Abstract
Heat tolerance is important for the sustainable production of many crops, including chile pepper. Tolerance to high temperature is complex and involves various component traits, with pollen viability being among the most important. in vitro pollen assays for heat tolerance have been widely used in chile pepper; however, associations between the pollen treatment and pollination have not been widely explored. The objectives of this study were to validate the utility of in vitro heat stress pollen characterization through in vivo pollination during summer and winter seasons and to evaluate the cross-compatibility among wild and domesticated species to initiate introgression population development. Seven entries of wild and domestic Capsicum species grown during the summer and winter seasons were used to evaluate pollination success rate. Pollen was either used directly or treated at 38 °C for four hours before making reciprocal self- and cross-pollination among all the entries. Significant associations between in vitro pollen treatment and pollination success rate during summer and winter seasons were identified. Heat treatment was a greater contributor to variability than the growing environment, which validates previous reports on the usefulness of studying pollen in vitro in selection for heat tolerance. Accessions of the wild progenitor C. annuum var glabriusculum, PBC 1969 and PBC 1970, were identified as a potential heat-tolerant source for use in breeding and future research. This work provides a basis for future research in exploring additional heat tolerance components as well as for the development of phenotyping assays for pollen or other floral traits.
Highlights
Chile pepper (Capsicum annuum L.) is consumed worldwide, and global production was 5.1 million tons in 2018, with approximately 65% of production occurring in Asia [1].The primary limitations to improving the productivity and quality of chile pepper are abiotic and biotic stresses, many of which lack sources of host tolerance or resistance for breeding [2]
In response to high temperatures, plants have various mechanisms to maintain cellular homeostasis to cope with heat stress, which has been widely studied in the vegetative stages of different plant species [30]; little is known about these mechanisms in developing pollen
While it is known that pollen viability, pollen tube germination, and pollen tube length are reduced under heat stress [17,23,24], it has not been empirically shown if this results in an actual reduction in pollination
Summary
Chile pepper (Capsicum annuum L.) is consumed worldwide, and global production was 5.1 million tons in 2018, with approximately 65% of production occurring in Asia [1].The primary limitations to improving the productivity and quality of chile pepper are abiotic and biotic stresses, many of which lack sources of host tolerance or resistance for breeding [2]. It can be anticipated that in many production regions it will become more difficult to grow chile pepper as temperatures increase beyond this optimal temperature range as a consequence of global climate change. In response to high temperatures, chile peppers abort reproductive organs (buds, flowers, and young fruits), resulting in a significant reduction in yield. Unlike other stresses, such as pests and diseases or short-term drought and flooding, it is difficult to manage the effects of heat stress in a farm setting, leaving genetic improvement as the best strategy to limit losses associated with high temperatures. Breeding for heat tolerance is complex and requires the evaluation of numerous component traits
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