RESUMEN
Rice, a staple crop for nearly half the planet's population, tends to absorb and accumulate excessive cadmium (Cd) when grown in Cd-contaminated fields. Low levels of Cd can degrade the quality of rice grains, while high levels can inhibit the growth of rice plants. There is genotypic diversity in Cd distribution and Cd tolerance in different rice varieties, but their underlying genetic mechanisms are far from elucidated, which hinders genetic improvements. In this study, a joint study of phenotypic investigation with quantitative trait loci (QTLs) analyses of genetic patterns of Cd distribution and Cd tolerance was performed using a biparent population derived from japonica and indica rice varieties. We identified multiple QTLs for each trait and revealed that additive effects from various loci drive the inheritance of Cd distribution, while epistatic effects between various loci contribute to differences in Cd tolerance. One pleiotropic locus, qCddis8, was found to affect the Cd distribution from both roots to shoots and from leaf sheaths to leaf blades. The results expand our understanding of the diversity of genetic control over Cd distribution and Cd tolerance in rice. The findings provide information on potential QTLs for genetic improvement of Cd distribution in rice varieties.
RESUMEN
Taking cold-tolerant rice cultivar 996 and cold-sensitive rice cultivar 4628 as test materials, a growth chamber experiment was conducted to investigate their pollen characters and flag leaf physiological and biochemical characteristics under the effects of low temperature stress. The plants were respectively treated with low temperature [ 19 degrees C (06:00-8:00; 19:00-23:00 )/21 degrees C (08:00-10:00; 16:00-19:00)/23 degrees C (10:00-16:00)/17 degrees C (23:00-06:00)] and optimal temperature [24 degrees C (06:00-8:00; 19:00-23:00)/26 degrees C (08:00-10:00; 16:00-19:00)/30 degrees C (10:00-16:00)/22 degrees C (23:00-06:00)] for seven days after heading. Low temperature stress decreased the anther dehiscence coefficient and pollen germination rate, as well as the sterile pollen rate of spikelets on middle and lower parts of panicles, with the anther dehiscence coefficient and pollen germination rate of cultivar 996 being significantly higher than those of cultivar 4628, indicating that cold-tolerant cultivar 996 had the capability to keep better pollination and pollen germination. Under low temperature stress, the flag leaf soluble protein and free proline contents and their increments of cultivar 996 were significantly higher than those of cultivar 4628, while the MDA content and relative conductivity and their increment were in adverse, indicating that cold-tolerant cultivar 996 had more quick and strong protective responses, and was able to keep stable membrane structure and function.