Concentrations Of Maleic Hydrazide Research Articles

Effect of Maleic Hydrazide and Waxing on Quality and Shelf-life of Mango (Mangifera indica L.) Fruits

The effect of post-harvest treatment of maleic hydrazide (MH)with and without waxing on the quality and shelf-life of ‘Kitchner’ and‘Abu-Samaka’ mango fruits at 18 ±1°C and 85% - 90% relative humiditywas studied. Maleic hydrazide and wax treatments delayed fruit ripening,reduced losses, maintained quality and extended shelf-life of mangofruits. MH at 500 and 1000 ppm significantly delayed fruit ripening bytwo and four days in both mango cultivars, respectively, compared withthe untreated fruits. The higher the concentration of MH, the more delayin fruit ripening. Waxing in addition to MH treatment resulted in ripeningdelay of six days in fruit ripening than treatment with MH alone. Theeffect of MH and waxing treatments in delaying mango fruit ripening,was indicated in retarded respiratory climacteric, reduced water loss,delayed peel colour development, fruit softening and total soluble solidsaccumulation and retained ascorbic acid content.

Effect of maleic hydrazide and pinching on growth and flowering behaviour of African marigold (Tagetes erecta L.)

An experiment was carried out at Experimental Research Farm, R.B.S College Bichpuri, Agra (U.P.) during rabi season of 2016-18 to study the effect of pinching and Maleic Hydrazide on growth and flowering behavior of African marigold (Tagetes erectaL.). The experiment was laid out in factorial randomized block design with three replications comprising of four different concentrations of Maleic Hydrazide (0, 250,500 and 750 ppm) and three pinching levels viz., no pinching, pinching at 20 and 40 (DAT). The results revealed that the application of 750 ppmMH recorded significantly maximum value of diameter of main stem (2.0 cm), plant spread N-S and E-W (44.7cm and 47.5cm), primary branches/plant (11.1), length of flower (7.0 cm), diameter of flowers(7.3 cm),flower/plant (79.5), and flower yield (170.9 qha-1 ), weight of flower/ plant (273.6 g), and dry matter content of plant (39.6g). The maximum plant height (72.4cm) and minimum days required for bud initiation (46.0days) were noticed under the control.Among the pinching treatments, pinching at 40 DAT recorded significantly maximum diameter of main stem (2.2 cm), plant spread N-S and E-W (47.0cm and 48.2cm), primary branches/plant (10.9), length of longest primary branches (38.6 cm), length of flower (7.6 cm), diameter of flowers(7.9cm),flower/plant (83.2), and flower yield (185.8qha-1 ), weight of flower/ plant (275.4g)and dry matter weight of plant (38.2g). Themaximum plant height (69.5cm) and minimum days taken to first flower bud initiation (47.4days)were recorded under no pinching. The interaction (P2xM3)recorded maximumnumber of primary branches (11.2), number of flowers per plant (86.3), size of flower (8.0cm) and yield of flowers (195.48qha-1 ) while minimumvalue were recorded under P0M0 treatment.

Molecular mechanism underlying the effect of maleic hydrazide treatment on starch accumulation in S. polyrrhiza 7498 fronds

BackgroundDuckweed is considered a promising feedstock for bioethanol production due to its high biomass and starch production. The starch content can be promoted by plant growth regulators after the vegetative reproduction being inhibited. Maleic hydrazide (MH) has been reported to inhibit plant growth, meantime to increase biomass and starch content in some plants. However, the molecular explanation on the mechanism of MH action is still unclear.ResultsTo know the effect and action mode of MH on the growth and starch accumulation in Spirodela polyrrhiza 7498, the plants were treated with different concentrations of MH. Our results showed a substantial inhibition of the growth in both fronds and roots, and increase in starch contents of plants after MH treatment. And with 75 µg/mL MH treatment and on the 8th day of the experiment, starch content was the highest, about 40 mg/g fresh weight, which is about 20-fold higher than the control. The I2-KI staining and TEM results confirmed that 75 µg/mL MH-treated fronds possessed more starch and big starch granules than that of the control. No significant difference for both in the photosynthetic pigment content and the chlorophyll fluorescence parameters of PII was found. Differentially expressed transcripts were analyzed in S. polyrrhiza 7498 after 75 µg/mL MH treatment. The results showed that the expression of some genes related to auxin response reaction was down-regulated; while, expression of some genes involved in carbon fixation, C4 pathway of photosynthesis, starch biosynthesis and ABA signal transduction pathway was up-regulated.ConclusionThe results provide novel insights into the underlying mechanisms of growth inhibition and starch accumulation by MH treatment, and provide a selective way for the improvement of starch production in duckweed.

Flow injection chemiluminescence sensor using molecularly imprinted polymers as recognition element for determination of maleic hydrazide

A novel flow injection chemiluminescence (CL) sensor for the determination of maleic hydrazide (MH) using molecularly imprinted polymer (MIP) as recognition element is reported. The MH-MIP was synthesized by thermal initiated polymerization in methanol, using methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker in the maleic hydrazide template molecule. Molecular modeling was employed to simulate the possible recognition process of the MIP, and to achieve high selectivity. Then the synthesized MH-MIP was employed as recognition element by packing into flow cell to establish a novel flow injection CL sensor. The CL intensity responded linearly to the concentration of MH in the range 3.5×10−4–5.0×10−2mg/mL with a detection limit of 6.0×10−5mg/mL (3σ), which is lower than that of conventional methods. The relative standard deviation (RSD) for the determination of 1.0μg/mL of MH was 2.7% (n=11). The sensor is reusable and has a great improvement in sensitivity and selectivity for CL analysis. As a result, the new MIP–CL sensor had been successfully applied to the determination of MH in vegetable samples.

Herbicide effects on freshwater benthic diatoms: Induction of nucleus alterations and silica cell wall abnormalities

Benthic diatoms are well known bio-indicators of river pollution by nutrients (nitrogen and phosphorus). Biological indexes, based on diatom sensitivity for non-toxic pollution, have been developed to assess the water quality. Nevertheless, they are not reliable tools to detect pollution by pesticides. Many authors have suggested that toxic agents, like pesticides, induce abnormalities of the diatom cell wall (frustule). High abnormal frustule abundances have been reported in natural diatom communities sampled in streams contaminated by pesticides. However, no direct link was found between the abundances of abnormal frustules in these communities and the pesticide concentrations in stream water. In the present study, a freshwater benthic diatom community, isolated from natural biofilm and cultured under controlled conditions, was treated with a known genotoxic herbicide, maleic hydrazide (MH). Cells were exposed to three concentrations of MH (5 × 10 −6, 10 −6, 10 −7 M) for 6 h followed by a 24 h-recovery time. After MH treatments, nucleus alterations were observed: abnormal nucleus location, micronucleus, multinuclear cell or disruption of the nuclear membrane. A dose-dependent increase of nuclear alterations was observed. The difference between the control (9.65 nuclear alterations per 1000 cells observed (9.65‰), S.D. = 4.23) and the highest concentrations (29.40‰, S.D. = 8.49 for 10 −6 M and 35.96‰, S.D. = 3.71 for 5 × 10 −6 M) was statistically significant (Tukey test, P < 0.05). Diatoms also exhibited frustules with deformed morphology and abnormal ornamentation. Significantly increased abundances of abnormal frustules were observed for the highest concentrations (10 −6 and 5 × 10 −6 M; Tukey test, P < 0.05). These two parameters tended to increase together (Pearson correlation = 0.702, P < 0.05). The results suggest that the induction of abnormal frustules could be associated with the genotoxic effects of MH. The alterations observed could be related to the effects of MH on the synthesis of the proteins involved in frustule formation or in the regulation of the cytoskeleton of the diatom cells.

Liquid Chromatographic Determination of Maleic Hydrazide in Technical and Formulated Products: Collaborative Study

Fourteen collaborating laboratories assayed maleic hydrazide (MH), 6-hydroxypyridazin-3(2H)-one, in technical and formulated products by reversed-phase liquid chromatography (LC) with sulfanilic acid as an internal standard. The active MH in the samples (6 lots) ranged from 16% (expressed as the potassium salt) to 98% (MH in the technical). A small amount of 1 M KOH was added to the technical MH and analytical standards to create the potassium salt of the analyte which is soluble in water. Test samples and standards were extracted with water containing the internal standard before analysis by LC on a C8 column with an ion-pairing eluting solution and UV detection at 254 nm. The concentration of MH was calculated by comparing the peak area response ratios of the analyte and the internal standard with those in the analytical standard solution. Eleven laboratories weighed each test sample twice with single analysis. Three laboratories weighed each sample once and made duplicate injections on the LC system. The data were analyzed using the 11 laboratories' results. A second data analysis was done including all laboratory results using a Youden pair approach, selecting one of 2 duplicate assay values randomly for each laboratory and sample. In the first data analysis, the repeatability standard deviation ranged from 0.07 to 1.39%; reproducibility standard deviation ranged from 0.22 to 1.39%. In the second data analysis (using all laboratory data), repeatability standard deviation ranged from 0.09 to 0.86%; reproducibility standard deviation ranged from 0.22 to 1.31%.

Conservation of Zingiber germplasm through in vitro rhizome formation

The effects of various concentrations of maleic hydrazide (MH; 2, 4, 6, 8 mg/l) and three light treatments (16-h, 24-h, 0-h) on in vitro rhizome formation and conservation of ginger ( Zingiber officinale Rosc. cv. Rio de Janeiro) were studied. In vitro rhizome formation occurred in all the above treatments. Addition of MH (2–8 mg/l) to the control medium (CM) comprising Murashige and Skoog's (1962) salts, 9% sucrose, 0.8% agar-agar, 0.1 mg/l α-naphthaleneacetic acid (NAA), 1 mg/l N 6-benzyladenine (BA), did not show any significant positive effects on rhizome formation as well as survival of cultures. A significant effect of light treatments was observed on survival of cultures but not on rhizome formation. More than 50% cultures survived up to 14 months on CM under 16-h and 24-h light conditions as compared to 20% cultures on same medium incubated under dark. A total of 33 genotypes of cultivated and wild species of Zingiber were subsequently tested for conservation through in vitro rhizome formation on CM under 16-h light condition. All genotypes produced rhizomes of varying size with numbers ranging from 3 to 15 per culture and were conserved for at least 12 months; some genotypes could be conserved even up to 16–20 months. Viability of rhizomes was determined by in vitro regeneration of shoots upon subculture and their subsequent establishment in soil. Following the protocol described in the present paper, some 160 genotypes of cultivated and wild species of Zingiber, collected from different geographical regions of India, are being conserved at In Vitro Genebank of National Bureau of Plant Genetic Resources, New Delhi.

Residues of free and bound maleic hydrazide in potato tubers

The method of Vadukul (1991) for determining maleic hydrazide (MH) was modified and gave recoveries of free MH of 89%±4%. The values recorded on individual tubers ranged from 2–14 mg kg−1. Maleic hydrazide was evenly distributed throughout the tuber (peel, outer and inner flesh) but concentration increased slightly as tuber size increased. The concentration of free MH decreased from 7 to 3 mg kg−1 over the storage period of 5 1/2 months. Acid hydrolysis released substantial amounts of MH particularly from older potatoes (13 mg kg−1) compared with 6 mg kg−1 from new potatoes, implying that free MH is gradually converted to a bound form with time after treatment. No evidence was found for the presence of a β-glucoside of MH.

Effect of leaf maleic hydrazide concentration on yield and dry matter partitioning in burley tobacco (Nicotiana tabacum L.)

Abstract Maleic hydrazide (MH) is commonly used to prevent axillary bud (sucker) development in tobacco (Nicotiana tabacum L.) after inflorescences have been removed by topping. Although MH provides an inexpensive and effective method to control sucker development, high concentrations (> 80 μg g−1) of MH ratidue in cured leaves are undesirable. The objective of this study was to determine the effect of a wide range of MH rates on leaf MH residue, yield, and dry matter partitioning among plant parts of burley tobacco. The feasibility of using near infrared spectroscopy as a method to rapidly screen tobacco samples for MH residue also was tested. MH was applied at rates of 0 (suckers manually removed), 1.68, 3.36, 5.04, 6.72, 10.08, and 13.44 kg ha−1, where 3.36 kg ha−1 corresponds to the usual commercial rate. Adequate sucker control was provided for up to 3 weeks by 1.68 kg ha−1 MH. Concentrations in the leaves (midribs removed) increased progressively with increasing rate of MH. Concentration of MH decreased over time but plants treated with rates above 3.36 kg ha−1 had MH concentrations at or above 80 μg g−1 in air-cured leaves of the upper third of the canopy. Leaf MH concentration decreased from the top to the bottom of the plant, and at MH rate above 6.72 kg ha−1, the MH concetration was above 80 μg g−1 in leaves at the bottom of the canopy. Air-cured leaf yield was slightly increased for the 1.68 kg ha−1 MH rate compared with hand-suckered controls, but higher MH rates did not further affect yield. A large portion of the yield increased cured-leaf moisture content of MH-treated plants. Additionally, MH-treatment decreased partitioning of dry matter in stalks. On a whole-plant basis, dry matter accumulation was similar for all treatments. The results indicated that MH rates above 3.36 kg ha−1 did not alter plant development, yield, or sucker control, but did lead to excessive undersirable leaf MH concentrations. For cured-leaf and especially midrib tissue, there was a significant relationship between MH concentrations determined by the chemical method and estimated by NIR spectroscopy. These results indicated that the potential exists to use NIR spectroscopy to rapidly estimate MH residue levels of tobacco leaf tissue.

Effect of some auxins and antiauxins on protonemal growth and bud formation in Bryum pallescens schleich. ex schwaegr. grown in vitro

Protonema of Bryum pallescens remained bud-free on Nitsch's basal medium (NB). Of the four auxins tried 2,4-dichlorophenoxyacetic acid (2,4-D) and β-naphthoxyacetic acid (NOA) promoted protonemal growth, but α-naphthaleneacetic acid (NAA) and indole-3-acetic acid (IAA) proved inhibitory. Buds failed to appear on media supplemented with 2,4-D, IAA and NAA but a few buds were induced by NOA. Both the antiauxins tested, maleic hydrazide (MH) and 2,3,5-triiodobenzoic acid (TIBA) enhanced protonemal growth. Buds were induced at higher concentrations of MH, whereas no buds were observed at any level of TIBA. Addition of MH (10−4 M) with IAA (10−8 M) led to the formation of a few buds.

Ação de hidrazida maleica e ethephon no crescimento da cana-de-açúcar

Este experimento foi efetuado com o objetivo de determinar o efeito da hidrazida maleica (MH) e do ethephon (CEPA) no crescimento da cana-de-açúcar 'NA 56-79'. 0 trabalho foi realizado em condições de casa-de-vegetação, sendo que o plantio dos toletes de uma gema foi efetuado em 8 de agosto. Em 28 de agosto pulverizou-se MH (21,7%) nas dosagens de 5, 9, 13 e 17 ml/1 e CEPA (480g/1)1,2,1 e 4 ,2 ml/l, sendo que em 18 de se tembro aplicou-se, em outras plantas, MH 5, 9, 13 e 17 ml/l e CEPA 4,2, 8,4 e 16,8 ml/l. A altura total e o comprimento do colmo foram determinados nas da tas de aplicação, e em 4 de setembro no primeiro ensaio e em 3 de novembro no segundo. As variações em altura e no comprimento, entre as datas, mostraram que a hidrazida maleica promoveu inibição no crescimento do cultivar 'NA 56-79', sendo que o ethephon causou drástica redução na altura da cana-de-açúcar. Ambos os reguladores vegetais exerceram efeitos mais pronunciados com aumento nas concentrações aplicadas, revelando-se promissores como agentes maturadores da cana-de-açúcar.

The Effect of Maleic Hydrazide Salts on Quality and Bulb Tissue Residues of Stored ‘Yellow Sweet Spanish’ Onions1

Abstract Diethanolamine and potassium salts of maleic hydrazide (MH) were applied to plants of ‘Yellow Sweet Spanish’ onion (Allium cepa L.) exhibiting maturity ratings of 0, 25, 50, and 100% green tops down. The K formulation of MH was equal to the diethanolamine formulation in sprout control of onions in storage. Lower application rates resulted in lower bulb residues; however, there were no consistent differences in bulb residues among the maturity treatments. Concentrations of MH were lowest in mature outer scales. Maleic hydrazide applications significantly reduced sprouting during storage, had no effect on the percentage of bulbs with storage rot, and reduced respiration rates and weight loss of bulbs stored at 10°C, but had no effect on respiration rate and only slightly reduced weight loss of bulbs stored at 4°. Root growth occurred on nontreated bulbs at both 4 and 10°, while root development was inhibited in MH-treated onions.

Effect of some growth regulators on sex expression of Momordica charantia L.

Gibberellin (GA), benzyladenine (BA), and maleic hydrazide (MH) promoted formation of female flowers in Momordica charantia L. GA was most effective. Low concentration of 2-chloroethyl trimethyl ammonium chloride (CCC) showed femineity, whereas high concentration showed a masculinizing effect. The effects of different concentrations of GA, BA, MH and CCC on flowering and sex expression are discussed. GA should not be considered as a general male sex hormone for all cucurbits.

Germinal cell mutagenesis in specially designed maize genotypes.

We have used three inbreds of Zea mays in our in situ and laboratory studies in environmental mutagenesis. Inbred W22 plants homozygous for wx-C were used in a study to detect the possible mutagenic properties of 32 pesticides or combination of pesticides under modern agricultural conditions. The large numbers of pollen grains analyzed and the ease in detecting mutant pollen grains enabled us to treat the experimental plants with field recommended rates of pesticides. In a current study we are evaluating the possible mutagenicity of Chicago municipal sewage sludge. We are measuring the frequency of mutant pollen grains in inbred M14 at both the wx-C and wx-90 heteroalleles. These plants were exposed to various concentrations of municipal sewage sludge under field conditions. We have inbred Early-Early Synthetic for five generations and tested this inbred with known mutagens. Early-Early Synthetic is a rapidly maturing inbred growing from kernel to anthesis in approximately 4 weeks and attaining a height of approximately 50 cm. Plants of this inbred have been chronically treated with ethylmethanesulfonate (EMS) or maleic hydrazide (MH) under laboratory conditions and forward mutation at the wx locus was measured in the pollen grains. EMS and MH were mutagenic at concentrations of 1 microM and 10 nM, respectively. The concentrations of EMS and MH were calibrated in Early-Early Synthetic to a linear increase in the frequency of forward mutant pollen grains. The construction of a maize monitor for environmental mutagens is currently in progress. This assay will measure forward or reverse mutation at the wx locus in pollen grains, point mutation in somatic cells and will incorporate a cytogenetic endpoint in root-tip cells.

Germinal Cell Mutagenesis in Specially Designed Maize Genotypes

We have used three inbreds of Zea mays in our in situ and laboratory studies in environmental mutagenesis. Inbred W22 plants homozygous for wx-C were used in a study to detect the possible mutagenic properties of 32 pesticides or combination of pesticides under modern agricultural conditions. The large numbers of pollen grains analyzed and the ease in detecting mutant pollen grains enabled us to treat the experimental plants with field recommended rates of pesticides. In a current study we are evaluating the possible mutagenicity of Chicago municipal sewage sludge. We are measuring the frequency of mutant pollen grains in inbred M14 at both the wx-C and wx-90 heteroalleles. These plants were exposed to various concentrations of municipal sewage sludge under field conditions. We have inbred Early-Early Synthetic for five generations and tested this inbred with known mutagens. Early-Early Synthetic is a rapidly maturing inbred growing from kernel to anthesis in approximately 4 weeks and attaining a height of approximately 50 cm. Plants of this inbred have been chronically treated with ethylmethanesulfonate (EMS) or maleic hydrazide (MH) under laboratory conditions and forward mutation at the wx locus was measured in the pollen grains. EMS and MH were mutagenic at concentrations of 1 microM and 10 nM, respectively. The concentrations of EMS and MH were calibrated in Early-Early Synthetic to a linear increase in the frequency of forward mutant pollen grains. The construction of a maize monitor for environmental mutagens is currently in progress. This assay will measure forward or reverse mutation at the wx locus in pollen grains, point mutation in somatic cells and will incorporate a cytogenetic endpoint in root-tip cells.

&lt;i&gt;in vitro&lt;/i&gt;培養におけるイチゴ果実の発育におよぼす数種の植物生長調節物質の影響

Fruits of strawberry, Fragaria × ananassa (Duch), cv. ′Hohkoh-wase′, one day prior to anthesis, were cultured in vitro to determine the roles of seeds in fruit development in relation to plant growth regulators.1. Fruits from which carpels were removed enlarged normally as intact fruits with carpels on the medium with α-naphthaleneacetamide (NAAm). The ripening of intact fruits with carpels on the NAAm medium was suppressed in comparison to that of fruits without carpels.2. When fruits with or without carpels were cultured on the medium with gibberellic acid (GA3), in either fruit, only the basal portion, which was originally devoid of carpels, swelled, but the upper portion, where there were carpels originally, showed no growth. With addition of GA3 to the NAAm medium, fruits with carpels enlarged into normal shape and their growth and ripening were promoted in comparison to those of fruits on the NAAm medium.3. When fruits with or without carpels were cultured on the medium with N6-benzyladenine (BA) and NAAm, the growth and ripening were suppressed in either fruit as the concentration of BA increased.4. When fruits with carpels were cultured on the medium with maleic hydrazide (MH) and NAAm, the browning of the carpels became severe as the concentration of MH increased, and the growth and ripening were promoted.Based on these results, it is suggested that auxin is more essential for the growth of strawberry fruits than gibberellin, and the carpel is the production site of cytokinin, which suppresses the growth and ripening of strawberry fruits.

Regrowth Reduction in American Elm and Sycamore by Growth Regulator Injection1

Abstract Water solutions of commercial formulations of growth regulators were pressure-injected into the trunks of topped American elm (Ulmus americana L.) trees in June to evaluate their ability to reduce sprout regrowth. Regrowth was significantly reduced by methyl 2-chloro-9-hydroxyfluorene-9-carboxylate (chlorflurenol), N-[4-methyl-3-[[(trifluoromethyl)sulfonyl]amino] = phenyl]acetamide (fluoridamid), l,2-dihydro-3,6-pyridazine-dione (maleic hydrazide), succinic acid,2,2-dimethylhydrazide (daminozide) and 2,3,5-triiodobenzoic acid (TIBA); α-cyclopropyl-α-(4-methoxypenyl)-5-pyrimidine = methanol (ancymidol) and (2-chloroethyl)trimethyl-ammonium chloride (chlormequat) were ineffective. Some undesirable effects on the tree and foliage were observed. Maleic hydrazide (MH) and daminozide (SADH) were selected for additional field tests at 3 concentration levels on topped American elm and American sycamore (Platanus occidentalis L.). Regrowth was significantly reduced and foliage condition was acceptable for the high concentration of SADH and the low concentration of MH. Successive measurements in both experiments showed that sprout regrowth was reduced by an amount equivalent to at least 1 year of growth during the first 2 seasons following treatment.

The effect of maleic hydrazide and exogenous DNA on chromosomes ofVicia faba

The mitotic activity of merstematic cells ofVicia faba, the frequency of chromosomal abnormalities and their interchromosomal distribution are evaluated in dependence on the concentration of maleic hydrazide (MH) and on the recovery period. The influence of exogenous DNA of different genetic origin on the course of repair of primary root cells damaged by MH was also studied. Isologous DNA which exhibited a strong repair effect in authors' previous experiments was quite ineffective in the case of maleic hydrazide. Heterologous DNA, on the other hand, had to some extent a parallel effect with MH in breaking down the structural integrity of chromosomes and increased the frequency of aberrations induced by maleic hydrazide in meristematic cells ofVicia faba.

Action of Maleic Hydrazide on Dormancy, Cell Division, and Cell Expansion

Maleic hydrazide (MH) can inhibit cell division in dormant lettuce seeds in which cell division occurs in the absence of growth by cell expansion. Concentrations of MH that inhibit normal growth of wheat seedlings by 85 to 90% have no effect on the growth of wheat from irradiated grain, which grows without any cell division. Thus MH affects mitosis in a system where gibberellic acid (GA) does not, and (MH has no effect on cell expansion in a system where GA is active. When wheat is treated with a combination of MH and GA, the two chemicals apparently act independently on growth, All these findings suggest that the effect of MH on seedling growth can be largely or entirely attributed to an inhibition of cell division and not to any appreciable effont on cell expansion. MH and GA do not appear to give specific interactions on lettuce seed gerraination, thereby providing further evidence against the theory that MH and GA affect growth through common mechanisms. A number of similarities between effects of MH and of ionizing radiation are discussed, including the capacity to permit gerraination and limited seedling growth of wheat without cell division. (auth)

DIFFERENTIAL EFFECTS OF MALEIC HYDRAZIDE ON THE GROWTH OF LEAF AND STEM RUSTS OF WHEAT

The effect of maleic hydrazide on leaf rust and stem rust of wheat was investigated, using intact plants supplied with maleic hydrazide through the roots, detached leaves floated on solutions of maleic hydrazide, and spores germinated on maleic hydrazide solutions in agar. In each case the growth of leaf rust was inhibited at concentrations of maleic hydrazide which had no effect on the growth of stem rust. Some resistant wheat varieties became susceptible to rust after treatments with levels of maleic hydrazide which were not inhibitory to rust development. In some experiments, leaf rust races reacted differentially to maleic hydrazide. Both nutritional and inhibitory factors could be involved in resistance and host–pathogen specificity.