Advances in Legume Research: Physiological Responses and Genetic Improvement for Stress Resistance

Phetole Mangena

• Publisher: Bentham Science Publishers
• Year: 2020
• ISBN:
  9789811479625
• Topic: Biological Sciences
• Subtopic: Botany
• Index: Biological Sciences

For centuries, legumes have been used as pulses or grains serving as the most critical sources of major protein/oil-producing crops for both human and animal consumption, and for providing raw materials for industrial processing. They are highly valued as soil-building crops, improving soil quality through their beneficial involvement in biological nitrogen fixation, a symbiotic partnership with rhizobia. Advances in Legume Research: Physiological Responses and Genetic Improvement for Stress Resistance serves as a unique source of information on the distinct aspects of basic and applied legume research for general readers, students, academics, and researchers. The book gives several insights on the morphological, physiological, and genetic responses to stresses via 8 concise chapters covering all aspects of legume growth, utilization, and improvement. The included chapters present research findings and succinct reviews concerning the strides continuously made in the improvement of legumes against biotic and abiotic stress factors. This comprehensive new legume reference book disseminates key information pertaining to genetic diversity, conservation, cultivation, manipulation through mutagenic techniques, plant transformation, and other breeding technologies. The book, therefore, continues to build on the need to acquire new knowledge about legume crops and ways to improve their existing agricultural yield for a sustainable and secure food market.

Determination of Drought Stress Tolerance Using Morphological and Physiological Markers in Soybean (Glycine max L.)

Paseka Tritieth Mabulwana^*, Phatlane William Mokwala

Department of Biodiversity, School of Molecular and Life Sciences, Faculty of Science and Agriculture, University of Limpopo, Private Bag X1106, Sovenga 0727, Republic of South Africa

Abstract

Soybean (Glycine max L.) is one of the most important leguminous crop plants worldwide. A lot of attention has been focused on soybean cultivation in South Africa. Its production is affected by several biotic and abiotic stress factors which reduce the yield and quality of the crop. The aim of this study was to evaluate drought tolerance in South African soybean cultivars that have the potential for cultivation in areas where water is a limited resource. Six South African (LS677, LS678, Mopani, Sonop, Knap and Pan1564) and two American (R01416 and R01581) cultivars were carefully studied for morphological and physiological markers using a greenhouse-based study in a randomised block design. The results showed that several morphological (stem length, leaf area, flowers, and seeds) and physiological (chlorophyll, moisture content, phenolics, flavonoids, ureide content and antioxidant activity) parameters were affected by drought stress. However, cultivars with high phenolic and flavonoids content were associated with high antioxidant activity and slightly increased their yields than other varieties. The anatomical analysis also showed some interesting differences in response to reduced water treatment, with the sizes of vascular tissues and sclerenchyma tissues decreasing under drought stress. In conclusion, this study indicated that reduced stem length and inability to reduce leaf area by soybean plants could lower plant growth and yield response under drought stress. In addition, increased chlorophyll and secondary metabolite content can improve soybean growth under limited water conditions.

Keywords: Anatomy, Antioxidant activity, Chlorophyll, Morphology, Phenolics, Soybean, Total flavonoids.

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^* Corresponding author Paseka Tritieth Mabulwana: Department of Biodiversity, School of Molecular and Life Sciences, Faculty of Science and Agriculture, University of Limpopo, Private Bag X1106, Sovenga 0727, Republic of South Africa; Tel: [phone]; E-mail: [email protected]

INTRODUCTION

Glycine max L. is considered to be one of the most important grain legumes in sub-Saharan Africa and the world at large.

The cultivation of this crop has also been going on for decades in many parts of Africa, particularly Nigeria and South Africa, where it amounts to over 35% of the total grain legume production in this region [1]. Soybean remains one of the less cultivated food crops in Africa compared to maize, cassava, and sorghum. In South Africa, the cultivation of this crop is widespread. According to earlier reports by the Department of Agriculture, Forestry and Fisheries; major areas of cultivation per province are the Mpumalanga highveld, Free State highveld, areas around Pietermaritzburg in the KwaZulu Natal province, Northwest province, Gauteng, and Limpopo. However, soybean production in the Southern part of South Africa, such as the Northern, Eastern and Western Cape remains very minimal due to cultivation conditions and unpredictable weather patterns. Furthermore, the chief soybean producers in Africa (Nigeria and South Africa), as well as other countries like Zambia, Tanzania and Zimbabwe, have also slightly increased their statistical production records in 2010 and beyond, whilst cultivation continues to show fluctuating results [1, 2].

The cultivation problems emanate from the various climatic challenges that largely affect crop growth and productivity, such as reduced seed viability, pod shattering and lack of genetically improved cultivars, especially those conferring tolerance to both biotic and abiotic stress factors. Generally, crop plant growth and yield become severely impacted by abiotic stress, such as the inadequate supply of water, resulting in decreased carbon assimilates contents, increased susceptibility to insect pests and diseases. Evidence of the occurrence of fungi and insect-induced stalk rots, wilts and foliar diseases caused by water deficit stress were also reported in soybean plants [2, 3]. As indicated by Singh and Singh [4], abiotic stress perpetuates challenges facing the growth and productivity of soybean, particularly, in developing countries where cultivation remains stagnated and very limited due to the increasing populations. As such, these impact negatively on the wellbeing of many people, and their gradually developing economies.

Additionally, these also pose more problems to the quantity and quality of processed soy-based products that are being locally manufactured. Some of those manufactured products include soy flour, milk, textured soy protein and oil. Soybean is also regarded as one of the most important sources of affordable protein and vegetable oil compared to wheat and maize [5]. Apart from being used as indicated above, it is also used as a source of biodiesel and animal feed [6]. This crop is also useful in the improvement of soil fertility and the capability to take fixed atmospheric nitrogen [2, 3]. Nitrogen fixation is brought about by a mutualistic relationship between soybean and Bradyrhizobium bacteria, which forms nodules in the roots. The microorganisms help the plant in fixing or converting nitrogen into forms usable by the plant-like NH₃, NO₃^- and NH₄⁺.

Among the major abiotic stressors, drought is one of the most damaging constraints that adversely affect soybeans in many critical aspects of their growth and metabolism. Soybean’s growth, development and productivity are severely diminished when soil and cell water potential bec...