Early Generation Selection for Resistance to Rice Kernel Fissuring Proves Effective.

Rice milling yield refers to the proportion of kernels remaining unbroken after mechanical removal of the hull and bran layers. Whole kernels have two to three times more market value than brokens. Any reduction in milling yield will directly result in financial losses for both producers and millers. Exposure of the rice kernels to severe moisture changes before or after harvest can cause them to fissure, and is one of the leading causes of reduced milling yield. ‘Cypress’, a southern U.S.A. rice cultivar released in 1993, is known for its resistance to kernel fissuring. This cultivar is not widely grown today, having been replaced with cultivars having higher yield potential and disease resistance. While breeders would like to incorporate Cypress’ fissure resistance into improved cultivars, their efforts are limited due to a lack of methods for identifying and selecting for fissure-resistance in early breeding generations. A laboratory method wherein small samples of seed are evaluated for fissure rates after controlled rewetting has proven to reliably identify fissure resistance among pure-breeding material grown in several replicated environments. This study investigated how effective the technique is as an F₂ selection tool. Seed from 300 unreplicated Cypress/LaGrue F₂ plants was evaluated for resistance to induced fissuring. The 10% most resistant (R), and 10% most susceptible (S) progeny were selected for planting into F₃ panicle rows in 2007. F₃’s were planted in two locations (TX and AR), two replications per location. Fissure resistance measured on seed harvested from five individual plants per F₃ row showed significant differences between the mean and distribution of the R and S populations. The average fissuring rate among the R selections was 20%, while the S selections averaged 35% fissuring. The efficacy of selection in the F₃ generation is the focus of further study.