February, 1909.] 



167 



Plant Sanitation* 



Water-melons in the South are seriously- 

 attacked by a soil disease (Neocosmos- 

 pora), which it has been impossible to 

 combat satisfactorily. Mr. Or ton first 

 made a study of all varieties of water- 

 lemons and related plants obtainable, 

 and found that all commercial varieties 

 were almost equally susceptible. He 

 found, however, that a form of citron 

 (hard fleshed melon) was very resistant, 

 but worthless commercially. He crossed 

 this with commercially desirable varie- 

 ties. The seed resulting from this 

 cross, when planted the next year, re- 

 vealed the fact that he had obtained 

 about a thousand new varieties, most of 

 which were either worthless commer- 

 cially or non-resistant. He selected a 

 few of the most promising of these for 

 further study, and found that he had 

 one variety commercially desirable, 

 profitable, and strongly resistant. 

 What has Been Done. 

 Let us see what has been accomplished 

 toward obtaining practical results in the 

 breeding or selection of disease-proof 

 varieties. I will speak briefly of some 

 of the most notable results obtained in 

 this country or applied to American con- 

 ditions. It is not my purpose to review 

 the observations (and they are many) 

 on resistant varieties of vegetable or 

 fruits that are in common use, but to 

 confine myself to a discussion of the 

 outcome of definite efforts to obtain 

 varieties resistant to specific diseases. 

 Wheat. 



We will agree that to spray a wheat 

 field for rust would be out of the ques- 

 tion from a practical standpoint, even 

 though such treatment might rid the 

 crop of the disease. It is evident that 

 in sections where wheat rust is especially 

 prevalent, disease-resistant varieties of 

 wheat would be of special value. Inves- 

 tigations have been made in Europe, 

 Australia, and the United States for 

 the purpose of obtaining rust-resisting 

 wheats. More or less success has been 

 obtained by all investigators, Carlton, 

 working in this country, has made a 

 study of all available varieties from all 

 countries and has found that certain 

 varieties of the Durum wheats are most 

 resistant to the black stem rust. In 

 this connection the recent work of R. H. 

 Biffen on the hybridization of wheats 

 bids fair to have a far-reaching influence 

 on future work in developing immune 

 varieties. He found that susceptibility 

 and immunity in certain varieties of 

 wheats are definite Mendelian charac- 

 ters, the former being the dominant one. 



Clover. 



Messrs. Bain and Essary of the Ten- 

 nessee Experiment Station have con- 



ducted experiments in selecting and 

 developing a variety of red clover resist- 

 ant to a new fungus disease belonging 

 to the anthranoses, that has for several 

 years threatened the cultivation of red 

 clover in Tennessee and the South. 

 They have practised selecting seed from 

 individual plants which survived in a 

 field very seriously attacked by the 

 disease and have obtained very satis- 

 factory results. 



Cow Pea. 

 This plant suffers in the South from 

 two serious troubles, a wilt disease and 

 a nematode root gall. Varieties have 

 been studied and the Little Iron cow- 

 pea has been found to resist the attack 

 of both these diseases. 



Potatoes. 

 Various potatoes resistant to the late 

 blight have been known for many years 

 in Europe. Recently the study and 

 selection of resisting varieties have 

 secured considerable attention in this 

 country. Jones and Stuart, working at 

 the Vermont Experiment Station, have 

 had very favourable results in selecting 

 varieties resitant to this trouble. The 

 work on potatoes resistant to this 

 disease has been largely a study of 

 varieties. It is still in progress. In con- 

 nection with the work with late blight 

 attention has been paid to sorts resis- 

 tant to scab. The Ohio and other Sta- 

 tions have had marked results in select- 

 ing varieties and individuals resistant 

 to the early blight (Alternaria) which is 

 not easily controlled by spraying. 



Tobacco. 



This crop is attacked in Connecticut 

 by a serious wilt disease. By selecting 

 seeds from individuals which have sur- 

 vived in a field nearly totally destroyed 

 by the disease, Shamel and Cobey have 

 succeeded in developing resistant strains. 

 A similai disease in North Carolina has 

 been investigated in the same way with 

 very favourable results. 



This plant is also attacked by 

 Nematode worms, which cause gall-like 

 swellings on the roots. Experiments 

 are now underway by officials of the 

 U. S. Department of Agriculture for the 

 selection of varieties resistant to this 

 trouble. 



Cotton. 



Very satisfactory results have been 

 secured in selecting varieties resistant to 

 the wilt of cotton in the South. The 

 work has been carried on by W. A. 

 Orton of the Department of Agriculture. 

 He has found that several varieties of 

 Egyptian cotton, as well as one Upland 

 cotton, give great promise of resistance- 



