 population derived from cross Gao146A/K103,one gene controlling the highly male- sterility,tentatively named as ms1,which linked to SSR marker b234 with genetic distance of 16.7 cM,was mapped on the chromosome VI.These results not only laid the foundation for fine mapping of this highly male-sterile gene,but also helped to accelerate the improvement of highly male-sterile lines by using molecular marker assisted breeding method.

AFLP Molecular Markers for Leaf Rust Resistance Genes in Foxtail Millet

Foxtail millet is not only a very useful experimental crop, but also a fodder crop and a staple food of people who live on the marginal agricultural lands, and it supplies high-quality protein for food products and industrial materials. However, leaf rust greatly reduces foxtail millet yields in susceptible varieties when weather conditions favor rust spread and development. Therefore, it is necessary to use molecular markers detecting and marking resistance genes. Compared with other molecular markers, AFLP maker is more efficient and powerful in the study of foxtail millet. In this study, AFLP analysis of 131 F2 individuals was performed and three AFLP makers were found to be linked to the rust resistance gene, with the genetic distances of 9.2, 9.8 and 12.4 cM, respectively. Cloning of rust re- sistance genes is of great importance and meaning in studying rust resistance of foxtail millet in the future. Furthermore, we may convert specific AFLP markers into single locus PCR markers, such as sequence characterised amplified region （SCAR） markers or cleaved amplified polymorphic site （CAPS） markers.

Study on Analysis Model of Millet Yield Loss Caused by Weeds in Summer Season Millet Field

Weed management in summer season foxtall millet field was studied by evaluating weed damage and exploring competition between weeds and foxtail millet, and a few fitting models were simulated and compared by employing field plot experiment and nonlinear regression analysis. The results showed that the millet yield losses and weed density were extremely significantly correlated. Among the tested models, the determination coefficient （ R2 ） of hyperbolic model was 0.997 12, and minimum residual sum of squares was 16.174, which was considered the optimal model to simulate the competition relation between weeds and millet. The predicted equation was Y = d/（ 1. 733 ＋ 0. 018d） ; the interspecific competitiveness of weeds was 0. 577 0 and the intraspecific competitiveness was 0.010 3 ; the maximum loss rate of millet yield was 55.56%. This study had established an analysis model with high gcodness-of-fit and practical prediction which could help weed management in summer season millet field.

Heat-tolerant maize for rainfed hot,dry environments in the lowland tropics:From breeding to improved seed delivery

Climate change-induced heat stress combines two challenges:high day-and nighttime temperatures,and physiological water deficit due to demand-side drought caused by increase in vapor-pressure deficit.It is one of the major factors in low productivity of maize in rainfed stress-prone environments in South Asia,affecting a large population of smallholder farmers who depend on maize for their sustenance and livelihoods.The International Maize and Wheat Improvement Center(CIMMYT)maize program in Asia,in partnership with public-sector maize research institutes and private-sector seed companies in South Asian countries,is implementing an intensive initiative for developing and deploying heat-tolerant maize that combines high yield potential with resilience to heat and drought stresses.With the integration of novel breeding tools and methods,including genomics-assisted breeding,doubled haploidy,fieldbased precision phenotyping,and trait-based selection,new maize germplasm with increased tolerance to heat stress is being developed for the South Asian tropics.Over a decade of concerted effort has resulted in the successful development and release of 20 high-yielding heat-tolerant maize hybrids in CIMMYT genetic backgrounds.Via public–private partnerships,eight hybrids are presently being deployed on over 50,000 ha in South Asian countries,including Bangladesh,Bhutan,India,Nepal,and Pakistan.

Evaluation of maize inbred lines for resistance to pre-harvest aflatoxin and fumonisin contamination in the field

Two important mycotoxins, aflatoxin and fumonisin, are among the most potent naturally occurring carcinogens, contaminating maize(Zea mays) and affecting crop yield and quality.Resistance of maize to pre-harvest mycotoxin contamination, specifically aflatoxin produced by Aspergillus flavus and fumonisin produced by Fusarium verticillioides, is a goal in breeding programs that screen for these important traits with the aim of developing resistant commercial hybrids. We conducted two years of field evaluations on 87 inbred lines originating primarily in China and Mexico and not previously screened for resistance.The objectives of our study were to identify resistant germplasm for breeding purposes and to examine possible relationships between resistances to the two mycotoxins. Aflatoxin and fumonisin were present in samples harvested from all lines in both years.Concentrations of total aflatoxin ranged from 52.00 ± 20.00 to 1524.00 ± 396.00 μg kg^(-1),while those of fumonisin ranged from 0.60 ± 0.06 to 124.00 ± 19.50 mg kg^(-1). The inbred lines TUN15, TUN61, TUN37, CY2, and TUN49 showed the lowest aflatoxin accumulation and CN1, GT601, TUN09, TUN61, and MP717 the lowest fumonisin accumulation. TUN61 showed the lowest accumulation of both mycotoxins. This study confirmed previous observations that high levels of aflatoxin can coexist with fumonisin, with 55 maize lines showing a positive correlation coefficient between the concentrations of aflatoxin and fumonisin and 32 lines showing a negative correlation coefficient. These selected lines,particularly TUN61, may provide sources of resistance to mycotoxin contamination in breeding programs. However, the mechanism of resistance in this germplasm remains to be identified. Future research should also address factors that influence the fungus–plant interaction, such as herbivory and environmental stress.

Relation of Leaf Stomatal Traits to Yield and Drought Resistance of Wheat

[ Objective] The study aimed to discuss the relation of leaf stomatal traits to yield and drought resistance of wheat. [ Method] Using the DH population of wheat cultivar Hanxuanl0/Lumai14 as the test object, the relation of leaf stomatal density （SD）, length （SL） and width （ SW）, stomatal conductance （g,）, photosynthetic rate （ Pn ）, transpiration rate （ Tr） to grain yield per plant and index of drought resistance （IDR） on the 10th and 20t＂ day after anthesis under the conditions of drought stress and normal irrigation were discussed by the methods of correlation analysis and path analysis. [ Result] Under the two water conditions, the correlations of these stomatal traits with yield components and IDR were mostly not significant on the 10t＂ day after anthesis, but there were significantly positive correlations between thousand kernel weight （TKW） and these traits on the 20^th day after anthesis. Path analysis showed that g,, Pn and Tt, were main factors affecting yield per plant （YPP） and IDR, and they had stron- ger direct effects on YPP and IDR, while their indirect interaction was also strong. The direct effects of SD, SL and SW on YPP and IDR were small, as well as their indirect action among SD, SL and SW. On the other hand, the correlations between SD and SL were significant, and the correlations of SL with SW, gn, P, and Tt, were extremely significant on the 10th and 20th day after anthesis under the two water conditions. However, the correlations of SD and SL with g,, P,, and Tr changed with water conditions or growth stages, showing that water conditions or growth stages had great effects on the correlations between two traits. Therefore, it is not always a good means to improve stomatal conductance, photosynthetic rate and transpiration rate and hence promote wheat yield by selecting stomatal density and size. [ Conclusion] The research could provide scientific references for revealing the roles of leaf stomatal traits in wheat breeding for drought resistance.

Diversity of Growth Habits and Their Association with VRN Allele of 81 American Wheat Lines

Eighty-one wheat accessions including 50 southern regional performance nursery （SRPN） lines and 31 northern regional performance nursery （NRPN） lines from the United States were tested to evaluate the growth habit by chilling treatments and to estimate the VRN allele variation with 19 pairs of published VRN primers. Two spring wheat accessions and 44 semi-spring wheat accessions were confirmed based on their chilling days＇ requirement and polymorphism was found at VRN loci. The Vrn-A1 allele had the highest frequency in the RPN accessions and VA1-CAPs markers identified growth habit of RPN lines. No polymorphism was found at the VRN3 loci and some polymorphism at the region of promoter and the first intron of VRN1 was not always consistent to growth habit in the wheat RPN accessions. The existence of variation in VRN alleles suggested that singly using the dominant Vrn allele is possible to extend the diversity of wheat accessions and improve their adaption to different environments in autumn-sowing region. This information will be useful for the cultivars exploitation and wheat breeding program.

Evaluation of maize inbred lines and topcross progeny for resistance to pre-harvest aflatoxin contamination

Pre-harvest aflatoxin contamination occurs in maize following kernel colonization by Aspergillus flavus. Aflatoxin contamination resistance is a highly desired trait in maize breeding programs.The identification of novel sources of resistance to pre-harvest aflatoxin contamination is a major focus in germplasm screening efforts. Here, we performed a field evaluation of 64 inbred lines over two years for pre-harvest aflatoxin contamination. Topcrosses were also performed with two testers, B73 and Mo17, to generate 128 F1 hybrids which were also evaluated over two years. Hybrid performance was used to calculate both general combining ability(GCA) of the inbreds, and observed heterosis for aflatoxin resistance. Over both years of the study, aflatoxin concentrations ranged from 80 ± 47 to 17,617 ± 8816 μg kg^(-1) for inbreds, and from 58 ± 39 to 2771 ± 780 μg kg^(-1) for hybrids with significant variation between years and lines. The inbred lines CML52, CML69, CML247, GT-603, GEMS-0005, Hi63, Hp301, and M37 W showed <1000 μg kg^(-1) of aflatoxin accumulation in both years of the study and less than the resistant check, Mp313 E, in at least one season. Among these, CML52, GT-603, and Hi63 also showed significant GCA with the testers in hybrid progeny. CML52, GT-603, and M37 W also showed heterotic effects of-13.64%,-12.47%, and-24.50%, respectively, with B73 resulting in reduced aflatoxin contamination. GT-603 also showed a similar heterotic effect for aflatoxin contamination,-13.11%, with Mo17 indicating that this line may serve as a versatile source of aflatoxin contamination resistance in breeding programs.

Study on Present Situation of Agriculture in Handan

This article studies present situation of agriculture in Handan from different aspects.It is thought that overall sustainable development level of Handan agriculture is enhanced somewhat,but there are some problems.According to the actual condition,some rationalization suggestions are proposed.