2018 ASHS Annual Conference

Broccoli is an economically important vegetable crop in the U.S. with an annual farm-gate value approaching a billion dollars. Nearly all commercial cultivars available to U.S. producers were developed for adaptation to relatively cool climates of California and other western states, where about 90% of broccoli production traditionally occurs. Head quality is negatively impacted by high temperatures (e.g., > 30 C) occurring during early stages of head development, and the resulting reduced quality can lead to significant marketable yield losses. There is renewed interest in breeding broccoli cultivars for East Coast production, but this effort is challenged by unpredictable high temperature spikes, higher nighttime temperatures during growing seasons, and limited knowledge of the genetic basis of heat tolerance. A doubled haploid broccoli population segregating for heat tolerance was evaluated in two summer field trials under conditions that readily cause head damage. The most and least tolerant broccoli lines were identified and then screened in two additional summer field trials. A subset of the most extreme tolerant and susceptible phenotypes were separately pooled for bulked segregant analysis using whole genome re-sequencing. Two novel QTL were identified that did not co-locate with previously characterized heat tolerance QTL.