An improvement program for disease resistance and horticultural traits in Cavendish banana cultivars was established using somaclonal variants as a source of variation. The improvement procedure included single plant selection, clonal evaluation and experimental variety trials. Resistance to Fusarium wilt (race 4) is the most important breeding objective of the program. Resistant clones were selected by the pot screening technique using the fungal pathogen as the innoculum. A large quantity of young plants derived from tissue culture were subjected to the challenge of the disease. Putative resistant plants were identified and were multiplied by tissue culture for further evaluation. Through this procedure, several promising clones showing a high level of resistance to Fusarium wilt were selected and subjected to further evaluation. Somaclonal variation is also an effective tool in the improvement of horticultural traits of banana. A semi-dwarf resistant clone, TC1-229, which is about 70 cm shorter, was identified. It was derived from 'Tai-Chiao No. 1' which is tall and susceptible to wind damage. This clone was registered as ' Tai-Chiao No. 3' in 2000 and released for commercial planting in 2001. Further selection from TC1-229 resulted in the identification of clones with improved bunch size and shape, and these are now undergoing further evaluation. Triploid Cavendish bananas are highly sterile and hence very difficult to improve by conventional hybridization method. Selection among somaclonal variants has proved to be an effective alternative in the improvement of Cavendish bananas.
Lignosulfonate (LS) is a by-product obtained during sulfite pulping process and is commonly used as a growth enhancer in plant growth. However, the underlying growth promoting mechanism of LS on shoot growth remains largely unknown. Hence, this study was undertaken to determine the potential application of eco-friendly ion-chelated LS complex [sodium LS (NaLS) and calcium LS (CaLS)] to enhance recalcitrant indica rice MR 219 shoot growth and to elucidate its underlying growth promoting mechanisms. In this study, the shoot apex of MR 219 rice was grown on Murashige and Skoog medium supplemented with different ion chelated LS complex (NaLS and CaLS) at 100, 200, 300 and 400 mg/L The NaLS was shown to be a better shoot growth enhancer as compared to CaLS, with optimum concentration of 300 mg/L. Subsequent comparative proteomic analysis revealed an increase of photosynthesis-related proteins [photosystem II (PSII) CP43 reaction center protein, photosystem I (PSI) iron-sulfur center, PSII CP47 reaction center protein, PSII protein D1], ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), carbohydrate metabolism-related proteins (glyceraldehyde-3-phosphate dehydrogenase 3, fructose-bisphosphate aldolase) and stress regulator proteins (peptide methionine sulfoxide reductase A4, delta-1-pyrroline-5-carboxylate synthase 1) abundance in NaLS-treated rice as compared to the control (MSO). Consistent with proteins detected, a significant increase in biochemical analyses involved in photosynthetic activities, carbohydrate metabolism and protein biosynthesis such as total chlorophyll, rubisco activity, total sugar and total protein contents were observed in NaLS-treated rice. This implies that NaLS plays a role in empowering photosynthesis activities that led to plant growth enhancement. In addition, the increased in abundance of stress regulator proteins were consistent with low levels of peroxidase activity, malondialdehyde content and phenylalanine ammonia lyase activity observed in NaLS-treated rice. These results suggest that NaLS plays a role in modulating cellular homeostasis to provide a conducive cellular environment for plant growth. Taken together, NaLS improved shoot growth of recalcitrant MR 219 rice by upregulation of photosynthetic activities and reduction of ROS accumulation leading to better plant growth.
Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most threatening fungal diseases affecting banana plantations across the globe. It was first discovered in Australia in 1874 and has now spread to numerous different regions in the world hinting at the persistency of the pathogen. Various management strategies have been devised aiming mainly on improving the plant's tolerance or suppressing the infection. Fungicide is commonly used to control the disease spread, but it does not provide total protection to the plants besides displaying selective effectiveness on certain Foc strains. Alternatively, farmers apply crop rotation, rice hull burning, biological soil disinfestation, and compound-supplemented soil in their banana plantations. Studies have also shown that certain biocontrol agents manage to curb the disease threat. Selection of somaclonal variants and genetic manipulation via induced mutagenesis and transformation are also among the alternatives that have been implemented in producing Fusarium-tolerant and Fusariumresistant banana plants. This chapter will describe Fusarium epidemics in banana, the effectiveness and challenges of different management approaches, as well as the future alternatives that can be adopted by taking advantages of the latest advances in omics technologies.
Vacuolar processing enzyme (VPE) is a cysteine protease responsible for vacuolar proteins’ maturation and regulation of programmed cell death (PCD). Four isoforms of Arabidopsis thaliana VPEs were identified previously, but only the functions of βVPE, γVPE, and δVPE were determined. The specific function of a gene is linked to the cis-acting elements in the promoter region. A promoter analysis found repetitive drought-related cis-elements in αVPE, which highlight its potential involvement in drought regulation in A. thaliana. The further co-expression network portraying genes interacting with αVPE substantiated its drought-regulation-related function. Expression of αVPE was upregulated after drought treatment in A. thaliana. To confirm the role of αVPE, a loss of function study revealed that αVPE knockout mutants remained green compared with WT after drought treatment. The mutants had reduced proline activity, decreased sucrose content, and lower MDA content, but increased photosynthetic pigments, indicating that αVPE negatively regulates drought tolerance in A. thaliana. Taken together, our findings serve as important evidence of the involvement of αVPE in modulating drought tolerance in A. thaliana.
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