Production of micronucleoli and onset of cotton fiber growth

Abstract

Experiments focused on the early development of ®ber cells of cotton (Gossypium hirsutum L. cv. MD51 ne) ovules produced two novel ®ndings: one biological, the other methodological. The ®rst concerns a micronucleolus in the nucleus of ®bers. This developmental marker appears at or a little before 4 days postanthesis (dpa) in about 10% of the ®bers and increases thereafter to nearly 80% provided the ®bers are growing on fertilized ovules. Micronucleoli are neither seen in nuclei of ®bers at 0±2 dpa nor in nuclei of non-®ber cells. Consequently, it is postulated that they are the product of speci®c developmental genes associated with ®ber growth. The second, methodological ®nding, involves a cytological means of directly counting the number of ®bers produced on young ovules at 1±4 dpa. The method provides quantitative data unavailable in the past. We used this method to show that emasculation caused a temporary 24-h delay in the initiation of ®bers, that 30% of the ®bers are aected, and that at 3 dpa both fertilized and unfertilized ovules have about 14 500 ®bers. These data indicate that the ®bers on fertilized and unfertilized ovules represent the same cell populations, a ®nding heretofore unknown.

Genetic Improvement of New Mexico Acala Cotton Germplasm and Their Genetic Diversity

“…To achieve the goal of increasing number of lint fibers, cotton breeders can either increase the number of lint fiber initials or reduce the short fiber content, or both. Van't Hof (1998) developed a technique that makes it possible to count the number of fiber cell initials on the ovules. However, a reliable and simple method in measuring fiber number is needed for practical use.…”