特用玉米种子沙引发处理对其萌发及幼苗生理特性的影响

以糯玉米、爆裂玉米和甜玉米3种特用玉米为材料,测定沙引发处理后种子萌发指标、幼苗形态和生理指标的变化。结果表明,沙引发能显著提高糯玉米和甜玉米的种子活力,对3种特用玉米的幼苗生长具有显著的促进作用,但对种子发芽率无显著影响。沙引发处理显著提高了3种类型特用玉米幼苗的过氧化物酶(POD)和超氧化物歧化酶(SOD)活性,显著降低了丙二醛(MDA)含量。沙引发效果受基因型影响,对种子萌发的促进作用表现为糯玉米>甜玉米>爆裂玉米;对幼苗生长的促进作用表现为甜玉米>爆裂玉米>糯玉米。沙引发能够提高幼苗体内抗氧化酶的活性,从而增强幼苗对外界环境的适应能力。     

Suppressive Effects of Low Seed-Soaking Temperatures on Germination of Long-Term-Stored Rice Seeds

Abstract

Abstract: We investigated the effects of soaking temperature and duration on the germinability of seeds of rice (Oryza sativa L., cv. Koganemochi, Gohyakumangoku, and Koshihikari) that had been stored for a long period. The germinability of the seeds soaked at 5ºC for 5 d was markedly lower than that of seeds soaked at 12ºC for 5 d. The germinability of the seeds soaked at 5ºC for 24 hr was not increased by subsequent soaking at 12ºC for 4 d. On the other hand, the germinability of the seeds soaked either at 12ºC for 24 hr or at 30ºC for 80 min was similar to that of seeds soaked at 12ºC for 5 d, even when followed by treatment at 5ºC. Thus, the soaking temperature during the first 24 hr was most important for the germination of rice seeds that had been stored for a long period. Western blotting analysis revealed characteristic expression patterns of α-amylase isoforms in cultivars correlating with the germinability after soaking at a low-temperature.     

提高超甜玉米耐冷性的研究

试验以2个南方超甜玉米品种和1个北方超甜玉米品种:甜8号、粤甜3号和华甜玉1号为试材,设计了7个种子处理方法,采用随机区组设计,在早春播种气温较低的条件下,进行增强超甜玉米耐冷性的研究。结果表明,在温度较低的早春播种,种子处理能显著地增强甜玉米种子的耐冷性。表现为提高田间出苗率、成苗率效果显著,最高可提高田间出苗率35.2%;以噻酮、丙酮、氮酮的处理效果最好。本研究首次报道了噻酮和氮酮用于增强作物耐冷性的研究。与以往的方法比较,本研究所提供的方法具有安全无毒、操作简便的优点,可以更好地应用于甜玉米生产实践。     

Evaluation of Cultivar Differences in Preharvest Sprouting of Common Buckwheat (Fagopyrum esculentum Moench)

Abstract

Preharvest sprouting of buckwheat (Fagopyrum esculentum Moench) is an important problem, but cultivar differences in preharvest sprouting and their causes have not been investigated. We detected cultivar differences under natural field conditions. Preharvest sprouting of three cultivars was significantly lower than that of the current main cultivar. Seeds collected before rainfall were threshed and incubated on a wet filter paper in a petri dish for 10 days at 10, 20, 30 and 40ºC in the dark, or at an alternating light and temperature condition of 8 h light at 30ºC and 16 h darkness at 20ºC. Germination was promoted by a higher temperature except for 40ºC, suggesting that the risk of preharvest sprouting in buckwheat is higher at a relatively higher temperature. The risk of preharvest sprouting in the field was highly correlated with germination at 20ºC (r = 0.98***) and 30ºC (r = 0.99***) in the dark, suggesting that germination test can be used to predict preharvest sprouting in the field. Preharvest sprouting was significantly correlated (r = ?0.77**) with main stem length, suggesting that ecotype is partly responsible for this phenomenon.     

基于SSR标记构建甜玉米群体的核心种质

利用40对SSR引物分别分析56份超甜玉米和88份普甜玉米群体材料,基于非加权算术平均配对法(UPGMA)聚类分析和位点优先取样法,分别筛选出14个超甜玉米核心材料和19个普甜玉米材料作为两个亚群体种质。t测验表明,两个亚核心种质与原始群体的等位变异无显著差异(P0.05),等位变异保留率分别为87.81%和89.13%,有效地保留了原始材料群体的遗传变异。两个亚群核心种质与原始材料群体13个表型性状的均值、标准差、极差、变异系数和Shannon-Weaver多样性指数(H’)的平均符合率都在80%以上,并且均值差异百分率(MD)和方差差异百分率(VD)均小于20%,极差符合率(CR)和变异系数变化率(VR)均大于80%,符合核心种质的质量评价标准。构建的甜玉米核心种质最大程度地保留了原始群体的遗传多样性和表型变异,能够有效地代表原始甜玉米材料群体。     

High Risk of the Formation of Milky White Rice Kernels in Cultivars with Higher Potential Grain Growth Rate under Elevated Temperatures

Abstract

Our objective was to clarify whether rice cultivars with a higher grain dry-matter increase rate (GIR) under elevated temperature condition show a higher percentage of milky white rice kernels (MWK). The rate of MWK judged using a rice-quality selector significantly varied with the cultivar and experimental year. The spikes of the cultivars detached 5–7 days after heading were solution-cultured with an adequate nutrient supply for one week at 25, 28 and 33ºC. GIR was overall the highest at 28ºC, and GIR at this temperature was considered to reflect the potential GIR in all the grains tested. There was a close correlation between the rate of MWK and the GIR at 28ºC under field conditions when temperatures during the grain-filling period were approximately over 25ºC. It was suggested that cultivars with a higher potential GIR under elevated temperature conditions have a higher risk of the formation of MWK.     

Synergic Effect of Flooding and Nitrogen Application on Alleviation of Soil Sickness Caused by Aerobic Rice Monocropping

Abstract

The “aerobic rice” system is the cultivation of high yielding rice cultivars under non-flooded conditions in non-puddled (aerobic) soil with supplemental irrigation. The major constraint in wide adoption of aerobic rice technology is soil sickness caused by continuous monocropping due to still unknown factors. The possible role of flooding and nitrogen application in alleviating the soil sickness caused by continuous monocropping of aerobic rice was examined by pot experiments. Plants were grown aerobically or anaerobically on the soil collected from a field grown with aerobic rice for 12 consecutive seasons. The results showed that flooding alleviated soil sickness, but not as much as soil oven-heating treatment (120ºC for 12 hr). Application of ammonium sulfate improved plant growth up to the level of oven-heating treatment, while ammonium sulfate application and flooding exceeded the soil oven-heating treatment significantly. The synergy of flooding with ammonium sulfate application was greater than that with urea. These results suggest that soil sickness caused by continuous aerobic monocropping can be alleviated by flooding and ammonium sulfate application.     

Soak conditions and temperature following sowing influence the response of maize (Zea mays L.) seeds to on-farm priming (pre-sowing seed soak)

On-farm seed priming of maize (i.e. soaking seed in water overnight, 17 h) in the semi-arid tropics has been shown to improve crop establishment and yield but the benefits can be variable. In previous work, this variation was thought to result from the interaction between primed seeds and conditions in the seedbed following sowing. To investigate this interaction, experiments were carried out under controlled temperature conditions that represented those of seedbeds in the semi-arid tropics. The conditions during seed priming and during subsequent germination and emergence were investigated as potential causes of variable seedling emergence relative to that of untreated seeds. Priming advanced emergence from moist sand cores at 30 °C/20 °C (day/night), reduced emergence at 35 °C/28 °C and delayed and reduced emergence at 40 °C/28 °C. In drier cores (drained 8 days) at 35 °C/28 °C, priming advanced germination time and did not decrease final percentage emergence. These results confirmed earlier field observations that the effect of priming in maize can vary and lead to positive, neutral or negative effects. Priming decreased the optimum and ceiling temperatures for germination, and unlike untreated seeds, the relationship between germination rate and sub-optimal temperature was not linear in all cases. Pre-humidifying seeds did not enhance the effect of priming, but aerating the soak water did. These results indicate that variable results from priming recorded in the field were not due to imbibitional damage, but may result from the negative effects of hypoxia during soaking exacerbated by moist conditions and high temperatures at sowing. These effects differed between seedlots of different cultivars, indicating the importance of selecting more tolerant maize hybrids to reduce variation in response to priming following sowing in the field. The implications of these findings for the use of primed seeds in the field are discussed.     

Haploid Plantlet Production through Somatic Embryogenesis in Anther-Derived Callus of Bupleurum falcatum

Abstract

This study was carried out to verify the production of haploid plantlets through somatic embryogenesis of Bupleurum falcatum in anther culture (2n=16). Flowers with anthers at the uninucleate stage, less than 200 µm in anther length, were exposed to 10ºC for 5 days (cold pretreatment) and the anthers were cultured on MS medium supplemented with 2,4-D and/or picloram at various concentrations at 30ºC. The optimal supplement for callus formation was a mixture of 0.075 mg L-¹ 2,4-D + 0.075 mg L-¹ picloram or 0.75 mg L-¹ 2,4-D without picloram. Only a few calli were induced from the anthers without cold pretreatment. The calli were transplanted to MS medium without phytohormones and cultured at 25ºC for plant regeneration. Among one hundred twenty root tips of the regenerated plantlets examined, 14.2% were haploid (n=8). However, in the plantlets regenerated from anthers without cold pre-treatment only 2.5% was haploid. In both haploid and diploid regenerated plantlets, the chromosome number was fixed without variation. Among the regenerated plantlets, one was albino. Haploid plantlets were transplanted to the field after acclimation in pots filled with vermiculite under 90% humidity for a month, and haploid plant were produced. The potential of haploid plants derived from anther culture for production of high-yield and good-quality cultivars is discussed.     

Responses of Eighteen Rice (Oryza sativa L.) Cultivars to Temperature Tested Using Two Types of Growth Chambers

Abstract

Genetic variation in the growth response to temperature is a basis for developing adaptation measures to global warming, but evaluation of cultivars for the temperature responses may depend on other environmental factors such as light. In this study, we tested the growth responses of 18 diverse rice cultivars to constant day/night temperature of 25, 28, 31 and 34ºC in artificially-lit growth chambers (ALC) in Wagga Wagga (7.8 MJ m-² d-¹), and in naturally-lit chambers (NLC) in Yanco (25 and 28ºC and 13.4 MJ m-² d-¹; 31 and 34ºC and 11.5 MJ m-² d-¹), both in NSW, Australia. There was a significant interaction between temperature and chamber type for total shoot and panicle biomass; total shoot biomass was largest at 31ºC in ALC, and at 25 and 28ºC in NLC. From the average of all temperatures, the total shoot biomass declined by 29.5% in plants grown in ALC compared with those grown in NLC. Importantly, cultivar performance in ALC was similar to that in NLC at these temperatures, as evidenced by the highly significant correlation in total shoot biomass between ALC and NLC. Among 18 cultivars, IR64, IR72, N22, Vandana, Takanari and Koshihikari commonly produced a larger total shoot biomass under higher temperature conditions. Leaf area at earlier measurement date was highly correlated with the final total shoot biomass at the higher temperature more than specific leaf area.     

Changes in NMR Relaxation of Rice Grains,Kernel Quality and Physicochemical Properties in Response to a High Temperature after Flowering in Heat-Tolerant and Heat-Sensitive Rice Cultivars

Abstract

Rice productivity is related to the ability of plants to adapt to heat stress. The heat-tolerant cultivars ‘Nikomaru’ and ‘Chikushi 64’ and heat-sensitive cultivar ‘Hinohikari’ were grown at 30ºC and 25ºC for 49 days after flowering. At 30ºC, only a few white immature kernels were produced in ‘Nikomaru’ and ‘Chikushi 64’, but about 22% of grains had immature kernels in ‘Hinohikari’. The high temperature(30ºC) caused no significant changes in grain dry weight, water content, and the NMR T₁ value during the early ripening stage in ‘Nikomaru’ and ‘Chikushi 64’. It also did not affect grain development, especially with respect to the nucellar epidermis, in ‘Nikomaru’ and ‘Chikushi 64’, but caused clear cessation of development of the nucellar epidermis at 14 days after flowering in ‘Hinohikari’. In addition, high temperature decreased the amylose content and increased hardnessvs. adhesion ratio of cooked rice in both ‘Nikomaru’ and ‘Chikushi 64’ resulting a softer, less sticky texture, but not in ‘Hinohikari’. The maximum viscosity and breakdown values were increased, and final viscosity decreased at 30ºC in all three cultivars. These results suggested that starch in the endosperm of grains changed from a fluid state to a doughy state more slowly in ‘Nikomaru’ and ‘Chikushi 64’ than in ‘Hinohikari’, in which the water content and NMR relaxation time decreased, and transported assimilates accumulated slowly during grain development.     

Physiological Response of Three Wheat Cultivars to High Shoot and Root Temperatures during Early Growth Stages

Abstract

Understanding wheat (Triticum aestivum L.) response to high shoot/root temperature during the early growth stages is important for successful production in tropical and subtropical environments. This study examined the physiological response of wheat cultivars to high shoot and/or root temperatures during early growth stages. Three cultivars; Imam, Fang and Siete Cerros were grown in soil and hydroponically at three shoot/root temperatures (23/23, 23/35 and 35/35ºC for the soil experiment; and 22/22, 22/38 and 38/38ºC for the hydroponic experiment). Leaf dry weight and leaf area plant-¹ were significantly decreased by high shoot/ root temperature (HS/HR, 35/35 and 38/38ºC) but was not affected by a normal shoot/high root temperature (NS/HR, 23/35 and 22/38ºC). The NS/HR (22/38ºC) and HS/HR (38/38ºC) treatments in the hydroponic experiment significantly decreased photosystem II quantum yield ( Φ_psii), photosynthetic rate (P_n) and specific leaf area (SLA) compared with the normal shoot/normal root (NS/NR, 22/22ºC) temperature treatment. Chlorophyll accumulation was significantly decreased by NS/HR, but increased significantly by HS/HR in most of the measuring dates. The heat-tolerant cultivar, Fang, always had the highest chlorophyll content, Φpsii and P_n under all temperature treatments, while the heat-sensitive cultivar, Siete Cerros, always had the greatest reduction in these traits especially towards the end of the experiment. Imam and Fang responded to HS/HR in the hydroponic experiment by immediate and greater reductions in leaf dry weight, total leaf area and SLA during the first wk of the treatments compared with Siete Cerros. The response changed with the treatments duration such that Imam showed the least reduction and Siete Cerros was the most affected cultivar towards the end of the experiment. Thus, wheat cultivars differentially responded to high shoot/root temperature by reducing the leaf weight and area and hence accumulating more chlorophyll in the diminished leaves. The failure to undergo such changes led to significantly lower chlorophyll accumulation, Φ_psii and P_n under high root temperature.     

Influence Of Temperature Shift After Flowering on Dry Matter Partitioning In Two Cultivars of Snap Bean (Phaseolus Vulgaris)That Differ In Heat Tolerance

Abstract

The Partitioning of Dry Matter (Ratio of Dry Weight of Individual Parts To That of Total Dry Matter) Was Analyzed In Snap Bean Cultivars, Haibushi, A Heat-Tolerant Cultivar, and Kentucky Wonder, A Heat-Sensitive Cultivar, At Four Temperatures After Flowering on The Subtropical Island of Ishigaki, Japan. The Temperature Regimes Included 27/23ºC (Day/Night) As Normal, 24/20ºC As Low, 30/26 As High, and 33/29ºC As Extremely High. Most Growth Traits Increased After Flowering Time (35 Das), Displaying A Plateau At 68-75 Das. The Total Dry Matter Was Similar Under All Temperature Conditions, But Differed With The Cultivar. Haibushi Had A Higher Value of Total Dry Matter Than Kentucky Wonder, Which Was Mainly Due To Higher Pod Dry Weight Although Stem and Root Dry Weights Were Lower In Haibushi. A Sharp Decline of Dry Matter Partitioning To Pods Was Observed At 33/29 ºC. In The Temperature Range of 24/20 To 30/26ºC, Haibushi Showed Higher Partitioning To Pods Than Kentucky Wonder, Independent of Temperature. on The Other Contrary, Kentucky Wonder Showed Higher Partitioning To Pods At 27/23ºC Than At 24/20ºC. These Results Showed That The Partitioning of Dry Matter, Which Varied With The Cultivar and Temperature, Played An Important Role In Achieving Higher Harvest Index In The Heat-Tolerant Than In The Heat-Sensitive Cultivars.     

Pod Dehiscence in Soybean : Assessing Methods and Varietal Difference

Abstract

The varietal difference of pod dehiscence in 25 soybean cultivars consisting of 16 Japanese and 9 Thai cultivars was examined at 3, 5, 7, 14, 21, 28 and 35 days after placing in a desiccator (desiccator method) and 2, 4 and 7 hrs after placing in an oven at 60ºC (oven-dried method). The cultivars examined were divided into susceptible and resistant groups according to the degree of pod dehiscence. Most of the Japanese cultivars (excepting Suzuotome) and NS1 were susceptible while most of the Thai cultivars (excepting NS1) and Suzuotome were resistant to dehiscence. The degrees of pod dehiscence measured by the desiccator and oven-dried methods were nearly the same, and the moisture content of the pods not dehisced was always higher than that of the dehisced pod. The effect of ambient humidity on pod dehiscence was examined in five soybean cultivars SJ5, Shirotae, Tamahomare, CM60 and Fukuyutaka. When the pods were exposed to 15 or 25% relative humidity (RH), the pods of susceptible cultivars, Shirotae, Tamahomare and Fukuyutaka, started to dehisce at 24 hrs after the start of the treatment, but those of resistant cultivars, SJ5 and CM60, did not dehisce for 72 hrs. None of the cultivars dehisced under 50 and 60% RH. These results revealed that placing the pods in the desiccator for 14 days (desiccator method) or exposing the pods to 60ºC for 7 hrs in an oven (oven-dried method) were useful methods for checking the degree of dehiscence.     

Current and Potential Role of Transgenic Crops in U.S. Agriculture

SUMMARY

Transgenic crop cultivars with resistance to insects, pathogens, and herbicides offer growers powerful new pest management tools. We reviewed the observed and potential farm-level impacts of transgenic cultivars, including those with regulatory approval and commercial availability as well as those still being researched and developed. Direct grower benefits, such as yield and production increases and decreased management costs, have led to rapid and extensive adoption of Bt corn and cotton, herbicide-resistant cotton, soybean, and canola, and virus-resistant papaya. Other transgenic crops, including Bt sweet corn and potato, and herbicide-resistant sugar beet and corn, have not been adopted despite strong agronomic and pest management performance, largely because growers fear there will be no market for their harvests. Despite inconsistent adoption of transgenic cultivars, demonstrated benefits of the technology encourage ongoing efforts to incorporate pest management traits into a wider variety of crops, including broccoli, tomato, lettuce, grape, citrus, pineapple, raspberry, peanut, wheat, barley, and rice. Potential impacts of these upcoming transgenic cultivars range from a decrease in weed management costs for lettuce and tomato growers, to the defense of stone fruit, grape, and citrus against devastating new pests.     

Response of Soybean Yield to Daytime Temperature Change during Seed Filling: A Long-Term Field Study in Northeast China

Abstract

Daytime temperature during seed filling is a crucial determinant of grain yield in pulse crops. Although there is much research about the effect of daytime temperature during seed filling on soybean yield in temperature-controlled chambers, the effect in the field has been little explored. Long-term manipulative field experiments are important tools to provide accurate information for revealing the impacts of climate change on crop yields. Using the field records of a long-term fertilization experiment conducted in Northeast China, we analyzed the response of soybean yields to mean daily maximum temperature during seed filling over the period 1987?2007. The results showed that there was a clear positive response of soybean yields to increased mean daily maximum temperature during seed filling ranged from 20 to 24ºC. When compared with the average soybean yields over the last two decades, grain yields increased by 6?10% for each 1ºC increase in mean daily maximum temperature during seed filling and more than 22% of yield trends can be explained. These findings provide a direct evidence for the response of soybean yield to climate change in the field study.     

Alpha-amylase inhibitor changes during processing of sweet potato and taro tubers

Alpha-amylase inhibitor changes during processing ofsweet potatoes (Ipomoea batatas) and taro (Colocasia esculenta)indicated that varietal differences profoundly influence the thermalinactivation profile. The -amylase inhibitors of taro were almosttotally inactivated during oven drying of the chips at 90 ^°C and100 ^°C for 24h, while 0.8–10% activity was retained in sweetpotato chips under the same conditions. Relatively better thermal stabilitywas exhibited by the sweet potato amylase inhibitors at lower temperatures(70 and 80 ^deg;C) as well. Cooking by boiling the tuber pieces inwater resulted in retention of 29–59% amylase inhibitor in sweet potatoand 11–16% in taro. Microwave baking was a better method forinactivation of amylase inhibitors in these tubers. Flour prepared from thetubers retained only trivial amounts of the inhibitor.     

Yield and quality losses caused by common rust (Puccinia sorghi Schw.) in sweet corn (Zea mays) hybrids

Yield and quality of fresh ears were measured in field plots of selected hybrids of sweet corn (Zea mays L.) that were affected by rust (Puccinia sorghi Schw.) or were nearly rust-free (mancozeb-sprayed). In 1978, 28 hybrids were tested. Losses in total yield ranged from zero in the more resistant entries to nearly 50% in more susceptible entries. In 1979, three cultivars were planted. Yield losses of these cultivars were similar in ranking order to those in 1978, although the loss was greater in late-planted plots because of the greater final severity of the disease. Losses in total yield in late-planted sweet corn were 18%, 26% and 49% for cv. Sugarloaf (most resistant), cv. Jubilee (intermediate) and cv. Style Pak (most susceptible), respectively.     

Development of Rice “Seed-Mats” Consisting of Hardened Seeds with a Cover of Soil for the Rice Transplanter

Conventional seedling mats for rice transplanters in Japan are heavy to carry, and much labor is required to collect, wash and store the nursery boxes. In addition, seeding time overlaps with the labor peak in spring. To reduce such labor, we developed a “seed-mat” consisting of hardened rice seeds (Oryza sativa L.) glued onto a molded rice-hull mat with a cover of soil glued on. Seed hardening, which is done by soaking seeds in water at 15ºC for 5 d followed by drying, and heating of the seeds at 50ºC for 5 or 7 d, reduced the time to 50% germination (T₅₀). In dormant seeds, the heating before the hardening enhanced the effect of the hardening more than the heating after the hardening. Seed hardening increased the dry weight of the shoots from the seed-mats. Covering the mat with soil also increased the percentage of seedling emergence, shoot length, number of leaves and shoot dry weight of the seed-mats. The hardened seeds maintained short T₅₀ and 95% or higher germination for 120 d at room temperature. In the seed-mat, the hardened seeds maintained 95% or higher seedling emergence for 208 d. In conclusion, superior seed-mats could be produced using the procedure involving both seed hardening and cover of soil. The seed-mats can be prepared in winter and stored until seedling-raising period in spring. By the seed-mats, seedling mats can be prepared for the rice transplanter without using nursery boxes, which take up storage space and require much labor.     

Heat-Induced Floret Sterility of Hybrid Rice (Oryza sativa L.) Cultivars under Humid and Low Wind Conditionsin the Field of Jianghan Basin,China

Abstract

Projected global warming is expected to increase the occurrence of heat-induced floret sterility (HIFS) in rice. However, there are few field-scale studies that could aid in predicting the potential risks to rice yield and developing countermeasures against yield losses. The aim of this study was to elucidate the factors that induce floret sterility under high temperature conditions during the flowering season in the field condition in China. Studies were conducted in irrigated paddy fields with the regional hybrid-rice cultivars grown in Jianghan Basin where air temperature is not so high during the flowering season but HIFS frequently occurs. The microclimate, panicle temperature, floret sterility, pollination, and size of dehiscence formed at the base of anthers were investigated. Significant losses in seed set were observed under the high temperature condition. Although the maximum atmospheric temperature was approximately 35ºC, the relative humidity was very high (around 70% at the time of maximum temperature), with low wind speeds, occasionally below 1 m s¹. Under such conditions sunlit panicle temperature exceeded atmospheric temperature by as much as 4ºC. Moreover, the anthers of some cultivars exhibited short basal dehiscence, and the dehiscence length was positively correlated with the percentage of sufficiently pollinated florets (r=0.859, P<0.05, n=7) and with seed set (r=0.827, P<0.05, n=7) across the cultivars. The results suggest that the combination of hot, humid, and windless climatic conditions with short basal dehiscence of anthers induces HIFS in hybrid rice grown in this region.