Phenotypic variation of kiwifruit in a factorial mating design (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson var. deliciosa) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science at Massey University

Abstract

Systematic evaluation of the New Zealand A.deliciosa var. deliciosa breeding population was conducted using a two-factor factorial mating design (FMD). Two separate populations were used to study the genetic properties of the New Zealand A.deliciosa germplasm. Crosses were made in spring 1991, between seven female and seven male parents, resulting in one population [referred to as Factorial One] and another population resulting from six female and seven male parents [referred to as Factorial Two]. These ninety-one biparental families each had thirty-six seedlings planted during spring 1992 in a randomised complete block (RCB) design. Trunk diameters on all seedlings (at 20 cm above ground level) were measured annually from 1993 to 1996. Flowering characters were measured from both male and female seedlings in spring 1995. The sexual maturity of these populations had reached 68 %, with a female to male ratio of 1:1.32 by the 1995 flowering season. From these sexually mature seedlings, almost six hundred females were assessed for various fruiting characters of interest during the 1996 fruit season. Significance tests for vegetative and fruiting characters were reported based on their 'female' (main effect), 'male' (main effect) and 'female by male' (interaction effect). Results from these statistics showed significant genetic variation exists for many of the vegetative, floral and fruiting characters measured within the two reference populations. Narrow sense (additive) heritabilities of ≥ 0.4 were reported in 11 of the 29 characters from Factorial One and 14 of the 29 characters in Factorial Two. The high additive genetic variation, present in both reference populations, indicates reasonable genetic advances are possible for at least some of these characters. Fruit weight and fruit shape characters in both factorial sets were highly heritable, while fruit quality aspects such as taste, flavour and texture generally had low heritabilities. Genetic and phenotypic correlations were also estimated for some selected vegetative and fruiting characters. These results showed distinct differences (as well as similarities) existed between the two reference populations. Genetic correlations r a of ≥10.71 were reported, in 8 and 9 of the 30 (selected) vegetative correlations in Factorials One and Two respectively. From the 34 (selected) fruiting correlations in Factorials One and Two there were 17 and 7 genetic correlations ≥ 10.71 respectively. When comparing the same r a correlations, between both Factorial data sets, it was evident that at least some of correlations could be in opposite directions to each other. General combining abilities (GCA), based on family means, were calculated and significant differences were evident amongst these means for several characters from both female and male classifiers of their half sib arrays. In addition, male (paternal) lines were equally as potent when compared to female (maternal) lines for their effects on their female offspring's fruiting characters. Therefore it is important to identify male parents breeding value (viz. progeny tests) for various characters, in order to improve the response to selection, because only half the genetic gain is possible when selecting one parent (female) as opposed to applying selection pressure to both parents (male and female). The ability to apply selection pressure to both parents, for a single character, could possibly lead to twice the genetic gain