Effects of drought stress on hybrids of Vigna radiata at germination stage

Drought is one the critical abiotic factors that reduces the germination, growth and yield of crops. Therefore the present project was designed with the objective to screen the best drought tolerant hybrid of Vigna radiata. Genetic variations for drought tolerance among these hybrids were assessed by simple and efficient technique. Seven hybrids of V. radiata (9801, 7002, 9706, 08003, 07007, 97012 and 08007) were used for screening against three levels of drought stress (zero, control), 5% (–0.05 MPa) and 10% (–0.1 MPa) induced by Polyethyleneglycol (PEG6000). A higher proline content was observed in 07007 (6.10 μg/g fresh weight) as compared to all other hybrids. Treated seedlings of each hybrid were compared with their respective control to evaluate the differences in their growth under drought. Different parameters such as percentage of germination, germination stress tolerance index (GSI), shoot and root weights (bath fresh and dry) and lengths, root length stress index (RLSI), dry matter stress index (DMSI) and plant height stress index (PHSI) showed considerable variations. Germination percentage, shoot weights, PHSI and DMSI decreased in all hybrids along with the increase of PEG induced drought stress (5% and 10% PEG). In contrary, root weights and RLSI were increased under drought. Overall 07007 showed a better performance, and can therefore be classified as a drought tolerant hybrid

Effect of pre-sowing hardening treatments using various plant growth substances on cowpea germination and seedling establishment

Seed germination and seedling establishment of two cowpea varieties IT87D-941-1 (IPI) and Kanannado (LPI) were carried out in the laboratory in Kano, Nigeria under the prevailing laboratory conditions of 25±2°C and 45-60% relative humidity. The cowpea seeds were presoaked in various solutions of 5ppm and 10ppm Indole acetic acid (IAA), Gibberellic acid (GA3) and Ascorbic acid (AA), concentrations respectively. The soaked seeds were air dried for 24hrs and thereafter sown in various flasks containing dried cotton wool. The result of the study showed significant difference in percentage germination among the cowpea varieties and hormone concentrations (

Triadimefon ameliorates negative effects of in vitro salt stress on two cultivars of alfalfa(Medicago sativa L.)

Triadimefon (TRD) is a member of triazol plant growth regulator group which is responsible for increasing stress tolerance. Effects of TRD on two cultivars of Medicago sativa (Hamedani and Yazdi) were investigated. The in vitro grown plantlets in MS medium were cultured in TRD at concentration 1.0, 2.0 and 4.0 mg/l combined with 0, 100 and 140 mM NaCl respectively. The changes in growth parameters, photosynthetic pigment, carbohydrate, α-tochopherol, glycine betain, proline and proline dehydrogenase (PDH) activity as well as its expression were measured after four weeks post treatment. NaCl treatment decreased overall plant growth and reduced the total chlorophyll, carbohydrate content, PDH activity and increased α-tochopherol, glycine betain content and proline content. The level of PDH transcript was changed in different combinations of NaCl and TRD, however, at 140 mM NaCl and 2 mg/l TRD expression was decreased. When plants were subjected to salt stress, TRD minimized the inhibitory effects of NaCl on plant growth by increasing, total chlorophyll, carbohydrate, α-tochopherol, glycine betaine content

The Resistance to Salt of Brassica sps. and Improved Resistance by Direct Selection and Mutagenesis

Salinity is one of the most serious environmental stresses influencing agriculture drastically decreasing the production of crop plants throughout the world. Due to salinity thousands of hectares of agricultural land are going out of production annually. To cope with the salinity problem, there is keen interest in the development of crop plants displaying resistance to the effects of salinity. A series of experiments was carried out under controlled environmental conditions to determine salt resistance in Rapid Cycling Brassica species (RCB's) at germination early seedling and late growth stage. The effect of increasing salinity concentration was determined in vivo using a compost based growing system and also in-vitro using adapted tissue culture techniques. At germination and during the early seedling stage, low salt concentrations (50-100 mM) stimulated germination and had no significant effect on growth in B. rapa and B. rapa appeared to have greater salt resistance than B. napus. There was no association between salt resistance at the early seedling stage and that at the adult stage. At later growth stages, salinity affected both the relative fresh and dry weights and tissue ion concentration with K: Na balance affected in favour of Na. The relative salt resistance in the six Brassica species was associated with the reduction in the total fresh weight of shoots of salt-treatment plants expressed as the percentage of control but was not associated with K., Na concentration or K/Na ratio in shoots. B. napus and B. carinata showed the greatest salt resistance, B. juncea, B. rapa and B. nigra were intermediate whilst B. oleracea was salt sensitive. Conventional selection for salt resistance was not successful in this study because B. oleracea, B. napus and B. carina/a were not able to complete either their vegetative or reproductive phases and died before completion of the first selection cycle. Whilst, ten percent of plants of B. rapa, B. nigra and B. juncea managed to complete the first selection cycle they failed to complete the second selection cycle. Although, callus induction and maintenance were successful for all 6 RCB's, regeneration of shoots from callus was poor. Also, callus-based selection for salt resistance was unsatisfactory and had variable results and it was concluded that this was not a promising avenue for improving salt resistance in RCB's A cauliflower curd meristem technique was adapted for in-vitro mutagenesis and selection. Mutagenesis was carried out using two mutagens N-nitroso-N-ethylurea or nitroso-methylurea at 1 mM and 2.5 mM. 300 green shoots were recovered from more than 1 ,000,000 explants mutagenised in liquid medium supplemented with 3 mM hydroxyproline as a selection agent. Of eighty in-vitro shoots which where measured for proline content, twelve showed higher proline level than controls. Leaf strip assays of the twelve selected in-vitro shoots and in-vivo weaned plants exposed to a 3 mM and 10 mM hydroxyproline assay showed greater resistance than controls. A few selections also had cross-resistance to salt at 550 mM NaCl and to frost at -7 °C. These results successfully indicated the existence of great opportunities for the production of stress resistance cauliflower plants via mutagenesis and hydroxyproline selection

Enhanced Abiotic Stress Tolerance of Vicia faba L. Plants Heterologously Expressing the PR10a Gene from Potato

Pathogenesis-related (PR) proteins are known to play relevant roles in plant defense against biotic and abiotic stresses. In the present study, we characterize the response of transgenic faba bean (Vicia faba L.) plants encoding a PR10a gene from potato (Solanum tuberosum L.) to salinity and drought. The transgene was under the mannopine synthetase (pMAS) promoter. PR10a-overexpressing faba bean plants showed better growth than the wild-type plants after 14 days of drought stress and 30 days of salt stress under hydroponic growth conditions. After re-moving the stress, the PR10a-plants returned to a normal state, while the wild-type plants could not be restored. Most importantly, there was no phenotypic difference between transgenic and non-transgenic faba bean plants under well-watered conditions. Evaluation of physiological parameters during salt stress showed lower Na+-content in the leaves of the transgenic plants, which would reduce the toxic effect. In addition, PR10a-plants were able to maintain vegetative growth and experienced fewer photosystem changes under both stresses and a lower level of osmotic stress injury under salt stress compared to wild-type plants. Taken together, our findings suggest that the PR10a gene from potato plays an important role in abiotic stress tolerance, probably by activation of stress-related physiological processes

Potassium fertilization in bareroot nurseries in the southern US: a review

This review covers most of the published literature on potassium (K) fertilization in bareroot seedbeds with the intent to concentrate on the southern United States. The timing and rates of K fertilization for bareroot seedlings are often based on logic and myths and, as a result, K recommendations vary considerably. Some recommend bareroot pine seedlings be fertilized with twice as much K as nitrogen (N) while others apply less than 100 kg ha-1. It was determined that several long-held claims about K fertilization are invalid. Nursery seedbeds do not need to contain four times as much available K as N and the belief that extra K fertilization will increase freeze tolerance or drought resistance of non-deficient seedlings is invalid. There are no data to support the claim that K fertilization increases root growth or assists in the formation of terminal buds. For sandy seedbeds, there is no need to apply K before sowing. Adding extra K during the fall does not increase seedling morphology or seedling performance when loblolly pine seedlings, at lifting, have more than 0.5% K in needles. A reduction of K fertilization can be achieved by reviewing foliar tests prior to K top-dressings