Ploidy manipulation in Citrus is a major issue of current breeding programs aiming to develop triploid seedless mandarins to address consumer demands for seedless fruits. The most effective method to obtain triploid hybrids is to pollinate tetraploid non apomictic cultivars with pollen of diploid varieties. Such non apomictic tetraploid lines are not found in the citrus germplasm and need to be created. In this work we describe a new methodology based on in vitro shoot-tip grafting combined with treatment of the micro-grafted shoot-tip with colchicine and oryzalin to achieve chromosome doubling and a dechimerization procedure assisted by flow cytometry. Stable tetraploid plants of Clemenules, Fina and Marisol clementines and Moncada mandarin have been obtained directly from shoot tip grafting combined with colchicine and oryzalin treatments or after dechimerization of mixoploids plants (2x–4x). These stable tetraploid plants have been used in 4x × 2x hybridizations, to recover over 3,250 triploid hybrids in 3 years.

Production of tetraploid plants of non apomictic citrus genotypes

Specialized populations and mutant genetic lines of poultry have contributed to the biological, biomedical, and the agricultural sciences for over 100 years. Despite extensive loss of these unique genetic resources, there is no funding mechanism or long-term strategy to conserve and develop these important research resources. As the draft sequence of the chicken genome is completed during the coming year, the
 authors
 of this Policy Forum urge national initiatives to maintain and use specialized avian genetic variants.

Poultry Genetic Resources--Operation Rescue Needed

Genetic variants for chick biology research: from breeds to mutants.

Cactus pear (O. ficus-indica) is increasingly being utilised in South Africa for fodder and fruit production. However, breeding efforts to increase productivity and fruit quality are hampered by the difficulty of varietal identification. AFLP markers were used to estimate the genetic diversity within the South African cactus pear germplasm. Estimates of genetic diversity are useful in plant breeding for organising germplasm, identification of varieties, and assisting in the selection of parents for crossings. Nine primer combinations used during AFLP analysis generated 346 fragments (per sample), of which 168 were polymorphic. A large number of the markers produced had a polymorphic information content (PIC) value between 0.3-0.5, indicative of good discriminatory value. The majority of the accessions grouped into four clusters using both the Jaccard and Simple Matching similarity coefficients. Cultivated varieties were evenly dispersed within the different clusters, with the greatest percentage clustered in group III. Varieties that originated from Botswana (R1251, R1259, and R1260) clustered together, whilst those from Israel (Sharsheret, Ofer, and Messina) were dispersed amongst groups II and III. Genotype specific fragments (GSF) were generated with the use of six primer combinations (E-AGG + M-CAT, E-ACT + MCAG, E-ACT + M-CAT, E-ACA + M-CAT, E-ACA + M-CTT, and E-ACA + M-CAG). Genotype specific fragments allowed the unique identification of nine varieties, three of which are commercially cultivated (Meyers, Roedtan, and Santa Rosa).

http://scholar.ufs.ac.za:8080/xmlui/bitstream/handle/11660/1415/MashopeBK.pdf;sequence=1

Characterization of cactus pear germplasm in South Africa

The present study was conducted to evaluate quality of different Cultivars of cactus pear traits in Mara Research Station. Seven Cultivars (Nepgen, R1251,Sharsheret, Cross X, Berg x Mexican, Santa Rosa, Morado) of cactus pear were planted in a completely randomized design. Orchard consisted of 10 plants per Cultivar planted in a single row. No irrigation supplementation was given and pruning, pad thinning were performed. Data on fruit quality traits were collected from two different years (2005 and 2006) and subjected to analysis of variance using the general linear model procedure of statistical analyses system (SAS). All Cultivars in the first year had peel thickness of less than 6.00 mm and in the second year more than 6.00 mm. All Cultivars in the year 2005 and 2006 exceptBerg x Mexican and Nepgen had the fruit mass of more than 120 g, recommended for international market. The mean fruit mass decreased from 143.4 g in the first year to 127.3 g in the second year. The decrease might be due to low rainfall and temperature. Due to a decrease in fruit length in the second year, fruit shape shifted from being elliptic to ovoid shape, however the equatorial diameter remained constant. Total soluble solids (TSS) content increased from 13.17 0Brix during the first year to 13.78 0Brix in the second year. It was then concluded that in each year, the fruit quality change as a function as the type of Cultivar.

	 

	Key words: Quality, cactus pear, cultivars, South Africa.

Candelario Mondragon Jacobo

Papers

Breeding and Biotechnology