In Vitro Selection and Identification of Drought-Tolerant Mutants in Sweetpotato

In vitro selection of drought-tolerant mutants in sweetpotato cv. Lizixiang was studied by using PEG6000 as selection stress. Embryogenic suspension cultures were cultured in MS medium containing 035% PEG6000 and 2 mg L 1 2,4-dichlorophenoxyacetic acid (2,4-D). The results indicated that 30% PEG6000 can be used for the optimal selection stress of drought-tolerance. Embryogenic suspension cultures irradiated with 80 Gy gamma-ray were cultured in MS medium containing 30% PEG6000 and 2 mg L 1 2,4-D and 20 drought-tolerant cell aggregates were obtained. These cell aggregates were transferred to solid MS me- dium supplemented with 2 mg L 1 2,4-D and formed embryogenic callus with somatic embryos. The embryogenic callus with somatic embryos was further transferred to MS medium supplemented with 1 mg L 1 abscisic acid (ABA), resulting in the germination of somatic embryos. In this study a total of 18 regenerated plants were obtained. The regenerated plants were transplanted in a greenhouse and 11 lines were formed. The analysis on drought treatment of seedlings, water retaining capacity of leaves and coefficient of drought-tolerance showed that 3 lines had significant drought-tolerance in comparison with the control plants.

Cloning and expression pattern of a dehydrin-like BDNI gene from drought-tolerant Boea crassifolia Hemsl.

A 500-bp cDNA fragment was amplified via RT-PCR from drought-induced total RNA of the drought-tolerant B. crassifolia Hemsl. using primers based on the sequence of published dehydrin conserved region. By using 5’ RACE, full-length coding region (1 148 bp) of BDN1 gene was produced. It is a new member of the dehydrin gene family. Southern analysis indicated that BDN1 is present in the 6. crassifolia genome as a single-copy gene. Northern analysis revealed that its expression is inducible by drought and cold stresses as well as ABA application.

Analysis of Plant Diversity Characteristics in Jiangxia Wetland

[Objectives]This study was conducted to explore the characteristics of plant diversity of Jiangxia Wetland in Lhasa River basin.[Methods]Based on the survey data of 37 plant community in three types of sample plots of Jiangxia Wetland in the Lhasa River basin,this study analyzed the diversity of plant community in different habitats of Jiangxia Wetland from Pielou evenness,Margalef richness,Simpson and Shannon Wiener diversity indexes of different types and levels.[Results]The Pielou index,Shannon-Wiener index and Simpson diversity index of dry land was higher than those of other plots,while the Margalef species richness index of the ecotone of seasonally flooded and dry land was higher than that of other plots.The Pielou index,Shannon-Wiener index,Simpson diversity index and Margalef species richness index of composite plants were higher than those of other herbaceous plants.The Shannon-Wiener index,Simpson diversity index and Margalef species richness index of hygrophytes were higher than those of other plants,while the Pielou index evenness index of aquatic plants was higher than that of other plants.Annual or perennial herbaceous plants occupied the primary position in the study area,and shrub plants occupied a secondary position,and floating plants took the lowest position.[Conclusions]The results of this study can provide theoretical support or reference basis for the scientific management of comprehensive wetland systems such as wetland ecosystem restoration and plant diversity protection in Jiangxia Wetland.

Improvement of Rice Production under Drought Conditions in West Africa:Application of QTLs in Breeding for Drought Resistance

Rice plays a paramount role in food and nutrition security in many West African countries.Despite the doubling of production during the last decade,rice consumption has grown faster,creating a deficit between the demand and supply.Although the West African sub-region remains the main rice-producing centre on the continent,production is severely hampered by biotic and abiotic stresses.Drought is one of the factors that most severely reduce grain yields of rice.Systems of production need to be established in order to mitigate yield loss as a result of drought.This review discusses the effects of drought on rice production in West Africa and its mitigation with an emphasis on the improvement of tolerance to drought stress.Yield stability can be achieved by developing drought-tolerant varieties through several processes encompassing profiling of known QTLs and identification of new ones,marker-assisted selection,genomic selection,and extensive multi-locational yield trials.We suggest a comprehensive strategy for breeding drought-tolerant rice varieties in West Africa.

Growth Performance of <i>Moringa oleifera</i>and <i>Moringa ovalifolia</i>in Central Namibia Semi-Arid Rangeland Environment

The objective of this study was to compare the field growth performance of Moringa oleifera and Moringa ovalifolia in semi-arid environment of central Namibia rangeland. This part of Namibia has both arid and semi-arid climates. These climates require the growing of drought-resistant fodder trees to aid in the provision of animal feed or supplement. This is paramount to livestock farmers who are striving to meet the feed demand of their animals especially during winter and drought periods. It is upon this background that both Moringa species were grown to evaluate their field growth performances. Moringa oleifera grew faster with 224.9 cm and 281.45 cm heights than Moringa ovalifolia that had 77.025 cm and 113.2 cm heights in 2014/2015 summer season (October 2014 to April 2015) and 2015/2016 summer season (October 2015 to April 2016), respectively, although Moringa ovalifolia is native to Namibia. In Namibia, summer usually starts October and ends April the follow year after which winter follows. Moringa oleifera grew significantly higher (P Moringa ovalifolia, though they belong to the Moringaceae family and were grown under the parallel conditions. Therefore, Moringa oleifera would serve as a better alternative for improving rangelands’ productivity under these adverse climatic and environmental conditions since it can grow faster than Moringa ovalifolia, whose characteristic leads to the rapid establishment of trees and large quantity of leaf-biomass production.

Development and drought tolerance assay of marker-free transgenic rice with OsAPX2 using biolistic particle-mediated co-transformation

Abiotic stresses such as drought, salinity, and low temperature cause–losses in rice production worldwide. The emergence of transgenic technology has enabled improvements in the drought resistance of rice plants and helped avert crop damage due to drought stress.Selectable marker genes conferring resistance to antibiotics or herbicides have been widely used to identify genetically modified plants. However, the use of such markers has limited the public acceptance of genetically modified organisms. Marker-free materials (i.e., those containing a single foreign gene) may be more easily accepted by the public and more likely to find common use. In the present study, we created marker-free drought-tolerant transgenic rice plants using particle bombardment. Overall, 842 T_0plants overexpressing the rice ascorbate peroxidase-coding gene OsAPX2 were generated. Eight independentmarker-free lines were identified from T_1 seedlings using the polymerase chain reaction.The molecular characteristics of these lines were examined, including the expression level,copy number, and flanking sequences of OsAPX2, in the T_2 progeny. A simulated drought test using polyethylene glycol and a drought-tolerance test of seedlings confirmed that the marker-free lines carrying OsAPX2 showed significantly improved drought tolerance in seedlings. In the field, the yield of the wild-type plant decreased by 60% under drought conditions compared with normal conditions. However, the transgenic line showed a yield loss of approximately 26%. The results demonstrated that marker-free transgenic lines significantly improved grain yield under drought-stressed conditions.

Evaluation of Tomato Genetic Resources for Response to Water Deficit

Water deficit strongly affects plant yield and quality. However, plants can minimize drought injury by adaptation mechanisms that have evolved to escape harmful conditions. The response to water deprivation is a complex trait controlled by several genes. In order to gain a deeper understanding of drought response mechanisms in tomato, a collection of 27 genotypes was studied under different water deficit conditions. Since developmental stages might be differently influenced by drought, analyses were carried out on young plantlets during fruit setting. The only genotype that showed good performances both as water retention and fruit production was the ecotype Siccagno. All the genotypes were analyzed at molecular level with the aim of detecting structural polymorphisms in selected stress-responsive genes. In addition, the expression level of a number of these genes was measured in the genotypes more tolerant to water deficit. Many polymorphisms were detected in six stress-responsive genes, and some could imply significant modifications in the protein structure. Furthermore, the expression analysis by RT-qPCR of three stress-responsive genes allowed arguing that a higher level of expression of the gene erd15 might be related to the better response to water deficit exhibited by Siccagno. Similarly, the lower expression of eight genes in the same genotype analysed through a microarray experiment confirmed the involvement of these stress-related genes in the tomato response to drought. Further investigations are required for a better comprehension of the mechanisms underlying response to water deficit in tomato by exploiting the genetic resource identified as more tolerant. The use of new technologies able to globally analyze structural polymorphism and expression level of genes will succeed to identify crucial genes involved in stress response in the ecotype Siccagno grown under different water regimes.