Intra-varietal variability and response to single plant selection inGossypium hirsutumL.: I. Phenotypic variability

Abstract

Populations of spaced plants of each of the four American upland cotton varieties Deltapine Smooth Leaf, Rex Smooth Leaf, Pope, and Rex and one African upland variety, Bar 7/8, were grown in the 1965-6 wet season at Kimberley Research Station, in the Ord River valley, Western Australia. The number of bolls, boll weight, lint percentage, seed cotton yield, lint yield, micronaire value, mature height, and morphological type were recorded for each plant.For all varieties the range of each attribute was wide; for example, for a typical variety, boll weight ranged from 3-0 to 7-8 g, lint percentage from 30-5 to 43-5%, micronaire value from 3-3 to 5-9 units, and mature height from 78 to 195 cm.The most variable varieties judged on coefficients of variation were those maintained at the station for the longest period without selection while the most recent accession was the least variable.Frequency distributions for all attributes in each population departed significantly from normality: the majority showed both significant skewness and kurtosis. Positive skewness shown for the yield parameters seed-cotton yield, lint yield, boll number and boll weight in all varieties suggested there was scope for improvement by selection. Negative skewness for lint percentage was found in three varieties, suggesting previous intense selection for this trait. The coefficient of variation of lint percentage with one variety (Deltapine Smooth Leaf) was considerably less than that recorded 30 years earlier for its predecessor D x PL 11 A.Covariance adjustments to seed cotton yield of individual plants, based on various hypotheses of the relationship between a plant's yield and that of its neighbours failed to give reductions of consequence in the variability of yield. It was concluded that inter-plant influences were far more complex than the models assumed.

Intra-varietal variability and response to single plant selection inGossypium hirsutumL.: II. Genotypic variability

“…The major possible sources of genetic variability include contamination with seed of other genetic stocks, out-crossing, residual genetic variability, N. J. THOMSOX and mutations. Contamination was deemed to be a factor only with the variety Rex (Thomson, 1973). In many environments hybridization through chance out-crossing could well be a major element but in these investigations it appeared to be of minor importance, particularly with the recent accessions, Rex S.L.…”

“…and Deltapine S.L. Both these varieties when grown in the field at Kimberley Research Station appeared uniform, in contrast to obvious diversity in growth of Rex and Bar 7/8 (Thomson, 1973). However, appreciable genetic variability was found in all varieties.…”

“…The experimental sites in each of the two seasons were chosen for uniformity, having a similar presowing history of land preparation and subsequent fertilization and cultural procedures as described in the first paper of this series (Thomson, 1973).…”

Intra-varietal variability and response to single plant selection in Gossypium hirsutum L.: III. Response to selection

“…2 and 0-33 % in Exp. 3) of the original populations of spaced plants (Thomson, 1973 a) were progenytested. The selection of progeny 1 of Pope is a striking example of the efficacy of the selection procedures followed.…”

Επιλογή διειδικών σειρών και βελτίωση συστημάτων παραγωγής διαπλοειδών φυτών από διειδικά υβρίδια βαμβακιού (G. barbadense x G. hirsutum)

“…Ο Thomson (1973aThomson ( , 1973b στη µελέτη του έδειξε ότι η αποτελεσµατικότητα της επιλογής είναι µεγαλύτερη στο επίπεδο του ατοµικού φυτού και µειώνεται στις µονές γραµµές, ενώ φθίνει ακόµα περισσότερο στα τεµάχια πολλαπλών γραµµών. Η παραλλακτικότητα εξαιτίας του διαγενοτυπικού ανταγωνισµού, ο οποίος αυξάνεται από το επίπεδο του ατοµικού φυτού προς το τεµάχιο πολλαπλών σειρών, θεωρείται ο λόγος που επηρεάζει την αποτελεσµατικότητα.…”