秸秆覆盖与氮肥运筹对杂交稻根系生长及氮素利用的影响

【目的】在我国稻-麦、稻-油等多熟制区域,富含氮素的小麦、油菜等水稻前茬作物秸秆被大量弃置、焚烧,造成极大浪费和环境污染,与此同时,稻季氮肥投入量却在逐年增加,因此在水稻生产中研究秸秆覆盖与氮肥配合施用的理论与技术,对实现秸秆还田与减少氮肥用量具有重要意义。本试验研究油菜、小麦2种秸秆覆盖方式下,3种不同的氮肥运筹方式对杂交稻主要生育时期根系生长、氮素吸收利用特征及产量的影响,并探讨其根系生长与氮素利用及产量间的关系,以期寻求最佳的秸秆还田与氮肥运筹搭配模式。【方法】本试验以杂交稻F优498为材料,采用两因素裂区试验设计,主区为小麦秸秆覆盖(S1)、油菜秸秆覆盖(S2)和无秸秆覆盖(S0);副区为氮肥运筹模式,在135 kg/hm2总施氮量条件下,设置基肥∶蘖肥∶穗肥为5∶3∶2(N1);基肥∶蘖肥∶穗肥为3∶3∶4(N2);基肥∶蘖肥∶穗肥为3∶1∶6(N3)3种氮肥运筹模式,以不施氮肥(N0)为对照。研究各处理杂交稻在移栽后20 d、移栽后30 d、齐穗期和成熟期根系生长及形态、各生育期的干物质与氮素积累,水稻茎鞘的干物质转运、产量及其构成因子以及各时期氮素积累及利用效率,同时对各生育时期根系生长与氮素利用及产量间的关系进行分析。【结果】结果表明,小麦秸秆覆盖均可有效促进杂交稻各生育时期的根系生长、改善根系形态、增加各时期的干物质与氮素积累,提高氮肥的利用效率及稻米产量。在不同种类秸秆覆盖下,基肥∶蘖肥∶穗肥(倒4叶龄期施入)为3∶3∶4(N2)时,可及时地对杂交水稻主要生育时期的根系生长进行调控,有效促进抽穗至成熟期的干物质积累与转运率,提高水稻主要生育时期的氮素积累及氮肥利用效率,显著增加稻谷产量,为本试验中最优的氮肥管理模式;而氮肥后移比例过高(基肥∶分蘖肥∶穗肥运筹比例为3∶1∶6),会限制齐穗期根系的生长,导致稻谷产量及氮肥利用效率降低。相关性分析表明,秸秆覆盖与氮肥运筹下主要生育时期根干重、根体积、总根长与产量及氮素吸收利用均存在显著或极显著的正相关(r=0.38*0.78**),尤其以齐穗期的根体积与总根长、根干重与氮素累积、产量及氮素回收利用率的相关性最好。【结论】小麦秸秆、油菜秸秆覆盖能够有效促进杂交稻根系的生长,增加干物质与氮素积累,提高氮肥利用效率,且小麦秸秆覆盖效果更显著。秸秆覆盖条件下,氮肥运筹以基肥∶蘖肥∶穗肥为3∶3∶4时的水稻根系生长旺盛,物质生产能力强,氮肥利用效率最高。因此,小麦秸秆覆盖与基肥∶蘖肥∶穗肥以3∶3∶4的比例配合的水稻的产量最高,为最优组合。     

秸秆还田下氮肥运筹对白土田水稻产量和氮吸收利用的影响

【目的】研究小麦秸秆直接还田条件下不同氮肥基追比例运筹方式对白土稻田水稻产量和氮素吸收利用的影响, 为华中低产白土稻田水稻合理施肥提供科学依据。【方法】设置2种小麦秸秆还田量(0和3000 kg/hm2)及3种氮肥基肥-分蘖肥-穗肥施用比例(80-0-20、 60-20-20 和40-30-30)和不施氮的对照, 共7个处理, 分别为N80-0-20、 N60-20-20、 N40-30-30、 N80-0-20+S、 N60-20-20+S、 N40-30-30+S和CK。水稻收获期采集代表性样品考察水稻产量结构性状, 同时测定水稻籽粒和秸秆产量, 分析籽粒和秸秆氮素含量, 计算水稻氮素吸收量和氮肥利用效率。【结果】基肥-分蘖肥-穗肥施用比例60-20-20的处理水稻籽粒产量最高, 两年试验较不施分蘖肥的对照分别增产9.4%~12.9%和7.4%~8.9%。实施小麦秸秆直接还田后, 水稻籽粒产量较不施秸秆的对照分别提高10.2%~23.4%和0.8%~5.5%。不施秸秆条件下, 基-蘖-穗肥施用比例60-20-20的处理水稻籽粒含氮量最高, 较不施氮的对照提高11.3%, 而秸秆含N量随中后期追肥比例的加大而提高。秸秆还田条件下, 氮肥后移能明显提高水稻籽粒和秸秆含氮量。水稻籽粒氮素吸收量, 基-蘖-穗肥比例60-20-20处理最多, 2011年较对照N80-0-20分别增加13.7%和24.8%, 2012年提高14.5%和9.2%; 秸秆氮素积累量则随中后期追肥用量的增加而增多, 基-蘖-穗肥比例40-30-30处理最多。不施秸秆条件下, 基-蘖-穗肥比例60-20-20的处理氮素干物质生产效率、 氮素稻谷生产效率、 氮收获指数均最高, 百公斤籽粒吸氮量最低。秸秆还田条件下, 氮素干物质生产效率和氮素稻谷生产效率均随中后期追肥量的增加而下降, 而百公斤籽粒吸氮量则最高。氮素农学效率、 氮肥回收利用率和偏生产力也是60-20-20比例的处理最高, 较对照N80-0-20农学效率分别提高4.90和2.44 kg籽粒/kg N, 氮肥利用率提高7.82和21.29个百分点, 偏生产力提高4.90和2.44个百分点。【结论】综合水稻产量、 氮素吸收量以及氮肥利用效率, 安徽省江淮丘陵低产白土地区, 小麦秸秆直接还田条件下, 单季中稻氮肥的基肥-分蘖肥-穗肥施用比例, 以60-20-20运筹方式较为适宜。     

改进施氮运筹对水稻产量和氮素吸收利用的影响

【目的】秸秆还田不仅可改良土壤和增加土壤有机质,还能提高作物产量和品质。但秸秆还田后,土壤有机酸积累和微生物固氮,抑制水稻前期生长。在长江流域稻麦两熟地区,当地农户往往通过增加施氮量来解决秸秆还田的负效应,造成肥料浪费和氮污染。因此,探索研究秸秆还田条件下水稻优化的氮肥运筹措施,阐明水稻产量形成和氮素吸收与利用对氮素响应特征,对于提高水稻产量和氮素利用效率具有重要意义。【方法】2012 2013年,以超级粳稻武运粳24号和宁粳3号为材料,在江苏省兴化市进行大田试验,在秸秆全量还田条件下,设置常规施氮300 kg/hm2(N1)、增加施氮量345 kg/hm2(N2)和常规施氮运筹(CFP,基肥∶分蘖肥∶穗肥=3∶3∶4)、改进施氮运筹(MFP,基肥∶分蘖肥∶穗肥=4∶3∶3),以无氮处理为对照,研究施氮量和氮肥运筹措施对水稻产量及其产量构成、干物质积累、氮素积累、氮素吸收速率和氮肥利用效率的影响。【结果】随着氮肥水平提高,水稻穗数显著增加,每穗粒数、结实率和千粒重下降,最终增产不显著。与常规施氮运筹比较,改进氮肥运筹显著增加穗数,显著提高群体颖花量并增产,在N1水平下,改进施氮运筹增产幅度为5.18%7.10%,高于N2水平的2.70%4.29%。随着施氮量增加,水稻分蘖中期、拔节期、移栽期至分蘖中期、分蘖中期至拔节期干物质积累量、氮素积累量显著增加,最终成熟期干物质积累量和氮素积累量有所增加,但差异不显著,而氮肥农学利用率、氮肥吸收利用率和氮偏肥生产力显著下降。与常规氮运筹处理相比,改进氮运筹显著增加水稻移栽期至分蘖中期干物质积累量、氮素积累量和氮素吸收速率,增加成熟期干物质积累量和氮素积累量,提高氮肥农学利用率、氮肥吸收利用率、氮肥生理利用率和氮偏肥生产力,在N1水平下成熟期干物质积累量和氮素积累量分别增加6.52%和5.55%,氮肥农学利用率、氮肥吸收利用率、氮肥生理利用率和氮偏肥生产力分别提高13.36%、8.55%、4.44%和5.29%,差异均达显著水平。【结论】秸秆全量还田条件下,增加氮肥用量水稻增产不显著,且氮肥利用效率低。不增加氮肥用量,通过适当提高基肥比例(基肥∶分蘖肥∶穗肥=4∶3∶3),可实现提高水稻产量、干物质积累量、氮素积累量和氮肥利用效率。     

不同氮肥用量与施肥时期对冷浸田单季稻 生长及农学效率的影响

冷浸田为福建省主要低产田类型之一。基于福建省浅脚烂泥田、青泥田与锈水田主要冷浸田类型,通过田间3个点试验研究不同氮肥用量(105、150与195 kg/hm~2)与施用时期(基蘖肥︰穗肥=10︰0与基蘖肥︰穗肥=7︰3)运筹组合对单季稻生长的影响。结果表明,增施氮肥促进了各类型冷浸田水稻分蘖期分蘖生长速率。不同氮肥组合的锈水田、青泥田与浅脚烂泥田水稻籽粒产量分别较不施肥(CK)增幅14.5%~45.5%、9.4%~13.5%和10.4%~15.9%,但在105 kg/hm~2用量基础上再进一步增施氮肥,籽粒增产效果明显放缓。施用氮肥显著增加了成熟期水稻有效穗数,但对每穗实粒数及千粒重影响不明显。105、150、195 kg/hm~2 3种氮肥用量下各类型冷浸田的农学效率均值分别为17.4、13.3与12.8 kg/kg。除浅脚烂泥田施用穗肥的秸秆产量有显著差异外,其余氮肥不同施肥时期的籽粒与秸秆产量均无显著差异。增施氮肥有提高籽粒氮的趋势,但同时降低了籽粒钾含量。鉴于冷浸田土壤氮素水平较高,单季稻氮肥经济用量宜控制在105~150 kg/hm~2中低水平,超过150 kg/hm~2,农学效率递减,且无明显增产效果。另从人工成本及效益考虑,宜选择基蘖肥︰穗肥=10︰0的施氮方式。     

秸秆还田下化肥减施对苏北地区水稻产量 与氮素吸收利用的影响

探究秸秆还田后化肥减施的响应机制，为苏北地区水稻的科学施肥提供理论依据。采用田间试验方法，在小麦秸秆全量还田条件下，以不施肥处理为对照(CK)，研究了当地常规施肥(T1，氮肥的基肥、分蘖肥、穗肥质量比为7∶2∶1)、不同类型肥料减量20%(T2、T3 和T4，氮肥的基肥、分蘖肥、穗肥质量比为5∶3∶2)和氮肥不同基追比例对水稻生长、产量、品质、氮素吸收利用及土壤养分的影响，以期为苏北地区稻麦轮作生产提供合理的施肥技术支撑。结果表明:秸秆还田下水稻分蘖盛期T1 处理群体茎蘖数量(486.2×104 个·hm-2)最高，且更有利于花前干物质的积累，积累率达到68%。化肥减施20% 下，T4 处理的群体茎蘖数最低，但是其成穗率最高，为86.4%，显著高于T1 处理；T2、T3 和T4 处理的花前干物质积累量、总积累量和花后积累率与T1相比均无显著差异，T4 处理更有利于花前干物质的转运，干物质转运量对籽粒的贡献率高达42.7% 以上。在产量构成方面，T2、T3 和T4 处理实际产量均有所增加，T4 处理产量最高，显著高于T1 和T2 处理12.6% 和11.2%，其主要原因在于有效穗数和结实率的提高。从水稻品质来看，CK 显著降低了稻米的整精米率、垩白粒率、垩白度和蛋白质含量，T4 处理精米率和整精米率、垩白粒率和垩白度与T1 相比无显著差异，但是各施肥处理间蛋白质含量无显著差异。成熟期各处理水稻植株地上部氮素积累量在籽粒部分占比达到60% 以上，T3 处理氮素积累量表现为最高，T2 和T4 处理的籽粒和茎叶氮素积累量相较T1 处理均无显著差异。T2、T3 和T4 处理的氮肥利用率、氮肥偏生产力和氮肥农学效率均高于T1，T4 处理的氮肥农学效率显著高于T1、T2 和T3。收获后T1 处理土壤有机质和全氮量最高，化肥减施20% 会减少田间氮素养分残留量。总体而言，苏北地区稻麦轮作体系中，小麦秸秆全量还田下化肥减施20%(氮肥基肥、分蘖肥、穗肥质量比为5∶3∶2)，不会影响当季水稻的正常生长和产量，且50% 水溶性有机硅缓释肥配施50% 氮肥有助于增产，提高氮肥利用率和减少稻田养分残留。     

氮肥用量与运筹对水稻氮素吸收转运及产量的影响

应用15N示踪技术研究了大田条件下氮肥用量与运筹对水稻氮素吸收、转运及籽粒产量的影响。试验分别设置3个氮肥水平(0、150和240 kg/hm2N)和两种基追比例(即基肥:蘖肥穗粒肥分别为40%︰30%︰30%(A)和30%︰20%︰50%(B)),共5个处理,依次记作N0、N150A、N150B、N240A、N240B。结果表明,在0~240 kg/hm2范围内,提高氮肥水平,显著增加水稻吸收的肥料氮素、土壤氮素数量以及肥料氮在土壤中的残留量。成熟期高氮处理(240 kg/hm2)水稻吸收的肥料氮素、土壤氮素及肥料氮在土壤中的残留量较多,分别为110.25、65.91、32.69 kg/hm2,而氮素的吸收利用率和土壤残留率下降,氮素损失率增加。在相同的氮肥水平下,采用基肥蘖肥穗粒肥比例为30%︰20%︰50%时,水稻吸收的肥料氮数量显著增加,氮素吸收利用率和土壤残留率提高,氮素损失率降低。适量施氮并增加穗粒肥的施氮比例,可以显著增加水稻产量。在本实验条件下,施氮量为240 kg/hm2及基肥蘖肥穗粒肥为30%︰20%︰50%的施氮处理是兼顾产量和环境的最佳氮肥运筹方式。     

麦秆还田氮肥运筹对水稻产量及土壤氮素供应的影响

通过田间对比试验,研究了小麦秸秆全量还田后不同N肥运筹模式对水稻生长及土壤N素供应的影响。结果表明,小麦秸秆全量还田使水稻增产5.3%,且N肥运筹模式由传统模式A(基蘖肥:穗肥=5:5,基肥:分蘖肥=6:4)优化为B(基蘖肥:穗肥=6.5:3.5,基肥:分蘖肥=8:2)时,增产幅度更大,达9.3%。秸秆全量还田主要通过提高水稻结实率和成穗率,增加有效穗数,实现水稻增产。秸秆还田影响了水稻生长进程,表现为抑制水稻前期(孕穗期)生长和N素累积,而促进后期生物量增加和N素累积。同一时期,N肥模式B水稻生物量、N素累积量均高于模式A。秸秆全量还田后,土壤矿质N发生变化,水稻生育前期较不还田处理(CK)低,而后期较CK高,且N肥运筹模式B较A高。秸秆还田提高了N肥利用率,RNA、RNB分别比CK增加4.1和8.6个百分点,且土壤N素表观盈余量表现为:RNBRNACK。因而,小麦秸秆全量还田,并采用N肥运筹模式B,是实现水稻高产,维持土壤N素平衡的有效措施。     

氮肥运筹对寒地水稻产量及光合物质生产的影响

为探讨氮肥运筹对寒地水稻产量及光合物质生产的影响,以粳稻品种垦粳7号和垦粳8号为试验材料,于2017～2018年在大田条件下设置5种氮肥运筹方式:零氮空白处理T0、农民常规施氮T1(施氮量150 kg/hm~2,基肥∶追肥1∶追肥2=6∶3∶1)、平衡施氮T2(施氮量150 kg/hm~2,基肥∶蘖肥∶调节肥∶穗肥=4∶3∶1∶2)、减氮10%施肥T3(施氮量135 kg/hm~2,基肥∶蘖肥∶调节肥∶穗肥=4∶3∶1∶2)、调节氮肥前移T4(施氮量150kg/hm~2,基肥∶蘖肥∶调节肥∶穗肥=5∶3∶0∶2),其中以T1为对照,研究氮肥运筹对寒地水稻产量、干物质积累与转运、高效叶面积、光合势、群体生长率和净同化率的影响。结果表明:与T1相比,T2和T3的增产幅度分别为4.12%～12.79%和2.17%～7.11%,T4减产幅度为3.91%～17.32%;T2、T3改善了寒地水稻齐穗期至成熟期的群体结构,提高了群体干物质量、阶段干物质积累量以及叶、茎、鞘的物质输出量、输出率、转化率;此外,T2和T3也分别提高了齐穗期和灌浆盛期的高效叶面积以及拔节至成熟期群体叶面积指数,并使结实期叶面积衰减率分别显著降低了17.92%和28.92%;T2、T3和T4虽然降低了分蘖盛期至拔节期水稻光合物质生产,但拔节至成熟期的光合势、群体生长势和净同化率均高于T1。综上所述,平衡施氮方式和减氮施肥方式能有效地控制移栽至拔节期的物质生产,提高了齐穗期至成熟期光合生产和干物质转化效率,获得较高的群体质量,从而提高水稻产量。     

氮肥运筹对苏打盐碱地水稻产量和氮肥利用率的影响

为探究氮肥运筹对苏打盐碱地水稻产量和氮肥利用率的影响,在大田条件下,于2017-2018年,以粳稻品种垦粳7号和垦粳8号为供试材料,设置5种氮肥运筹,即不施氮肥(N0)、农民常规施氮(N1,纯N总量150 kg·hm^-2,基肥:蘖肥:穗肥=6:3:1)、平衡施氮(N2,纯N总量150 kg·hm^-2,基肥:蘖肥:穗肥=4:3:3)、平衡减氮施肥(N3,纯N总量135 kg·hm^-2,基肥:蘖肥:穗肥=4:3:3)、氮肥前移(N4,纯N总量150 kg·hm^-2,基肥:蘖肥:穗肥=5:3:2),其中以N1为对照,研究不同氮肥运筹下其产量、产量构成因素、地上部分植株含氮量、穗部氮素积累量以及氮肥利用率的变化。结果表明,与N1相比,N2和N3的产量分别增加了11.45%和5.71%,且N2与N1间差异达显著水平,而N4的产量减少了10.43%;N2和N3齐穗期和成熟期地上部植株含氮量及穗部氮素积累量均得到显著提高,而N4显著降低;N2和N3显著提高了氮肥吸收利用率(NRE)、氮肥农学利用率(NAE)和氮肥偏生产力(NFP),显著降低了土壤氮素依存率(SNDR),且N2的NRE和NAE高于N3,而N4显著降低了NRE,显著提高了SNDR。综上,平衡施氮和平衡减氮施肥通过调整施氮量、施氮比例及施氮时期,可协同实现苏打盐碱地水稻高产和氮肥的高效利用。本研究结果为苏打盐碱地区水稻的氮肥运筹方式提供了理论依据。     

氮肥运筹对苏打盐碱地水稻养分积累、转运及分配的影响

为明确适合苏打盐碱地水稻增产和养分高效利用的氮肥运筹方式。以粳稻品种垦粳7号为供试材料,于2017～2018年,在大田条件下设置5种氮肥运筹方式:不施氮肥(N0)、农民常规施氮(N1,N总量150kg/hm~2,基肥∶蘖肥∶穗肥=6∶3∶1)、平衡施氮(N2,N总量150 kg/hm~2,基肥∶蘖肥∶穗肥=4∶3∶3)、减氮处理(N3,N总量135 kg/hm~2,基肥∶蘖肥∶穗肥=4∶3∶3)、平衡氮肥前移(N4,N总量150 kg/hm~2,基肥∶蘖肥∶穗肥=5∶3∶2),其中以N1为对照。分别在齐穗期和成熟期测定植株氮、磷、钾含量,并分别计算氮、磷、钾积累量及转运量、转运贡献率,收获后测定实际产量。结果表明,与N1相比,N2和N3有利于提高水稻的实际产量,平均分别提高14.23%和5.64%,其中N2与N1间差异达显著水平,而N4产量显著降低了7.98%;N2和N3提高了齐穗期和成熟期的叶片、茎鞘和穗部的氮、磷、钾养分积累量,且以N2最高,与N1间差异显著,同时,N2和N3提高了齐穗至成熟期叶片和茎鞘氮、磷、钾养分转运量、转运率、转运贡献率以及穗部养分增加量,尤其N2叶片氮、磷、钾转运量以及叶片氮转运率平均分别显著提高了83.27%、71.33%、74.54%和20.26%,而N4表现出与N2和N3相反的趋势。此外,水稻产量与成熟期叶片、茎鞘和穗部的氮、磷、钾养分积累量以及养分转运贡献率均呈极显著正相关,且各养分转运贡献率间存在协同性。综上所述,平衡施氮和减氮处理能提高水稻齐穗期和成熟期植株氮、磷、钾养分积累量,促进齐穗至成熟期养分的转运,利于苏打盐碱地水稻增产及对养分的高效利用。     

Agricultural potential of Mediterranean grain and forage legumes: Key differences between and within Vicia species in terms of phenology, yield, and agronomy give insight into plant adaptation to semi-arid environments

In order to identify key adaptive traits which affect productivity in Mediterranean grain and forage legumes and simultaneously determine the agricultural potential of a wide range of Vicia species, germplasm collected from the wild throughout the eastern Mediterranean was grown under semi-arid conditions in Tel Hadya, Syria (313 mm growing season rainfall). These included species currently in use in Mediterranean agriculture, such as V. sativa L., as well as those more widely used in the past-such as V. ervilia L., but also a broad selection from Section Narbonensis (B. Fedtsch. ex Radzhi) Maxted, including V. narbonensis L, V. johannis Tamamsch., V. hyaeniscyamus Mout., V. serratifolia Jacq., and V. kalakhensis Khattab et al. V. faba, a near relative of the taxa in Section Narbonensis, was included as a domesticated control. Where applicable, a representative range of subspecies was used. Accessions were chosen from a wide range of habitats in terms of latitude (31.02–40.72 decimal^o), longitude (27.1–43.17 decimal^o), altitude (20–1510 m), rainfall (180–1700 mm/yr) and soil depth (5–50 cm) in order to maximise diversity within species. Agricultural potential was determined by measuring seed, hay and biological yield, as well as agronomic traits such as harvest index, standing crop height, and seed size. The comparative influence of phenology and key agronomic traits such as plant habit and seed size on productivity varied tremendously between species, depending on their reproductive strategies. In V. sativa and V. ervilia, the smaller seed species which rely on long vegetative phases and growing seasons to accumulate sufficient biomass to set seed, and in which there was comparatively little agronomic variation, phenology had a large impact on yield. In early emerging taxa such as V. ervilia and V. s. subsp. sativa, with built-in long vegetative phases and growing seasons, seed yield was negatively correlated with flower ing (r = –0.86 to –0.88), whereas the opposite was the case for later emerging taxa such as V. s. subsp. nigra (L.) Ehrh. (r = 0.95). Within V. narbonensis and relatives, the larger seeded Vicia species which rely on more conservative reproductive strategies where high seedling vigour associated with large seeds enables the species to enter reproductive phases relatively early, phenology had a much smaller impact on yield than did variation of key traits such as seed weight, plant habit and pod shattering. Among the undomesticated germplasm harvest indices ranged from 0.09–0.31, hay yields from 0.1–3.4 t/ha, seed yield from 0–2.0 t/ha, and dry matter at maturity from 1.6–6.5 t/ha. Sub-specific taxonomy was crucial in determining agronomic potential. V. narbonensis var. aegyptiaca Kornhuber ex Asch. et Schweinf. showed the most potential, combining an upright habit, large seeds (212 mg) and tendency to retain intact pods after maturity, with the highest yield, harvest index and crop height of all the wild Vicia species. V. sativa subsp. sativa, V. ervilia and V. narbonensis var. narbonensis were less productive, but still showed agricultural potential. The smaller seeded V. narbonensis, var. affinis, var. jordanica H. Schäf. and var. salmonea (Mout.) H. Schäf., and their close relatives V. johannis, V. hyaeniscyamus, V. serratifolia and V. kalakhensis have little to offer Mediterranean agriculture on the basis of poor agronomy.     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Control of pitch pine seed germination and initial growth exerted by leaf litters and polyphenolic compounds

We investigated the influence of three concentrations of water extracts of three leaf litter species (pitch pine, huckleberry and white oak) and a mixture of all litters on the germination of pitch pine seeds and initial seedling growth in a microcosm experiment. All three plant species are important components of the pine barrens ecosystems in New Jersey, where it has been seen that pine seedling recruitment occurs only after stand replacing fire or in disturbed sites, where surface organic soil horizons and leaf litter have been removed. Leaf litter extracts did not influence seed germination, but significantly reduced seedling growth at high concentrations. There was little difference between the leaf litter species in growth suppression. As charcoal is a natural residue on the forest floor following fire, its influence on growth suppression was examined; it has been shown to immobilize polyphenols. Charcoal removed the inhibitory effect of leaf litter extracts and allowed the fertilizer effect of nutrients leached from the leaves to enhance seedling growth, particularly at the higher concentration of litter extract used. Responses to litter extracts were compared to four pure phenolic compounds, catchecol, p-coumaric acid, p-hydroxybenzoic acid and tannic acid. None of these compounds suppressed pine seedling growth, suggesting that these phenolics are not allelopathic to pine seedlings. The results are discussed in the context of fire as a driving factor in these oligotrophic and seasonally dry ecosystems and the interactions between nutrient supply and allelopathic chemistry of different leaf litters.     

Phylogenetic relationships of Actinidia and related genera based on micromorphological characters of foliar trichomes

The phylogenetic relationships within the genus Actinidia and among 3 allied genera Clematoclethra, Saurauia, and Sladenia have been very controversial. In order to understand the systematic implication of foliar trichomes in those genera, the micromorphological characteristics of foliar trichomes from 34 taxa were examined by means of light microscopy and scanning electron microscopy (SEM). The observed micromorphological characteristics were classified into eight main types. A phylogenetic analysis of Actinidia and related genera based on 15 micromorphological characters of foliar trichomes was conducted using Wagner parsimony method and Sladenia celastrifolia, Rhododendron hybridum and R. simsii as a complex outgroup. In the resulting phylogenetic tree, Actinidia is shown to be a monophyletic group, and Clematoclethra and Saurauia form another monophyletic group. This study also presents the phylogenetic relationships among 4 sections within the genus Actinidia: the monophyly of sect. Leiocarpae and of sect. Strigosae, and polyphyly of sect. Maculatae and of sect. Stellatae.     

Effects of mixing radiata pine needles and understory litters on decomposition and nutrients release

A microcosm experiment was conducted to understand the impacts of mixing radiata pine (Pinus radiata D. Don) needle litter and understory (gorse—Ulex europaeus L., broom—Cytisus scoparius L., bracken—Pteridium aquilinum L., and lotus—Lotus pedunculatus L.) litter materials on decomposition and nutrient release dynamics. Mixing of pine needle litter with understory litter material had significant impacts on both the rate of decomposition and nutrient release patterns of pine litter as well as that of the understory species. Incubation in microcosms over 10 months resulted in significantly lower mass loss of radiata pine needle litter mixed with broom and lotus litters (35.8±8.4 and 41.3±0.8%, respectively) than pure pine needle litter (63.5±2.3%). Mixing with pine needle litter significantly increased the mass loss of broom (53.1±6.1%) compared to that of pure broom (30.2±1.0%). Significant transfers of nutrients, especially of magnesium and potassium, were observed in litter mixture treatments. Concentration of K in litter materials was found to be the most limiting factor for the decomposing microorganisms in the present study. The findings of this study suggest that management of understory litter composition via weed control could be used to manipulate carbon turnover and nutrient release in the forest floor. Also, initial selection of understory species will be important and could be managed.     

Effect of agroforestry woody species on earthworm activity and physicochemical properties of worm casts

The effects of five agroforestry woody species (Dactyladenia barteri, Gliricidia sepium, Leucaena leucocephala, Senna siamea andTreculia africana) on the surface aasting activity ofHyperiodrilus africanus were studied in an Alfisol (Oxic Paleustalf) in southwestern Nigeria. Casting activity under the woody species decreased in the following order:Dactyladenia sp. (26.4 Mg ha^-1 year^-1)>Gliricidia sp. (24.4 Mg ha^-1 year^-1)>Treculia sp. (22.9 Mg ha^-1 year^-1)>Leucaena sp. (18.6 Mg ha^-1 year^-1)>Senna sp. (18.3 Mg ha^-1 year^-1). These differences in casting activity were partly explained by microclimatic effects. Irrespective of the woody species, the worm casts were higher in clay and silt contents, bulk density, water-stable aggregates, pH, organic C, exchangeable cations, effective cation exchange capacity, and extractable P levels than the corresponding surface soils. The woody species did affect the physicochemical properties and P sorption of the worm casts. The content of water-stable aggregates of worm casts decreased in the following order:Dactyladenia sp.>Treculia sp.>Senna sp.>Leucaena sp.>Gliricidia sp. Large differences in extractable P levels were observed.Senna sp. was associated with the highest extractable P level (11.5 mg kg^-1) andTreculia sp. the lowest (4.9 mg kg^-1). P sorption was highest on worm casts underDactyladenia sp. and lowest on those underTreculia sp. Without fertilizer application, there were no significant differences in the dry weight of maize grown in the different worm casts. With NPK applications, the dry weight of maize grown in worm casts associated withTreculia sp. was significantly lower than that of maize grown in the other worm casts, mainly due to the low extractable P level. Despite a high organic C and exchangeable K status, maize grown in the worm casts still responded significantly to N and K applications. The N uptake by maize grown in worm casts associated withTreculia sp. was lower than that in the other treatments.     

Allelic diversity of HMW and LMW glutenin subunits and omega-gliadins in French bread wheat (Triticum aestivum L.)

Wheat endosperm storage proteins, namely gliadins and glutenins, are the major components of gluten. They play an important role in dough properties and in bread making quality in various wheat varieties. In the present study, the different alleles encoded at the 6 glutenin loci and at 3 -gliadin loci were identified from a set of 200 hexaploid wheat cultivars grown primarily in France using SDS PAGE. At Glu-A1, Glu-B1 and Glu-D1, encoding high molecular weight glutenin subunits (HMW-GS), 3, 8 and 5 alleles were observed respectively. Low molecular weight glutenin subunits (LMW-GS) displayed similar polymorphism, as 5 and 11 alleles were identified at loci Glu-A3 and Glu-B3 respectively. Four alleles were observed at Glu-D3 loci. Omega-gliadin diversity was also very high, as 7, 13 and 9 alleles were found at Gli-A1, Gli-B1 and Gli-D1, respectively. A total of 147 (or 149) patterns resulted from the genetic combination of the alleles encoding at the six glutenin loci (or Glu-1 and Gli-1 loci). Although Glu-1 and Glu-3 loci were located on different chromosome arms and were theoretically independent, some associations were revealed due to pedigree relatedness between some French wheat cultivars. The usefulness of allelic identification of LMW-GS together with HMW-GS and gliadins for future genetic and technological wheat improvement is discussed.     

Prospects for control of Pythium damping-off of lettuce with Trichoderma,Gliocladium and Enterobacter spp.

Summary Damping-off of lettuce (Lactuca sativa) caused by Pythium ultimum was studied in pots containing a non-sterile potting mix in the glasshouse. Fifty P. ultimum sporangia g^-1 compost reduced the plant stand to 15% and shoot dry weight to 18%, but this reduction was totally prevented by applying Trichoderma harzianum at 2×10⁵ viable propagules g^-1 potting mix. Gliocladium virens and Enterobacter cloacae also alleviated the damping-off. E. cloacae did not adversely affect the action of the fungal antagonists. The co-existence of the bacterial and fungal antagonists was revealed on the root surface and inner surface of the testa by scanning electron microscopy, indicating the compatibility of the biocontrol agents.     

Genetic Diversity within and Between Populations of Lathyrus genus (Fabaceae) Revealed by ISSR Markers

In order to evaluate the genetic diversity in Lathyrus genus, the Inter Simple Sequence Repeats method (ISSR) was exploited in five populations. These consisted of two cultivated species belonging to section Lathyrus (L. sativus L. and L. cicera L.) and a wild one belonging to the section Clymenum (L. ochrus DC.). Two 3′anchored ISSR primers and two unanchored ones, generated a total of 60 useful polymorphic DNA bands. Our data provide evidence of high molecular polymorphism at the intra- and the inter-specific levels showing that both wild and cultivated forms constitute an important pool of diversity. Moreover, among the generated DNA bands, a 500 bp band, totally absent in the banding patterns of the section Clymenum, appears to be a molecular marker of section Lathyrus. Results provided for lineage and suggest recent origin of these species that might have evolved from a common ancestor producing both L. ochrus species and the two other species L. sativus and L. cicera. These relationships support previous studies based on morphological variation and molecular analysis.