Batte, Michael (2019). Increasing efficiency of the breeding pipeline for East African highland bananas. Diss. (sammanfattning/summary) Alnarp : Sveriges lantbruksuniv., Acta Universitatis

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TitleBatte, Michael (2019). Increasing efficiency of the breeding pipeline for East African highland bananas. Diss. (sammanfattning/summary) Alnarp : Sveriges lantbruksuniv., Acta Universitatis
DescriptionBanana breeding is a technically challenging endeavor due to the low reproductive fertility, low seed germination, long selection cycle period and large space requirement for field evaluation, among others. Innovations in the current breeding program are required to increase the rate of genetic gain delivery to farmers. This study considers five approaches to tackle this challenge; 1) assessment of the available minimum descriptor list for suitability to characterize the East African highland banana (EAHB) germplasm, 2) analysis of crossbreeding data of EAHB for the first 21 years (from 1995 to 2015) at the International Institute of Tropical Agriculture as a basis for designing future interventions, 3) path analysis to determine a breeding ideotype for EAHB, 4) estimation of heterobeltiosis (hybrid vigour) for the NARITA hybrids (mostly secondary triploids ensuing from the 4x × 2x), and 5) phenotyping a diploid banana population (‘Calcutta 4’ × ‘Zebrina GF’ ) for resistance to Radopholus similis. Ten out of 31 descriptors studied were stable but had similar scores in EAHB cultivars and therefore are not suitable to distinguish between them. The month of pollination did not result in significantly different (P = 0.501) pollination success, implying that pollination of EAHB can be conducted throughout the year. However, the seed set, and rate of germination were still low. Thus, further research about seed production and germination is required. Twenty-seven NARITAs were selected for further evaluation in the East African region. Path analysis revealed that fruit length, circumference and number, number of hands and plant cycle number had a direct positive effect on the bunch weight (a proxy for edible yield). Significant progressive heterobeltiosis for bunch weight was found in all the NARITAs. Half of the NARITAs had negative heterobeltiosis for stature. The diploid population was found to segregate for resistance to R. similis. Results from Dunnett’s test grouped the population in three main phenotypic classes, with 75 susceptible, 17 intermediates and 19 resistant genotypes. Chi-square goodness of fit test revealed that this resembles a phenotypic ratio of 9:3:4 suggesting recessive epistasis.
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