Sittichai Lordkaew

Grain set failure in boron deficient wheat

Effects of boron (B) deficiency on reproductive development and grain set in wheat was studied in experiments in a sand culture in which grain set was increased by increasing B supply in the nutrient solution. Early vegetative response was also studied in a solution culture experiment with 5 μM B and without added B. Effects of B deficiency on the male and female part of the wheat flower were studied in a cross fertilization experiment involving B deficient and B sufficient wheat plants. An international trial (the Boron Probe Nursery) was conducted as a collaboration between Chiang Mai University, CIMMYT and National Agricultural Research Systems in various countries, to verify the B response in non-traditional, warm wheat-growing areas.

Boron requirement for reproductive development in wheat

The effect of boron (B) deficiency on reproductive development was examined in a wheat line SW41 at 4 B levels in a field experiment. The soil B levels (designated BO, B1, B2, B3) ranged from 0.1 to 0.2 mg hot water soluble B kg-1. No effect on vegetative growth was detected at any of the B levels, but the number of grains per ear increased with B, from 7 in BO to 21 in B3; and Grain Set Index (GSI) also increased from 22 to 60%. At ear emergence, B content (mg B kg-1 DW) of the ear ranged from 2.2 to 3.1, and of the flag leaf from 4.1 to 4.7, but these bore slight to no relationship to the number of grains per ear or GSI. Higher B concentrations were found in the carpel, and higher still in the anthers. More significantly, grain set was closely correlated with B in the carpel (R2 = 0.86) and anthers (R2 = 0.77). The significant correlation between GSI and carpel and anther B was confirmed with a larger set of data. With 7 mg B kg-1 DW in the anthers and 5 mg B kg-1 DW in the carpel, the number of grains per ear was doubled when cross pollination with B deficiency tolerant Fang 60 growing near by was allowed. In ears with 9 mg B kg-1 in the anthers and 8 mg B kg-1 in the carpel the effect of cross pollination was smaller, but still significant. The critical deficiency concentration (CDC) of B for the anthers was determined at 10 mg B kg-1 and for the carpel at 8 mg B kg-1.

Comparison of BOR1-like gene expression in two genotypes with different boron efficiencies in commercial crop plants in Thailand

Abstract In Thailand, boron (B) deficiency in soil is found in the north region where wheat (Triticum aestivum L.), maize (Zea mays L.) and rice (Oryza sativa L.) are promoted cereals. Physiological analysis and genetic variation in B efficiency among plant genotypes have been reported; however, the molecular and genetic mechanisms of low B tolerance remain unclear. In this present study, we investigated the molecular basis of low B tolerance in wheat, maize and rice. Transcript levels of BOR1-like genes, efflux-type B transporters, were compared between B-efficient and B-inefficient genotypes in different organs using quantitative real-time polymerase chain reaction (PCR). The results revealed that the transcript levels of BOR1-like genes are differential between two different genotypes. We found the tendency that transcripts of BOR1-like gene are accumulated to higher levels in B deficiency tolerant cultivar than the sensitive ones in most tested tissues. It is possible that the expression levels of BOR1-like genes are correlated with the B deficiency tolerance in plants. Moreover, BOR1-like genes can be useful as gene expression biomarkers for crop breeding in wheat, maize and rice by selecting appropriate tissues and growth stages.

Genotypic variation in response to low boron in eucalypt clones.

Eucalypts are increasingly important in the tropics for meeting growing demand for timber, wood chips, paper pulp and biofuel. Many new plantations are planted on low boron (B) soils, with adverse effects on plant growth and productivity. Two experiments in sand culture with different levels of added B, from 0 to 10 μM B, examined the effect of B deficiency on growth, wood yield and morphology of fibres of three commercially available eucalypt clones: K7 (Eucalyptus camaldulensis × E. deglupta), K51 (E. brassiana × E. grandis) and K57 (E. camaldulensis). In plant height, dry weight and wood production, K7 was more tolerant of B deficiency, but K57 and K51 were more responsive to increasing B. At the level of B that depressed growth by up to 54% and wood yield by up to 65%, no significant effect of B deficiency was observed on fibre morphology. However, as the wood:shoot ratio in K51 and K57 increased with increasing B, there is a possibility that B has a direct effect on wood production in some genotypes, in addition to an indirect effect via better growth. These results indicate that attention to B nutrition in eucalypt plantations would be beneficial to plant growth and productivity before effects of B on individual wood fibres becomes detectable. Selection for B-efficient genotypes could be useful for plantations on low B soils, and the full potential of sites where B is not limiting could be better realised with B-responsive genotypes.