No abstract

Cassava cultivars are self-compatible, sufficient pollination and fertilization are important factors affecting the rate of fruit set and fruit quality, but the effects of compatible pollination relationships on cassava pollen development and fruit set are poorly understood. In the present study, in situ pollen germination and compatible relationship were investigated by using self-pollination and cross-pollination between two cassava cultivars (SC5 and SC7). The observation in situ pollen germination was carried out with toluidine blue staining method under the fluorescence microscope. The result shows that after self-pollination for 20 min, the pollens, released from SC5 anthers, started to produce pollen tubes and the maximum germination rate (GR) was 39.2%. It cost 60 min for the pollen tubes carrying sperm cells to penetrate through the pistil extracellular matrices of the transmitting tract to the ovary. However, after cross-pollination for 10 min, the pollens started to germinate and maximum GR was 66.8%. It took 30 min for the pollen tube trip to reach ovary. Additionally, the analysis of fruit set indicated that pollination compatibility in cross-pollination was significantly higher than that in self-pollination. This work provided cassava cross breeding a clue that foreign pollen may facilitate fertilization and increase fruit set.

The QTLs associated with cassava yield traits were detected by two-QTL model (unconditional and conditional QTLs) approaches after planting for 90 d, 180 d and 270 d in the present study. A genetic linkage map was constructed with a segregating F1 population derived from a cross of 2 heterozygous parental plants from the cultivars South China 6 and Mianbao, and analysed with 39 SSR markers. The constructed linkage map of cassava consisted of 12 linkage groups covering a total length of 694.59 cM with a mean distance of 17.81 cM between two markers. The F1 population was evaluated for components of yield including fresh root yield (FRY), harvest index (HI), and starch content in dry root weight (SC) at 90 d, 180 d and 270 d. The identification of QTLs for yield traits at three growth periods explained 56.4% for FRY, 16.3% for HI and 27.3% for SC, suggesting characterization of yield components. The work made a step closer to understand the persistence of quantitative genetic variations of cassava in different development periods.