Genome-wide association study reveals candidate genes for gummy stem blight resistance in cucumber

Gummy stem blight(GSB),caused by Didymella bryoniae,is a serious fungal disease that leads to decline in cucumber yield and quality.The molecular mechanism of GSB resistance in cucumber remains unclear.Here,we investigated the GSB resistance of cucumber core germplasms from four geographic groups at the seedling and adult stages.A total of 9 SNPs related to GSB resistance at the seedling stage and 26 SNPs at the adult stage were identified,of which some are co-localized to previously mapped Quantitative trait loci(QTLs)for GSB resistance(gsb3.2/gsb3.3,gsb5.1,and gsb-s6.2).Based on haplotype analysis and expression levels after inoculation,four candidate genes were identified within the region identified by both Genome-wide association study(GWAS)and previous identified QTL mapping,including Csa3G129470 for gsb3.2/gsb3.3,Csa5G606820 and Csa5G606850 for gsb5.1,and Csa6G079730 for gsb-s6.2.The novel GSB resistant accessions,significant SNPs,and candidate genes facilitate the breeding of GSB resistant cucumber cultivars and provide a novel idea for understanding GSB resistance mechanism in cucumber.

QTL mapping of drought tolerance traits in soybean with SLAF sequencing

Drought stress is an important factor affecting soybean yield.Improving drought tolerance of soybean varieties can increase yield and yield stability when the stress occurs.Identifying QTL related to drought tolerance using molecular marker-assisted selection is able to facilitate the development of drought-tolerant soybean varieties.In this study,we used a high-yielding and drought-sensitive cultivar‘Zhonghuang 35’and a drought-tolerant cultivar‘Jindou 21’to establish F6:9 recombinant inbred lines.We constructed a highdensity genetic map using specific locus amplified fragment sequencing(SLAF-Seq)technology.The genetic map contained 8078 SLAF markers distributing across 20 soybean chromosomes with a total genetic distance of 3780.98 c M and an average genetic distance of0.59 c M between adjacent markers.Two treatments(irrigation and drought)were used in the field tests,the Additive-Inclusive Composite Interval Mapping(ICIM-ADD)was used to call QTL,and plant height and seed weight per plant were used as the indicators of drought tolerance.We identified a total of 23 QTL related to drought tolerance.Among them,seven QTL(q PH2,q PH6,q PH7,q PH17,q PH19-1,q PH19-2,and q PH19-3)on chromosomes 2,6,7,17,and 19 were related to plant height,and five QTL(q SWPP2,q SWPP6,q SWPP13,q SWPP17,and q SWPP19)on chromosomes 2,6,13,17,and 19 were related to seed weight and could be considered as the major QTL.In addition,three common QTL(q PH6/q SWPP6,q PH17/q SWPP17,and q PH19-3/q SWPP19)for both plant height and seed weight per plant were located in the same genomic regions on the same chromosomes.Three(q PH2,q PH17,and q PH19-2)and four novel QTL(q SWPP2,q SWPP13,q SWPP17,and q SWPP19)were identified for plant height and seed weight per plant,respectively.Two pairs of QTL(q PH2/q SWPP2 and q PH17/q SWPP17)were also common for both plant height and seed weight per plant.These QTL and closely linked SLAF markers could be used to accelerate breeding for drought tolerant cultivars via MAS.

The effect of enzymes on release of trace elements in feedstuffs based on in vitro digestion model for monogastric livestock

Background: This experiment was conducted to study the effect of different feed enzymes(phytase,xylanase,β-glucanase) on release rate of trace elements(Fe,Cu,Mn and Zn) in 6 commonly used feedstuffs(corn,wheat,barley,soybean meal,wheat bran,wheat middlings) by using an in vitro model,simulating the digestive processes in stomach for 2 h and then in small intestine for 6 h at 39 °C.Results: Phytase raised(P < 0.05) the release rate of Cu and Zn in corn,Cu,Zn and Mn in wheat,Cu in barley,Cu,Zn and Mn in soybean meal,Zn,Fe in wheat bran and Zn,Fe,Mn in wheat middlings.The release rate of various trace elements in feedstuffs was increased after xylanase addition.Compared with the control group,the release rate of soluble Cu in corn,wheat,barley and soybean meal,soluble Zn in corn,wheat and wheat middlings and soluble of Mn in corn,wheat,barley and wheat bran increased(P < 0.05) after xylanase treatment.After the treatment of β-glucanase,the release rate of soluble Cu in corn,wheat and wheat bran,soluble Fe in barley,soybean meal and wheat bran and soluble Mn in corn and wheat bran all increased(P < 0.05) compared with the control group.In each feedstuff,after corresponding enzyme treatment,the contents of phytic acid,xylan and β-glucan were significantly lower than those of the control group(P < 0.05).Conclusions: Results showed that bound trace elements in feedstuffs can be released by feed enzymes.It may be necessary to take the trace elements in feedstuffs into account in the actual feed preparation including feed enzymes.