Mehmet Babaoglu

Mechanisms of boron tolerance and accumulation in plants: a physiological comparison of the extremely boron-tolerant plant species, Puccinellia distans, with the moderately boron-tolerant Gypsophila arrostil.

The physiological characteristics of the extremely boron (B)-tolerant plant species, Puccinellia distans, were compared with those of the moderately tolerant Gypsophila arrostil, two species collected from a B-mining area of Eskişehir, Turkey. Boron was supplied to plants hydroponically at B concentrations ranging from 0.5 to 50 mg B/L for G. arrostil, and from 0.5 to 2000 mg B/L for P. distans. The results show that P. distans has a strikingly greater tolerance to B than G. arrostil. While G. arrostil was unable to survive B supply concentrations greater than 50 mg B/L, P. distans grew at B supply concentrations exceeding 1250 mg B/L. Our research supports the conclusion that from 0.5 to 50 mg B/L, P. distans is better able to restrict the accumulation of B in the whole plant, and the transport of B from root to shoot, than G. arrostil. We propose that P. distans uses several strategies to achieve B tolerance including the ability to restrict the accumulation of B relative to its accumulation of biomass, the ability to restrict the transport of B from root to shoot, and, to a lesser extent, the ability to tolerate high concentrations of B in its shoot and root tissues.

Yield and Yield Attributes of Durum Wheat Genotypes as Affected by Boron Application in Boron-Deficient Calcareous Soils: An Evaluation of Major Turkish Genotypes for Boron Efficiency

Abstract Field studies were conducted to determine yield and yield attributes of six durum wheat (Triticum durum Desf.) genotypes namely; Kızıltan-91, Ç-1252, Selçuklu-97, Kunduru-1149, Yılmaz-98, and Çakmak-79, as affected by applications of different levels of boron (B) (0, 1, 3, and 9 kg B ha−1 delivered as boric acid, H3BO3) in soils deficient in available B (0.19 mg B kg−1) and high in lime (CaCO3) content (20.7%) during two consecutive growing seasons; 2000–2001 and 2001–2002. Agronomic characteristics such as grain yields, spike sterility rates, number of grains per spike, number of spikelets per spike, number of spikes per m2, grain weight per spike, thousand grain weights, test weights, and flag leaf B concentration were investigated. Grain yields in all genotypes were significantly increased by B applications compared to the control. Applications of 1 and 3 kg B ha−1 increased yield an average of 11 and 9% respectively, while 9 kg B ha−1 resulted in lower overall yield increase (7%). Genotypes studied have shown significant variations with respect to their responses to additional B. Kunduru-1149 and Çakmak-79 gave the highest grain yield (4080 and 4315 kg ha−1 respectively) at 1 kg B ha−1, whereas Kızıltan-91 and Yılmaz-98 yielded best (4475 and 5010 kg ha−1 respectively) at 3 kg B ha−1. Interestingly, other two genotypes, Ç-1252 and Selçuklu-97, reached to the highest level of grain yield (4320 and 4360 kg ha−1 respectively) at the highest B level (9 kg ha−1). Yield attributes also showed significant variations with respect to their responses to B application. Kızıltan-91 and Kunduru-1149 appeared to have high sensitivity to B deficiency. On the other hand, Çakmak-79 and Selçuklu-97 were B deficiency tolerant genotypes. The study clearly showed that B deficiency could result in significant yield losses in durum wheat under experimental conditions tested. Hence, B contents of soils for the cultivation of durum wheat should be analyzed in advance to devoid of yield losses. Plant tissue analyses can also result in grain yield predictions. Genotypes proven as tolerant/sensitive to high/low B levels may offer valuable genetic materials for use in B-related breeding programs. Considering relationships between flag leaf B concentrations and grain yield, it was clear that when climatic conditions (second year) suit wheat cultivation, B application in B-deficient soils can make profound contributions to grain yield in wheat compared to adverse climatic conditions (first year). Clear positive contribution of B application to grain yield in durum wheat can be more evident under better climatic conditions.

Boron Content of Cultivated Soils in Central-Southern Anatolia and its Relationship with Soil Properties and Irrigation Water Quality

Boron toxicity may occur in semi-arid regions due to high levels of B in soils, in the ground water, in fertilisers or in irrigation water (U.S. Salinity Lab. Staff, 1954; Nable et al., 1997).

STUDIES ON DIFFERENTIAL RESPONSE OF SPRING CANOLA CULTIVARS TO BORON TOXICITY

Although many states recommend boron (B) fertilizer for many field crops, information about B toxicity of canola is lacking. This experiment was carried out at Central Anatolia, Turkey from 2002 to 2003, to determine genotypic range in B efficiency of eight spring canola cultivars, to identify the B-inefficient cultivars and to identify specific responses. The cultivars were grown under B moderate deficiency (extractable B 0.56 mg kg−1) and toxic B applied (15 kg B ha−1) conditions. According to the results, seed yield varied significantly among the cultivars and B application decreased the seed yield by 31% on average. Also, toxic B application reduced protein and oil contents similar to seed yield, and increased leaf B concentration in all varieties. This study has shown that leaf B concentration has increased considerably when B is applied to Pactol and Star cultivars, but seed yield of +B and −B has not shown significantly a change. It is possible to say that Star and Pactol—which have not been affected by the toxic B application—are genotypes that are tolerant to B toxicity and may be cultivated at B toxic lands.

Yield and Yield attributes of Durum Wheat (Triticum durum Desf.) as Affected by Boron Application

Boron (B) deficiency causes grain set in bread wheat to fail (Rerkasem and Jamjod, 1997). Rarkasem et al. (1993) reported that B deficiency lowered the number of grains per spike and grain yield in wheat via suppression of the growth of flowering organs. In another study, Rerkasem et al. (1997) found that B deficiency clearly depressed seed yield, number of grains per ear, and grain set index of bread wheat, without any apparent effect on number of ears per m2, number of spikelets per ear, average size of the ear, and component florets per spikelet. Boron deficiency was considered to be the main reason for sterility in susceptible wheat genotypes since B application reduced sterility from 42.6 to 4.5 % (Subedi et al., 1997). Since B has important effects in pollen tube elongation, and on pollen grain germination and growth (Dickinson, 1978), the main effects of B deficiency are usually expressed during generative development rather than in vegetative plant parts (Rerkasem and Jamjod, 1997; Huang et al., 2000).

Boron Hyperaccumulation Mechanisms in Puccinellia distans as Revealed by Transcriptomic Analysis

Boron is an essential plant micronutrient; but is toxic at high concentrations. Boron toxicity can severely affect crop productivity in arid and semi-arid environments. Puccinellia distans (Jacq.) Par1., common alkali grass, is found throughout the world and can survive under boron concentrations that are lethal for other plant species. In addition, P. distans can accumulate very high levels of this element. Despite these interesting features, very little research has been performed to elucidate the boron tolerance mechanism in this species. In this study, P. distans samples were analyzed by RNA sequencing to identify genes related to boron tolerance and hyperaccumulation. Abundance levels of selected differentially expressed transcripts were validated by real-time PCR. The results indicated that the hyperaccumulation mechanism of P. distans involves many transcriptomic changes including those that lead to: alterations in the malate pathway, changes in cell wall components that allow sequestration of excess boron without toxic effects, and increased expression of at least one putative boron transporter and two putative aquaporins. Elucidation of the boron accumulation mechanism is important to develop approaches for bioremediation of boron contaminated soils.