Breeding for crop improvement.

Abstract

The topics covered include: cytotaxonomy of the genus Manihot; flower behaviour, hybridization techniques and seed management; breeding strategy (for Africa; for Latin Americas; for Asia); breeding for high yield; breeding for root quality (starch and dry matter content); breeding for low content of cyanogenic glucosides; breeding for high content of protein and other nutritional elements in the root; breeding for resistance to cassava mosaic disease and to cassava brown streak disease; breeding for resistance to cassava bacterial blight (Xanthomonas campestris pv. manihotis [Xanthomonas axonopodis pv. manihotis]); breeding for resistance to fungal diseases; breeding for resistance to mites, mealybugs and whiteflies; breeding for efficient use of basic resources; and cassava breeding in the future, i.e. the role of biotechnology.

Physiological characteristics of cassava tolerance to prolonged drought in the tropics: implications for breeding cultivars adapted to seasonally dry and semiarid environments

“…Similar responses were observed in the Sudan Savanna zone of Nigeria using variation in the soil-water (Okogbenin et al, 2003). These findings support the sound breeding strategy for developing cultivars for specific ecozones (Hershey and Jennings, 1992;El-Sharkawy, 1993;Iglesias et al, 1995;Jennings and Iglesias, 2002). Plant ecophysiologists have proposed a sort of "classification/ terminology" scheme based on mechanisms underlying plant adaptation to water deficits (for more information see for example, Levitt, 1980;Turner, 1986;Ludlow and Muchow, 1990).…”

High‐Throughput Phenotyping and Improvements in Breeding Cassava for Increased Carotenoids in the Roots

“…There are several advantages in implementing these changes: (i) whatever the difference between seedling and cloned plants is, it will no longer affect the selection process because selection will be made on cloned plants not seedlings; (ii) NIR predictions allow for a shorter harvesting season (1-2 mo depending on the number of genotypes that need to be screened), therefore offering a more uniform condition (regarding age of the plants and environmental conditions at harvesting time; (iii) because there are three plants per genotype available, quantification of carotenoids can be made in the ideal conditions (one plant harvested by the middle of the dry season), but harvesting of plants that serve as source of planting material is delayed until the arrival of the rains, thus generating a short storage period of the planting material and, therefore, optimal conditions for the agronomic performance trials that follow; and (iv) the availability of two standing plants in the field as source of planting material for the following agronomic evaluations offers the possibility of planting two separate SRTs in two different locations. Growing seedling plants for only 6 mo was an established practice for the cassava breeding program at CIAT and was called F1C1 (Jennings and Iglesias, 2002).…”

Breeding Open-Pollinated, Hybrid and Transgenic Outcrossing Species

“…In summary, the target of this cassava breeding strategy was broadly based breeding populations that would be further selected by national researchers and local partners according to their needs (Jennings and Iglesias 2002). Hence, crossing among local cultivars was high in the IITA's cassava breeding approach as well as incorporating judiciously exotic germplasm into the desired gene complexes, but minimizing inbreeding and restoring heterozygosity to escape from inbreeding depression (Ortiz et al 2006).…”