2,4-D和干燥处理对谷子成熟胚离体再生体系的影响

谷子离体再生体系不够稳定、转化效率低，已成为谷子功能基因研究和品种改良的瓶颈。为了建立谷子成熟胚稳定的离体再生体系，以当地高产优质的6个谷子品种成熟胚为外植体，以不同2,4-二氯苯氧乙酸（2,4-dichlorophenoxyacetic acid，2,4-D）浓度及对胚性愈伤的不同干燥处理时间为变量，通过单因素实验和正交实验考察各因素对谷子愈伤组织分化及成苗的影响。结果表明，晋谷21在2,4-D浓度为9 μmol·L-1、4 h干燥处理的条件下所建立的再生体系最好，分化率为64.35%，成苗率为29.06%。研究通过探索谷子组织培养的最适条件，为谷子高效稳定遗传转化体系的建立和利用基因工程手段进行品质改良提供了依据。     

Sampling techniques, spatial distribution and cultural control of millet spike worm, Raghuva albipunctella (Noctuidae: Lepidoptera)

Spike washing and direct count methods were equally effective for sampling eggs and young larvae of millet spike worm, Raghuva albipunctella (Noctuidae: Lepidoptera) in Senegal, but spike washing is a more economical method. Most eggs (70%) were laid on emerging millet spikes and the spike apex was the preferred oviposition site. Most larvae pupated 10–30 cm from millet hills. The maximum number of pupae was found in the upper layer (< 10 cm) in loamy soil and deeper (20–30 cm) in sandy soil. Ploughing fields after millet harvest reduced the population of spike worm pupae significantly, but may prove impracticable or socially unacceptable to farmers.     

Methylation analysis revealed salicylic acid affects pearl millet defense through external cytosine DNA demethylation

The cytosine DNA methylation and demethylation have a role in regulating plant responses to the environment by affecting the promoter regions of most plant defense-related genes through the CpG islands or the CCGG motifs. Salicylic acid, a defense and signaling plant hormone, is seen playing crucial role in the variation of the methylome. In this study, the effects of salicylic acid and feeding of the millet headminer (Heliocheilus albipunctella de Joannis) on pearl millet DNA methylome changes were evaluated through MSAP epigenotyping during panicle development. The results showed that millet headminer feeding increased the level of genomic methylation while application of salicylic acid caused DNA demethylation occurring mostly at external cytosine and accompanied by a decrease of the number of larvae per panicle. This suggests that hemimethylation (external cytosine methylation) has key role in regulating defense responses and conferring tolerance to pearl millet through salicylic acid application.     

The effects of sowing date and planting method on stem borer damage in dauro millet

In field trials conducted at Samaru, Nigeria in 1983, 1984 and 1985, damage to dauro millet by the millet stem borer, Coniesta ignefusalis Hampson (Lepidoptera: Pyralidae), varied between years and dates of planting. The crop was almost completely destroyed by the stem borer during 1984. Based on 1983 and 1985 data, the period between 10 July and 2 August appears to be best for planting dauro millet at Samaru for least stem borer damage while planting between 11 and 30 July appears to be optimum for grain yields. The direct sown crop suffered more damage than the transplanted crops in all years but only in 1985 was the difference significant. There was no significant difference between slant and upright transplanting in terms of stem borer damage and grain yield. It is concluded, therefore, that the choice of planting method would depend on its convenience to the farmer.     

Weighted regression analysis for comparing varietal adaptation

Summary The normally used joint linear regression analysis (OLS) is not appropriate for comparing estimates of stability parameters of varieties when the error variances of site means are heterogeneous. Weighted regression analysis (WLS), in these situations, yields more precise estimates of stability parameters. A comparison of the two analytical methods using the grain yield (kg ha^–1) data of 12 varieties and one hybrid of pearl millet [Pennisetum typhoides (Burm.) S. & H.], tested at 26 sites in India, revealed that the weighted regression analysis yields more efficient estimates of regression coefficients (b _i ) than the ordinary regression analysis, and that the standard errors of b _i values were reduced by up to 43%. The estimated b _i differed with the two procedures. The number of varieties with b _i ssignificantly deviating from unity was not only more (five varieties) with weighted regression analysis than the ordinary regression analysis (one variety), but the classification of varieties as possessing general or specific adaptation differed with the two procedures.     

Genetic analysis of alcohol dehydrogenase isozymes in pearl millet (Pennisetum typhoides)

Pearl millet (Pennisetum typhoides) produces three ADH isozymes, sets I, II, and III, with set III being expressed only in anaerobically treated seeds or seedlings. Variant strains have been identified which produce ADH isozymes with altered electrophoretic mobilities for sets I and II but not for set III activity. Based on genetic analysis of these variants and on dissociation-reassociation experiments, we propose that the three ADH isozymes are dimers of subunits coded by two structural genes, Adh1 and Adh2, with set I being a homodimer specified by Adh1, set III a homodimer specified by Adh2, and set II a heterodimer formed between the products of Adh1 and Adh2.This work was supported by BRSG Grant RR 07080 awarded by the Biomedical Research Grant Program, Division of Research Grants, National Institutes of Health, to D. R. H., and by funds from the Margenroth Endowment to F. B.-B., who is a PHS Research Service Award Trainee in Genetics.     

Solute accumulation, solute potential, germinability and seedling vigour of seeds of finger millet (Eleusine coracana Gaertn.) raised under rain-fed conditions and under irrigation

Abstract The nature of the solutes accumulated in the grains of ten finger millet genotypes grown under rain-fed conditions with moisture stress during panicle and grain development were determined. Although grain yield decreased under stress, the solute potential (SP) of seeds from stressed plants was significantly lower (more negative), probably due to the increase in sucrose content. There were no significant changes in the content of total amino acids, free proline, reducing sugars or potassium. The contribution of sucrose to total solute potential was approximately 32% in seeds obtained from stressed plants as compared with only 15% in seeds from irrigated treatment. The germinability and seedling vigour of the seeds from stressed plants was significantly higher under simulated stress with polyethylene glycol (PEG), but was similar to that of seeds of non-stressed plants under normal conditions.     

Silencing ZmPP2C-A10 with a foxtail mosaic virus (FoMV) derived vector benefits maize growth and development following water limitation

• Global climate change is causing more frequent and severe droughts, which can have negative impacts on plant growth and crop productivity. Under drought conditions, plants produce the hormone ABA (abscisic acid), which regulates adaptive responses, such as stomatal closure and root elongation. Plant viruses have been used in the lab to convey new traits to plants and could also be used to increase production of ABA or to enhance downstream plant drought resistance responses.
• In this study, foxtail mosaic virus (FoMV) was used to silence ZmPP2C-A10, a negative regulator of ABA signalling, in maize (Zea mays L.). Both silenced and control plants were exposed to an 8-day drought treatment, followed by a 30-day period of rewatering, after which indicators of drought resistance were measured.
• After drought treatment, we observed a nearly twofold increase in expression of a stress-mitigation gene, ZmRAB17, reduced chlorophyll fluorescence changes (indicator of stress), and increased plant biomass and development in the ZmPP2C-A10-silenced maize compared to controls.
• These results demonstrate that the FoMV system can be used to silence endogenous expression of ZmPP2C-A10 and increase maize tolerance to drought. This could offer a useful tool to improve crop traits and reduce yield loss during the growing season.

     

In vitro morphogenesis of pearl millet [Pennisetum glaucum (L.) R.Br.]: efficient production of multiple shoots and inflorescences from shoot apices

 This report presents a procedure for high-frequency multiple shoot production from cultured shoot apical meristems of pearl millet [Pennisetum glaucum (L.) R. Br.]. Shoot apices from 1-week-old aseptically germinated seedlings were cultured in vitro on MS medium containing various concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and benzyladenine (BA) with biweekly subculture. A low concentration of 2,4-D coupled with four different concentrations of BA induced the production of adventitious shoots from the enlarged shoot apical meristems. Somatic embryogenesis was also observed at higher concentrations of BA. The use of higher levels of 2,4-D resulted in callusing of shoot apical meristems, while the shoot tips produced many leaves and in vitro flowering in 2,4-D-free media containing BA. All four pearl millet genotypes produced similar results. Fertile pearl millet plants were produced from in vitro-produced multiple shoots. Received: 1 April 1999 / Revision received: 8 July 1999 / Accepted: 17 August 1999     

Responses to drought induced oxidative stress in five finger millet varieties differing in their geographical distribution

The study presents the impact of drought stress on five finger millet varieties (PR202, VL146, VL315, PES400 and VR708), representing contrasting areas of Indian sub-continent. Drought stress induced increase in the activity of superoxide dismutase, ascorbate peroxidase and glutathione reductase was higher in PR202 and VL315, while the activity was lower in the varieties PES400 and VR708. Ascorbate peroxidase : superoxide dismutase ratio, which is a crucial factor in alleviating drought stress, was higher in varieties PR202 and VL315, whilst the varieties PES400 and VR708 exhibited a lower ratio under stress. The variety PES400 recorded maximum stress induced damage, as indicated by higher accumulation of malondialdehyde and hydrogen peroxide; whereas the variety PR202 recorded least stress induced cytotoxic damage. The results clearly indicate that better drought tolerance of the variety PR202 is positively related to the capacity of its antioxidant system to scavenge reactive oxygen species, resulting in a reduced incidence of oxidative damage. Ascorbate peroxidase : superoxide dismutase ratio is found to be a critical factor governing the stress tolerance potential of different varieties. Therefore, varieties PR202 and VL315 were found to be tolerant while PES400 was susceptible to drought stress.