Identification of candidate genes for early-maturity traits by combining BSA-seq and QTL mapping in upland cotton(Gossypium hirsutum L.)

Cotton breeding for the development of early-maturing varieties is an effective way to improve multiple cropping indexes and alleviate the conflict between grains and cotton in the cultivated fields in China.In the present study,we aimed to identify upland cotton quantitative trait loci(QTLs)and candidate genes related to early-maturity traits,including whole growth period(WGP),flowering timing(FT),node of the first fruiting branch(NFFB),height of the node of the first fruiting branch(HNFFB),and plant height(PH).An early-maturing variety,CCRI50,and a latematuring variety,Guoxinmian 11,were crossed to obtain biparental populations.These populations were used to map QTLs for the early-maturity traits for two years(2020 and 2021).With BSA-seq analysis based on the data of population 2020,the candidate regions related to early maturity were found to be located on chromosome D03.We then developed 22 polymorphic insertions or deletions(InDel)markers to further narrow down the candidate regions,resulting in the detection of five and four QTLs in the 2020 and 2021 populations,respectively.According to the results of QTL mapping,two candidate regions(InDel_G286-InDel_G144 and InDel_G24-InDel_G43)were detected.In these regions,three genes(GH_D03G0451,GH_D03G0649,and GH_D03G1180)have nonsynonymous mutations in their exons and one gene(GH_D03G0450)has SNP variations in the upstream sequence between CCRI50 and Guoxinmian 11.These four genes also showed dominant expression in the floral organs.The expression levels of GH_D03G0451,GH_D03G0649 and GH_D03G1180 were significantly higher in CCRI50 than in Guoxinmian 11 during the bud differentiation stages,while GH_D03G0450 showed the opposite trend.Further functional verification of GH_D03G0451 indicated that the GH_D03G0451-silenced plants showed a delay in the flowering time.The results suggest that these are the candidate genes for cotton early maturity,and they may be used for breeding early-maturity cotton varieties.

Yield Stability of Direct-sowing and Early-maturing Excellent Brassica napus (Attar No.8)

[Objective] The aim was to analyze yield stability of attar No.8, which is direct sowing and early-maturing. [Method] Analysis was made on yielding ability, stability and adaptability of attar No.8 in Yunnan Province during 2006-2009 with DPS software and stability assessment was conducted on yield and major economic characters of the variety in different periods and experimental plots. [Result] Average yield of attar No.8 during three years in 24 plots achieved 3 379.17 kg/hm2; it grew tightly and is featured with early matureness. In addition, grain density, pod number and annul production differed little in different years and the variety in eight ecological conditions all showed high production potential, yielding ability and stability, which proved that attar No.8 is suitable to be grown in Yunnan and southern early-maturing areas in China. [Conclusion] The research provided references for selection and breeding of rapeseeds＇ variety which enjoys high and stable yield.

Influence of the Number of Reserved Fruit on Fruit-bearing Branch of Early-maturing Citrus unshiu Marc. on Fruit Growth and Development

In order to provide theoretical references for early-maturing Citrus unshiu Marc. in terms of fruit thinning, timely fertilization and harvesting, as wel as for for-mulation of of Early-maturing Citrus unshiu Marc. Cultivation Technique Standards in Guizhou Province, the dynamic changes of fruit longitudinal diameter and trans-verse diameter of 11-year-old and 12-year-old early maturing Citrus unshiu Marc. were tested in two consecutive years and the effects of single-fruit bearing branch on fruit growth and development were compared. The results showed annual varia-tion of longitudinal and transverse diameter of the fruit in Guizhou grew faster at the beginning and then slowed down gradual y, maintaining a slow-growth period after October; the growth curve final y was flat in mature stage. General y, the growth and development stage of fruit showed four growth peaks, showing an in-creasing S-shape curve and fruit net increase also had four growth peaks with a double S-shape curve. Specifical y, longitudinal diameters growth alternated with transverse diameter growth and the former proved much stronger. In terms of ef-fects of single-fruit bearing branch on longitudinal and transverse diameter growth, the number of reserved fruits had direct effects on the growth, net increase of weight, time of growth peak, fluctuation and the number of growth peak. The growth and development, and quality of fruits in the treatments with two or three fruits re-served on single fruit-bearing branch proved better compared with the control with four left fruits. It suggested that early June and early July are the best time for fer-tilization of early-maturing Citrus unshiu Marc. in Guizhou Pprovince and would have better effect if combined with foliage spraying. The suitable harvest time is in the end of October. The preferred number of reserved fruit on single fruit-bearing branch is 2-3. In actual production, the implementation of flower and fruit thinning should also takes tree age, balance of tree vigor, strength of fruit bearing branch, alternate bearing phenomenon and other factors into consideration.

Germination and Expression of α-Amylase of KF0680-1 and KF0680-2(Cultivars of Sweet Sorghum) under Salt Stress

[Objective] The aim was to study on germination and expression of α-amy- lase of KF0680-1 and KF0680-2 （cultivars of sweet sorghum） under salt stress. [Method] In the research, KF0680-1 and KF0680-2, cultivars of sweet sorghum, were used to measure related indices of germination and expression of co-amylase to discuss effect of salt stress on two cultivars. [Result] Germination of sweet sorghum would be promoted if treated with salt in low concentration and inhibited if treated in high concentration. In the latter condition, roots and seedlings were smaller than that of control group in length, but expression of s-amylase in the two cultivars was pro- moted under proper salt stress. [Conclusion] The research indicates that KF0680-1 and KF0680-2 are inhibited in growth by salt stress and the latter is stronger in salt resis- tance than the former under low salt concentration. In addition, expression of α-amy- lase could be promoted by salt in proper volume. The results provide references for selection of sweet sorghum which could be planted in northwestern areas.

Study on the Control Technique of "On" and "Off" Years of Early Maturing Citrus unshiu

In order to change the universal phenomenon of alternate bearing of early- grown Satsuma orange （Citrus unshiu Marc.） in north Guizhou province, and provide references for setting scientific cultivation techniques and rational management mea- sures for Satsuma orange gardens, cultivation techniques for controlling alternate bearing of the early-grown Satsuma orange were tested and optimized for 7 years （2005 to 2011）. The results showed that production of local early-grown Satsuma or- ange orchards could be significantly improved through the application of cultivation techniques such as rational trimming, strengthening soil, fertilizer and water manage- ment, conducting flower and fruit management pertinently, effective and comprehen- sive control of disease and insects. The yield difference between ＂on＂ and ＂off＂ years was 10%-15%, and the orchards with serious alternate bearing phenomenon were changed into the one with high and stable yield. Meanwhile, the commercial rate of early-grown Satsuma orange fruit enhanced, leading to good economic benefits.

High-efficiency breeding of early-maturing rice cultivars via CRISPR/Cas9-mediated genome editing

Rice is a staple food for more than half of the human population.It has been estimated that by 2030,40%more rice needs to be produced in order to meet the growing demand（Khush,2005）.One of the strategies to improve rice productivity is to enlarge rice growth areas, such as the northward expansion of the growth region in Heilongjiang Province, the northernmost region of China （Li et al., 2015）. However, the northward cultivation is accompanied with daylength extension and temperature decrease, which are unfavor- able for rice, a tropical short-day plant, to complete flowering and seed setting. Thus, the need for early-maturing rice cultivars with extremely low photoperiod sensitivity is urgent.

A genome-wide association study of early-maturation traits in upland cotton based on the CottonSNP8oK array

Genome-wide association studies （GWASs） efficiently identify genetic loci controlling traits at a relatively high resolution. In this study, variations in major early-maturation traits, including seedling period （SP）, bud period （BP）, flower and boll period （FBP）, and growth period （GP）, of 169 upland cotton accessions were investigated, and a GWAS of early maturation was performed based on a CottonSNPSoK array. A total of 49,650 high-quality single-nucleotide polymorphisms （SNPs） were screened, and 29 significant SNPs located on chromosomes A6, A7, A8, D% D2, and D9, were repeatedly identified as associated with early-maturation traits, in at least two environments or two algorithms. Of these 29 significant SNPs, I, 12, 11, and 5 were related to SP, BP, FBP, and GP, respectively. Six peak SNPs, TM47967,TM13732, TM2o937, TM28428, TM5o283, and TM72552, exhibited phenotypic contributions of approximately lo%, which could allow them to be used for marker-assisted selection. One of these, TM72552, as well as four other SNPs, TM72554, TM72555, TM72558, and TM72559, corresponded to the quantitative trait loci previously reported. In total, 274 candidate genes were identified from the genome sequences of upland cotton and were categorized based on their functional annotations. Finally, our studies identified Gh_DoIGo34o and Gh_DoIGo34~ as potential candidate genes for improving cotton early maturity.