Parent-offspring regression analysis for total carotenoids and some agronomic traits in cassava

Abstract

Six cassava cultivars, three yellow and three white-fleshed roots were crossed in a 3 9 3 topcross mating design to generate nine F 1 populations. One thousand, one hundred and ten botanical seeds from the 9 populations were sown in pots and maintained for 42 days in a screenhouse. The emerged seedlings were transplanted to the field in April, 2010 alongside their parents (from stem cuttings), family by family. Four hundred and sixty-four progenies survived and were harvested. Both field and laboratory data were used to evaluate total carotene content (TCC), dry matter content (DMC), storage fresh root yield (SFRY) and other root quality traits. Seed germination for different populations ranged between 15.5 and 80.9 % with a mean of 43.19 %. Phenotypic variation in DMC, TCC, SFRY, biomass, root number, harvest index and cassava mosaic disease (CMD) were recorded in all the families. Average values for the populations were TCC: 4.59 lg g -1 , DMC, 33.58 % and SFRY, 18.42 t ha -1 . Narrow sense heritability by midparent-offspring regression analysis and genetic gains were estimated for TCC, DMC, SFRY and reaction to CMD. TCC, DMC and CMD gave high heritability estimates of 0.73, 0.83 and 0.84, respectively. SFRY, on the other hand, had a low heritability estimate (0.15). TCC was negatively correlated with DMC across all evaluation stages and locations. There were very high levels of variation in the segregating F 1 progenies for all the traits. Also, narrow sense heritability estimate showed that genetic factors played a more important role than environmental factors for TCC, DMC and CMD, suggesting that reliable selection with simple recurrent phenotypic selection would be rewarding.

Carotenoids in Cassava Roots

“…Parent-offspring regression analysis confirmed high heritability (˃0.60) for the trait [53][54][55]. High heritability for carotenoids content in cassava is further confirmed in stability studies assessing the relative importance of genotype, environment, and genotype-by-environment interaction [56][57][58] and estimations of general and specific combining ability effects [59].…”

Provitamin A biofortification of cassava enhances shelf life but reduces dry matter content of storage roots due to altered carbon partitioning into starch

“…These findings suggest that reduced DMC may be a more general phenomenon in provitamin A‐biofortified starch crops. Similar to the transgenic cassava reported here, conventionally bred yellow‐fleshed cassava also showed reduced DMC (Esuma et al ., ,b; Njoku et al ., ). Ceballos et al .…”

Progress update: Crop development of biofortified staple food crops under HarvestPlus

“…Carotenoid content was found to be inversely correlated with DMC in African cassava clones [38], but not so in Latin American germplasm [38]. The development and introduction to Africa of additional parent materials that combine high carotenoid content and high dry matter content will broaden the genetic base of biofortified germplasm for Africa.…”

“…Screening of cassava accessions from the International Center for Tropical Agriculture (CIAT) germplasm collection found a range of 0-19 ppm of provitamin A in existing cassava varieties, exceeding the breeding target of 15 ppm [33,34]. Studies on GxE interaction for carotenoid content did not find significant changes in the relative ranking of genotypes, and found high (>0.6) heritability of carotenoid content in cassava roots [35,36,37,38]. Rapid-cycling recurrent selection was used to shorten the normal breeding cycle from eight years to two to three years for high carotenoid content [39].…”