Good Drought Tolerance Research Articles

Transcriptome Analysis Reveals the Vital Role of ABA Plays in Drought Tolerance of the ABA-Insensitive Alfalfa (Medicago sativa L.)

Drought stress severely affects alfalfa (Medicago sativa L.) growth and production. It is particularly important to analyze the key networks of drought in alfalfa through physiological and molecular levels. However, how to quickly screen drought-tolerant alfalfa germplasm and how to elucidate the molecular pathways of alfalfa responding to drought are less studied. In this study, based on our previous research, we further verified the association between the heritability of ABA sensitivity during seed germination and drought tolerance of plants and identified the key pathways of drought tolerance differences between ABA-sensitivity (S1-0) and -insensitivity (S1-50) plants via RNA-seq and analysis. The results showed that the sensitivity to ABA in alfalfa seeds can be inherited and that plants that are insensitive to ABA during germination show stronger drought tolerance. An analysis of the differentially expressed genes (DEGs) revealed that ABA biosynthesis and signaling, amino acid metabolism, LEA, and wax synthesis-related pathways may be the key pathways that can be used for drought tolerance improvement in alfalfa. DEGs such as NCED, PYR/PYL, and PP2C may contribute to drought tolerance in the S1-50 plant. The study further confirms that screening with ABA at the seed germination stage can select alfalfa lines with good drought tolerance, which provides a new theoretical basis for alfalfa drought tolerance breeding. The expression of the key genes of alfalfa in response to drought stress was also tested.

The Critical Period for Weed Control in Safflower Fields of Turkey

Crop-weed competition is among the most significant topics in field crops if the crop is a weak competitor in this rivalry. Safflower is a valuable oil seed crop that is drought tolerant and used as a raw material in the food and biofuel industries. Although it has good drought tolerance, it is a sensitive crop against weed competition, especially wild mustard. The critical period for weed control (CPWC) is a useful tool to decide which time period is more suited for weed control economically. In this study, the beginning and end of the CPWC were determined for the summer safflower fields of Turkey. Weeds caused 50.61, 65.87, and 63.34% safflower yield reductions in 2017, 2018, and 2019, respectively. The beginning of the CPWC was 165, 198, and 225 air growing degree days (air GDD) for these years, while the end of CPWC varied 1348, 1837, and 2268 at 5% acceptable yield loss.

A study on creating highly yielded and drought-tolerant QTL gene-possessed lines of peanut

In the trend of global climate changes and heavily occurring drought, particularly resulting in decreased productivity and cultivated areas of peanut production, the breeding and screening of highly yielded and drought-tolerant QTL gene-possessed peanut lines is considered a strategic and effective solution. In this study, the on-field assessment in combination with drought-tolerant gene screening was implemented and 6 peanut cultivars named TK10, Chum Nghe An, Sen Nghe An, L20, L23, and L14 were regarded as hybrid parents for the crossing-breeding program. Of 5 cross-breeding combinations (Chum Nghe An played the role of mother; 5 others were the fathers) 15 elite peanut lines of the F3 generation with high yield (over 29 quintals/ha) and 5 of them coded F3-6, F3-12 (Chum Nghe An × L23), F3-9, F3-10 (Chum Nghe An × Sen Nghe An), and F3-13 (Chum Nghe An × L14) possessed the locus for drought tolerance determined by electrophoresis technology. It is also particularly mentioned that all these lines had a good recovery (92.8-94.6, 84.4-88.4, and 80.0-83.4%, respectively), average productivity loss (30.56-34.10%), and good drought tolerance (point 3: G=21-40%).

Integration of the metabolome and transcriptome reveals the molecular mechanism of drought tolerance in Plumeria rubra.

Plumeria rubra L. cv. Acutifolia is an ornamental tree that displays a good drought-tolerance level. However, the molecular mechanisms of P. rubra adaptation to drought stress remains unclear. Here, drought-simulating pot experiments were conducted to explore drought stress response mechanism of P. rubra. Transcriptome analysis revealed 10,967 differentially expressed genes (DEGs), 6,498 of which were increased and 4,469 decreased. Gene Ontology (GO) analysis revealed that the DEGs were enriched in binding category, in metabolic process category, and in catalytic activities category. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that 9 pathways were significantly enriched, including biosynthesis of secondary metabolites (ko01110), plant hormone signal transduction (ko04075) and so on. In addition, the transcription factor families of AP2/ERFs, bZIP, and C2H2 were significantly upregulated while the families of bHLH, MYB-related, and NAC were significantly downregulated. Moreover, the results of metabolomics analysis indicated that some compounds were accumulated under drought stress, especially flavonoids. Overall, it was speculated that under drought stress, P. rubra first activates the plant hormone signal transduction pathway to regulate hormone contents. Then osmotic regulating substances such as organic acids and amino acids are accumulated to maintain osmotic balance. Finally, flavonoid levels are increased to scavenge reactive oxygen species. These results preliminarily revealed the molecular mechanisms adopted by P. rubra in response to drought stress.

Nutritional and Phytochemical Composition of Bambara Groundnut (Vigna subterranea [L.] Verdc) Landraces in Kenya

Bambara groundnut (Vigna subterranea) is a highly nutritious legume with good drought tolerance attributes and is therefore a suitable candidate for food and nutritional security especially in drought prone areas. This study was conducted to determine the nutritional and phytochemical composition of seventeen Bambara groundnut landraces that were collected from Vihiga, Kakamega, Bungoma, Busia, and Kisumu Counties in Kenya. Prior to characterization, a field experiment was set up in Ishiara Ward in Mbeere North Sub-County in Embu County for two cropping seasons to standardize and multiply the seeds. The experiment was laid out in a Randomized Complete Block Design with three replicates. The harvested seeds were analyzed for their proximate, nutritional, and phytochemical composition using standard procedures. The moisture content ranged from 3.47 to 6.24%, total ash from 3.17 to 4.69%, crude protein from 21.18 to 26.00%, and fats from 4.56 to 7.02%. Iron levels ranged from 4.07 to 5.13 mg/100 g, sodium from 25.14 to 129.66 mg/100 g, potassium from 819.34 to 1,131.80 mg/100 g, and zinc from 0.06 to 0.42 mg/100 g. The tannin levels ranged from 0.01 to 0.04 mg/g, saponins from 0.82 to 1.06 mg/100 g, alkaloids from 0.01 to 0.12 mg/100 g, and flavonoids from 4.07 to 8.45 mg/100 g. The landraces BG-125, BS-148, and BS-145 with relatively higher nutrients composition and those with high levels of phytochemicals such as BS-104 and MU-137 are recommended to plant breeders for further selection and production of certified seeds. These selections will also be promoted to the farmers for production through various extension programs.

Water Savings and Performance of ‘KSUZ 0802’ Hybrid Zoysiagrass in Response to Irrigation Strategy

Irrigation methods that can minimize water use are needed, and the performance of recently released ‘KSUZ 0802’ hybrid zoysiagrass (Zoysia matrella × Zoysia japonica) has not been evaluated under such management. Therefore, field experiments were conducted in Manhattan, KS, and Dallas, TX, USA, to compare the amount of water applied and ‘KSUZ 0802’ performance and recovery resulting from irrigation using the following: 1) routine irrigation (1.2 inches/week), 2) evapotranspiration (ET)-based irrigation (60% of reference ET), 3) soil moisture sensor (SMS)-based irrigation, and 4) no irrigation. The experiment was conducted under a rainout shelter in Kansas from 15 Jul to 27 Sep 2019 and 8 Jun to 19 Oct 2020, and in Texas the experiment was conducted under open field conditions from 22 Jun to 9 Sep 2020. The SMS-based irrigation method in Kansas reduced water application by 68% and 52%, respectively, compared with routine or ET-based irrigation. In Texas, the corresponding water savings were 29% and 13%, respectively. The water savings discrepancy was mainly due to differences in local weather conditions and irrigation demand. Visual turf quality of turf receiving SMS-based irrigation remained above the minimally acceptable level throughout the study in Kansas, whereas in Texas, turf quality declined below acceptable level after 2 weeks. In Kansas, turf retained acceptable quality for more than 21 days with no irrigation, and after rewatering, nonirrigated turf recovered back to significant green cover (93% in 2019 and 67% in 2020). ‘KSUZ 0802’ demonstrated good drought tolerance and recovery in Kansas.

Iris lactea var. chinensis plant drought tolerance depends on the response of proline metabolism, transcription factors, transporters and the ROS-scavenging system

BackgroundIris lactea var. chinensis, a perennial herbaceous species, is widely distributed and has good drought tolerance traits. However, there is little information in public databases concerning this herb, so it is difficult to understand the mechanism underlying its drought tolerance.ResultsIn this study, we used Illumina sequencing technology to conduct an RNA sequencing (RNA-seq) analysis of I. lactea var. chinensis plants under water-stressed conditions and rehydration to explore the potential mechanisms involved in plant drought tolerance. The resulting de novo assembled transcriptome revealed 126,979 unigenes, of which 44,247 were successfully annotated. Among these, 1187 differentially expressed genes (DEGs) were identified from a comparison of the water-stressed treatment and the control (CK) treatment (T/CK); there were 481 upregulated genes and 706 downregulated genes. Additionally, 275 DEGs were identified in the comparison of the rehydration treatment and the water-stressed treatment (R/T). Based on Quantitative Real-time Polymerase Chain Reaction (qRT-PCR) analysis, the expression levels of eight randomly selected unigenes were consistent with the transcriptomic data under water-stressed and rehydration treatment, as well as in the CK. According to Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, proline metabolism-related DEGs, including those involved in the ‘proline catabolic process’, the ‘proline metabolic process’, and ‘arginine and proline metabolism’, may play important roles in plant drought tolerance. Additionally, these DEGs encoded 43 transcription factors (TFs), 46 transporters, and 22 reactive oxygen species (ROS)-scavenging system-related proteins. Biochemical analysis and histochemical detection showed that proline and ROS were accumulated under water-stressed conditions, which is consistent with the result of the transcriptomic analysis.ConclusionsIn summary, our transcriptomic data revealed that the drought tolerance of I. lactea var. chinensis depends on proline metabolism, the action of TFs and transporters, and a strong ROS-scavenging system. The related genes found in this study could help us understand the mechanisms underlying the drought tolerance of I. lactea var. chinensis.

Result of purification for the Te do rice variety of Dien Bien province

Te do is a local rice variety planted in some districts of Dien Bien province (Tuan Giao, Muong Cha, Tua Chua...). This variety has high nutritional content, very good drought tolerance and is resistant to some major pests and diseases such as rice blasts, leaf blight, and brown planthopper. Te do is considered to have great potential in the set of varieties to be included in the agricultural production technology solutions to adapt to climate change, and at the same time increase economic value for growers in the northern mountainous region of Vietnam. The purification process of this rice variety was carried out from 2018 to 2020. From the results of monitoring in the field, 200 individuals (with the same flowering and maturing day) were selected for futher laboratory evaluation; then, 30 G1 lines with the same total growth duration and many similar traits were selected for the next growing season. After evaluation of 30 G1 lines, 10 satisfactory G1 lines were selected for the next growing season (G2). In the G2 generation, the best 6 qualified lines were selected from the 10 initial evaluation lines and the seeds of these 6 lines were mixed to get 400 kg which was tested and certified as registered seeds by the Center for Testing of Variety, the National Plant based on the national technical regulations on the quality of rice seeds.

Empire Turf ® chemical fertilization grown on three substrates

Empire Turf® was the first national cultivar developed, compared to traditional Emerald grass, the Empire is characterized by fast establishment, high erosion control, tolerance to irrigation with non-drinking water, firmer carpets, good drought and salinity tolerance, shading and low demands on soil fertility. However, despite all these desirable characteristics, the development and establishment of the grass will depend on its handling and especially on the substrate in which it is installed. Thus, this study evaluated the development of Empire Turf® conducted on three substrates, with chemical fertilization. The experiment was carried out in containers (volume of 8.5 L) filled with the treatments: T1 - soil; T2 - soil + sand + soil conditioner (1v:1v:1v) and T3 - soil + sand (1v:1v), forming a completely randomized design with three treatments and three repetitions, considering each container as an experimental unit. On March 30, 2019, the first evaluation was carried out, then the treatments received chemical fertilization (NPK+S 13-5-13+14), using 20g of the commercial product diluted in 2L of water, being a single dose per container. After 15 days, in the 2nd evaluation, it was evaluated: foliar chemical analysis, the foliar chlorophyll index (FCI), fresh mass (FM) and dry mass (DM). The results indicated that Empire Turf® presents a rapid response of 15 days, after maintenance fertilization with 10g L-1 of NPK+S (13-5-13+14), having better development when cultivated in soil + sand compound substrate (1v:1v).

‘Tropical Sunki’ mandarin and hybrid citrus rootstocks under ‘Pera’ sweet orange in cohesive soil and As climate without irrigation

The search for alternative rootstocks to the ‘Rangpur’ lime tree is a challenge to the sustainability of citrus in the Tabuleiros Costeiros (Coastal Tablelands) of Northeastern Brazil. New varieties should meet high drought tolerance with water deficit, cohesive soils, resistance to citrus diseases and inducing high production of fruit. In this work, the performance of ‘Pera’ sweet orange was evaluated on ‘Tropical Sunki’ mandarin and 27 hybrid citrus rootstocks in Umbaúba, Sergipe. A local selection of the ‘Rangpur’ lime was the control. Planting was in 2013 at tree spacing of 6.0 × 3.0 m, without irrigation. Tree size, fruit yield and quality, tree survival rate and graft-compatibility were assessed until 2019. Experimental design was completely randomized blocks with 29 treatments, three replicates and four plants in the plot. Two selection indices were applied to the data to assist in decision making. The ‘Tropical Sunki’ mandarin induced similar cumulative fruit yield in relation to the ‘Rangpur’ lime, suggesting a good drought tolerance of the former rootstock. The TSKC × (LCR × TR) - 073 induced slightly lower productivity, compensated by higher productive efficiency and higher concentration of soluble solids, whereas LCR × TR - 001 and HTR - 166 were highly efficient dwarfing rootstocks. The multiplicative and the rank sum indices showed high correlation, both classifying ‘Tropical Sunki’ mandarin, ‘Santa Cruz Rangpur’ lime, LVK × LCR - 010 and - 038, HTR - 127, in addition to the three aforementioned hybrids, as superior to the local selection of ‘Rangpur’ lime.

RB0442 - drought tolerant sugarcane cultivar

Abstract Sugarcane cultivar RB0442 has a high yield, late maturation and good drought tolerance. It is recommended for planting in restrictive environments, mainly with water-deficient soils, and is resistant to the major sugarcane diseases of the Northeastern region of Brazil.

Effects of exogenous proline on the physiological characteristics of Triticum aestivum L. and Lens culinaris Medik. under drought stress

Proline, which is an indicator of stress, is often considered as a good parameter for the testing of plants with good drought tolerance capacity. Thus, exogenous application of proline is a possible technique to avoid the deleterious effects of the drought on plant growth. The objectives of this study are to investigate the impact exogenous proline on the physiological behavior of two plant species, bread wheat, a monocot, and lentil, a dicot, under drought stress conditions. After several preliminary tests, optimal concentrations of exogenous proline were determined (6 mM for bread wheat and 2 mM for lentil) and both species were treated in normal and drought conditions. The results showed that water deficit affected both species leading to a reduction in growth, chlorophyll content and relative water content. Likewise, 15 % PEG-6000, which is equivalent to osmotic potential of -0.31MPa, caused a high accumulation of proline. In almost of cases we also noted a remarkable decrease in catalase (Cat), ascorbate peroxidase (APX) and gaiacol peroxidase (GPX) activities which was probably due to the oxidative stress caused by drought stress. The application of proline in stressful conditions reduced the deleterious effects caused by the stress on both species, due, particularly, to the accumulation of free endogenous proline and the increase of Cat, APX and GPX activities.

Differential Physiological Responses and Genetic Variations in Fine Fescue Species for Heat and Drought Stress

Summer decline is typically characterized by heat and drought stress and is a major concern for fine fescue species (Festuca). The objectives of this study were to examine whether heat or drought stress is more detrimental, and to determine the genotypic variations in heat and drought tolerance for fine fescues. A total of 26 cultivars, including seven hard fescues (Festuca trachyphylla), eight chewings fescues (Festuca rubra ssp. commutate), seven strong creeping red fescues (Festuca rubra ssp. rubra), two sheep fescues (Festuca ovina ssp. hirtula), and two slender creeping red fescues (Festuca rubra ssp. littoralis) were subjected to prolonged heat or drought stress in growth chambers. Several physiological parameters, including turf quality (TQ), electrolyte leakage (EL), photochemical efficiency (Fv/Fm) chlorophyll content (Chl), and relative water content (RWC) were measured in plants exposed to heat or drought stress. The results indicated that heat stress was more detrimental than drought stress for fine fescue species. Based on TQ and major physiological parameters (EL and Fv/Fm) under heat stress, several cultivars with good heat tolerance were selected, including ‘Blue Ray’, ‘Spartan II’, ‘MN-HD1’, ‘Shoreline’, ‘Navigator II’, ‘Azure’, ‘Beacon’, ‘Aurora Gold’, ‘Reliant IV’, ‘Marco Polo’, ‘Garnet’, ‘Wendy Jean’, ‘Razor’, and ‘Cindy Lou’. Based on TQ and major physiological parameters (EL, RWC, and Fv/Fm) under drought stress, several cultivars with good drought tolerance were selected, including ‘Spartan II’, ‘MN-HD1’, ‘Reliant IV’, ‘Garnet’, ‘Azure’, and ‘Aurora Gold’. These cultivars could be used in hot, dry, or both environments and as breeding germplasm for developing heat tolerance, drought tolerance, or both.

Effect of Limited Drip Irrigation Regime on Yield and Yield Components of Sesame under Mediterranean Conditions

Sesame is one of the most important oilseed crops in the world. Irrigation is of great importance to sesame production due to its positive effect on growth parameters. Although sesame has good drought tolerance compared with many other crops, it is particularly susceptible to drought damage during the seedling, flowering and seed filling stages and this can lead to yield loss. The aim of this study was to determine the response of sesame landraces to different irrigation applications during the 2015 growing season. The experiment was set up as a split plot design with three replicates, four main plots (irrigation treatments, designated as 100%, 75% 50% and 0 of the daily crop evapotranspiration) and two sub-plots (sesame landraces, Limnos and Evros). Different characteristics such as plant height, number of seeds per capsule, and number of capsules per plant, seed yield, 1000-seed weight and % capsules without seeds, were recorded. The results indicated that all traits except 1000-seed weight were significantly affected by irrigation regimes. Plant height, shattering losses and number of capsules per plant decreased with increasing water shortage. Seed yield and number of seeds per capsule were less affected by irrigation level and showed higher values in the 50% of the daily crop evapotranspiration treatment. Limnos produced higher seed yield and number of seeds per capsule under all irrigation regimes. Evros showed higher plant height and shattering losses than Limnos. The results of this study suggest that sesame landraces can use water efficiently, are locally adapted and associated with traditional farming systems.

Marker-trait association analysis for agronomic and compositional traits in sainfoin (Onobrychis viciifolia).

Sainfoin (Onobrychis viciifolia) is a perennial forage legume with great potential for use in sustainable agriculture due to its low input requirements, good drought tolerance, and production of forage rich in polyphenolic compounds, which are beneficial for animal health. However, its distribution and cultivation are limited due to its moderate agronomic performance and a general lack of well adapted, highly yielding cultivars. Faster progress in breeding is imperative, but is often hampered by the complex inheritance of traits and limited knowledge on the genetic composition of this tetraploid, outbreeding species. Molecular genetic tools might aid phenotypic selection; however, to date no information on marker-trait associations is available for sainfoin. Hence, the goal of the present study was to detect marker-trait associations in a biparental F1 population. Single plants were screened for recently developed genetic markers and phenotyped for important agronomic traits and concentrations of different polyphenolic compounds. Significant trait-associated markers (TAM) were detected for plant height (11), plant vigor (1), and seed yield (7). These three traits were positively correlated with each other and shared some TAMs. Correlations among markers suggested that two independent loci control these three vigor-related traits. One additional, independent TAM was detected for the share of prodelphinidins in total condensed tannins. Our results provide insight into the genetic control of important traits of sainfoin, and the TAMs reported here could assist selection in combination with phenotypic assessment.

Enhancing forage quality through appropriate nitrogen dose, seed rate and harvest stage, in sorghum cultivars grown in Pakistan

AbstractSorghum is an important forage crop having good drought tolerance and high dry matter accumulation in a short growing season, and grown under diversified environments. Based on this, a 2‐year field study was executed to evaluate the effect of seed rate and nitrogen (N) levels on the fiber quality of forage sorghum cultivars harvested at different growth stages under semiarid condition. Three forage sorghum cultivars (‘JS–2002’, ‘JS–263’ and ‘Chakwal Sorghum’) were sown with three N levels (0, 60 and 120 kg ha−1) by using three seed rates (75, 100 and 125 kg ha−1). Results showed that cv. ‘JS–2002’ had higher contents of neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL) and cellulose, while ‘JS–263’ produced greater soluble carbohydrate, total digestible nutrients (TDN), relative feed value (RFV) and net energy (NE) than other cultivars. Increasing N rates (0–120 kg ha−1) enhanced ADF, ADL, RFV and NE, but not NDF and TDN. Similarly, increased seed rate enhanced accumulation of NDF, ADF and ADL, while caused reduction of TDN, RFV and NE. In conclusion, cv. ‘JS–2002’ performed better than the other two cultivars, whereas, sorghum seeded at 75 kg ha−1 with 120 kg N ha−1 application produced better quality forage at 50% heading stage.

Cold Hardiness and Its Relationship with the VRN1 Genotypes in Wheat Varieties in the Yellow-Huai-Hai River Valley Region of China

Winter freezing injury is one of the major natural disasters in wheat production. The effect of VRN1 genes on cold hardness was analyzed with phenotypic data and the allelic variations of VRN-A1, VRN-B1, VRN-D1 in 71 wheat varieties grown in Yellow-Huai-Hai River Valley region. The results indicated that the cold hardiness of wheat was correlated with other stress tolerances, and strong cold hardiness was found in most varieties showing good salinity tolerance, drought tolerance or water-saving feature in production and the National Variety Regional Trial. VRN1 is a critical locus in the genetic network of wheat cold hardiness. The presence of the dominant gene VRN1 was often accompanied with a significant decrease in cold hardiness, and weak cold hardiness was usually detected in the varieties with two or three VRN1 genes. Coexistence of recessive genes vrn-A1, vrn-B1, and vrn-D1 was found to be an indispensable prerequisite for strong cold hardiness. Therefore, the vrn-A1vrn-B1vrn-D1 genotype is suggested in wheat production and variety improvement in the northern part of Yellow-Huai-Hai River Valley region of China.

Comparative study of putative 9-cis-epoxycarotenoid dioxygenase and abscisic acid accumulation in the responses of Sunki mandarin and Rangpur lime to water deficit

Abscisic acid is a plant hormone that participates in essential plant physiological processes, especially during adaptation to many environmental stresses, such as water deficit. The relationship between ABA accumulation and the expression of putative carotenoid cleavage dioxygenase (CCD) genes was investigated in the pot-cultivated leaves and roots of the 'Rangpur' lime and 'Sunki Maravilha' mandarin plants. Transpiration, stomatal resistance and leaf growth were evaluated when these genotypes were subjected to continuous water deficit. Under water deficit conditions, the 'Rangpur' lime extracts used greater amounts of water when compared to the 'Sunki Maravilha' plants, which reached the greatest stomatal resistance 5days before 'Rangpur' lime. When subjected to water deficit, the roots and leaves of 'Sunki Maravilha' showed a progressive increase in ABA accumulation; however, in 'Rangpur' lime, alternations between high and low ABA concentrations were observed. These results suggest a retroactive feeding regulation by ABA. In 'Rangpur' lime the NCED2, NCED3 and CCD4a genes were expressed at the highest levels in the roots, and NCED5 was highly expressed in the leaves; in 'Sunki Maravilha', the NCED2 and NCED5 genes were most highly expressed in the roots, and NCED2 was most highly expressed in the leaves. However, for both genotypes, the transcription of these genes only correlated with ABA accumulation during the most severe water deficit conditions. The 'Rangpur' lime behaved as a vigorous rootstock; the leaf growth remained unaltered even when water was scarce. However, 'Sunki Maravilha' adaptation was based on the equilibrium of the response between the root and the aerial tissues due to water restriction. The use of the Sunki mandarin in combination with a scion with similar characteristics as its own, which responds to water deficit stress by accumulating ABA in the leaves, may display good drought tolerance under field conditions.

MOLECULAR ANALYSIS OF BAMBARA GROUNDNUT, AN UNDERUTILISED AFRICAN LEGUME CROP AS PART OF THE BAMLINK PROJECT - WHAT LESSONS CAN WE LEARN?

MOLECULAR ANALYSIS OF BAMBARA GROUNDNUT, AN UNDERUTILISED AFRICAN LEGUME CROP AS PART OF THE BAMLINK PROJECT - WHAT LESSONS CAN WE LEARN?

Comparative Evaluation of Water Deficit Tolerance Capacity of Extra-early and Early Maize Genotypes under Controlled Conditions

Maize is an important staple food crop in Tropical Africa including Nigeria. However, the production of the crop is constrained by inadequate soil moisture resulting from erratic rainfall distribution. There is therefore the need to breed and select for drought tolerant genotypes for production especially in the southern Guinea savannah ecology responsible for over 60% of maize production in Nigeria. Controlled experiments using potted plants were therefore conducted during the dry periods between November 2007 and April 2008. The study evaluated moisture deficit tolerance capacity of two maize maturity groups, consisting of 15 extra-early and 12 early genotypes along with two local checks, subjected to two moisture levels 25% (stressed) and 100% (unstressed) soil available moisture) determined gravimetrically. Crop establishment parameters (% germination and mean germination time (MGT), morphological growth parameters (number and area of leaves, plant height, flowering characteristics), physiological growth indices (leaf area index, crop growth rate, relative growth rate, net assimilation rate and leaf area ratio) were measured during growth. Yield components (harvest index, shelling percentage and number of kernels per cob) and grain yield were determined at harvest. The data were analyzed using the general model of ANOVA and significant means were separated by the Least Significance Difference (LSD) at 5% probability level. The results showed that there were no appreciable differences between the two maturity groups for most measured parameters. However, across the two groups, crop establishment parameters, morpho-physiological growth parameters, yield components and grain yield were significantly reduced by soil moisture deficit, while flowering characteristics were significantly delayed by soil moisture stress with significant variable genotypic responses. Grain yield reduction due to water stress was significantly related to drought susceptibility index (DSI) of the genotypes in the two maturity groups. Conclusively, whereas extra-early genotypes showed good yield potentials but poor drought tolerance which suggested poor yield stability and therefore may not be suitable for the southern Guinea savanna (SGS) ecology in the event of severe stress. However, early genotypes, though showed lower yield potential, had good yield stability and hence are promising genotypes for the SGS ecology.