Cotton germplasm improvement and progress in Pakistan

Cotton(Gossypium spp.)contributes significantly to the economy of cotton-producing countries.Pakistan is the fourth-largest producer of cotton after China,the USA and India.The average yield of cotton is about 570.99 kg.hm^(−2) in Pakistan.Climate change and different biotic stresses are causing reduction in cotton production.Transgenic approaches have unique advantage to tackle all these problems.However,how to confer permanent resistance in cotton against insects through genetic modification,is still a big challenge to address.Development of transgenic cotton has been proven to be effective.But its effectiveness depends upon several factors,including heterogeneity,seed purity,diffusion of varieties,backcrossing and ethical concerns.Cotton biotechnology was initiated in Pakistan in 1992–1993 with a focus on acquiring cotton leaf curl virus(CLCuV)-resistant insect-resistant,and improving fiber quality.This review summarizes the use of molecular markers,QTLs,GWAS,and gene cloning for cotton germplasm improvement,particularly in Pakistan.

减氮配施稻秆生物炭对稻田土壤养分及植株氮素吸收的影响

通过2018年早稻和晚稻田间试验,研究化学氮肥减量及配施稻秆生物炭对稻田土壤养分特性及植株氮素吸收的影响。试验包括6个处理:不施氮(CK)、常规施氮(N100)、减氮20%(N80)、减氮20%配施生物炭(N80+BC)、减氮40%(N60)、减氮40%配施生物炭(N60+BC)。结果表明:与常规施氮相比,单纯减氮20%和40%或配施生物炭对早晚稻不同生育期土壤pH、有机质、全氮、铵态氮、全磷、有效磷、全钾、速效钾无显著影响;减氮20%配施生物炭显著增加晚稻分蘖期的土壤阳离子交换量(CEC),而减氮40%配施生物炭则显著增加晚稻抽穗期的电导率(EC)值。与单纯减氮相比,N80+BC的土壤速效钾含量在早晚稻抽穗期均显著升高,土壤pH值、全氮在晚稻成熟期显著增加;N60+BC的土壤全钾含量在早稻成熟期显著升高。不同处理早稻土壤硝态氮含量随生育进程逐渐降低,与分蘖期相比,抽穗期和成熟期的常规施氮土壤硝态氮含量分别降低50.0%和71.6%,而配施生物炭处理则降低6.3%~45.5%,减氮配施生物炭显著降低了硝态氮的流失。在晚稻抽穗期,减氮配施生物炭植株吸氮量显著高于常规施氮和单纯减氮,增加幅度为34.8%~52.4%。综上,适度的减氮或配施稻秆生物炭能有效保持土壤养分,促进水稻对氮素的吸收,提高氮素利用率。