Carlos Jorge Rossetto

Resistência de soja a Nezara viridula e Piezodorus guildinii em condições de campo

The soybean cultivars Parana. Vicoja and Santa Rosa, the line IAC 73-228 and the introductions PI 171451 and PI 229358,e were tsted in Campinas, State of Sao Paulo, Brazil, in relation to the stink bugs Nezara viridula L. and Piezodorus guildinii Westw. The line IAC 73-228 had the least percentage of damaged seed (48,l%) in the superior half of the plant, whereas Parana had the highest (96,8%). The introductions PI-171451 (71,1%) and PI 229358 (79,1%) had intermediate degrees of damaged seeds. This difference in damaged seeds could be due to actual resistance to the stink bugs, to resistance to Nematospora coryli transmitted by these insects or due to host evasion. It has been observed by DAUGHERTY et al. (1964) and LINK & COSTA (1974), that varieties with shorter period from flowering to harvest are less damaged by stink bugs and this would be a case of pseudo resistance called host evasion according to PAINTER (1951). There was a high positive correlation between percentage of seeds damaged and green stems at harvest. This feature could be used for field selection against these insects. There was positive significant correlation between damage and seed size. The seed size may be linked in some way to susceptibility to stink bugs. The damage was higher in the superior half of the plants than in the inferior.

Two new Ceratocystis species associated with mango disease in Brazil

The National Research Foundation (NRF), members of the Tree Protection Co-operative Programme (TPCP), the THRIP initiative of the Department of Trade and Industry, and the Department of Science and Technology (DST)/NRF Centre of Excellence in Tree Health Biotechnology (CTHB).

Resistência de soja a insetos: VI. Comportamento de genótipos em relação a percevejos

The performance of 35 soybean germplasms including 16 cultivars, 6 plant introductions and 13 lines derived from the soybean improvement program against stink bugs, was evaluated for two consecutive years, 1983/1984 and 1984/1985, in relation to the stink bugs (Hemiptera, Pentatomidae) species Piezodorus guildinii (Westwood), Euschistus heros (F.) and Nezara viridula (L.). The two experiments were conducted under field conditions at the Experimental Center of Instituto Agronomico located in Campinas, State of Sao Paulo, Brazil. A complete randomized block design with 35 treatments and 4 replications was used. The individual plot was a single row 2 meters long. Artificial infestations with adults were made to supplement the natural field infestation of stink bugs. The infestation level was moderate in the first year and severe in the second. Three criteria were used to judge the resistance to stink bugs: the percentual index of pod damage, the percentage of foliar retention after pod maturation and yield. The percentual index of pod damage is given by the formula 1/2 (% of pods with intermediate damage) + % of pods completely damaged. The percentage of foliar retention was visually estimated upon maturation of the pods. The cultivar Parana was the most susceptible treatment being recommended for use as a susceptible check for stink bugs. The lines IAC80-4228 and IAC80-598-2-4, obtained through the soybean breeding program for resistance to stink bugs, had good performance. They still present however some undesirable agronomic features and cannot be recommended for distribution to the farmers.

Preferência de alimentação de adultos de Diabrotica speciosa (Germar) e Cerotoma arcuata (Oliv.) em variedades de soja

The preference for feeding in 5 soybean varieties of two species of leaf beetles, D. speciosa (Germar) and C. arcuata (Oliv.) (Coleoptera, Chrysomelidae) was tested at Campinas, State of Sao Paulo, Brazil, under greenhouse conditions, in a free choice type of experiment. Two Brazilian commercial soybean varieties Santa Rosa and Parana, were compared with the PI 227 687, PI 229 358 and PI 171 451. The PI 227.687 was less preferred for feeding by D. speciosa than the commercial varieties and the other two PIs were intermediate. The C. arcuata leaf beetle showed a significant preference for young leaves of the variety Santa Rosa over the young leaves of PI 227.687, but in general there was no conspicuous feeding preference for the commercial varieties as much as there was for D. speciosa.

Efeito de genótipos de milho no desenvolvimento de Spodoptera frugiperda (J.E. Smith)

The effect of corn (Zea mays) genotypes on the biology of Spodoptera frugiperda (J.E.Smith) was evaluated to identify possible sources of resistance. The development of the insect was compared on 5 inbred lines from Mississippi (EUA), 5 genotypes from Instituto Agronomico de Campinas and one genotype from Central America (Zapalote Chico). Results showed that the duration of larval stage and larval weight 10 days after emergence were affected by genotypes Mp707, Zapalote Chico, Mp701, Mp706 and Mp705. Viability of larval stage was affected by genotypes Mp705 and Mp706, while the pupal weight was smaller on genotype IAC103 BPl. The duration and viability of pupal stage, sexual ratio, and % of malformed adults were less important to discriminate these cultivars. It was concluded that the least suitable genotypes for development of the insect were Mp707 and Zapalote Chico, followed by Mp706, Mp705 and Mp701, while the most adequates were IAC103 N, IAC701 N and Mp496.

Seca-da-mangueira XXII: sobrevivência de variedades poliembriônicas

A doenca seca-da-mangueira e causada pelo fungo Ceratocystis spp., que provoca a morte de mangueiras em diversos estados brasileiros. O objetivo do trabalho foi avaliar a sobrevivencia de variedades de mangueira, utilizadas como porta-enxertos, em condicoes de campo e casa de vegetacao. Variedades poliembrionicas de mangueira foram testadas para resistencia a Ceratocystis spp.pelo metodo de inoculacao do fungo via solo, em casa de vegetacao. As plantas sobreviventes foram plantadas como pe-franco na Estacao Experimental de Pindorama (IAC), e as consideradas promissoras foram multiplicadas por enxertia em diversos porta-enxertos. Apos 17 anos do plantio, avaliou-se o numero de plantas mortas e verificou-se que, para o porta-enxerto Manila , considerado resistente, todas as plantas estavam vivas, enquanto Coquinho, considerado suscetivel, apresentou 58,3% de plantas mortas. Dois isolados de C. mangicola M. van Wyk and M.J. Wingf. foram utilizados para avaliar a resistencia das variedades de mangueira, em casa de vegetacao. O patogeno foi cultivado em meio de cultura BDA e transferido para o meio liquido BD. Foram realizadas oito inoculacoes sucessivas, com intervalo minimo de 30 dias. As avaliacoes foram realizadas pelas porcentagens de plantas mortas. O delineamento experimental utilizado foi blocos ao acaso, com 15 variedades e quatro repeticoes. O metodo de inoculacao via rega de solo, com 5 mL de inoculo a concentracao de 106 esporos . mL-1 foi eficiente para selecionar porta-enxertos de mangueira resistentes a C. mangicola. As variedades Vitoria, IAC 112, Dura e Bocado mostraram ser resistentes ao isolado de C. mangicola neste experimento. A variedade Juliana apresentou o mesmo nivel de suscetibilidade da variedade Coquinho. Recomenda-se evitar essas duas variedades para uso como porta-enxertos em areas onde ocorre a doenca.

Herança da resistência da variedade de sorgo AF-28 a Contarinia sorghicola Coquillet

Reciprocal crosses were made between the sorghum varieties AF-28 resistant to the sorghum midge, and Sart susceptible. In 1975 under field conditions at Campinas, State of Sao Paulo, Brazil, the average damage of the Fl of these crosses was 8.5, the average damage of Sart was 9.2 and of AF-28 was 1.2 showing that susceptibility to sorghum midge is dominant or incompletely dominant. Inflorescences of F2 plants were bagged at random and F2 derived families in the generation F3 (S1 lines) were studied under field conditions in 1977. Fourteen families out of a total of 216 from the cross Sart x AF-28, did not differ significantly at the 5% level from the resistant parent AF-28. The chi-square between the observed ratio of 14:202 and the expected ratio of 14:210 was not significant. This result fits into the hypothesis of a minimum of two genes governing the resistance to sorghum midge in the variety AF-28. Three families out of a total of 109 from the cross AF-28 x Sart did not differ significantly at the 5% level from the resistant parent AF-28. The observed ratio of 3:106 does not fit properly into the expected ratio of 3:45 for two pairs of genes or into the expected ratio of 3:189 for 3 pairs of genes. The hypothesis that a minimum of 2 recessive pairs of genes are responsible for the resistance to the sorghum midge in the variety AF-28 is still sustained by the observed ratio 3:106. The lowest mean damage observed among the F3 families was 0.86 in the cross AF-28 x Sart while the mean damage of the resistant parent was 0.79. The lowest damage among the F3 families from the cross Sart x AF-28 was 0.937 while the mean damage of the resistant parent AF-28 was 0.9027. There was no F3 line among the 325 observed, which had a mean damage equal or lower than the resistant parent. This suggests that at least 2 recessive pairs of major genes are responsible for the resistance, but other genes with minor effects might be present. Some lines derived from F3 families with low mean damage showed good agronomic characteristics together with good level of resistance showing that the resistance can be transferred and recombined to produce resistant cultivars or hybrids.

Comportamento de populações paternais e F1 de soja em relação a Colaspis sp. e Diabrotica speciosa (Germar, 1824)

Em condicoes de casa de vegetacao, avaliou-se a resistencia a Colaspis sp. (possivelmente C. occidentalis L.) e Diabrotica speciosa (Germar, 1824), em soja obtida de cruzamentos entre o PI 227.687 e os cultivares comerciais Santa-Rosa e Parana. A infestacao foi artificial e os adultos tiveram livre chance de escolha para alimentacao. A avaliacao dos danos foi feita visualmente, estimando-se a porcentagem de area foliar danificada pelos adultos. Os resultados obtidos evidenciaram alta resistencia do PI 227.687 para os dois insetos, quando comparado com os cultivares Santa-Rosa e Parana. As populacoes F1 sofreram danos semelhantes ao pai resistente, tanto para C. occidentalis como para D. speciosa, sugerindo que a resistencia do PI 227.687 em relacao a esses insetos seja dominante. O numero de peciolos cortados pela D. speciosa tambem foi uma forma de comparar a resistencia e o comportamento das cinco populacoes de soja, que foi semelhante ao encontrado para a porcentagem de area foliar danificada.

Técnica de amostragem para comparar o dano causado pela lagarta-da-espiga, Heliothis zea (Boddie), em cultivares de milho

A study was made to determine the sample size for research on corn resistance to corn ear worm Heliothis zea (Boddie). The damage was measured using the Widstrom centimeter scale. The criteria used to select the sample sizes were such that a difference between two treatments of ten percent or twenty percent of the overall mean should be detected by the statistical test, and that each treatment mean can be estimated with a standard error of 0.10 y or a standard error of 0.20 y. The data were obtained from two field experiments, carried out in Instituto Agronomico, Campinas, State of Sao Paulo, Brazil. The treatments were: cultivar Asteca Prolifico VRPE VII, which is resistant to Heliothis zea; Hmd 7974, a susceptible double hybrid; cultivars Maya XVI and HS 7777. A randomized complete block design with ten replicates was used, and each plot consisted of four rows with 50 plants per row. The variance components method was used to define the type of sampling. The most important variance component was due to the variability among units within rows. The following minimum sample sizes can be used to detect the difference between two means: 6 blocks with 4 rows of 24 plants for a difference of 0.10 y and 5 blocks with 3 rows of 6 plants for a difference of 0.20 y. For estimating the mean damage with 0.10 y as the half confidence interval on the mean of the population, the following minimum sample sizes can be used: for cultivar Asteca, 7 blocks with 4 rows of 30 plants per row; for the hybrids Hmd 7974, HS 7777 and cultivar Maya, 5 blocks with 2 rows of 24 plants per row. If a 0.20 y is specified, as the half confidence interval on the mean, it can be used 5 blocks with 3 rows of 12 plants for cultivar Asteca and 5 blocks with 2 rows of 6 plants for the other three cultivars.

Métodos de analise dos danos da lagarta da espiga¹, em médias de gerações envolvendo IAC Maya e Zapalote Chico

The line Zapalote Chico 2451 (ZC 2451) resistant to the corn earworm, Heliothis zea, the commercial synthetic Brazilian variety IAC Maya XII, the F1 and F2 obtained with their cross, and the two back crosses between the F1 and both parents, were planted in the field in a randomized block with 10 replications. The earworm damage done to the ears was graded utilizing the revised scale described by WIDSTROM (27). The data obtained was analised by two different ways. The grades were distributed at first in two different classes: grades 0 and 1 and grades > 2. The grades were afterwards distributed in the following two classes: grades 0 and grades > 1. The chi-square test was applied to verify which of the two types of classes adjusts better with their respective expected ratios. The results showed that when the grades were divided in the classes 0+1 and > 2 the data were more uniform within each treatment. The analysis of variance for each damage class separately, presented F values highly significant for the classes zero and zero plus one, whereas for the classes > 1 and > 2 the damage averages were very similar and the F values were not significant. The class zero plus one had F value higher and the coefficient of variation smaller than the class zero. The ZC 2451 corn compared to the variety IAC Maya XII, exibited good resistance to the corn earworm, under the field conditions of Campinas, State of Sao Paulo, Brazil. This resistance is of the type non preference and or antibiosis, because there was a higher percentage of ears of ZC 2451 free of earworm damage.