FLESH-COLLAPSE IN STURMER APPLES.

New Zealand Journal of Agriculture, Volume XXXVI, Issue 2, 20 February 1928, Page 88

FLESH-COLLAPSE IN STURMER APPLES.

COOL-STORAGE EXPERIMENTS, 1927.

R. Waters.

Plant Pathologist, Biological Laboratory, Wellington.

Among the fruit-storage problems presented from various parts of New Zealand is a trouble occurring in Sturmer Pippins and certain other apple varieties. Here and abroad it is recognized as a functional disease —one liable to occasion much damage to the stored fruit. Here it is more prevalent in certain lines and stores, and is commonly diagnosed as flesh-collapse or internal breakdown. The study of the disease commenced in Nelson in 1920, and last year was pursued in Hawke's Bay and Auckland, using fruit from three selected orchards. These orchards represented a group, the Stunners from which —in certain —had previously developed flesh-collapse abundantly.- The three lines were studied in six different cool stores under usual and under modified commercial conditions. While this procedure has special merits, it may not make, for the same scientific accuracy and proof as that obtainable in a laboratory equipped for fundamental research, with smaller quantities at stake and with more precisely controlled and recorded conditions.

INFLUENCE OF DIFFERENT STORAGE CONDITIONS. Last year’s work showed how one set of storage conditions compared with another may influence the onset and intensity of flesh-collapse. In three of the stores traces of the disease were found as early as August—-that is, after four months’ storage. In the three unaffected stores, moreover, there was still no appearance of flesh-collapse in October —after six months’ storage. The position is set out in the following table: —

These results, coupled with the examinations made from time to time ■of the stocks of the unaffected stores, demonstrate in a general manner a matter of the first importance in this investigationnamely, that the prevention of extensive damage from collapse to relatively “ susceptible ” lines in cool stores is possible and practicable for at least six months.

The next examination was made in October — about eight months’ storage. The bulk of stored apples . in New Zealand is unloaded by this time, and there remains a comparatively small proportion consisting of long-storage varietiesamong which are Sturmers —that may require to be held a few weeks longer. Table 2 shows that these selected Stunner lines were all affected to some extent in all the stores after eight months, the intensity of the disease being much greater in one store than in another.

The figures in this table are liable to convey a worse impression ■of the condition of each line than is justified. The slightest trace of collapse was recorded. The percentage under the heading “ Barely damaged ” is that of apples which had suffered little or no commercial damage from collapse. Further remarks on the intensity of the disease are made later. “ SUSCEPTIBILITY ” OF DIFFERENT LINES OF THE SAME VARIETY. Table 2, which is based on larger counts than Table..!, indicates that while all experimental lines had some collapse by . October, two of them —“ BX ” and “ RB ’’—suffered at least twice as badly as “ RX ” in all the stores. A. marked difference in the “resistance” to collapse of one line compared with others of the same variety is here indicated,

a feature that has been well brought out in former experiments. An analysis is being made of the results to elicit more specific reasons for this difference. -

THE IMMEDIATE PROBLEM.

Where flesh-collapse has occurred freely the immediate problem is to provide such storage conditions as will enable lines of moderate “ susceptibility ” to be held satisfactorily with those more “ resistant " of the same varieties. In one store “ susceptible ” varieties totalling some 17,000 cases were so grouped last year that the prescribed treatment could be given them without interfering with those varieties storing well under customary conditions. The initial separation of the fruit in this way enabled a great improvement to be made in the condition of long-storage varieties, more particularly Sturmers. The separation of the pip-fruits generally into groups, so that each may subsequently be treated according to its requirements, is a means of improving the health and lengthening the life of the fruit in certain cool stores in New Zealand. Having provided the storage conditions most suitable for each group of fruit, the next problem is to discover the factors which make for “ susceptibility." The figures obtained from last year’s work promise to add some useful evidence to that already obtained in this direction.

INTENSITY OF THE DISEASE.

The experimental fruit was brought . out of store and held for a week or more before being cut for examination. The disease when present was commonly localized in the pith, a portion of the tissue confined to a small region about the core. Here it frequently occurred merely as a slight discoloration —one to five pinkish or light-brown flushes or patches. Sometimes, however, the colour was darker. Apples externally healthy in appearance and internally showing no discoloration of the cortex or main body of the flesh but only a slight discoloration about the core were classified as “ Barely damaged ” (Fig. la). They were such as would be auctioned, retailed, and thereafter consumed without any serious cause for complaint. The term “ Slightly damaged ” was used when the pith was darkly discoloured, or when the disease was lightly diffused through the flesh (Fig. ib). “ Slightly damaged” apples would invariably escape detection until they reached the consumer. The “ Badly damaged ” and “ Very badly damaged ” would sometimes show injury externally, and, where repacking is not practised, would be of still greater detriment on • the market (Fig. i c and d). GENERAL. The . 1927 experiments were to some extent duplications or extensions of previous work at Motueka. They disclose further problems of importance in fruit cool storage. The figures obtained are now being examined, and a further presentation of results, supported by such evidence as is available, will later be made in the Journal. Thanks are due to Messrs. N. J. Adamson and W ; H. Rice, Orchard Instructors of the Horticulture Division at Hastings and Auckland respectively, for their hearty co-operationthe former more particularly in the work of securing uniformity among the fruit picked and packed for experimental purposes, and the latter in the final examination and classification of the fruit. (To be. continued.)

Store. Line. Number of Apples examined. Unaffected. Intensity of Flesh-collapse. Total damaged. Barely damaged. Slightly damaged. Badly damaged. Very badly damaged. Per Cent. Per Cent. Per Cent. Per Cent. Per Cent. Per Cent. F RX 50 Per Cent. IOO Per Cent. Per Cent. Per Cent. Per Cent. Per Cent. RB 51 IOO E .. BX ' 100 100 B RX too 49 31 12 7 I 51 BX too 90 IO IO RB 100 90 7 2 1 ,, IO C . . RX 108 100 BX 126 100 • RB TOO too c . f A RX 100 97 3 ,3 BX too 95 5 5 RB too 99 1 1 D RX 0 RB 0

Table I. — Comparison of the Three Experimental Lines in respect to Damage suffered from Flesh-collapse after Six Months’ Storage.

Store. Line. Number of Apples examined. Una fleeted. • Intensity of Flesh-collapse. - Total damaged. Barely . damaged . Slightly damaged. Badly damaged. Very badly damaged. F RX 500 Per Cent. 91 Per Cent. 9 Per Cent. Per Cent. Per Cent. Per Cent. 9 RB 461 59 - ' 41 41 E BX 433 70 29 1 30 B RX 366 78 20 I I 22 BX 266 54 40 4 2 46 46 RB 416 53 35 9 2 I 47 C RX 244 92 8 8 BX 186 38 54 8 62 RB 332 . 35 65 65 A RX 231 7i 26 3 % 29 BX 287 41 - 29 15 14 I • 59 RB ■384 48 ' 33 1,7 2 52 D RX 233 66 15 13 ■ 4 34 RB 385 37 32 1 28 3 63

Table 2.—Comparison of the Three Experimental Lines in respect to Damage suffered from Flesh-collapse after Eight Months’ Storage.