Iron Toxicity Tolerance of Rice Genotypes in Relation to Growth,Yield and Physiochemical Characters

Iron(Fe)toxicity,generated from excess reduced ferrous Fe(Fe^(2+))ion formation within the soil under submerged condition,is a potent environmental stress that limits lowland rice production.Total 11 diverse Thai rice genotypes,including a recognized tolerant genotype Azucena and a susceptible genotype IR64,were evaluated against 5 Fe^(2+)levels[0(control),150,300,600 and 900 mg/L]to screen the tested genotypes for their Fe-toxicity tolerance and to classify them as a sensitive/tolerant category.The evaluation was conducted by a germination study,followed by a polyhouse study on growth,yield and physiochemical performances.Results showed significant variations in Fe^(2+)-tolerance across genotypes.Increasing Fe^(2+)level beyond 300 mg/L was detrimental for germination and growth of all the tested genotypes,although germination responses were negatively affected at Fe^(2+)≥300 mg/L.Physiochemical responses in the form of leaf greenness,net photosynthetic rate,membrane stability index and Fe contents in leaf and root were the most representative of Fe^(2+)-toxicity-mediated impairments on overall growth and yield.Difference in physiochemical responses was effectively correlated with the contrasting ability of the genotypes on lowering excess Fe^(2+)in tissues.Analysis of average tolerance and stress tolerance index unveiled that the genotypes RD85 and RD31 were the closest to the tolerant check Azucena and the sensitive check IR64,respectively.The unweighted pair group method with arithmetic means clustering revealed three major clusters,with cluster Ⅱ(four genotypes)being Fe^(2+)tolerant and cluster Ⅰ(four genotypes)being Fe^(2+)sensitive.Principal component(PC)analysis and genotype by trait-biplot analysis showed that the first two components explained 90.5%of the total variation,with PC1 accounting for 56.6%and PC2 for 33.9%of the total variation.The identified tolerant rice genotypes show potentials for cultivation in Fe^(2+)-toxic lowlands for increased productivity.The findings contribute to the present understanding on Fe^(2+)-toxicity response and provide a basis for future genotype selection or rice crop improvement programs against Fe^(2+)-toxicity.

Selection of Cowpea [(Vigna unguiculata (L.) WALP] Genotypes for Drought Tolerance Using Selection Indices

Cowpea [(Vigna unguiculata (L.)] is one of the most important arid legumes cultivated for pulse and forage production. However, in cowpea, not much is known about the base index selection method in breeding for drought tolerance. Consequently, the present study has been conducted to: 1) evaluate the yield performance of cowpea genotypes under artificial drought and well-watered condition;2) develop a base index using multiple traits for ranking genotype performance. The experiment was a 25 × 2 factorial laid out in a Randomized Complete Block Design (RCBD) with three replications. The experiment was carried out in the screen house at the Department of Horticulture at KNUST. The result showed that KPR1-96-73, Simbo, CZ06-4-16, Wilibaly and Agyenkwa were high yielding in well-water condition while Ghana Shoba, Sangaraka, NKetewade, Ghana-Shoni and Korobalen were high yielding genotypes in water stress condition. The average yield reduction was 60.6% for grain respectively. The biplot displays revealed four groups among the genotypes tested which was based on their yielding capacity and drought tolerance. In cluster B high yielding and drought tolerant genotypes were identified, high yielding and drought susceptible have been identified in cluster A, low yielding and drought tolerant in cluster D, and lastly low yielding and drought susceptible in cluster C. Genotypes in cluster B, were the best due to the fact that it combines high yield and tolerance to drought. They were Ghana Shoni, Nketewade, Sangaraka and Ghana shoba. These genotypes might be suitably employed in further drought tolerance breeding program of cowpea.

Evaluation on Chinese Bread Wheat Landraces for Low pH and Aluminum Tolerance Using Hydroponic Screening

Aluminum （Al） toxicity often takes place in acidic soils with a pH of 5.5 or lower. Breeding and cultivation of Al tolerance wheat can partially protect wheat escaping from Al toxicity. The scarcity of the tolerant sources impedes the wheat breeding. In order to find new Al tolerance sources, we screened 173 bread wheat landraces from Tibet of China using hydroponic screening. It was indicated that： （1） There were diversities on the root regenerate length （RRL）. The RRL of a large of landraces were longer than 7.00 cm in pH 7 （58.38%） and pH 4.5 （66.47%）, but shorter than 5.00 cm in pH 4.5 ＋50μM Al^3＋ （80.93%）. The low pH showed either promotion or restraining effects depend on landraces, but Al toxicity under low pH only showed restraining effects on the root elongation. （2） There were also diversities on root tolerance index of low pH （RTI 1） or root aluminum tolerance index （RTI2） among cultivars. The RTI1 varied from a narrow range but with relatively high value （0.8722-1.2953） in comparison with that of RTI2 （0.3829-1.0058）, and the RTI1 of approximately 60% landraces was higher than 1.0000, the RTI2 of only 19.07% landraces was higher than 0.7000, suggesting that Al toxicity acted as an important factor for the reduction of the root elongation under acidic soils. （3） The RTI 1 of many wheats was higher than 1.0000, and As2256 and As2295 were the most tolerant for low pH, with RTI1 1.2953 and 1.2925, respectively. （4） Based on RTI2, seven wheats showed similar or higher tolerance to Al toxicity than Chinese Spring （CS）, a known tolerance wheat. Much better tolerance existed in landraces of As1543 and As1242, which can be used as the new parents for Al tolerant breeding.

Predictive models of drought tolerance indices based on physiological,morphological and biochemical markers for the selection of cotton(Gossypium hirsutum L.)varieties

The use of tolerant crop varieties is a strategy that mitigates the water deficit effect in a sustainable way.The generation of these varieties is more efficient when variables associated with this tolerance have been identified,since they can facilitate the breeding processes.This study aimed to establish the relationships between water deficit tolerance of four cotton varieties(Nevada-123,Oasis-129,Guatapuri,and Festivalle)and morphological variables(monopodial branches,boll weight,root/shoot ratio,and leaf and root dry matter),physiological variables(relative water content,net photosynthesis,stomatal conductance,electron transport rate,photochemical quenching,photochemical efficiency of PSII,chlorophyll a/b ratio(Chl a/b),C^(12)/C^(13)isotope ratio,and electrolyte leakage),and biochemical variables(contents of sugars,proline,carotenoids,and malondialdehyde).Furthermore,calibrated predictive models of the drought tolerance indices were developed based on the key variables identified.For this purpose,a pot experiment was established where plants were subjected to a moderate or severe water deficit during the blooming stage for 12 days.The stress tolerance index(STI)and mean productivity(MP)were calculated.For the evaluated variables,the differences between well-watered and water deficit plants(Δ)were calculated and ANOVA,partial least squares,Pearson’s correlation,and multiple linear regression analyzes were performed.A model was generated that explained 95% of the STI and was composed of Δmalondialdehyde,Δproline,and Δboll weight.For MP,the model was comprised of Δstomatal conductance,Δroot/shoot ratio,and ΔChl a/b,and explained 89% of the MP.The analysis of the assessed variables allowed the identification of key variables and the development of calibrated predictive models that can be used in screening to obtain cotton varieties with different levels of water deficit tolerance.

Beneficial effects of continual jejunal interposition after subtotal gastrectomy

Background The ideal post-gastrectomy reconstruction procedure should maintain the normal digestive function and restore intestinal transit to improve the patient quality of life. The aim of this study was to evaluate the effects of integral continual jejunal interposition after subtotal gastrectomy on the nutritional status, glucose levels, and gastric-intestinal motility. Methods The study investigated the effects of the integral continual jejunal interposition, the Billroth I and Billroth II operations, and the isolated jejunal interposition following subtotal distal gastrectomy on the blood glucose, insulin, routine blood parameters, liver function, and myoelectrical activity in Beagle dogs. Results The weights of the dogs decreased during the first post-operative weeks. Dogs in the integral continual jejunal interposition, Billroth I, and Billroth II groups gained significantly more weight by 8 weeks. The prognosis nutrition index of the dogs decreased in the first 2 post-operative weeks and increased significantly by 4 weeks in the integral continual jejunal interposition and Billroth I groups. The group with duodenal exclusion （Billroth II） had significantly higher glucose levels compared to the normal control group. The insulin curve was much higher in dogs that underwent the Billroth I, continual jejunal interposition, and isolated jejunal interposition than the Billroth II and normal groups. The frequencies of fasting and postprandial jejunal pacesetter potentials （PPs） were greater in the continual jejunal interposition and Billroth I groups than that in the isolated jejunal interposition and Billroth II groups. The percentage of aboral propagation of PPs was greater in the continual jejunal interposition group than the Billroth I, isolated jejunal interposition, and Billroth II groups. Conclusion Continual jejunal interposition after subtotal gastrectomy avoids jejunal transection, maintains the duodenal Dassaqe and food storaae baas, and reduces the influence of blood qlucose and insulin.