Automated and estimation methods to count nodule number in common bean

Abstract

The nodulation on legume roots is an important trait to evaluate the symbiotic efficiency, but very laborious and time spending, what can limit the effectiveness of legume breeding programs. Based on the need to simplify the assessment of nodule number, this work aimed to evaluate the accuracy and time spent to assess nodule number in common bean using different methods of estimation and counting, compared to manual count (MC), which was considered the standard method. The estimation methods consisted of two simple techniques with two sampling range: graph paper with sampling range from 10 to 20 nodules (GPR1) and graph paper with sampling range from 21 to 40 nodules (GPR2), Petri dish with sampling range from10 to 20 nodules (PDR1), Petri dish with sampling range from 21 to 40 nodules (PDR2). The counting was also performed using automated methods: the seeds counters Seedburo and Sanick. The time spent in each of the seven methods was recorded. Among the alternative methods, the automated counting methods stood out. The Seedburo 801 and Sanick ESC2011 counters showed high accuracy and reduced more than 50% of the time spent compared to MC. Among the estimation methods, GPR2 showed good accuracy with 10% reduction in time spent when compared to manual counting, being a good alternative when there are no automated counters.