Excretion of dibutyl phthalate by sorghum roots under Fe‐stress: Evidence of its action on chlorosis recovery

Sorghum (Sorghum bicolor L. Moench) cv. CSH‐7, an Fe‐efficient hybrid was grown and subjected to Fe‐deficiency stress. The nutrient medium was extracted for isolation of reductant chemicals. By means of thin layer chromatography, I.R. spectrum and HPLC analysis, dibutyl phthalate was identified as the principal component. This chemical was not found in the nutrient medium extracted before the onset of chlorosis or in that after the plants recovered from chlorosis. Furthermore, synthetic dibutyl phthalate and that obtained from the exudate when supplied to the nutrient medium caused greening of chlorotic sorghum in 24 hours. Evidence that the root medium of the Fe‐efficient sorghum can induce recovery of an Fe‐inefficient sorghum grown together, has also been obtained. It is concluded that dibutyl phthalate released by the Fe‐efficient sorghum subjected to stress, is responsible for making Fe available for utilisation. The mechanism of action of dibutyl phthalate on chlorosis recovery is still an open question.     

Fe‐deficiency tolerance in papaya (Carica papaya L.): Ph reduction and chlorosis recovery in response to stress

The phenomenon of Fe‐stress response mechanism was examined using papaya as a test fruit plant species. This plant behaved like the many Fe‐efficient crop cultivars, reduced the pH of the minus Fe nutrient medium, followed by recovery from chlorosis. The response mechanism was observed in both the 2 cultivars, CO‐1 and CO‐3. Evidence obtained with this plant supports the widespread occurrence of the mechanism in diverse crop species ‐ grain, vegetable and fruit crop plants too.     

Effects of Dibutyl phthalate and phthalic acid on chlorosis recovery in iron‐deficiency stressed sorghum cultivars

The effects of DBP (Dibutyl phthalate) and PA (Phthalic acid) supplied to the nutrient medium of Fe‐deficiency stressed sorghum cultivars, CSH‐5, 2077‐A, and CS‐3541 were examined. It was found that both the chemicals (50 mg/1) caused recovery of the cultivars CSH‐5 and 2077‐A in 4 days of treatment. Furthermore, the growth of roots, especially the adventitious roots, was increased by the chemicals.     

Tumorous crown gall response to iron‐deficiency stress in Fe‐efficient T3238fer and Fe‐inefficeent T3238fer tomatoes

Abstract

Although sunflower (Helianthus annus L.) is an Fe efficient plant, tumorous crown gall tissue development and tissue ability to reduce Fe³⁺ to Fe²⁺ were both diminished by Fe‐deficiency stress. Crown gall also develops readily on Fe‐efficient and Fe‐inefficient tomato cultivars (Lycopersicon esculentum Mill.). The objective of this study was to determine if the effect of a limited Fe supply on the growth, nutrition and reduction of Fe³⁺ to Fe²⁺ by tumorous crown gall would differ between Fe‐efficient T3238FER and Fe‐inefficient T3238fer tomato. Healthy green 25‐day‐old plants were either stem‐inoculated with Agrobacterium tumefaciens to induce tumorous crown gall tissue development or were left uninoculated for comparison. Plants were grown in modified Hoagland nutrient solutions containing 0.0, 0.15, 0.6 and 2.0 mg Fe L^?1. Yield of tumorous crown gall tissue was not diminished by low solution Fe in T3238FER, but was in T3238fer. This was attributed to inability of the T3238fer tomato to make Fe available to itself. Tumor tissue from both cultivars contained more Fe, Cu and P than normal stem tissues, which confirms a modified metabolism in these tissues previously observed in sunflower. An abundant supply of Fe enhances the development and growth of the tumorous crown gall tissue, but a deficient supply of Fe retards its growth.     

Zinc‐stress response in some sorghum hybrids and parent cultivars: Significance of pH reduction and recovery from chlorosis

Zinc deficiency was induced in two sorghum hybrids and their parent cultivars by growing them in complete nutrient medium for 30 days and then transferring to minus zinc medium at pH 6.4. The onset of Zn chlorosis and recovery as well as the change in the pH of the nutrient medium under Zn‐stress conditions were recorded. It was found that chlorotic symptoms due to Zn deficiency appeared after 2 days of stress and persisted for a long period in the cultivars, 36‐A and 168, while the hybrid CSH‐7 (36‐A X 168) recovered from chlorosis after 12 days. The hybrid CSH‐8 (36‐A X PD‐3) was chlorotic after 2 days, but recovered after 15 days.

A significant hybrid vigor was observed for Zn‐stress tolerance in the hybrid CSH‐7 and CSH‐8.     

Fe‐deficiency stress tolerance and pH reduction: Some contrasts in the cultivars of sesame and lentil

Fe‐deficiency chlorosis was induced in 4 lentil (Lens esculenta Moench) and 7 sesame (Sesamum indicum L.) cultivars by growing them in full nutrient solution for 20 days and then in the nutrient medium without Fe. In lentil cv. VL‐1, a mild chlorosis appeared but turned green after 14 days of stress. However, this recovery was not paralleled by a decrease in pH of the medium. In sesame, there were differences in the degree of tolerance. The cv. T‐13 did not develop any chlorosis, and the pH was found to steadily decrease to 4.5. The cv. SP‐1181 lowered the pH to only 5.6, and did not recover from the chlorosis. A second pattern was noted in VS‐2, TS‐25, TMV‐3 and TMV‐4; these cultivars reduced the pH to between 4.1 and 4.5; these showed a mild chlorosis which disappeared later.

The results show that the pH reduction is not a requisite for chlorosis recovery, at least in some crop cultivars. There are obviously some other mechanism which makes Fe available to the chlorotic leaves. It is suggested that a retranslocatlon of Fe from the older leaves may take place under the stress condition through some physiological process.     

Effect of seed‐placed fertilizer on the emergence (germination) of soybeans (Glycine max L.) and snapbeans (Phaseolus vulgaris L.)

Abstract

Field trials were established on a loamy fine sand and a silt loam using snapbeans and soybeans as test crops, respectively. Row fertilizer was placed with the seed (seed‐placed). Treatments were arranged in a 3×3×3 factorial experiment, and N, P, and K were applied in all combinations at three rates (0, 3.4, and 6.8 kg/ha). Ammonium nitrate (AN), monoammonium phosphate (MAP), concentrated superphosphate (CSP) and potassium chloride (KCl) were used as sources of N, P and K. Additional treatments compared MAP with diammonium phosphate (DAP) and KCl with potassium nitrate (KNO₃).

The salt index of each treatment was inversely related to emergence, i.e. as the salt index increased, the emergence decreased. Level of N was more important than level of P or K in regards to reduction in emergence. Snapbeans grown on a loamy fine sand were extremely sensitive to damage from seed‐placed fertilizer, even at rates as low as 3.4 kg/ha of N, P or K. Soybeans planted on a silt loam soil were less sensitive than snapbeans planted on a loamy sand. The soybeans were able to tolerate up to 10.2 kg/ha of seed‐placed P plus K or 6.8 kg/ha of seed‐placed N plus P or N plus K without causing a significant delay in emergence.     

Effects of Kocide 101® on the bean (Phaseolus vulgaris L.)‐Rhizobium symbiosis

A glasshouse study was undertaken to investigate the effects of the copper fungicide Kocide 101 and its residues in soil on the growth, nodulation and nitrogen fixation of beans (Phaseolus vulgaris L.). The soil used was a sandy clay loam classified as Typic Rhodustalf. The bean variety SUA 90 was used as test crop. The bean rhizobia strains CIAT 899, PV, and a local isolate were used. Kocide 101 applied at the recommended rate (equivalent to 1.7 mg kg^‐1 soil) had no significant negative effects on the growth, nodulation or nitrogen fixation of bean plants. Higher levels of Kocide 101 significantly (P < 0.05) reduced plant growth, nodulation and nitrogen fixation. The bean plants inoculated with the “local isolate”; rhizobia had the highest dry matter weights, nodule numbers and nodule dry weights, and also had more N fixation. They were followed by those inoculated with the PV, strain and, lastly, those inoculated with CIAT 899. The growth and nodulation of bean plants were still curtailed by the Kocide 101 residues four months after the fungicide was first applied to the soil. Therefore, occurrence of high levels of Kocide 101 in soils can have long‐term effects on the performance of the bean‐rhizobia symbiosis.     

Effect of peat moss‐shrimp wastes compost on the growth of barley (Hordeum vulgare L.) on a loamy sand soil

Abstract

A greenhouse experiment was conducted to determine the effect of peat moss‐shrimp wastes compost on barley (Hordeum vulgare L.) grown on a limed loamy sand soil. A control, four rates of compost applied alone and in combination with three rates of nitrogen, phosphorus, and potassium (NPK) chemical fertilizer were evaluated. Applications of compost to limed soil substantially enhanced the growth of barley over the control. When considering all treatments, the main effect of compost rates on straw yield, numbers of tillers, plant height, and number of ears was more important than that of fertilizer. A significant interaction on barley growth parameter values was obtained with compost and fertilizer rates. A combination of moderate application of compost and fertilizer gave in some instances, more yield than compost or fertilizer applied alone. Nutrient content of barley increased with rate of compost applied to soil over the control. A significant relationship was found between soil organic carbon (C) and straw yield, number of tillers, plant height and number of ears whereas grain yield was correlated with soil total N. Results from this study indicate that peat moss‐shrimp wastes compost could represent a potential means of renovating low fertility sand soils.     

Does the Sulfur Assimilation Pathway Play a Role in the Response to Fe Deficiency in Maize (Zea mays L.) Plants?

Abstract

The finding that the methionine is the sole precursor of the mugineic acid family phytosiderophores induced us to evaluate whether sulfur assimilation pathway has a role in plant response to Fe deficiency. Maize plants were grown for 10 days in nutrient solution (NS) containing 80 µM Fe in the presence (+S) or absence (?S) of sulfate. After removing the root extraplasmatic iron pool, half of the plants of each treatment (+S and ?S) were transferred to a new Fe deficient NS (0.1 µM final Fe concentration) (?Fe). The remaining plants of each pre‐culture condition (+S and ?S) were transferred to a new NS containing 80 µM Fe (+Fe). Leaves were collected 4 and 24 hours from the beginning of Fe deprivation period and used for chemical analysis and enzyme assays. Results showed that iron content in the leaves was lower in plants grown in S‐deficiency than in those grown in the presence of the macro‐nutrient. Iron deprivation produced an increase in the level of SH compounds in both nutritive conditions (+S and ?S). These observations are suggestive of some relationship between S nutrition and Fe uptake. For this reason, we next investigated the influence of Fe availability on S metabolism through the evaluation of changes in ATPs and OASs activity, the first and the last enzyme of S assimilation pathway respectively. Results showed that S‐starvation increased the activity of both enzymes, but this effect disappeared in plants upon Fe deficiency suggesting that S metabolism is sensitive to Fe availability. Taken together these evidences suggest that S metabolism is sensitive to soil Fe‐availability for plant nutrition and support the hypothesis of S involvement in plant response to Fe deprivation.     

Interactions of oxygen‐nitrogen‐salinity stresses on plant growth and mineral content of sunflower (Helianthus annuus L.) in sand culture

Reports relating the separate and combined influences of soil aeration, nitrogen and saline stresses on the germination, growth and ion accumulation in sunflowers are lacking in the literature. The sunflowers of this report were grown in sand culture in the greenhouse. Separate and combined treatments of two levels of aeration, three levels of nitrogen and three levels of NaCl were applied to plants which were harvested at 40 and 56 days. Seed germination was excellent in all treatments. Plant height and dry weight decreased with each type of stress. Low oxygen (0.20 μg O₂ cm^‐2 min^‐1) and nitrogen (10 ppm) combined with 70 meq/1 NaCl caused the greatest reduction of plant growth. Leaf number was reduced by low nitrogen and excess salt. Low oxygen reduced the accumulation of K, Ca and Mg and increased the Na and N‐NO₃ content of sunflower leaves. Potassium to sodium ratios in plant on sunflower growth could be partially ameliorated with the tissue were decreased by greater EC values of the nutrient solution and low soil ODR. The adverse effects of salt and oxygen stresses addition of nitrogen. Ion accumulation was an earlier indicator of plant stress than plant growth and both parameters provided excellent methods for assessing plant tolerance to soil aeration, nitrogen and saline stresses.     

Effect of nitrogen deficiency on growth and some biochemical characteristics in salt‐tolerant and salt‐sensitive lines of Lentil (lens cul1naris medic.)

The response of a salt‐tolerant line ILL 6793 and a salt‐sensitive line ILL 6439 of lentil (Lens culinaris) to N deficiency was studied in a pot experiment under glasshouse conditions. Plants of the two lines were treated with 56, 28, 14 and 7 mg N L^?1 in Rorison's nutrient solution. The salt‐tolerant line excelled the salt‐sensitive line in relative biomass production (per cent of control basis) under varying N regimes. Of the various physiological/biochemical variables measured in the present study only chlorophyll b and total soluble sugars proved to be helpful in discriminating the lines. Chlorophyll b was significantly greater in ILL 6793 as compared with ILL 6439 at the two lower N levels. Total soluble sugars increased consistently in both lines with decrease in N level of the growth medium and the salt‐tolerant line ILL 6793 had significantly greater soluble sugars than the salt‐sensitive ILL 6439 at 28 and 14 mg N L^?1. Chlorophyll a and free amino acids were uniformly reduced in both lines with decrease in N levels. The salt‐tolerant line showing high efficiency for N utilization could be of great economic value in terms of its use in salt‐affected soils which are usually deficient in N provided it also produces reasonable grain yield.     

The effect of an NH4 +‐enhanced nitrogen source on the growth and yield of hydroponically grown maize (Zea mays L.)

Increased above‐ground dry matter and grain yields were found for two hydroponically grown maize hybrids (Pioneer‐3925 and Pioneer‐3949) when plants were supplied with an NH₄ ⁺‐enhanced nutrient solution (31 percent of total N) compared with a control (4 percent of total N as NH₄ ⁺). The major difference in yield developed between silking and 2 weeks post‐silking and silking and 4 weeks post‐silking for the P‐3925 and P‐3949 respectively. The reduced nitrogen content of the stover (leaves plus stalk) was consistently higher on the NH₄ ⁺‐enhanced nutrient solution. The decreased production of the control treatment may have resulted from a reduced photsynthetic capacity.     

Genotypic differences in the antioxidant and carbon–nitrogen metabolism of acid-tolerant and acid-sensitive rice (Oryzasativa L.) cultivars under acid stress

A pot experiment was conducted to investigate differences in antioxidative defence and carbon–nitrogen metabolism between acid-tolerant (YJSM) and acid-sensitive (YHSM) rice cultivars under acid stress. Acid-tolerant and acid-sensitive rice were planted in both acidic soil (pH 4.21) and normal soil (pH 6.13). Forty-eight days after sowing, rice shoots and roots from four treatments were collected, and the other four replicates were harvested at seed maturity. The results revealed that the grain yield of acid-tolerant YJSM was significantly higher than that of acid-sensitive YHSM under acid stress. The activities of antioxidant enzymes (superoxide dismutase and catalase) and contents of non-enzymatic antioxidants (ascorbate and reduced glutathione) of acid-tolerant YJSM were both higher than those of acid-sensitive YHSM under acid stress. Moreover, the enzyme activities (nitrate reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase) and product contents (soluble sugar and soluble protein) of carbon–nitrogen metabolism of acid-tolerant YJSM were higher than those of acid-sensitive YHSM under acid stress. The NO₃^–N and carbon (C) contents in leaves of acid-tolerant YJSM were both significantly higher than those of acid-sensitive YHSM under acid stress. This study suggests that the acid-tolerant rice cultivar has better antioxidative defence and carbon–nitrogen metabolism systems than the acid-sensitive rice cultivar and is more effective in resisting acid stress.     

Identification and relationships of accessions grown in the grapevine (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.) Germplasm Bank of Castilla y Léon (Spain) and the varieties authorized in the VQPRD areas of the region by SSR-marker analysis

A total of sixty-five accessions from the Spanish region of Castilla y León including those authorized in the VQPRD areas were characterized for six SSR loci. All the samples but one unknown were identified by comparison to other databases. Thirty synonymous samples and three cases of homonymy were found out, confirming in most cases ampelographic expectations. Five unique genotypes belonging to local varieties in risk of extinction were detected. Several parameters were calculated to assess the usefulness of the chosen loci in this work. A dendrogram representing the genetic similarities among the accessions was constructed using the neighbor-joining method to investigate possible parentage relationships in the sample, and to explain them from an historical and cultural point of view.     

Farmers’ adoption of maize (Zea mays L.) hybrids and the persistence of landraces in Southwest China: implications for policy and breeding

This paper examines changes in the distribution of maize hybrids and landraces in the mountainous areas of southwest China over 1998–2008, farmers’ reasons for cultivar adoption and the implications for national policies in relation to seed production and breeding, based on baseline data and a survey conducted in Guangxi, Yunnan and Guizhou. The study traced the dynamic changes in the adoption of hybrids and landraces in farmers’ fields, explored how individual farmer’s choices can influence local landrace distribution, and investigated the space for conducive policy and innovative action for on-farm conservation of maize genetic resources. The research showed that although there is strong farmers’ interest in accessing modern maize hybrids, farmers also express strong reasons for maintaining at least some of the landraces that satisfy local agronomic context and social preferences. Farmers recognized that hybrids have a number of advantages but they also indicated some disadvantages of the current available hybrids e.g. with respect to seed quality, local adaptability, taste and cost of seeds, but also lack of information on the performances of the new hybrids. Based on farmers’ reasoning and experiences, the requirements have been identified for improving yield combined with local preferences (agronomic, cultural and socio-economic). The paper concludes by identifying options for how China might seek to develop resilient seed systems for smallholder farmers in poor areas, under changing climatical conditions and volatile markets. Participatory Plant Breeding is among the options considered for bringing farmers’ needs into conservation and breeding strategies for improving local adaptation.     

Assessing a suitable extractant and critical limits of nickel in soil and plant for predicting the response of barley (Hordeum vulgare L.) to nickel grown in Inceptisols

ABSTRACT

Nickel (Ni) is an essential element for plants. Abundant information exists on Ni toxicity in soil–plant system but not much is available on its critical level of deficiency (CLD) in soils and plants. Five chemical extractants were evaluated to find a suitable extractant for Ni in Inceptisol. Twenty-one soils having low to high levels of Ni were used to grow barley (Hordeum vulgare L). The amount of Ni extracted was correlated with Ni concentration and uptake by barley. The diethylene triamine penta acetic acid-calcium chloride (0.005 M DTPA-CaC1₂) was identified as the most promising soil extractant for Ni. The CLD of Ni for 0.005 M DTPA-CaC1₂ in soil was 0.22 mg kg^?1 whereas in barley plant it was 2.14 mg kg^?1. Application of 7.5 mg kg^?1 Ni in soil caused a significant increase in Ni concentration in the shoot of barley in all the soils irrespective of the initial Ni status.     

Effects of a ‘one film for 2 years’ system on the grain yield,water use efficiency and cost-benefit balance in dryland spring maize (Zea mays L.) on the Loess Plateau,China

‘One film for 2 years’ (PM2) has been proposed as a practice to control the residual film pollution; however, its effects on grain-yield, water-use-efficiency and cost-benefit balance in dryland spring maize production have still not been systematically explored. In this study, we compared the performance of PM2 with the annual film replacement treatment (PM1) and no mulch treatment (CK) on the Loess Plateau in 2015–2016. Our results indicated the following: (1) PM2 was effective at improving the topsoil moisture (0–20 cm) at sowing time and at seedling stage, but there was no significant influence on soil water storage, seasonal average soil moisture or evapotranspiration; (2) PM2 induced significantly higher cumulative soil temperatures compared to CK, and there was no significant difference between PM2 and PM1; (3) no significant differences were identified in grain-yield and water-use-efficiency between PM1 and PM2, and compared to CK, they improved by 16.3% and 15.5%, respectively; (4) because of lower cost of plastic film, tillage, film laying and remove in PM2, economic profits improved by 21% and 70% compared to PM1 and CK. This research suggested that PM2 was effective at alleviating the spring drought and was beneficial in reducing poverty traps in dryland.