Genetic variability for susceptibility to seed coat mechanical damage and relationship to end-use quality in kidney beans

Authors: WANG, WEIJIA - Michigan State University; Cichy, Karen

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2023
Publication Date: 11/23/2023
Citation: Wang, W., Cichy, K.A. 2023. Genetic variability for susceptibility to seed coat mechanical damage and relationship to end-use quality in kidney beans. Crop Science. 64(1):200-210. https://doi.org/10.1002/csc2.21122.
DOI: https://doi.org/10.1002/csc2.21122

Interpretive Summary: Kidney beans are prone to seed damage in the form of seed coat cracks that occur during mechanical harvest. Since kidney beans are generally offered to consumers as whole dry or canned beans, seed coat damage is readily detected and impacts the value of the final product. Kidney bean cultivars that are more resilient to mechanical harvest and less prone to seed coat cracking may help to increase farmer profits and consumer acceptability of end products. The goals of this project were to 1) develop a screening method to easily assess seed coat mechanical damage, 2) explore the genetic variability of North American kidney bean germplasm for resilience to seed coat mechanical damage and 3) explore the relationship with seed coat mechanical damage and downstream end use quality factors, including canning quality and cooking time; 4) identify potential germplasm resources for future variety improvement. An iodine staining test method was used to measure the seed coat damage in beans harvested with both gentle and harsh threshing conditions. This method was useful in identifying genetic variation for seed quality among 69 kidney bean lines. The method was most effective under harsh threshing conditions as compared to gentle threshing. Seed coat damage severity score was correlated with end product quality such that beans with higher seed coat damage scores had lower canning quality scores. Kidney bean germplasm were identified with more resilience to seed coat mechanical damage in the dark red, light red, and white kidney market classes. These findings will be applied to breed kidney bean varieties for better seed and end-use quality.

Technical Abstract: Kidney beans are a type of common bean (Phaseolus vulgaris L.) in the Andean gene pool with strict market specifications for seed characteristics and end-use quality. Kidney beans are usually sold to US consumers as dry seeds or canned products. One major quality concern is the appearance of cracks/checks in the seed coat that result from mechanical damage that happens at harvest and post-harvest. Genetic variability and control of seed coat checks (SCC) in response to mechanical damage has not been well characterized in kidney beans. The objective of this study was to explore the genetic variability for mechanically induced seed coat damage in kidney bean and characterize through seed coat check and seed coat thickness measurements and its relationship to end-use quality including canning quality and cooking time, and to identify potential germplasm resources for genetic improvement. A collection of dark red kidney (DRK), light red kidney (LRK) and white kidney (WK) beans were grown over two years and harvested with two threshing methods to mimic mild and severe treatments of mechanical damage. Belt threshing produced mild damage (SCC severity score 1.1±0.1) and combine threshing produced severe damage (SCC severity score 1.7±0.4). Seed coat thickness was not correlated with SCC of the combine threshed beans but was negatively correlated with the belt threshed beans at r = -0.33. Seed moisture content played an important role in SCC abundance and was challenging to keep constant during the study. Higher SCC severity scores resulted in lower canning quality appearance scores (r = -0.51). Compared to DRKs and LRKs, WKs are thinner in seed coat, shorter in cooking time and are more vulnerable to mechanical seed coat damage. Genotypes with low SCC severity score while having good canning quality and short cooking time were selected from each market class and can be used for future breeding programs. The SCC severity score of combine threshed seeds can be used as a selection factor in variety improvement for resilience to mechanical damage.