Selection criterion to assess wheat boron tolerance at seedling stage: primary vs. Total root length

Excess boron may exhibit detrimental effect on wheat (Triticum aestivum L.). An effective technique for assessing the response of wheat genotypes to excess boron is required to create high yielding tolerant cultivars. Filter paper assay, based on seedling's primary root length reduction in the presence of excess boron, is commonly used for distinguishing tolerant and sensitive genotypes. The study was undertaken to investigate the effect of excess boron on both primary and lateral root length, number of roots, number of days from imbibition to germination and germination percentage on the sample of 25 wheat cultivars, differing in origin and boron tolerance. The experiment included control and three boron treatments. On average, excess boron reduced root length and number and had no effect on number of days from imbibition to germination and germination percentage; however, significant differences have been found among the genotypes. The imposed boron treatments demonstrated 5.2% stronger effect on lateral root length in comparison to primary root length. In 10 out of 25 cases, boron tolerance estimated from primary root length reduction was not consistent with the estimation from lateral root length reduction; therefore, total root length reduction may be more valuable selection criterion for boron tolerance in wheat