Abstracts Category : Other

Improving mango breeding efficiency through improvedpollen storage, fruit retention and understanding of theheritability of quantitative tree architectural traits.

by Habat Ullah Asad

Mango is one of the most important tropical/subtropical fruit crops (Chapman, 2000), with a world production of 45.225 million tonnes (FAOSTAT, 2014b). Worldwide mango breeding programs aim to develop novel cultivars that fulfill the needs of modern mango industries (Campbell and Zill, 2009). The conventional breeding technique involves crosses between selected parents and evaluating the resulting progenies for desirable characters. A lack of pollen availability, poor selection, a low rate of fruit set and retention are major problems in conventional breeding for mango crop improvement (Iyer and Dinesh, 1997; Iyer and Degani, 1997; Roizman, 1986). The aim of this research is to address these issues and to improve the efficiency of traditional breeding techniques. This research focusses on higher breeding efficiency by extending pollen storage, and investigates the improved methods of assessing tree vigour via an understanding of the heritability of quantitative traits related to dwarf phenotypes. Furthermore, this work explores enhanced hybridised fruit set and retention through application of plant growth regulators (PGRs) and micronutrients.Short-term storage and retrieval of mango pollenTwo storage media in combination with four different storage temperatures were evaluated to extend the storage and viability of mango cv. NMBP-1201 pollen. Subsequent evaluations revealed that pollen stored in hexane at room temperature and pollen stored alone at -20C and -80C retained the highest viability following one week of storage. Pollen viability was significantly reduced following one week of storage in all conditions. Analysis of pollen germination rates showed that, following storage for one and two weeks, the phytotoxic effect of paraffin oil on mango pollen was greater than that of hexane at all temperatures. However, paraffin oil exhibited phytotoxic effects at all storage temperatures. These findings suggest that paraffin oil has higher phytotoxic effects on mango pollen compared to that of hexane; however, pollen stored in hexane retained a significantly higher level of viability for one week at room temperature. Thus, hexane may be a suitable pollen storage option for routine mango breeding work.Identification and heritability assessment of the most efficient method to assess tree vigourFrom twelve analysed tree morphological traits, trunk cross-sectional area (TCA) displayed the highest correlation with tree vigour, and thus was determined to be the most suitable trait for rapid vigour assessment. The heritability of TCA was assessed across several mango breeding populations growing on two research stations. TCA was recorded in 1909 progeny across 41 mango breeding families. Subsequent assessment revealed poor heritability for TCA (h2 = 0.23) among the tested mango breeding population. Poor heritability indicates that environment has a greater influence on TCA than genotype. However, a number of potential low-vigour families were identified that could serve as parental lines in future crosses to