THE RESPONSE OF PISUM-SATIVUM L GERMPLASM TO HIGH-CONCENTRATIONS OF SOIL BORON

Tolerance to high levels of boron in the soil is an important aspect of the adaptation of crop varieties to southern Australian conditions. This paper reports investigations aimed at exploring the extent of genetic variation in Pisum sativum and at defining appropriate selection criteria for selection for boron tolerance in breeding programs. A collection of 617 accessions of Pisum was screened in controlled conditions and visually assessed for symptoms of boron toxicity. A high proportion of accessions were sensitive with only 3.5% being more tolerant than any of the Australian varieties. Relatively high proportions of tolerant and moderately tolerant accessions originated from Asia and South America. In a second experiment the responses of selected tolerant accessions were evaluated with respect to different parameters. The objectives were to confirm the performance of the putative boron tolerant accessions and identify appropriate parameters for selecting boron tolerant genotypes. In addition to the visual assessment of boron toxicity, measurements at the time of harvest included dry matter yield and concentration of boron in tissues. Symptom expression was highly correlated with dry matter yield and concentration of boron in tissues under high boron conditions and so could be used as a non-destructive selection criteria. A low degree of symptom expression by tolerant accessions could usually be attributed to low levels of boron in the vegetative tissues. The results of this study indicate that considerable genetic variation exists among exotic accessions of Pisum sativum and tolerance to boron could be transferred to sensitive varieties.