Differential ozone sensitivity of rice cultivars as indicated by visible injury and grain yield

Surface ozone pollution may cause reductions in rice ( Oryza sativa L.) yield. Ozone sensitivity in rice cultivars is often evaluated based on visible leaf injury at an early growth stage. However, it is not clear whether reduction in grain yield is related to visible injury. Therefore, visible damage and grain yield reduction were examined in Japanese and Asian rice cultivars exposed to ozone. In experiment 1, 3-week-old rice seedlings were exposed to ozone (min.: 20 nl·l⁻¹, max.:120 nl·l⁻¹) for 12 h in open-top chambers (OTCs). Visible leaf injury was quantified according to a leaf bronzing score. In experiment 2, rice plants were exposed to ozone in OTCs throughout the cropping season until grain harvest. Daily mean ozone concentrations were maintained at 2, 23, 28, 42, and 57 nl·l⁻¹ with a regular diurnal pattern of exposure. After harvest, grain yield was determined. Based on visible injury to the uppermost fully expanded leaf, the indica cultivar 'Kasalath' was most tolerant, and the japonica cultivar 'Kirara 397' was most sensitive to ozone. However, grain yields for both 'Kasalath' and 'Kirara 397' were significantly decreased after ozone exposure. The indica cultivar 'Jothi' suffered severe injury after ozone exposure but had no reduction in grain yield. Therefore, ozone sensitivity of rice cultivars evaluated by visible injury did not coincide with that evaluated by the reductions in grain yield. These results suggest that mechanisms that induce acute leaf injury do not relate to chronic ozone toxicity that reduces yield.     

稻米品质性状对开放式空气二氧化碳浓度增高的响应

利用开放式空气CO2浓度增高(FACE)系统平台。研究大田栽培条件下粳稻武香粳14号稻米品质性状对CO2浓度增高200μmol·mol^-1的响应。结果表明．FACE处理稻谷的出糙率平均比CK高1．4个百分点,整精米率平均比CK低12．3个百分点,较低的供N水平有利于提高FACE条件下的出糙率．较高的供N水平有利于提高FACE条件下的整精米率;FACE处理的稻米垩白略有增加。垩白粒率平均比CK高11．9个百分点,垩白度平均比CK平均高2．8个百分点,较高的供N和供P水平有利于降低FACE条件下垩白大小、垩白粒率和垩白度;FACE处理稻米糊化温度平均比CK平均高0．52℃,胶稠度有提高的趋势,但对稻米直链淀粉含量影响较小,较高的供N和供P水平有利于降低FACE条件下稻米的直链淀粉含量,较低的供N和较高的供P水平有利于降低FACE条件下稻米胶稠度,较低的供N水平有利于降低FACE条件下稻米糊化温度;FACE处理使稻米蛋白质含量比CK平均低0．6个百分点,较低的供N和供P水平有利于降低FACE条件下稻米蛋白质含量。     

氮肥水平对不同基因型水稻氮素利用率、产量和品质的影响

以不同基因型的水稻品种日本晴、N70、N178和OM052为供试品种,氮肥采用尿素,按基肥(70%)和蘖肥(30%)两次施用,设置3个施氮水平(N用量设0、120、270 kg·hm^-2)的田间小区试验,研究氮素水平对水稻产量、氮素利用效率和稻米品质的影响,以期为氮肥合理施用和氮高效水稻品种创制提供科学依据.结果表明:施氮能增加水稻品种产量的原因是提高了有效穗数和每穗实粒数;与对照(0 kg·hm^-2)相比,当施氮量为120和270 kg·hm^-2时,OM052籽粒产量在4个品种中增幅最大,分别为41.1%和76.8%;品种产量增幅不同是由于氮素利用效率的差异,在120、270 kg·hm^-2氮处理下,4个供试品种中,日本晴籽粒产量和氮素农学利用率(40.90 g·g^-1、18.56 g·g^-1)都最低,为氮低效品种,OM052籽粒产量和氮素农学利用率(145.9 g·g^-1、81.24 g·g^-1)都最高,为氮高效品种.施N能够增加各品种的直链淀粉和蛋白质含量,使胶稠度变长,降低垩白率、垩白度和碱消值;随施氮量增加,热浆黏度、峰值黏度、回复值和崩解值递减,而消碱值递增.相关性分析表明,低N水平下,供试品种产量及产量构成因子与外观品质、蒸煮食味的相关性更显著.综上,OM052是一个籽粒产量和氮素利用效率“双高”基因型品种,合理施用氮肥可以显著增加水稻的有效穗数和每穗粒数,改善稻米籽粒品质,实现高产和优质的协同.     

Effect of azoxystrobin and kresoxim‐methyl on rice blast and rice grain yield in China

Sensitivity to azoxystrobin and kresoxim‐methyl of 80 single‐spore isolates of Magnaporthe oryzae was determined. The EC₅₀ values for azoxystrobin and kresoxim‐methyl in inhibiting mycelial growth of the 80 M. oryzae isolates were 0.006–0.056 and 0.024–0.287 µg mL^?1, respectively. The EC₅₀ values for azoxystrobin and kresoxim‐methyl in inhibiting conidial germination of the M. oryzae populations were 0.004–0.051 and 0.012–0.105 µg mL^?1, respectively. There was significant difference in sensitivity to azoxystrobin or kresoxim‐methyl between the tested isolates representing differential sensitivity to carbendazim (MBC) and kitazin P (IBP); however, there was no correlation between this difference in sensitivity to azoxystrobin or kresoxim‐methyl and sensitivity to MBC or IBP, indicating that there was no cross‐resistance between azoxystrobin or kresoxim‐methyl and MBC or IBP. In the protective and curative experiments, kresoxim‐methyl exhibited higher protective and curative activity than azoxystrobin when applied at 150 and 250 µg mL^?1 accordingly, while azoxystrobin exhibited stronger inhibitory activity against M. oryzae isolates than that of kresoxim‐methyl in the in vitro test. The results of field experiments also suggested that both azoxystrobin and kresoxim‐methyl at 187.5 g.a.i. ha^?1 gave over 73% control efficacy in both sites, exhibiting excellent activity against rice blast. Taken together, azoxystrobin and kresoxim‐methyl could be a good substitute for MBC or IBP for controlling rice blast in China, but should be carefully used as they were both at‐risk.     

结实期水分胁迫对不同氮肥水平下水稻产量及其品质的影响

以生产上广泛使用的3个水稻品种为材料,研究了结实期适度水分胁迫对不同氮肥水平下稻米产量及其品质的影响.结果表明,正常施氮水平下,水分胁迫使3个品种籽粒产量降低11.6%～14.7%,虽整精米率有所提高,但垩白度却显著增加(18.7%～33.1%),外观品质变劣;而高氮水平下,水分胁迫处理的产量增加18.8%～22.2%,垩白粒率和垩白度分别降低15.3%～37.2%和13.7%～29.9%,外观品质变优.稻米RVA谱特征值和米饭质地也明显受到结实期土壤水分和施氮水平的影响.正常施氮水平下,水分胁迫处理的最高粘度和崩解值(扬稻6号除外)要低于水层灌溉处理,而其消减值却明显高于水层灌溉处理,水分胁迫使得正常施氮处理的米饭口感较硬,弹性较差,粘性降低,且咀嚼有渣感.而高氮水平下,水分胁迫利于米粉糊化过程中早期粘度的上升,最高粘度增加,崩解值也明显高于水层灌溉,消减值却明显减小,米饭的硬性和凝聚性减小,松弛性和粘附性增大,米饭质地有变优的趋势.     

云南香型软米水稻资源农艺性状遗传效应研究

选取5份云南地方香型软米水稻种质资源和6份自育香型软米保持系按5×6不完全双列杂交设计(NCⅡ)配制成30个组合,采用加性-显性-上位性遗传模型,分析云南香型软米11个农艺性状的遗传效应。结果表明,云南香型软米多数农艺性状的遗传主要受加×加上位性效应、加性×环境效应、显性×环境效应的影响,还存在不同程度的加性效应和显性效应,单株产量受基因加性效应、显性效应、加×加上位性效应、加性×环境效应、显性×环境效应的影响;株高、有效穗的遗传率以普通狭义遗传率为主,其他性状的普通狭义遗传率和互作狭义遗传率均达极显著水平;产量构成性状之间存在不同类型和不同程度的遗传相关,多数性状之间以加×加上位性、加性×环境和显性×环境互作效应显著。     

Reaction of incompatible isolate of Pyricularia grisea on rice leaves stripped of epicuticular wax reflects blast conduciveness of soils

Upland rice cultivars were evaluated in the greenhouse for susceptibility to the rice blast disease caused by Pyricularia grisea Sacc., on two upland soils from the Philippines previously considered to be “blast conducive” and “blast non-conducive”. Under monocyclic inoculation tests plants grown in conducive soil showed significantly greater lesion development than plants of the same cultivar grown in non-conducive soil: cultivars considered to be susceptible to the isolates used showed increased number of susceptible-type lesions; resistant cultivars showed increased number of hypersensitive resistant-type lesions. A similar effect was observed under polycyclic tests where several generations of the pathogen were allowed to develop on the test plants. Dilution of conducive soil with non-conducive soil resulted in a corresponding reduction of disease severity, although this was most pronounced on resistant cultivars. Removal of leaf epicuticular waxes (LEW) using organic solvents increased the number of resistant-type lesions on resistant cultivars grown in both soils following inoculation. Susceptible plants were not suitable for quantifying the relative blast conduciveness of a soil because of the extreme environmental sensitivity of the bioassay and the tendency of lesions to coalesce. Comparing numbers of resistant-type lesions on leaves of plants stripped of LEW and inoculated with an incompatible P. grisea isolate among plants grown in different soils proved to be a satisfactory means of distinguishing the relative blast conduciveness of soils under controlled conditions. This method was field tested in eastern India and results corroborated farmer assessment of which soils were blast conducive. Using incompatible isolate-cultivar combinations and LEW-free leaves is proposed as a simple bioassay for assessing blast conduciveness of soils and should prove useful in regional characterization of rice blast risk.     

Nitrogen form and silicon nutrition effects on resistance to blast disease of rice

The effect of N form and Si nutrition on rice (Oryza sativa L.) susceptibility to blast disease (caused by Pyricularia oryzae Cav.) was assessed in the greenhouse with nutrient solution culture. The N form supplied to the susceptible cultivar IR50 affected the relative infection efficiency (RIE) of P. oryzae measured as lesions/cm² leaf. Plants given NO₃ ^- were more susceptible than plants receiving NH₄ ⁺-N. This result may partially explain why plants grown in nonflooded soil, where NO₃ ^- is the main source of inorganic N, are more susceptible to blast than plants grown in flooded soils, where NH₄ ⁺ is the main inorganic N source. Nitrate-N and Mn concentration were higher in leaf blades of plants grown with NO₃ ^-. Total-N, Si, and Fe concentration were not affected by N form. The addition of Si significantly increased IR50 resistance to blast. With 2.2 mol m^-3 Si in solution, RIE values were lower by more than 90% than the control with no Si added in solution. The effect of Si accumulation in leaves at various positions was further studied in cultivars having differing levels of resistance (IR50, IR36, and IAC165). Silicon addition significantly reduced RIE in the three cultivars. Silicon concentration in the topmost leaves (the only leaves showing typical blast lesions) was not significantly different among the three cultivars when 2.2 mol m^-3 Si was used. Silicon was an important component in the mechanism of resistance to blast and it was effective regardless of the original level of resistance of the cultivar used. Contribution from the Agronomy Unit, Agronomy-Physiology-Agroecology Division, International Rice Research Institute (IRRI), P.O. Box 933, 1099 Manila, Philippines, and Colegio de Postgraduados, Mexico. Part of a thesis submitted by the senior author in partial fulfillment of the requirements for the M.S. degree.     

播栽期对水稻产量和产量构成因素及生育期的影响

研究了不同播栽期对水稻产量和产量构成因素及生育期的影响。结果表明 ,随播栽期推迟 ,水稻产量有所降低。每穗成粒数减少是推迟播栽期引起水稻减产的主要原因 ,其次是千粒重的下降和成穗数的降低。针对目前的生产实际 ,提出了一些应对播栽期推迟的技术措施。     

Diallel analysis to predict heterosis and combining ability for grain yield,yield components and bread-making quality in bread wheat (T. aestivum)

Combining ability for grain yield, yield components, and several agronomic and qualitative traits, was studied in a seven-parent diallel cross. The 21 F₁ hybrids and the seven parental cultivars were grown in replicated plot trials sown at normal seed density in three locations in the years 1992 and 1993. The effects of general combining ability (gca) were highly significant for all the traits measured with the exception of seeds per spikelet, while the specific combining ability (sca) effects were statistically significant for grain yield, plant height, heading time, for all the yield components, and for the Chopin alveographic parameters P and P/L ratio. For the majority of the traits measured gca was greater than sca. Standard heterosis (sh) for grain yield, i.e., the superiority of the hybrids over the best pure line cultivar(cv Eridano), was only 3.3%, confirming previous finding which indicate sh effects in the range of 10%. The most interesting hybrid derived from the cross Maestra x Golia revealed a yield level approaching that of the highest yielding cv Eridano but appeared more interesting because of its reduced plant height and superior bread-making quality, signifying a selling price 30% higher. It was concluded, therefore, that the first generation of hybrids, likely to appear on the market in the next few years, will be characterized by a yield potential only slightly superior to that of the best standard cvs but associated with other desirable traits, such as bread-making quality.     

激素混喷对杂交稻制种产量的影响

汕优63制种穗期用4种激素处理喷施母本．结果表明,花调灵或花信灵与920混合喷施比单喷920花时提早,开花进程加快,柱头外露率和异交结实率提高,增产效果明显,可加快普及应用．88速效灵与920混喷效果尚需进一步试验验证．     

普通野生稻中增产相关QTL的发掘

普通野生稻(Oryza Rufipogon)是重要的遗传资源,发掘其优良等位基因将对水稻遗传改良产生重要影响。文章从以珍汕97为轮回亲本,普通野生稻为供体的BC2F1群体中选择一个与珍汕97表型明显不同的单株BC2F1-15,经过连续自交获得回交重组自交系BC2F5群体。均匀分布于12条染色体的126个多态性SSR(Simplesequence repeats)标记基因型分析,发现BC2F1-15单株在30%的标记位点为杂合基因型;利用该群体共检测到4个抽穗期、3个株高、4个每穗颖花数、2个千粒重和1个单株产量QTL。在第7染色体RM481-RM2区间,检测到抽穗期、每穗颖花数和产量QTL,野生稻等位基因表现增效作用;其他3个每穗颖花数QTL位点,野生稻等位基因也均具有增效作用。结果表明野生稻携带有增产相关的等位基因,这些有利等位基因无疑是水稻遗传改良可资利用的新资源。     

水稻抗稻瘟病天然免疫机制及抗病育种新策略

稻瘟病是水稻最严重的病害之一,由子囊菌(Magnaporthe oryzae)引起。利用抗病品种是防治稻瘟病最经济、最有效的措施。近年来,稻瘟病已发展为研究植物与病原真菌分子互作机制的模式系统,在水稻与稻瘟菌互作和寄主抗性分子生物学、基因组学和蛋白组学等领域取得了一系列重要的研究成果。文章综述了近年来水稻抗稻瘟病两种天然免疫机制,即病原菌相关分子模式诱导和效应蛋白诱导的抗病机制研究的最新进展,讨论了GWAS、TALLEN、CRISPR和HIGS等基因组研究新方法和新技术在水稻抗病育种中的应用,并对目前稻瘟病抗性机制研究和抗病育种中的问题和挑战进行了探讨和展望。     

云南地方稻种持久抗瘟性的研究

1996～1999年,在不同纬度、不同海拔和不同稻作生态类型的重病区设立5个持久抗性稻瘟病鉴定圃.试验材料为云南的74份地方稻种资源,其中粳稻56份,籼稻18份(含野生稻3份).通过多个抗性组分进行了系统研究,初步表明大白谷(粳、墨江县)、毫弄早(籼、勐海县)、毫玉浪(籼、勐海县)、疣粒野生稻(野、西双版纳自治州)等具有持久抗瘟性能;其中疣粒野生稻高抗细菌性条斑病,对白叶枯病抗性为0级,接近免疫,中抗稻瘟病.通过对品种多抗性组分分析和品种抗性系统聚类分析,提出在不同生态类型时、空动态的病叶片上的产孢量和病斑表型可作为简易、快速鉴定持久抗瘟性指标.     

Analysis of genetic effects on nutrient quality traits in indica rice

Nine cytoplasmic male-sterile lines and five restorer lines were used in an incomplete diallel cross to analyze seed effects, cytoplasmic effects, and maternal gene effects on nutrient quality traits of indica rice (Oryza sauva L.). The results indicated that nutrient quality traits were controlled by cytoplasmic and maternal effects as well as by seed direct effects. Maternal effects for lysine content (LC), lysine index (LI), and the ratio of lysine content to protein content (RLP) were more important than seed direct effects, while protein content (PC) and protein index (PI) were mainly affected by seed direct effects. Cytoplasmic effects accounted for 2.41–20.80% of the total genetic variation and were significant for all nutrient quality traits. Additive genetic effects were much more important than dominance effects for all of the traits studied, so that selection could be applied for these traits in early generations.     

不同土壤水分处理对水稻光合特性及产量的影响

为探明土壤水分对水稻生长发育的影响机理,以武香粳14和两优培九为试验材料,分析了不同土壤水分处理下(W1、W2、W3和CK分别表示土壤体积含水量为20%、30%、40%和5cm水层灌溉)的水稻光合特性、产量及水分生产率等。结果表明,轻度水分胁迫(W3)具有处理间最大的叶片气孔导度、蒸腾速率和净光合速率,其他处理规律不显著。灌浆初期各水分处理下叶位间光合指标均表现为:剑叶＞顶2叶＞顶3叶>顶4叶,其他生育期规律不显著。与对照处理(CK)相比,武香粳14的W1、W2和W3处理的产量分别减少61.14%和29.13%、增加0.96%,水分生产率分别减少10.69%、增加1.53%和20.61%;两优培九的产量分别减少64.11%和28.76%,增加2.08%,水分生产率分别减少16.39%,增加2.46%和22.13%。研究结果为水稻精确灌溉和节水生产提供了技术支撑。