Viability and receptivity of reproductive structures in Lima bean (Phaseolus lunatus L.) for improvement programs

M.P.L Silva,K.L.S Borges,S.C Silva,P.A Barroso,A.M Medeiros

doi:10.5039/agraria.v16i4a8639

Abstract

Artificial hybridization in Phaseolus lunatus L. is still little used in genetic improvement programs in Brazil due to the low establishment percentages. This work aimed to evaluate pollen viability and stigma receptivity in different Lima bean genotypes throughout the day. Accessions ‘Roxinha -MT’ and ‘Cana Longa-PB’ were used in the experiment. Five flower buds were collected from each genotype at 6:00 a.m., 10:00 a.m., 2:00 p.m., and 6:00 p.m. The stigma receptivity was determined using 3% hydrogen peroxide, whereas pollen viability was determined with 2% acetocarmine colouration. The genotype and time factors acted independently on the percentage of viable and non-viable pollen grains and stigma receptivity. The genotype ‘Roxinha’ presented 88.54% viable pollen grains, a value 84.27% higher than that of the ‘Cana Longa’ genotype. This percentage varied as a function of time, with the highest means observed at 6:00 a.m. Stigma receptivity was influenced only by the time of the day, undergoing a great reduction in receptivity, from 88% in the early morning to slightly more than 40% around noon. These results indicate that 6:00 a.m. is the most suitable time to perform artificial crosses in Lima bean plants.

Highlights

Phaseolus lunatus L., known as Lima bean, is a legume species with great variability dispersed throughout the country, especially in the northeastern states
Artificial hybridization in Phaseolus lunatus L. is still little used in genetic improvement programs in Brazil due to the low establishment percentages
The work was conducted at the Federal University of Piauí (UFPI), Campus Professora Cinobelina Elvas (CPCE), in Bom Jesus, PI, at 09°04’28’’ south latitude, 44°21’31’’ west longitude, and 277 m elevation

Summary

Introduction

Phaseolus lunatus L., known as Lima bean, is a legume species with great variability dispersed throughout the country, especially in the northeastern states. The mean yield observed in Brazil is still far from the indices obtained in other producing regions. In the United States, for example, which is considered to be one of the largest producers, mean yields above 2.500 kg ha-1 were achieved (USDA, 2018; IBGE, 2020), compared to the 313 kg ha-1 produced in the entire Northeast Region of Brazil in 2018 (IBGE, 2020). Artificial crossing can be employed in the improvement of Lima bean to gather in a cultivar the agronomical traits that make this variety superior to its parents and with that obtaining greater profitability to the producer

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