Heterosis for Resistance to Insect Herbivores in a 3-Line Hybrid Rice System

• Published in: Insects (Basel, Switzerland) Switzerland), 2024-02, Vol.15 (3), p.164
• Main Authors: Horgan, Finbarr G, Bernal, Carmencita C, Ramal, Angelee F, Almazan, Maria Liberty P, Mundaca, Enrique A, Crisol-Martínez, Eduardo
• Format: Article
• Language: English
• Subjects: Agricultural production; Biomass; Borers; Botanical research; brown planthopper; Damage; Experiments; Females; Fertility; Field tests; Fulgoroidea; Genes; Genetic diversity; Genomes; Greenhouses; Herbivores; herbivory tolerance; Heterosis; host plant resistance; Hybrid rice; Hybrid systems; Hybrids; Hypotheses; Inbreeding; Insect resistance; Insects; leaffolders; Males; Nilaparvata lugens; Outbreeding; Pest resistance; Plant biomass; Plant breeding; Plant growth; Plant physiology; Plants; Pollen; Rice; Risk reduction; Scirpophaga incertulas; Seeds; Sogatella furcifera; Susceptibility; Virulence
• ISSN: 2075-4450; 2075-4450
• DOI: 10.3390/insects15030164

Three-line hybrid rice is produced by crossing male sterile (A line) rice with a fertility-restorer (R line). Fertile lines (B lines) are also required to maintain A line seed for breeding programs. We used a range of hybrids and their parental lines to assess the frequency and nature of heterosis for resistance to the whitebacked planthopper ( ), brown planthopper ( ) and yellow stemborer ( ). Heterosis is defined as trait improvement above the average of the parental lines as a result of outbreeding. Based on the results from a greenhouse study that challenged hybrids and their parental lines with each herbivore species, we found that susceptibility to planthoppers was associated with one of the eight A lines tested, but resistance was improved by crossing with a relatively resistant restorer. Higher frequencies of heterosis for susceptibility in comparisons between hybrids and their B lines suggest that susceptibility was not related to the cytoplasmic genomes of the associated sterile A lines. Furthermore, because none of the parental lines possessed currently effective resistance genes, improved resistance against planthoppers was probably due to quantitative resistance. In a related field trial, hybrids had generally higher yields than their fertile parents and often produced larger grain; however, they were often more susceptible to stemborers, leaffolders ( ) and other caterpillars ( ). This was largely a consequence of hybrid heterosis for plant biomass and was strongly affected by crop duration. We make a series of recommendations to improve hybrid breeding to reduce the risks of herbivore damage.