Reproductive barriers in cassava: Factors and implications for genetic improvement

Area of Science:

• Plant Breeding
• Reproductive Biology
• Genetics

Background:

• High flower abortion rates in cassava (Manihot esculenta) impede efficient recombination and hinder breeding progress.
• Understanding reproductive barriers is crucial for developing strategies to improve crossing success in elite cassava clones.

Purpose of the Study:

• To analyze reproductive barriers in intraspecific cassava crossing.
• To evaluate pollen-pistil interactions for optimizing hand pollination.
• To identify the population structure of elite parental clones to guide breeding strategies.

Main Methods:

• Conducted 5,748 hand crossings over three years (2016-2018) to estimate abortion and fertilization rates.
• Utilized 16,300 single nucleotide polymorphism markers for population structure analysis.
• Employed mixed models to assess parental effects on reproductive success and analyzed pollen viability and pollen tube dynamics.

Main Results:

• Significant parental effects on abortion and fertilization rates were identified, indicating reproductive barriers among cassava clones.
• Parental matching ability significantly influenced pollen adhesion, germination, and ovule fertilization, with non-additive genetic effects playing a role.
• Fertilization abnormalities, including callose deposition and pollen tube growth cessation, were observed, alongside variable pollen viability and stigma receptivity.

Conclusions:

• Reproductive barriers and pollen-pistil interaction issues contribute to flower abortion in cassava.
• Optimizing parental selection and understanding genetic control of reproductive traits can enhance crossing efficiency.
• These findings provide insights for practical cassava crossing, aiming to maximize recombination of desirable traits.