PRODUCTIVITY AND TOBACCO BUDWORM RESISTANCE OF COTTON DEVELOPED BETWEEN 1890 AND 1986

There is a paucity of information on the relationships between modern (i.e., released in or after 1978) and historically obsolete cotton (Gossypium hirsutum L.) cultivars with respect to their ability to yield when grown in the presence of high levels of tobacco budworm (TBW), Heliothis virescens F. The objective of this study was to compare 18 cultivars of cotton developed between 1980 and 1986 for ability to yield when grown with and without TBW infestations. This comparison was accomplished by growing cultivars for 2 yr under two regimes: (i) artificial infestation with TBW (w/TBW) and (ii) complete control of all insect pests (w/o TBW). The regression equation for lint percentage w/o TBW on lint yield w/o TBW was Y = 26.8 + 0.0076 X, with an R2 of 0.58. Thus, lint percentage has increased 0.76% for every 100 kg-1 increase in lint yield. The regression equation for number of bolls w/o TBW on lint yields w/o TBW was Y = 73,689 + 402 X, with an R2 of 0.83. The regression equation for lint yield w/TBW on lint yield w/o TBW was Y = -48.4 + 0.69 X, with an R2 of 0.84. Thus, for every 1.00 kg of lint yield increase due to breeding during the 96-yr period there was a corresponding lint yield increase under TBW infestation of only 0.69 kg. The newer cultivars yielded more than the older cultivars, with number of boils per unit area and lint percentage being the primary components involved in increased yields. Some of the newer cultivars yielded as much w/TBW as some of the older cultivars w/o TBW. In addition, the newest cultivar (DES 119; 1986) yielded significantly more than any other cultivar when grown w/o TBW. It also yielded significantly more when grown w/TBW than any cultivar developed before 1982.