RAIN ON THE IDES
SEASON TO DATE
TCM?S MID-YEAR MEETING
BLOOM
SOMATIC ROOTSTOCKS
CITRUS BLIGHT
NOSTALGIA

RAIN ON THE IDES-

Unlike for Caesar, the Ides of March were indeed fortunate for Valley citrus growers, inasmuch as unseasonal rains occurred pretty much Valley wide. In fact, the more than three inches that fell at Brownsville broke the record that had stood for over a century. It seems that everyone got at least an inch and a half, some reported up to five inches.

The rains were a boon for practically everyone in the agricultural sector, as farmers and growers were preparing to irrigate newly emerged crops across such as corn, cotton, cane and grain, as well as existing vegetables. For citrus growers, the rain was especially timely to incorporate fertilizer, herbicides and Temik.

While the projected rains for the end of March did occur, they were mostly scattered. However, some general rains fell through the first few days of April; after all, it is getting to be tradition to have rain around Onion Fest. I don't know about you, but I could get used to rain every couple or three weeks-especially during this critical fruit set and fruit size determination period.

SEASON TO DATE-

Early and mid season oranges are all but finished, with the total volume of earlys and navels at 59,649 tons, 8.0 percent above the USDA crop estimate. The increase occurred in earlys and mids, as the fresh navel volume was down 10.04 percent from the 2002-03 season. Fresh utilization of early and navels combined was 3.4 percent above the final for the last season.

Grapefruit, while battered by concerns of prescription drug interactions, has performed remarkably well this season, with total fresh utilization being about 6.2 percent above the season-to-date volume of last year. Though the USDA crop estimate is down some 5.73 percent, the industry is obviously moving more of the crop into fresh channels.

Packinghouse eliminations of grapefruit are running only about 72 percent of last season, reflecting the overall better quality of this season's crop. But for the inability to fully control late season rust mites because of the extended rains of last fall, the eliminations percentage would have been even lower.

TCM'S MID-YEAR MEETING-

Normally, I would provide a recap of some of the highlights of this annual program, but all I can say is that I heard that it was a pretty good meeting. Family activities during my children's spring break week took priority.

BLOOM-

As anticipated, grapefruit bloom has been delayed by cooler weather. As a rule, a later bloom often leads to a substantial increase in the incidence and severity of sheepnosing in Rio Red grapefruit. It is too early to predict, however, as the weather in March has also been a little on the cooler side of normal, with another cool front predicted to bring rain during the last couple of days of March. There is usually a little cold snap just before Easter, but Easter is not until April 11 this year-a little later than normal. So we'll just have to wait and see what happens regarding fruit shape.

SOMATIC ROOTSTOCKS-

At the University of Florida Citrus Research and Education Center at Lake Alfred, Dr. Jude Grosser is making great strides in the development of new citrus rootstocks by somatic hybridization, a process whereby the complete DNA of two different parents is combined into one through fusion of individual cells in a petri dish. If you are familiar with the work of Dr. Elezer Louzada at the TAMU-K Citrus Center, then you know how the process works. Dr. Grosser is attempting to development "a better mousetrap", in this case, a sour orange that is resistant to citrus tristeza virus, among other attributes, as well as other rootstocks having desirable traits.

As a background primer, genetic analyses of citrus indicate that sour orange is probably a hybrid of pummelo (one of the parents of grapefruit) and mandarin orange. The particular pummelo and mandarin parents are unknown, obviously, but Dr. Grosser is combining tristeza resistant pummelos (and pummelo seedlings selected from other tests) and widely adapted mandarins to develop "mandelo" somatic hybrids. These "mandelo" hybrids are tested for tristeza resistance, and then entered into field trials with grapefruit and orange scions for horticultural evaluation.

The entire program for rootstock development involves a lot of other scientists with the CREC and the USDA-and it involves a lot more work than indicated here. For example, work includes the development and/or improvement of greenhouse screening tests for tristeza, Phytophthora, Diaprepes, salinity, nematodes and other factors to which resistance is desirable. Field trials are essential and rely heavily on the cooperation of Florida's citrus growers.

Just as Dr. Louzada's work may produce a superior red grapefruit, and Dr. Eric Mirkov's work may provide tolerance to a number of pests and other attributes, the work by Dr. Grosser and others may give us a rootstock with the attributes of our beloved sour orange that is also resistant to tristeza. I can see it already-a deep red grapefruit with smooth skin, flat shape, great taste, long on, tree storage life and a high content of all that is good for you (with no drug interactions!), growing on a tree that is more compact, resistant to rust mites, other insects, and diseases, is high yielding, extremely cold tolerant and also tolerant to a wide variety of soil and climatic conditions. All that and more are possible, and may come sooner than you can imagine.

CITRUS BLIGHT-

Citrus blight is not a problem for Texas citrus, but it is a major cause of tree losses in other citrus-production areas. Blight is a root problem that affects many rootstocks, especially those whose ancestry includes citron. Citranges and citrumelos are among the rootstocks that are blight-susceptible.

Work by Drs. Derrick, Beretta and Barthe at the University of Florida Citrus Research and Education Center at Lake Alfred has focused on this problem for many years. Recently, they reported on their success in extracting a unique RNA sequence from the roots of blighted trees that appears to be associated with citrus blight. This particular RNA clone reacted with extracts from the roots of 21 blighted trees, but did not react with extracts from the bark or leaves of those trees. In addition, the sequence reacted weakly with 3 of 15 apparently healthy trees from a blight-prevalent grove, suggesting that this RNA clone might be able to detect citrus blight before decline symptoms appear.

This work is especially noteworthy when you consider that citrus blight has not followed one of the major pathological protocols for diseases, i.e., a causal organism has not previously been isolated and identified. That this particular RNA clone came from the roots rather than the tree top and does not react with extracts from the bark or leaves of blighted trees helps explain why so many transmission studies were unsuccessful-the rootstock is the susceptible part of the tree, not the scion.

Aside from its possible use in diagnostics, this particular RNA clone if it does prove to be the cause of citrus blight, could lead to the engineering of blight-resistant rootstocks. For example, it should have immediate applicability in screening somatic hybrid rootstocks for blight tolerance (see the preceding article).

NOSTALGIA-

Some of the research that is occurring today reminds me of just how far we have come from the days of my youth. On trips upstate over the last couple of weekends in March, I had occasion to tune in to XM radio channel 5-the 50's. Aside from the music of that era, the station occasionally ran some of the radio commercials that we used to hear-Pepsodent, Oldsmobile, Pabst Blue Ribbon, Wildroot and on and on. One of my favorites was the parrot singing the praises of Gillette Blue blades, remember those? I wasn't shaving in the 50's, but I still remember my dad trying to get an extra shave or two by sharpening the blade inside a water glass.

Transistors replaced vacuum tubes, only to be replaced in turn by integrated circuits and then by microchips, Sputnik ushered in the space age and cell phones replaced the once familiar "Number please" of the local telephone operator. Strangely, we seem to be busier today than in those days before HDTV, AC (house or car), pre-packaged foods, fast food chains, convenience stores, microwave ovens and communications, computers, e-mail, CD's, digital cameras and whatever else we now take for granted.

The past is kind of like the Charlie Pride song about home "it's nice to think about it, maybe even visit, but I wonder could I live there anymore". Not me, I can't wait to see what changes are in store in the next 5 to 10 years!

JULIAN W. SAULS, Ph.D.
Professor & Extension Horticulturist
2401 East Highway 83
Weslaco TX 78596