http://nhjy.hzau.edu.cn/kech/ssyy/qysd/njsl/21.pdf

Potential biochemical indicators of salinity tolerance in plants

Publisher Summary The subject of salt tolerance has received a tremendous amount of attention during the past two decades. The concept of developing salt-tolerant plants, even to the degree that they can be grown with seawater, captures the imagination of both the scientific and the public sector. There is a wide range of salt tolerance in vascular plants. Several genera include species that are extreme halophytes and are ecologically competitive only under saline conditions. Crop species primarily are glycophytes, salt-sensitive, and grow well only under cultivated conditions. Domesticated species are provided optimum conditions to obtain high yields. There is currently a need to develop new direction and cohesive impetus in the area of salt-tolerant crops development. Realistic short- and long-range goals need to be established and continually pursued. The information that is known is extensive but fragmented. This chapter outlines some of the issues and strategies concerning selection and breeding for plant salt tolerance, highlights crucial advances in knowledge in recent years, and identifies some of the fundamental gaps in our understanding.

Adaptation of Plants to Salinity

The effect of colonization with the arbuscular mycorrhizal (AM) fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe on the growth and physiology of NaCl-stressed maize plants (Zea mays L. cv. Yedan 13) was examined in the greenhouse. Maize plants were grown in sand with 0 or 100 mM NaCl and at two phosphorus (P) (0.05 and 0.1 mM) levels for 34 days, following 34 days of non-saline pre-treatment. Mycorrhizal plants maintained higher root and shoot dry weights. Concentrations of chlorophyll, P and soluble sugars were higher than in non-mycorrhizal plants under given NaCl and P levels. Sodium concentration in roots or shoots was similar in mycorrhizal and non-mycorrhizal plants. Mycorrhizal plants had higher electrolyte concentrations in roots and lower electrolyte leakage from roots than non-mycorrhizal plants under given NaCl and P levels. Although plants in the low P plus AM fungus treatment and those with high P minus AM fungus had similar P concentrations, the mycorrhizal plants still had higher dry weights, soluble sugars and electrolyte concentrations in roots. Similar relationships were observed regardless of the presence or absence of salt stress. Higher soluble sugars and electrolyte concentrations in mycorrhizal plants suggested a higher osmoregulating capacity of these plants. Alleviation of salt stress of a host plant by AM colonization appears not to be a specific effect. Furthermore, higher requirement for carbohydrates by AM fungi induces higher soluble sugar accumulation in host root tissues, which is independent of improvement in plant P status and enhances resistance to salt-induced osmotic stress in the mycorrhizal plant.

Improved tolerance of maize plants to salt stress by arbuscular mycorrhiza is related to higher accumulation of soluble sugars in roots.

A chimeric gene was constructed consisting of the promoter of the nopaline synthase gene of Agrobacterium and the structural gene of the aminoglycoside phosphotransferase of Tn5. This chimeric gene was recombined into the T-DNA of Agrobacterium. When this strain was used in a cocultivation experiment, transformed calli could be selected out of a pool of non-transformed calli when kanamycin was added into the growing medium

Chimeric genes as dominant selectable markers in plant cells

Agricultural production and quality are adversely affected by various abiotic stresses worldwide and this will be exacerbated by the deterioration of global climate. To feed a growing world population, it is very urgent to breed stress-tolerant crops with higher yields and improved qualities against multiple environmental stresses. Since conventional breeding approaches had marginal success due to the complexity of stress tolerance traits, the transgenic approach is now being popularly used to breed stress-tolerant crops. So identifying and characterizing the critical genes involved in plant stress responses is an essential prerequisite for engineering stress-tolerant crops. Far beyond the manipulation of single functional gene, engineering certain regulatory genes has emerged as an effective strategy now for controlling the expression of many stress-responsive genes. Transcription factors (TFs) are good candidates for genetic engineering to breed stress-tolerant crop because of their role as master regulators of many stress-responsive genes. Many TFs belonging to families AP2/EREBP, MYB, WRKY, NAC, bZIP have been found to be involved in various abiotic stresses and some TF genes have also been engineered to improve stress tolerance in model and crop plants. In this review, we take five large families of TFs as examples and review the recent progress of TFs involved in plant abiotic stress responses and their potential utilization to improve multiple stress tolerance of crops in the field conditions.

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Recent Advances in Utilizing Transcription Factors to Improve Plant Abiotic Stress Tolerance by Transgenic Technology

Tolerance to salinity in plants - new concepts for old problems response of plants to salinity in interaction with other abiotic and biotic factors perception of salt signals by higher plants uptake and role of ions in salt tolerance cell permeability under salt stress salinity and its effects on growth, yield and some physiological processes of crop plants nitrogen metabolism in plants under salt stress carbon metabolism in salt stress polyamines and salt stress a plant biochemical regulator improves salt tolerance flowering and sexual reproduction under salt stress breeding for salt resistance in plants genetics of salt tolerance in higher plants wild germplasm for salt tolerance in plants the potential of plant tissue culture and related techniques for the improvement of salt tolerance in higher plants salt responsive proteins/genes in crop plants molecular biology of salt stress cultivation of salt tolerant conventional and halophytic plants under saline environments improvement of salt tolerance in some native pulse crops.

Strategies for improving salt tolerance in higher plants

The effect of TDZ on organogenesis and somatic embryogenesis in pigeonpea (Cajanus cajan L. Millsp)

Sexually-mature mungbean (Vigna radiata (L.) Wilczek) plants were efficiently regenerated from cotyledonary node explants. The explants were capable of directly developing multiple shoots on basal media devoid of any growth regulators. The shoot multiplication was influenced by media composition, growth regulators, age of donor seedling and explant type. The explants with both the cotyledons attached to the embryonic axis excised from 4-d-old seedlings, produced the highest number of shoots (5 or 6) in 100% of the cultures within 2 weeks on B5 basal medium (BBM) containing BAP or 2-iP, respectively, (at 5x10−7M) and 3% sucrose. Shoots elongated and developed better using BAP. Increasing micronutrients, carbohydrate and nitrogen levels in the medium above the original formulation of B5 basal medium appeared to be of no benefit for increasing the number of shoots. The shoots were rooted on basal MS medium or MS containing 10−6 of NAA, IAA or IBA. This protocol was found applicable to six other cultivars of mungbean. One hundred rooted shoots were successfully established in soil in the glasshouse, where 90% of them survived. The regenerated plants flowered precociously, but produced normal pods and viable seeds.

Plant regeneration from cotyledonary node explants of mungbean (Vigna radiata (L.) Wilczek).

Rice is a staple food for more than 3 billion people in more than 100 countries of the world but ironically it is deficient in many bioavailable vitamins, minerals, essential amino- and fatty-acids and phytochemicals that prevent chronic diseases like type 2 diabetes, heart disease, cancers, and obesity. To enhance the nutritional and other quality aspects of rice, a better understanding of the regulation of the processes involved in the synthesis, uptake, transport, and metabolism of macro-(starch, seed storage protein and lipid) and micronutrients (vitamins, minerals and phytochemicals) is required. With the publication of high quality genomic sequence of rice, significant progress has been made in identification, isolation, and characterization of novel genes and their regulation for the nutritional and quality enhancement of rice. During the last decade, numerous efforts have been made to refine the nutritional and other quality traits either by using the traditional breeding with high through...

Progress and challenges in improving the nutritional quality of rice (Oryza sativa L.)

Agrobacterium tumefaciens-mediated high frequency genetic transformation of an Indian cowpea (Vigna unguiculata L. Walp.) cultivar and transmission of transgenes into progeny

Pawan K. Jaiwal

Papers

Strategies for improving salt tolerance in higher plants

The effect of TDZ on organogenesis and somatic embryogenesis in pigeonpea (Cajanus cajan L. Millsp)

Plant regeneration from cotyledonary node explants of mungbean (Vigna radiata (L.) Wilczek).

Progress and challenges in improving the nutritional quality of rice (Oryza sativa L.)

Agrobacterium tumefaciens-mediated high frequency genetic transformation of an Indian cowpea (Vigna unguiculata L. Walp.) cultivar and transmission of transgenes into progeny