The effect of defoliation practice in Western Australia on tiller development of annual ryegrass (Lolium rigidum) and Italian ryegrass (Lolium multiflorum) and its association with forage quality

The effect of defoliation on the vegetative, early reproductive and inflorescence stages of tiller development, changes in the dry‐matter yield of leaf, stem and inflorescence and the associated changes in forage quality was determined on plants of annual ryegrass (Lolium rigidum Gaud.) and Italian ryegrass (L. multiflorum Lam.). The field study comprised seventy‐two plots of 1 m × 2 m, sown with one annual ryegrass and seven Italian ryegrass cultivars with a range of heading dates from early to late; defoliation commenced 6 weeks after germination. During the vegetative stage of growth, plots were defoliated when the tillers had three fully expanded leaves (three‐leaf stage). During the early reproductive stage of growth, to simulate a cut for silage, plots were defoliated 6–7 weeks after 0·10 of the tillers displayed nodal development. The subsequent regrowth was defoliated every 3 weeks. Assessments of changes in tiller density, yield and quality were made in the growth cycle that followed three contrasting cutting treatments during the winter–spring period (from 10 July). In treatment 1, this growth cycle (following closing‐up before a subsequent conservation cut) commenced on 7 August following two defoliations each taken when the tillers were at the three‐leaf stage. In treatment 2, the growth cycle commenced on 16 October following: for early‐maturing cultivars, two cuts at the three‐leaf stage, a cut for silage and an additional regrowth cut; for medium‐maturing cultivars three cuts at the three‐leaf stage and a cut for silage; and late‐maturing cultivars, five cuts at the three‐leaf stage. In treatment 3, defoliation up to 16 October was as for treatment 2, but the growth cycle studied started on 27 November following two additional regrowth cuts for early‐ and medium‐maturing cultivars and cut for silage for the late‐maturing cultivars. Tiller development for all cultivars was classified into three stages; vegetative, early reproductive and inflorescence. In treatment 1, in vitro dry‐matter digestibility (IVDMD) and crude protein (CP) content were negatively associated with maturation of tillers. IVDMD ranged from 0·85 to 0·60 and CP ranged from 200 to less than 100 g kg^–1 dry matter (DM) during the vegetative and inflorescence stages respectively. This large reduction in forage quality was due to an increase in the proportion of stem, inflorescence and dead material, combined with a reduction in the IVDMD and CP content of the stem. A high level of forage quality was retained for longer with later‐maturing cultivars, and/or when vegetative tillers were initiated from the defoliation of early reproductive tillers (treatments 2 and 3). However, 15 weeks after the closing‐up date in treatment 1, defoliation significantly reduced the density of inflorescences with means (±pooled s.e_m.) of 1560, 1178 and 299 ± 108 tillers m^–2, and DM yield of inflorescence with means of 3·0, 0·6 and 0·1 ± 0·15 t ha^–1 for treatments 1, 2 and 3 respectively. This study supports the recommendation that annual and Italian ryegrass cultivars should be classified according to maturity date based on the onset of inflorescence emergence, and that the judicious defoliation of early reproductive tillers can be used to promote the initiation of new vegetative tillers which in turn will retain forage quality for longer.     

Variation in inflorescence characters and inflorescence development in ecotypes and cultivars of Lolium perenne L.

A sufficient database of seed yield components is the prerequisite to predict which component contributes most to the seed yield complex and to dissect the biology of the complex quantitative trait seed yield. Phenotypic variation of eleven vegetative and reproductive traits was characterized for 2481 individuals from fifty Lolium perenne L. (perennial ryegrass) ecotypes and cultivars. Considerable levels of among‐ and within‐population variation were found across several inflorescence characters. Principal component and canonical variate analysis separated ecotypes from cultivars, and cultivars generally had later dates of ear emergence, better spring and summer growth, longer rachis length and more spikelets per spike than ecotypes. Strong positive relationships were seen between inflorescence characters using both correlation and regression analyses. The strong relationship between rachis length and other inflorescence characters suggested that rachis length could be used as a performance predictor for several other characters of the spike. This phenotypic study has helped to determine basic patterns of morphological diversity and correlations between characters. It is discussed in which way further developmental genetic studies can be directed.     

不同玉米杂交种耐盐碱性鉴定

在不同盐碱含量的试验地,通过整个生育期对供试材料耐盐碱指标进行测定,评价不同玉米杂交种的耐盐碱性,并对供试材料的耐盐碱性划分等级。研究结果表明,成株率耐盐碱指数与出苗率、最终产量耐盐碱指数均呈正相关关系,且均达显著水平。开花散粉期较短的ASI和较高的成株率、生殖生长期较多的绿色叶片数和穗粒数是耐盐碱性较高的品种获得高产的基础。与其他杂交种相比,辽1127和铁研39不仅表现出较高的耐盐碱性,且具有良好的生产潜力。     

Modelling leaf production and crop development in maize (Zea mays L.) after tassel initiation under diverse conditions of temperature and photoperiod

Prediction of the initiation, appearance and emergence of leaves is critically important to the success of simulation models of crop canopy development and some aspects of crop ontogeny. Data on leaf number and crop ontogeny were collected on five cultivars of maize differing widely in maturity and genetic background grown under natural and extended photoperiods, and planted on seven sowing dates from October 1993 to March 1994 at Gatton, South-east Queensland. The same temperature coefficients were established for crop ontogeny before silking, and the rates of leaf initiation, leaf tip appearance and full leaf expansion, the base, optimum and maximum temperatures for each being 8°C, 34°C and 40°C. After silking, the base temperature for ontogeny was 0°C, but the optimum and maximum temperatures remained unchanged. The rates of leaf initiation, appearance of leaf tips and full leaf expansion varied in a relatively narrow range across sowing times and photoperiod treatments, with average values of 0.040 leaves (°Cd)⁻¹, 0.021 leaves (°Cd)⁻¹, and 0.019 leaves (°Cd)⁻¹, respectively. The relationships developed in this study provided satisfactory predictions of leaf number and crop ontogeny (tassel initiation to silking, emergence to silking and silking to physiological maturity) when assessed using independent data from Gatton (South eastern Queensland), Katherine and Douglas Daly (Northern Territory), Walkamin (North Queensland) and Kununurra (Western Australia).     

Cold temperatures and boron deficiency caused grain set failure in spring wheat (Triticum aestivum L.)

Boron (B) deficiency and cold temperatures during the reproductive development of wheat (Triticum aestivum L.) cause failure of grain to set. A pot experiment at the Plant Environment Laboratory, The University of Reading, UK, in 1996 examined whether wheat cultivars differ in response to these stresses, if any stage during reproductive development was more sensitive than another, and whether the effects of B deficiency and cold temperature were reversible. The experiment comprised a full four-factor combination of two cultivars of spring wheat with different field responses to B and cold temperature (Annapurna-3 and NL-683), three B treatments (no B added, 20 μM B L⁻¹ from sowing to maturity and 20 μM B L⁻¹ from flag leaf first visible (GS 37) to maturity), two temperature regimes (ambient UK temperatures and 8°/2°C day/night temperatures in growth cabinets), and three stages for different temperature regimes to be applied [flag leaf ligule visible (GS 39) to awn first visible (GS 49), from GS 49 to full ear emergence (GS 59) or from GS 59 to the completion of anthesis (GS 69)]. Control plants remained outdoors throughout. An additional B treatment was also applied in which 20 μM B L⁻¹ was supplied only until GS 37 without any cold treatments. NL-683 was more sensitive to cold temperature, producing >80% sterility, than Annapurna-3 (40% sterility). In contrast, Annapurna-3 was more susceptible to B deficiency (22% sterility compared to only 14% in NL-683). The principal effect of cold was to impair pollen viability: anthers were poorly developed, small, shrivelled and rarely dehisced. More than 75% of pollen grains were dead in NL-683 compared to about 25% in Annapurna-3. All periods from GS 39 to GS 69 were vulnerable to cold damage although the first stage (GS 39–49) was relatively more sensitive. The adverse effect of cold was irreversible even if ear emergence and anthesis of the stressed plants was in ambient temperatures. Cold temperature significantly reduced the response of plants to B and when cold stressed the cold susceptible cultivar (NL-683) accumulated less B. The effect of added B in terms of improved fertility was smaller in the main shoot ear but the fertility of tillers was greatly enhanced. Plants were more responsive to added B after the emergence of the penultimate leaf: the interruption of B supply during this stage led to a similar degree of sterility, as in plants grown without B throughout. However, resupply of B at this stage in the plants initially grown without B led to similar B concentrations and grain set as in plants grown with adequate B throughout. Boron concentrations in the flag leaf and ear also increased considerably from GS 39 to GS 60 indicating that these are the most sensitive stages for B nutrition and wheat plants can recover all of their B requirements if supply is not restricted from GS 37 onwards.     

Cropping calendar options for rice-wheat production systems at high-altitudes

The onset of rains during dry to wet transition fallow periods in rice-wheat production systems in Nepal cause substantial losses of soil nitrogen if the system is improperly managed. To make use of available nutrients and water, this transition period can either be shortened by early rice planting, or be extended by late planting, allowing a third crop to be grown. Shifting planting dates would require rice genotypes adapted to the different environments. Crop duration is influenced by both vegetative and reproductive development, which in turn is influenced by the photo-thermal environment and genotypic responses to it. An experiment was conducted to derive genotypic photo-thermal constants from phenological observations on diverse rice cultivars, which were then applied to the concept of the phenological model RIDEV to design cropping calendar options. Environmental effects on variation of crop duration were determined by planting at different dates. The risk of yield losses to sterility caused by low temperatures was estimated by simulation. Thirty-one different genotypes of rice were planted at 8 dates in 15-day intervals starting 27 April 2004 at the experimental field of the Regional Agriculture Research Station, Lumle, Nepal. The shortest duration to flowering was observed for planting dates in late May and early June. Simulation of flowering dates with RIDEV yielded correct results only for the early planting dates. For later planting dates simulated flowering dates showed an increasing deviation from the observed. In most cultivars, minimum air temperature below 18 °C during booting to heading stages caused near-total spikelet sterility and a specific delay in flowering. However, the chilling tolerant cultivars Chomrong and Machhapuchre-3 cultivated at high altitude showed less than 30% spikelet sterility even at 15 °C. Simulating crop durations with the derived thermal constants allowed evaluating the different calendar options for high altitude systems.     

Effect of planting date,fungicide timing and cultivar susceptibility on severity of narrow brown leaf spot and yield of rice

Narrow brown leaf spot (NBLS) of rice (Oryza sativa L.) is caused by Cercospora janseana (Racib). O. Const. (Synonyms: Cercospora oryzae Miyake, Passalora janseana Racib. U.). Experimental studies were conducted at Rice Research Station, Louisiana State University, and Agricultural Center, Crowley, to manage NBLS by fungicide application of propiconazole at different growth stages of rice cultivars having different susceptibility levels to NBLS in different planting dates. Results of these studies revealed that April (early) had less NBLS severity as compared to May (late) planting. Very susceptible cultivars, CL131 and Cheniere, had the highest and resistant cultivars, Della and Presidio, had the lowest NBLS severity at both the planting dates. Propiconazole application significantly reduced the NBLS severity in comparison to untreated. Fungicide application at panicle initiation was the most effective time to manage NBLS on the very susceptible and susceptible cultivars at both planting dates. NBLS on moderately susceptible cultivars was best managed by applying fungicide either at panicle initiation or early boot stage in early planting but panicle initiation was the best time to apply fungicide in late planting. Resistant cultivars did not need fungicide in April planting but did need in May planting. Rice yield was determined to be higher in April than May planting. Fungicide application at early boot stage protected the yield by 9.4% in April planting and 34.2% when applied at panicle initiation in May. Susceptible cultivar, Cheniere, exhibited the greatest yield and resistant cultivars had lowest yield in both the planting dates regardless of its susceptibility level to NBLS. Yield of very susceptible to susceptible cultivars was reduced in late planting but no effect was observed on yield of moderately susceptible and resistant cultivars.     

油菜发育过程及生育期机理模型的研究Ⅰ.模型的描述

将油菜发育的温度效应曲线化,以发育生理生态过程为基础,利用作物生理发育时间为尺度,系统地预测油菜的物候发育,包括出苗期、现蕾期、始花期、终花期、成熟期.模型中用来描述特定品种发育遗传差异的参数有温度敏感性、生理春化时间、光周期敏感性、基本营养生长期因子和基本灌浆期因子,前三者分别体现了不同油菜品种在热效应、春化作用、光周期反应方面的遗传特性,后两者分别体现了不同油菜品种的基本的营养生长期和灌浆期长短的遗传特性,5个遗传参数共同决定了不同品种到达各发育阶段的生理发育时间.     

Amount and quality of grass harvested for first-cut silage for differing spring-grazing frequencies of two mixtures of perennial ryegrass cultivars with contrasting heading date

There are potential advantages and disadvantages associated with grazing spring perennial ryegrass swards designated for first‐cut silage. These may differ for intermediate‐heading (0·50 ear emergence in the second half of May) and late‐heading (0·50 ear emergence in the first half of June) cultivars. The interactions between cultivar type, spring‐grazing frequency, silage‐harvest date and year were examined in an experiment with a randomized complete block (n = 4) design with a factorial arrangement of treatments, conducted in Ireland. The factors were (i) two perennial ryegrass mixtures: intermediate‐ vs. late‐heading cultivars, (ii) three spring‐grazing regimes: no grazing, grazing in mid‐March or grazing in both mid‐March and mid‐April, (iii) four first‐cut silage‐harvest dates that were at c. 10‐d intervals from 19 May and (iv) 2 years (1998 and 1999). The effects of cultivar mixture on herbage mass of the swards in spring were small and not statistically significant. The late‐heading cultivars provided lower amounts of herbage dry matter for harvesting for first‐cut silage but herbage with higher in vitro organic digestibility values compared with intermediate‐heading cultivars. To achieve the same amount of herbage for silage, the late‐heading cultivars needed to be harvested 8 d later than the intermediate‐heading cultivars. Even with this delay in harvest date, the late‐heading cultivars had higher in vitro organic digestibility values than the intermediate‐heading cultivars. The late‐heading cultivars could be harvested up to 30 d later and produce a higher amount of herbage for first‐cut silage with similar digestibility values compared with the intermediate‐heading cultivars.     

Developmental patterns in wheat and resistance to cereal aphids

As wheat develops it varies in its suitability for the grain aphid, Sitobion avenae, so the duration of each developmental stage determines aphid population growth. Simulations of aphid population development on spring and winter wheat cultivars revealed that, as the length of the preferred earing phase was found to be relatively constant, peak population size is determined by the number of aphids at ear emergence. This can be reduced by growing early-maturing varieties, which in terms of crop developmental stage effectively delays the start of the spring migration. Breeding wheat that matures as early as winter barley would greatly reduce the number of aphid outbreaks and make the prophylactic spraying of insecticides unnecessary.     

Leaf development of spring wheat cultivars in an irrigated heat-stressed environment

Wheat (Triticum aestivum L.) is expanding into lower latitudes of the Nile Valley Region, where maximum air temperature can reach 38–40°C during the short growing season. Genotype and environment, particularly temperature, affect the rate of leaf appearance. Field experiments were conducted at the Gezira Research Station, Wad Medani, Sudan in 1992–94. The study aimed to determine the effect of high temperature (by manipulating sowing dates) on leaf and tiller appearance and growth of nine spring wheat cultivars. Linear response was found between rate of leaf appearance and thermal time and it was faster before double-ridge stage than after double ridge. Phyllochron ranged between 99°C d and 122°C d. Differences in phyllochron interval (PI) were pronounced among cultivars and early-maturing cultivars had faster leaf appearance compared with late-maturing ones. Mean final leaf number on the main stem ranged from 8.1 to 12.2 and it was highly correlated with thermal time from sowing to double ridge stage (r=0.71**). Genetic constitution of cultivars had larger effect on number of leaves per main-stem than temperature. Tillers were initiated at leaf stage 2.9 and cultivars differed in their tillering capacity and only 1.5–2.0 reproductive tillers per plant were produced. About 810°C d were needed to produce tillers 1 and 2 and about 1140°C d for tillers 3 and 4. Leaf senescence started at leaf stage 6.1 for cv. Wadi El Neil and 4.2 for Debeira. Cultivars sown late exhibited delayed senescence of their leaves. High temperature accelerated maturity and the cultivars suited for the irrigated tropical environment were found to be early-sown late-maturing types.     

VARIATION IN HEADING DATES OF PERENNIAL RYEGRASS CULTIVARS AS INFLUENCED BY SPRING AND EARLY SUMMER TEMPERATURES

Ear emergence data for 9 cultivars of perennial ryegrass have been recorded in Northern Ireland at the Plant Testing Station, Crossnacreevy, each year since 1967. These data show that while early spring (March-April) temperatures have a marked effect on the heading of early cultivars such as Gremie and Aberystwyth S24, the behaviour of later cultivars is more directly affected by temperatures at the time of their stem internode elongation. Ear emergence dates of late cultivars bear no fixed relationship to those of early cultivars. It is concluded that while records of early spring temperatures can be used to predict, with reasonable accuracy, the heading dates of early cultivars, such records do not provide a reliable basis for the prediction of heading dates of later cultivars. In Northern Ireland, reliable prediction of cutting dates for later cultivars to obtain herbage of a required level of digestibility is only possible on a short-term (one-two week) basis. Such predictions must take account of growing conditions in each individual year.     

Nitrogen studies in Lolium perenne grown for seed. II. Timing of nitrogen application

The effects of applying nitrogen at different growth stages to S24 and S23 perennial ryegrass grown for seed were investigated in a series of field experiments from 1971 to 1976. These varieties of ryegrass were found to be insensitive to timing of nitrogen application from apex initiation to the stage when ears first emerged. However, if nitrogen application was delayed until about 30% or more of the ears had emerged, yields were lower compared with earlier applications, this effect being significant when nitrogen was delayed until 70–80% ear emergence because of a decrease in both numbers of fertile tillers and number of seeds per unit area. No advantages were found for splitting nitrogen applications between apex initiation and ear emergence.     

大麦顶端发育和物候期的模拟

为了能直观反映大麦生长发育进程,利用生理发育时问恒定的原理,建立了系统预测大麦顶端发育阶段和物候期的模拟模型。模型的检验结果表明,模型对大麦大多数发育阶段的绝对模拟误差都在0～6d,平均差平方和的根值（Root mean square error,RMSE）不超过4d。模型对出苗期、成熟期的模拟误差较小,RMSE分别为1．0和1．6d;对雌雄蕊分化期的模拟误差较大,RMSE为3．7d;对于比较重要的单棱期和药隔形成期,RMSE分别为1．8和3．2d,均没有超过4d。模型表现出较强的机理性和实用性。     

TILLERING IN GRASSES—ITS SIGNIFICANCE AND CONTROL*

Tillering is examined in relation to the morphology and habit of growth of the perennial herbage grasses; particular reference is made to the effects of cutting and grazing. The importance of tillering in establishment and regeneration or perennation of a grass sward is considered; greater importance is attached to the role of tillers in the regrowth of swards cut for conservation at the reproductive stage of growth. Amounts of regrowth are related to both the number and size of vegetative tillers present at the base of reproductive tillers at the time of cutting. The probable inhibition of the replacement tiller buds by the developing inflorescence is suggested as a reason for the poor growth of grass swards in the favourable environment of midsummer. The physiological mechanisms which control tillering during reproductive development are examined. Spring and winter wheat (Triticum aestivum), Lolium temulentum and Phalaris tuberosa are used as physiological tools to demonstrate that tillering is restricted during reproductive development, and that stem extension may be more important than changes at the stem apex in controlling this restriction of tillering at the base of the inflorescence-bearing stem. It appears from results of the application of a range of growth regulators that substances derived from the meri-stematic centres, in either the elongating stem or the terminal meristem, indirectly control the metabolic activity of the lateral buds from which new tillers are derived. The degree of apical dominance is shown to depend on the light intensity in which the plants are grown. Finally, the physiological results are used to suggest reasons for the commonly found apparent inability of heavily fertilized perennial ryegrass (Lolium perenne) swards to regrow after cutting at the inflorescence-emergence stage of growth.     

关中平原小麦品种穗部温度演替特征及其与产量的关系

为探究关中地区小麦品种穗部温度的演替特征及其与产量的关系,以关中平原过去80年主推品种为研究对象,对各品种开花期、花后7 d、花后14 d、花后21 d、花后28 d和成熟期穗部温度、穗数、穗粒数、千粒重、穗粒重和产量及其关系进行分析。结果表明,小麦品种开花期和花后穗部温度随审定年份的递进分别呈现逐渐升高和降低趋势,穗数、穗粒数、千粒重、穗粒重和产量均呈现逐渐增加趋势。开花期穗部温度与穗粒重、产量及其构成因素均呈正相关,而花后穗部温度与之均呈负相关。这说明穗部温度在开花期较高、在花后较低时有利于小麦产量形成,可作为小麦高产品种选育的参考指标。     

Dynamic characteristics of floret primordium development in wheat

This study was undertaken to determine the time-course of floret primordium initiation and degeneration in relation to thermal time after sowing in various cultivars and tiller positions of wheat (Triticum aestivum L.). The field experiment was carried out on the experiment station of Nanjing Agricultural University of China, and included three sowing dates: early planting of 30 September, middle planting of 30 October and late planting of 2 March and two wheat cultivars: winter type ‘Jing 411’ and spring type ‘Yangmai 158’. Quadratic and linear relationships could describe floret initiation, degeneration and abortion in response to growing-degree-days after sowing for main stem and first and second tillers of middle planting plants of both cultivars. The floret development patterns on the third tillers for all treatments deviated from the basic models and were associated with poor floret fertility. The growing-degree-days from sowing to floret initiation were significantly different between the three sowing dates and between the two cultivars. These results help quantify the dynamic processes of apical development and explain the differences in floret development of wheat with different environments, cultivars and tiller positions.     

Tuber initiation and development in irrigated and non-irrigated potatoes

Tuber initiation and development are processes basic to potato production and are particularly critical in areas with short growing seasons. It is important to know how and to what extent management decisions affect these processes in order to maximize the yield of marketable tubers. A two-year field study, conducted in southcentral Alaska, examined top growth, tuber initiation, and tuber development in eight potato cultivars grown with and without irrigation. Plants of the cultivars Allagash Russet, Bake-King, Green Mountain, Kennebec, Lemhi Russet, Russet Burbank, Shepody, and Superior were harvested weekly throughout the growing season, and top dry weight, numbers of tubers, and individual tuber fresh weights were recorded. Top dry weight was reduced by moisture stress shortly after emergence in 1993, and about one month following emergence in 1994, when early-season soil moisture was greater. The weight of tubers was similarly affected within approximately 5 wk of emergence in 1993 and 6 weeks in 1994. Tuber weight at harvest was increased two-to three-fold by irrigation in all cultivars. The number of tubers each plant set was affected by irrigation in most, but not all, cultivars. Some varieties (Lemhi Russet in 1994, Allagash Russet both years) set more tubers than were maintained through the growing season. Tuber remnants found during sample collection indicated that tuber reabsorption had occurred. Irrigated Green Mountain had more than one tuber initiation period during the season, whereas other varieties such as Shepody maintained a relatively constant number of tubers following initial tuber set. Tuber size distribution at the end of the growing season showed that larger tubers were favored by irrigation.     

不同时期干旱胁迫对水稻产量和生长特性的影响

为明确水稻生长过程中的水分敏感时期,探索水稻抵御干旱的栽培措施,以常规粳稻楚粳29号和云粳39号为材料,通过盆栽试验准确控制土壤水分(水势),研究不同时期干旱胁迫对水稻产量和生长特性的影响。结果表明,楚粳29号干旱胁迫处理较对照减产10.63%~47.60%,云粳39号干旱胁迫处理较对照减产6.19%~47.27%,减产程度依次为穗分化前期干旱胁迫(T2)﹥有效分蘖期干旱胁迫(T1)﹥穗分化后期干旱胁迫(T3)﹥孕穗期干旱胁迫(T4)。与对照相比,2个品种有效分蘖期干旱胁迫降低了有效穗数,穗分化前期干旱胁迫使每穗粒数明显减少,穗分化后期干旱胁迫使每穗实粒数减少和结实率明显降低,孕穗期干旱胁迫对结实率或千粒重有影响。     

Alleviative effects of mixed-cropping with rice on the growth inhibition of pearl millet caused by flooding at reproductive stage

Flooding has globally become common, and thus cultivation techniques to adapt to the stress are required. We have developed a technique called “close mixed-planting” using flood-adapted rice (Oryza sativa L.) and upland crops with tangled root systems, showing that this technique can mitigate the damage caused to upland crops by flooding. However, the plant response during the reproductive stage has not yet been examined. In this study, we estimated the alleviative effects of close mixed-planting on the growth inhibition and physiological damage to pearl millet (Pennisetum glaucum) caused by flooding at the reproductive stage in northern Namibia. Pearl millet and NERICA4 (Oryza spp., interspecies of O. sativa and O. glaberrima) were used. Four-week-old single- and mixed-crop pearl millets were transplanted and grown for 22 days, and then flooding treatment was administered for 28 days. The growth and physiological parameters of single pearl millet were significantly decreased by flooding stress, and the parameters did not recover during a 14-day recovery period compared with those of unflooded single and mix-cropped pearl millet. On the other hand, the damage to mix-cropped pearl millet by flooding was suppressed. Thus, the mixed-cropping mitigated the anoxic stress of pearl millet caused by flooding at the reproductive stage and contributed to the improved growth after the recovery period. This result suggested that the close mixed-planting with rice can contribute to the mitigation of flooding damage not only at the vegetative stage but also at the reproductive stage of pearl millet in the semi-arid African country, Namibia.