IMPROVEMENT OF PHORMIUM TENAX.

New Zealand Journal of Agriculture, Volume XXXVI, Issue 2, 20 February 1928, Page 112

IMPROVEMENT OF PHORMIUM TENAX.

RESEARCH ON BREEDING AND CULTIVATION OF THE PLANT.

During the past few months Dr. J. S. Yeates, of Wellington, has been conducting an investigation into the improvement of Phormium tenax (New Zealand flax) under the auspices of the Council of Scientific and Industrial Research. Progress reports by Dr. Yeates,, dated sth and 12th December respectively, have been made available as under : The following is a summary of the work done in the last three months on the cytology and genetics of phormium. It will be recollected that my task was primarily to find the chromosome numbers of phormium species and varieties, with a view to hybridizing. There are two species, and many of the varieties are supposed to be hybrids between these two species. If the chromosome number is not the same in all species and varieties, then hybridizing will lead to irregular results.. Such difficulty has been found in crossing some kinds of wheat. I have made preparations and counted the chromosomes of over thirty varieties of flax, including representatives of both species. The chromosome number in all these is the same—namely, 16 —and the behaviour of the chromosomes is regular throughout. From the breeder's point of view this result is extremely satisfactory. It means that cross - fertilization between any two . varieties should give normal Mendelian results. By using a new rapid method the above work was done in a small part of the time ; the remaining time has been spent in studying (1) the courses of the fibre-strands through the leaf ; (2) the differences between varieties, commerical and otherwise ; (3) the question of whether or not the varieties breed true from seed. The general conclusions are as follows : (a) That it should be possible to cross successfully any two varieties of flax which flower at about the same time. (&) That, in general, varieties do not come true from seed, (c) That in the near future planting will be done chiefly with hybrid seedlings which will be the first generation from crosses between suitable parent varieties. The parent varieties will be selected for resistance to disease, quality of fibre, and yield per acre. The hybrid offspring should grow more vigorously and combine the desirable qualities of two or more natural varieties. It has already been stated in a preliminary report that the chromosome numbers of flax varieties have been found very favourable for breeding-work. This aspect requires no further mention here. The brief reference made in the report concerning the failure of flax to come true from seed needs some qualification. It would be presumptuous to say at the present time that no flax breeds true. It is highly probable that pure breeding strains do exist in some isolated, localities where cross-pollination is difficult. My view that most

varieties do not breed true is based on examination of several batches of nursery-grown seedlings, each batch nominally being of one variety. In every case it was found that there were seedlings obviously of different varieties. The differences are sometimes so marked that certain kinds of seedlings are “ weeded ” out from the rows of young flax-plants. Two separate aspects of this failure to breed true need consideration here. First, there can be no doubt that a fairly large proportion of the seedlings resemble the seed parent. It is therefore possible to select from the seedlings plants which resemble the parent. The main objection to this is the great amount of extra expense involved in selecting*the right seedlings and in growing the rejected plants until they are old enough to be distinguished. The second objection is concerned with a loss of hybrid vigour in the plants. A self-pollinated flax-plant produces mixed seedlings because the plant itself is already a hybrid. The seedlings, however, will show the effects of hybrid vigour much less than does the original hybrid. In America, for instance, it has been found that crossing two varieties. of plants may give a hybrid with 50 to 100 per cent, more vigour of growth than either parent. The seed from these hybrids, however, grew into plants with about one-half of this hybrid vigour. This loss of vigour appears to be the same as the effect of close “ inbreeding ” of animals. From this it should be plain why hybrid flax-seedlings are considered best. If seedlings are to be planted they should be as vigorous as possible ; in other words, they should be the original hybrids. A single pod or capsule of flax produces about a hundred seeds, and this number of plants would result from a single cross-pollination. About 1,500 seedlings are required to plant 1 acre, so that the task of raising hundreds of acres of seedlings from artificial pollination should be quite possible and profitable. - It is hardly necessary to add that hybrid vigour is a secondary aim in crossing. The combination of desirable qualities is the main object. In the short time at my disposal I have paid some attention to the characters which are most desirable in flax. The most outstanding of these are (1) resistance to diseaseespecially yellow-leaf ; (2) strength of fibre ; (3) percentage of fibre ; (4) vigour of growth ; (5) colour of leaf-buttwhite or otherwise ; (6) shape of leaf-tip. Resistance to yellow-leaf is one of the most important problems. So little is known about the disease -that only careful examination of affected areas can show what varieties, if any, are immune. Strength of fibre is a matter which needs a great deal of attention. Flax-fibre sells for its strength, and failure to maintain a good standard in this respect will create a prejudice against the fibre which would be very difficult to overcome. There are varieties of flax which produce fibre stronger than manilia, and there is no reason why, in time, our fibre should not approach that standard. Strength is estimated at present by breaking in the hand. Strength of fibre no doubt varies from plant to plant, from leaf to leaf, from one part of the leaf to another, and even from fibre to fibre in one part of the leaf. There is great need here for accurate strength tests made by suitable machines so that results can be given in actual figures.

... The question of . fibre percentage is a difficult one. When flaxcultivation becomes further developed the yield of fibre per acre will be of more significance. Yield per acre will depend partly on percentage of fibre, but also on the manner and rate of growth of leaves and roots of the plant. That white-butted varieties produce fibre of better colour cannot be questioned. Such plants are comparatively rare, and it is doubtful if they are the best fibre-plants from other points of view. Crossing to combine white-butt with other required qualities is the obvious remedy. The shape of the leaf has a close bearing on uniformity of length in the fibre. I have definite information of one variety at -Shannon the leaf-tips of which are almost square. This character should give a leaf which has many fewer short fibres “ running out ” along the margin owing to taper of the leaf. Besides these characters, there are others which must be kept in mind with a view to changing conditions in the industry. For example, cultivation of flax in rows will create a demand for types especially suited to. these conditions. An exceedingly rigid, moderately tall, and close-growing plant should allow closer planting, or more easy access for cultivation, and would be much more suitable than drooping types for cutting by machinery. A good plan of work for flax-improvement should be as follows : There should be a central experimental nursery in which varieties of phormium could be collected for comparison and breeding. The flax areas throughout the country should be 'carefully examined and selected plants sent to the central nursery. A survey of this kind would aim at finding and describing all varieties, determining by their associations any possible relationships between the varieties, the effect of environment on. growth, and, in yellow-leaf areas, much should be found as to immune varieties. Hybridizing should begin at once, but from five to eight years would be required before any improved varieties could be ready for planting. For more immediate planting, seed should be collected from the best types and either the seed or the seedlings supplied to flax-growers. Experimental work should be undertaken in conjunction with growers to decide several questions which are most urgent. The chief one of these problems is that of the effect on flax of changed conditions and cultivation. For instance, one grower has found on ' the high country around Mount Ruapehu flax which produces good leaf there. Seed of this flax has been grown near sea-level. The question is, Will the plant produce the same quality and quantity of fibre under the new conditions ? The same doubt exists concerning changes from sanddune to swamp, and vice versa. Only careful work can be trusted in things of this kind. Fans of one large bush, which would all be the same, should be planted in different localities and careful records kept of their growth and production of fibre.

Experiments on manuring and cultivation should be treated in the same way. The fundamental principle should be that comparison should always be between sets of plants of one variety. It is hoped that growers may be induced, when planting, to set aside small test areas in which only one selected variety would be planted.

In conclusion, it may be emphasized that the time is overdue when flax-growing should be placed on a scientific basis. Keen competition in the world’s markets demands both an improvement in quality and in uniformity, and a reduction of labour costs, the latter being one of the largest items in the production of phormium fibre. Everything seems to indicate systematic cultivation and mechanical handling of flax as the chief remedy.

It is only to be expected that repeated cutting of heavy crops off uncultivated swamps would lead to deterioration both in quality and quantity —an expectation which appears to be fully borne out by the experience of millers. In addition, the swamp has the disadvantages of expensive cutting and carrying, and of mixed varieties. Cultivated flax would almost certainly be cut by mechanical means, and the same tractor used for cutting would be available for hauling.

The preliminary work on selection, breeding, and cultivation should be done before planting begins on an extensive scale. That it is really worth doing is shown by the fact that much has been done already by individual millers. Messrs. A. and L. Seifert, B. B. Wood, A. Wall, and G. Seifert may be mentioned especially. Valuable as work by individual concerns may be, there can be no doubt that combined work by all interested has everything in its favour. It is waste for several men each to spend time and money on the same problem ; nor can one man, or a company, often afford to look far enough ahead in its programme of research. The industry in New Zealand is small; it must stand or fall as a unit. The pooling of experience already gained, and co-ordination in future research, appear to offer the most hopeful lines of advance.