Relationship cotton genotypes and ramularia leaf spot in Mato Grosso | Reaction of cotton genotypes to ramularia leaf spot (Ramularia areola Atk)

English. The objective of this study was to evaluate the performance of cotton genotypes and resistance ramularia leaf spot in two sowing dates. The experimental design was a randomized block with 18 genotypes of cotton and 5 repetitions. They assessed the area under the disease progress curve (AUDPC) and yields, to which were held 8 reviews of disease severity in each third of the plant, lower, middle and upper. The IMA 08-12427 genotype showed lower average total AUDPC, regardless of sowing time. Regarding yield, TMG 82 WS genotypes BRS 371, DP 555 BG RR, FM 982 GL and BRS 372 obtained the highest yield in the first seeding time, ranging from 3,021.97 to 3,623.57 kg ha-1, and classified as resistance as MR, MR, MS, S, MS, respectively. Among the 18 genotypes, the first sowing had seven MR six MS-five S, while in the second epoch presented three MR four MS ten S and AS.

Portuguese. Cotton cultivation is of great importance for Brazilian agribusiness, however, diseases such as the ramularia leaf spot cause serious damages to yield, therefore, it is sought to produce genotypes less susceptible to this disease. The objective of this study was to evaluate the productive performance of cotton genotypes and the resistance to ramularia leaf spot in two sowing times. A randomized complete block design was used, with 18 cotton genotypes and five replicates. The first sowing times was in December 2013 and the second times in January 2014, where the area under the disease progress curve (AUDPC), production and number of bolls were evaluated separately in each third of the plant, yield, index relative resistance and class of resistance of the genotypes of cotton to Ramularia areola. The genotype IMA 08-12427 showed lower AUDPC per plant, regardless of the sowing times. The genotypes TMG 82WS, BRS 371, DP 555BG RR, FM 982GL and BRS 372 obtained the highest yields in the first sowing times, ranging from 3,021.97 to 3,623.57 kg ha-1 of seed cotton and classified as moderately resistant (MR), MR, moderately susceptible (MS), susceptible (S) and MS, respectively. The first sowing times was more adequate for the study region, because the genotypes presented better performance in relation to the disease, having seven MR, six MS and five S, already in the second times were only three MR, four MS, ten S and one highly susceptible (AS).