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Starches from sixteen cassava germplasms harvested at the same time in the Hainan region were evaluated for their physicochemical and structural properties. The granule morphology of all the isolated cassava starch samples showed round, bell or oval shapes and exhibited the same A-type crystalline pattern. The crystallinity range was 26.6–30.8%. The selected cassava germplasms showed a wide variation in granule size distribution: The D[4,3] (the average particle size) ranged from 13.49 μm to 306.27 μm. The water absorption capacity (192.6–226.7%), oil absorption capacity (185.0–216.9%) and transparency (6.8–16.5%) indices varied significantly among the cassava germplasms. However, the retrogradation rates of the cassava starch pastes increased rapidly during the first 1 h and then stabilized. The solubility of starch increased with the temperature. In addition, the FTIR (Fourier Transform Infrared Spectrometer) ratios of 1045/1022 cm−1 and 1022/995 cm−1 of the sixteen cassava starches varied in the range of 1.06–1.78 and 0.78–1.04, respectively. These results indicated that the granule size, relative crystallinity, degree of short-range order, water and oil absorption capacities, solubility and transparency of the cassava starches were greatly influenced by the variety of cassava, which could help in determining the advantages of these starches for applications in different food and nonfood industries.

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 F1population 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.

In order to exploit the induced female 2n gametes for cassava (Manihot esculenta) breeding, a detailed histological observation of female gametogenesis was conducted to correlate with the morphological characteristics of inflorescences and female flower buds. The SC5 gynoecia at the stage of prophase I were selected for unreduced megaspores induction with 0.3 % colchicine and 1 % dimethyl sulfoxide-soaked cotton plugs for 2 days. The resulted female cyathia were artificially pollinated with ploidy-level mixed pollens of SC10. Out of 250 hybrid progenies, two plants which exhibited morphological variations were confirmed as sexual tetraploids by flow cytometry and chromosome counting. Our results demonstrated that induction of 2n gametes combined with hybridization can be an effective approach for sexual tetraploid production for cassava.

Thirty-six pairs of polymorphic SRAP markers were used to construct DNA fingerprint of 18 cassava ( Manihot esculenta Crantz) varieties. Among the total 320 amplified bands, 235 (73.4%) were polymorphic with an average of 6.5 bands per primer pair. The unweighted pair-group method with arithmetic average (UPGMA) cluster showed 4 major groups at similarity index of 0.734. Two primer combinations, Me1/Em5 and Me24/Em10, had the highest efficiency to distinguish cassava varieties, which were applicable to develop the DNA fingerprints of the 18 cassava varieties. The amplified bands were converted into binary codes with presence (1) and absence (0), and each variety had a unique 18-digital code. The confident probability of the DNA fingerprint was as high as 99.9996%.