Broad bean (Vicia faba L.) is an important leguminous crop worldwide. High seed yield will increase grain reserve and profit for farmers. Previous studies on increasing the seed yield of broad bean have mainly focused on breeding new varieties, improving environmental conditions and agricultural management on the whole population level. Little attention has been paid to the contributions of different plant types or pod types within the population to the seed yield. 

Under the supervision of Prof. YANG Yongping, Ph. D. student LI Xiong from Kunming Institute of Botany of Chinese Academy of Sciences through agricultural practice and field observation found that local mature pods of broad bean could be divided into three types according to the seeds number per pod. They were designated as Pod I (containing one seed), Pod II (containing two seeds), and Pod III (containing three seeds). Based on the pod types, the broad bean plants were classified into four categories: Category I (only containing Pod I), Category II (only containing Pod II), Category III (containing either Pod I or Pod II), and Category IV (at least containing one Pod III).  

By investigating and analyzing 15 quadrats of 2 × 2 m² in the farmland, the researchers found that the distribution of four plant categories in the unit area of farmland varied and was consistent with the statistics rule. Therefore, if different plant categories have diverse average seed yields, changing the distribution ratio of per unit area will affect the total seed yield of broad bean.  

With the statistics and measurement of 50 plant individuals for each plant category, the average pods number, seeds number and single seed weight per plant were calculated, respectively. Correlation analysis showed that there was a trade-off between the pod size and number, which resulted in different plant categories containing different number of seeds. However, single seed weight of different plant categories had no difference. Broad bean seed yield per plant was decided by the seeds number. 

When the distribution proportion of different plant categories in unit area hypothetically increased by 10% or up to 100%, total seed yield of broad bean per unit area were affected. The increase in plant Category II could most effectively improve the total seed yield of broad bean. 

The study indicated that when the condition of broad bean varieties and planting density was certain, regulating the allocation proportion of different plant categories (or pod types) within the population would help to improve the seed yield of broad bean. The reasons that lead to the generation and allocation of different plant categories (or pod types) need further study.  

This study was published on the international journal Scientific Reports entitled “A novel perspective on seed yield of broad bean (Vicia faba L.): differences resulting from pod characteristics”.