Discrimination of boron tolerance in Pisum sativum L. genotypes using a rapid, high-throughput hydroponic screen and precociously germinated seed grown under far-red enriched light

Richard G. Bennett, Federico M. Ribalta, Maria Pazos-Navarro, Antonio Leonforte, Janine S. Croser

Boron (B) tolerance has been identified as a key target for field pea improvement. Screening for B tolerance in the field is problematic due to variability in space and time, and robust B molecular markers are currently unavailable in field pea. There has been recent progress in developing protocols that can accelerate the life cycle of plants to enable rapid generation turnover in single seed descent breeding programs. A robust B screening protocol that can be fully integrated within an accelerated single seed descent system could lead to rapid identification and introgression of B tolerance into field pea genotypes. Integration with an accelerated single seed descent system requires: (1) screening under artificially lit, temperature-controlled conditions; (2) capacity to use immature precociously germinated seed (PGS); (3) recovery of lines without significant time penalty; and (4) good correlation with results from established screening protocols. We present herein a B toxicity screening system for field pea based on hydroponic growth of PGS in a light and temperature controlled environment that allows recovery of seedlings for rapid seed production. Screening results were compared to traditional methods for B tolerance screening in B-laced soil and with published field tolerance ratings. B tolerance was scored 17 days after sowing using leaf symptoms as a metric. Plants were then transferred to soil with maximum of six days delay in flowering compared to a typical accelerated single seed descent system generation. The use of PGS had minimal impact on B tolerance rankings compared to plants grown from mature seed. The leaf tolerance rankings from hydroponic-grown plants correlated well with those from soil-grown plants, and consistently identified the most tolerant genotypes. Our 17 day screening protocol represents a major time-saving over previously published B screening protocols for field pea, thereby extending the application of the protocol to traditional single seed descent systems or RIL screening. We anticipate that small modifications to the proposed technique will make it applicable to screen for other individual abiotic stresses, or allow studies of the interactions between B tolerance and stresses such as salinity.